Muscle Anatomy and Functions Quiz

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Questions and Answers

What is the smallest muscle in the human body?

Flexor digiti minimi

Temporalis

Stapedius (correct)

Sternocleidomastoid

Which of the following muscles is considered the biggest in the human body?

Gluteus Maximus (correct)

Latissimus Dorsi

Rectus Abdominis

Biceps Brachii

Skeletal muscle tissue can be characterized by which of the following features?

Involuntary control

Smooth shaped cells

Multinucleate and striated (correct)

Branching filaments

What function does cardiac muscle primarily serve?

Pumping blood throughout the body Signup and view all the answers

Which type of muscle tissue is controlled voluntarily?

Skeletal muscle Signup and view all the answers

How many muscles are typically found in the human face?

60 Signup and view all the answers

What characteristic of muscle tissue allows it to respond to stimuli?

Excitability Signup and view all the answers

Which of the following statements about muscle control is false?

Smooth muscle is voluntary. Signup and view all the answers

In which situation is temporal summation likely contributing to tetany?

Carrying a very heavy load Signup and view all the answers

What could be a characteristic of Olympic medalist Hidilyn Diaz regarding her muscle contractions?

She has a higher ratio of fast-twitch muscle fibers compared to most people Signup and view all the answers

Which statement about muscle hypertrophy in Olympic weightlifters is most likely accurate?

Her muscles have mostly experienced functional hypertrophy Signup and view all the answers

When would central fatigue likely be reduced in an athlete like Hidilyn Diaz?

If she utilizes proper technique during lifts Signup and view all the answers

What might differentiate Hidilyn Diaz's muscle attachments compared to an average individual?

Her muscles may have a greater cross-sectional area Signup and view all the answers

What is the primary role of the diaphragm during respiration?

Separates the thoracic cavity from the abdominal cavity. Signup and view all the answers

Which muscle group is primarily responsible for flexing the leg at the knee?

Hamstring group Signup and view all the answers

Which muscle allows for the rotation of the forearm laterally during supination?

Supinator Signup and view all the answers

What is the characteristic shape of a unipennate muscle?

Feather-shaped Signup and view all the answers

Which muscle is involved in abducting the thigh and rotating it medially?

Gluteus medius Signup and view all the answers

What types of connective tissues attach muscles to bones?

Tendons and aponeuroses Signup and view all the answers

Which muscle group primarily extends the leg at the knee?

Quadriceps group Signup and view all the answers

Which skeletal muscle is responsible for closing the jaw?

Masseter Signup and view all the answers

Which term refers to the fleshy part of the muscle between the origin and insertion?

Belly Signup and view all the answers

What does a pennate arrangement of muscle fibers allow for?

Enhanced strength Signup and view all the answers

Which type of muscle contraction is characterized by muscle length changing during contraction?

Both B and C Signup and view all the answers

What primarily contributes to cellular damage after exercise?

Eccentric contraction Signup and view all the answers

What causes central fatigue in muscle performance?

Decreased ability to activate motor neurons Signup and view all the answers

Which method of energy production for muscle contraction utilizes the body’s stored glucose?

Aerobic respiration Signup and view all the answers

What is the primary symptom associated with peripheral fatigue?

Muscle soreness Signup and view all the answers

Which process occurs during oxygen debt when skeletal muscles are used strenuously?

Conversion of pyruvic acid to glucose Signup and view all the answers

What are the conditions causing muscle fatigue?

Build-up of lactic acid and blood supply interruption Signup and view all the answers

What characterizes the process of muscle remodeling?

Continuous increase or decrease in mass Signup and view all the answers

What is the role of creatine phosphate in muscle energy production?

Facilitates rapid ATP regeneration Signup and view all the answers

Which of the following is NOT a type of muscle contraction?

Static contraction Signup and view all the answers

What is the primary function of DHPR in heart muscle contraction?

To cause an influx of Ca+2 into the muscle cell Signup and view all the answers

Which of the following proteins is involved in binding Ca+2 within the muscle cell?

Histidine-rich calcium-binding protein Signup and view all the answers

Which channel blocker specifically affects heart muscle contraction?

Nifedipine Signup and view all the answers

What role does SERCA play during muscle relaxation?

It pumps Ca+2 back into the terminal cisternae Signup and view all the answers

How does RYR function in skeletal muscle compared to cardiac muscle?

RYR is mechanically linked to DHPR. Signup and view all the answers

Which statement accurately describes the sliding filament theory?

The power stroke involves myosin pulling actin filaments. Signup and view all the answers

What is observed in the latent period of a muscle twitch myogram?

Electrical activity begins without measurable tension. Signup and view all the answers

What is the role of calsequestrin in muscle cells?

It serves as a high-capacity Ca+2 binding protein. Signup and view all the answers

What initiates the release of Ca+2 from the sarcoplasmic reticulum in muscle contraction?

Mechanical linkage between DHPR and RYR Signup and view all the answers

Which process is affected by the decrease in Ca+2 levels in muscle cells?

The exposure of actin binding sites Signup and view all the answers

What does elasticity refer to in the context of muscle function?

The capability of a muscle to regain its original length after stretching Signup and view all the answers

Which of the following describes the action of a depressor muscle?

Lowers a part Signup and view all the answers

Which term best describes the action of an abductor muscle?

Moves a part away from the midline Signup and view all the answers

What is the naming basis for the muscle known as tibialis anterior?

Location of the muscle Signup and view all the answers

What action does a constrictor muscle perform?

Compresses a body part Signup and view all the answers

Which base pertains to the shape of the muscle known as serratus?

Saw-toothed Signup and view all the answers

What does the term 'flexor' refer to in muscle classification?

Muscle that bends a part near the joint Signup and view all the answers

Which orientation is indicated by the muscle name 'deltoid'?

Triangular Signup and view all the answers

What type of muscle contraction occurs when the muscle length remains constant while tension is developed?

Isometric contraction Signup and view all the answers

How does fiber diameter influence muscle contraction?

Larger diameter fibers are less effective in fine movements. Signup and view all the answers

What is the relationship between the number of active motor units and force produced?

More active motor units yield a stronger force. Signup and view all the answers

Which type of contraction occurs when the muscle fibers shorten while generating external work?

Isotonic contraction Signup and view all the answers

What determines the amount of tension that a muscle fiber can develop?

The length of the muscle fiber and the number of active fibers. Signup and view all the answers

Which muscle primarily compresses the abdominal wall?

Transverse abdominis Signup and view all the answers

What is the primary action of the gluteus maximus muscle?

Extends the thigh Signup and view all the answers

Which muscle is involved in lateral rotation of the forearm?

Supinator Signup and view all the answers

How does the diaphragm contribute to respiration?

Expands the thoracic cavity Signup and view all the answers

What is a characteristic of the circular muscle arrangement?

Sphincter-like Signup and view all the answers

Which muscle group flexes the arm at the elbow and simultaneously rotates the hand laterally?

Biceps brachii Signup and view all the answers

Which term describes the connective tissue that connects muscle to bone?

Tendon Signup and view all the answers

Which muscle group is known for extending the leg at the knee?

Quadriceps group Signup and view all the answers

What type of arrangement do muscles like the deltoid exhibit?

Multipennate Signup and view all the answers

Which muscle allows the lips to pucker?

Orbicularis oris Signup and view all the answers

What role does acetylcholinesterase play in muscle contraction?

It degrades acetylcholine to prevent continuous stimulation. Signup and view all the answers

Which channel is primarily responsible for propagating the action potential in muscle fibers after acetylcholine binds to its receptors?

Voltage-gated Na+ channels Signup and view all the answers

How does Ca+2 contribute to muscle contraction during excitation-contraction coupling?

It facilitates the interaction between myosin and actin. Signup and view all the answers

What is the primary action that takes place at the neuromuscular junction to trigger muscle contraction?

Release of acetylcholine into the synaptic cleft. Signup and view all the answers

What occurs after the action potential travels along the sarcolemma and into the T-tubules?

Dihydropyridine receptors activate ryanodine receptors. Signup and view all the answers

Which of the following statements about Ca+2 during muscle relaxation is accurate?

Ca+2 is actively transported back into the sarcoplasmic reticulum. Signup and view all the answers

Which component primarily interacts with Ca+2 to facilitate muscle contraction?

Troponin Signup and view all the answers

What initiates the release of Ca+2 from the sarcoplasmic reticulum?

Depolarization of the T-tubules by action potential. Signup and view all the answers

What is the role of the ryanodine receptor (RYR) in muscle contraction?

It facilitates the release of Ca+2 from the sarcoplasmic reticulum. Signup and view all the answers

What occurs during the period of relaxation in muscle contraction?

Calcium ions are pumped back into the sarcoplasmic reticulum. Signup and view all the answers

What characterizes complete (fused) tetanus?

Individual contractions are indistinguishable. Signup and view all the answers

What is the primary function of extrafusal fibers?

To provide the main force-generating structure of the muscle. Signup and view all the answers

Which type of motor neuron innervates intrafusal fibers?

Gamma motor neurons. Signup and view all the answers

How does incomplete (unfused) tetanus differ from complete (fused) tetanus?

Incomplete tetanus exhibits a noticeable oscillation of peak tension. Signup and view all the answers

What is the definition of a motor unit?

A motor neuron and the muscle fibers it innervates. Signup and view all the answers

What leads to smooth and continuous muscle movement?

Summation of individual twitches at high frequency. Signup and view all the answers

Which function is primarily associated with the lateral rectus muscle?

Abducting the eye. Signup and view all the answers

What happens to contractile force during the decline of active cross bridges?

Contractile force gradually declines. Signup and view all the answers

What type of muscle contraction occurs when a muscle lengthens while under tension?

Eccentric contraction Signup and view all the answers

Which of the following contributes most to cellular damage after exercise?

Eccentric contraction Signup and view all the answers

What is the primary cause of peripheral fatigue in muscle fibers?

Accumulation of metabolic waste Signup and view all the answers

What is the primary effect of oxygen debt in muscle metabolism?

Accumulation of lactic acid Signup and view all the answers

Which of the following is NOT a characteristic of muscle remodeling?

Fatigue resistance Signup and view all the answers

What is the primary function of skeletal muscle tissue?

Movement of bone Signup and view all the answers

Which type of muscle tissue is characterized by multinucleated fibers?

Skeletal muscle Signup and view all the answers

Which muscle is considered the longest muscle in the human body?

Sartorius Signup and view all the answers

What characteristic of muscle tissue allows it to be stretched beyond its normal length?

Extensibility Signup and view all the answers

Which of the following describes the control mechanism of smooth muscle?

Involuntary control Signup and view all the answers

Which muscle is known as Ms. Mhin's favorite muscle in the body?

Rectus Abdominis Signup and view all the answers

What is the primary role of cardiac muscle tissue?

Beating of the heart Signup and view all the answers

What is the biggest muscle in the human body?

Gluteus Maximus Signup and view all the answers

What is the primary function of the diaphragm during respiration?

Separates the thoracic cavity from the abdominal cavity Signup and view all the answers

Which muscle is responsible for flexing the arm at the elbow?

Brachialis Signup and view all the answers

What type of muscle arrangement is described as strap-like?

Parallel Signup and view all the answers

Which of the following muscle groups is primarily responsible for extending the leg at the knee?

Quadriceps group Signup and view all the answers

Which muscle allows for the rotation of the forearm medially during pronation?

Pronator teres Signup and view all the answers

What do tendons connect?

Muscle to bone Signup and view all the answers

What is the primary role of the orbicularis oris muscle?

Puckering the lips Signup and view all the answers

Which muscle group assists in compressing the abdominal wall?

Rectus abdominis Signup and view all the answers

Which of the following muscles is part of the hamstring group?

Semitendinosus Signup and view all the answers

What is the action of the flexor digitorum profundus muscle?

Flexes the distal joints of the fingers Signup and view all the answers

What type of contraction involves muscle length being held constant while tension is generated?

Isometric Signup and view all the answers

How does the diameter of a muscle fiber affect force production?

Larger diameter leads to more force Signup and view all the answers

What determines the type of movement produced by muscle fibers per motor unit?

Fewer fibers lead to finer movements Signup and view all the answers

What happens to muscle fibers during isometric contraction?

They remain the same length Signup and view all the answers

Which of the following factors contributes to the strength of contraction in muscles?

Fiber length and diameter combined Signup and view all the answers

What characterizes an isotonic contraction?

Change in muscle length with constant force Signup and view all the answers

The force generated by a muscle fiber is affected by what relationship between fiber length and tension?

Longer fibers generate more tension Signup and view all the answers

Which statement correctly describes the relationship between the number of active motor units and the force produced?

More units activated lead to greater force production Signup and view all the answers

Which factor does NOT affect the threshold of a muscle fiber?

Fiber length Signup and view all the answers

The active shortening of sarcomeres contributes to what type of muscle contraction?

Isotonic Signup and view all the answers

What initiates the release of Ca+2 from the sarcoplasmic reticulum?

Action potential traveling through T-tubules Signup and view all the answers

What is the role of acetylcholinesterase at the neuromuscular junction?

To degrade acetylcholine Signup and view all the answers

Which step follows the influx of Ca+2 into the muscle fiber?

Interaction of myosin and actin occurs Signup and view all the answers

What primarily causes muscle relaxation after contraction?

Ca+2 being pumped back into the sarcoplasmic reticulum Signup and view all the answers

What is the primary function of dihydropyridine receptors (DHPR) in muscle contraction?

Activating ryanodine receptors Signup and view all the answers

Which process follows the binding of acetylcholine to its receptor on the muscle membrane?

Opening of voltage-gated Na+ channels Signup and view all the answers

What structure facilitates the transmission of action potentials deep into muscle fibers?

T-tubules Signup and view all the answers

Which ions are primarily involved in the muscle contraction mechanism?

Ca+2 and Na+ Signup and view all the answers

What occurs at the terminal cisternae during muscle contraction?

Release of Ca+2 into the myofibril Signup and view all the answers

What is the term used for the process by which muscle fiber depolarization initiates contraction?

Excitation-contraction coupling Signup and view all the answers

What does elasticity of a muscle refer to?

The ability of a muscle to recoil to its original length after being stretched Signup and view all the answers

Which term describes a muscle that raises a body part?

Levator Signup and view all the answers

How is the muscle 'Deltoid' classified based on its shape?

Triangle Signup and view all the answers

Which of the following muscles moves a part towards the midline of the body?

Adductor Signup and view all the answers

What is the primary action of a flexor muscle?

Bends a part near the joint Signup and view all the answers

Which muscle is located on top of the temporal bone?

Temporalis Signup and view all the answers

What type of muscle is described as 'constrictor'?

Closes or compresses openings Signup and view all the answers

How is the muscle named 'Tibialis anterior' classified?

By its location Signup and view all the answers

Which situation is most likely to contribute to temporal summation leading to tetany?

Carrying a very heavy load Signup and view all the answers

Which statement is likely true regarding Hidilyn Diaz's muscle activity while lifting?

The lifting involves primarily concentric contractions. Signup and view all the answers

Which of the following statements about Hidilyn Diaz's muscles might be true?

She experiences less central fatigue compared to most people. Signup and view all the answers

Which factor might influence the muscle contractions of an Olympic weightlifter?

The muscle insertion point relative to the fulcrum. Signup and view all the answers

Which factor is less likely to be true about the muscle contractions of elite athletes?

They typically exhibit lower levels of muscle endurance. Signup and view all the answers

What initiates the opening of RYR in heart muscle contraction?

Influx of Ca+2 from DHPR Signup and view all the answers

What role does SERCA play in muscle relaxation?

Pumps Ca+2 into the sarcoplasmic reticulum Signup and view all the answers

Which of the following proteins is responsible for binding Ca+2 in muscle cells?

Calsequestrin Signup and view all the answers

How does DHPR interact with RYR in skeletal muscle?

They are mechanically attached Signup and view all the answers

What is the significance of the latent period in a muscle twitch myogram?

Cross bridges begin to cycle without measurable tension Signup and view all the answers

What happens to tropomyosin when Ca+2 levels decrease in muscle cells?

It blocks the actin binding site again Signup and view all the answers

What is the primary action of calcium channel blocker drugs in heart muscle?

Prevent Ca+2 influx Signup and view all the answers

What is the primary function of DHP in muscle contraction?

Opening calcium channels Signup and view all the answers

What anchors calsequestrin near RYR in muscle cells?

Triadin Signup and view all the answers

During muscle relaxation, how many Ca+2 ions does SERCA pump back into the terminal cisternae per ATP hydrolyzed?

2 Signup and view all the answers

What is the primary role of the interaction between thick and thin filaments in a sarcomere?

Enabling muscle contraction Signup and view all the answers

Which protein is responsible for binding to actin and regulating myosin binding?

Tropomyosin Signup and view all the answers

What component of a sarcomere is responsible for holding thick filaments together?

M line Signup and view all the answers

What distinguishes the I band from the A band in a sarcomere?

The I band only contains thin filaments Signup and view all the answers

Which part of the sarcomere does the actin filament attach to?

Z disc Signup and view all the answers

What is the function of calcium ions in muscle contraction?

To initiate the binding of myosin to actin Signup and view all the answers

How many binding sites does a myosin head possess?

Two: one for actin and one for ATP Signup and view all the answers

Which component of muscle cells prevents myosin from binding to actin in the absence of calcium?

Tropomyosin Signup and view all the answers

What is the H zone in a sarcomere?

A lighter region surrounding the M line containing only thick filaments Signup and view all the answers

Which statement accurately describes myofibrils?

They are long, cylindrical organelles within muscle fibers Signup and view all the answers

What occurs during the period of relaxation in muscle contraction?

Pumping of Ca2+ back into the SR Signup and view all the answers

What characterizes incomplete (unfused) tetanus?

Distinct individual contractions are visible Signup and view all the answers

Which statement about motor units is true?

The smallest functional unit of muscle is a motor unit Signup and view all the answers

What happens to contractile force during the period of contraction?

It increases as the number of active cross bridges increases Signup and view all the answers

What type of muscle fiber is primarily responsible for generating the bulk of muscle force?

Extrafusal fibers Signup and view all the answers

What is the primary characteristic of complete (fused) tetanus?

Sustained higher force without relaxation Signup and view all the answers

Which factor does NOT contribute to the diversity in contraction speed among different muscles?

Location of muscle in the body Signup and view all the answers

What is the result of decreasing intervals between successive stimuli in muscle contraction?

Twitches are indistinguishable and fused Signup and view all the answers

Which type of motor neuron innervates intrafusal fibers?

Gamma motor neurons Signup and view all the answers

What allows for smooth and continuous movements in muscle function?

Summation of twitches at high-frequency stimulation Signup and view all the answers

Which situation is most likely to involve temporal summation leading to tetany?

Lifting a very heavy object Signup and view all the answers

What is the primary contraction type employed by weightlifters during a clean and jerk maneuver?

Concentric contraction Signup and view all the answers

Which characteristic might differentiate an Olympic weightlifter's muscles from those of a typical individual?

Increased cross-sectional area of fibers Signup and view all the answers

What could explain a reduced level of central fatigue in elite athletes like Hidilyn Diaz?

Improved neuromuscular efficiency Signup and view all the answers

Which factor is most likely associated with the muscle adaptations of Olympic lifters compared to non-competitive individuals?

Changes in muscle fiber type distribution Signup and view all the answers

What does elasticity in muscle tissue specifically refer to?

The capability to recoil to original resting length after being stretched Signup and view all the answers

Which term describes a muscle that moves a body part away from the midline?

Abductor Signup and view all the answers

Which of the following muscles is named for its location on the cranial bone?

Temporalis Signup and view all the answers

What does the term 'depressor' indicate about a muscle's action?

It lowers a body part Signup and view all the answers

Which of the following best describes the action of a flexor muscle?

It bends a part near the joint Signup and view all the answers

The muscle named 'Serratus' is best described by which characteristic?

It has a saw-toothed appearance Signup and view all the answers

Which classification of muscle action is associated with opening spaces or widening openings?

Dilator Signup and view all the answers

How is the Deltoid muscle primarily classified?

By shape, resembling a triangle Signup and view all the answers

What type of injury is classified as a strain?

Over-stretched muscles or tendons Signup and view all the answers

Which condition is characterized by the production of more muscle fibers?

Hyperplasia Signup and view all the answers

What does RICE stand for in the treatment of muscle strains and sprains?

Rest, Ice, Compression, Elevation Signup and view all the answers

What is a common symptom of Myasthenia Gravis?

Muscle weakness Signup and view all the answers

Which of the following is NOT a recommended practice for preventing muscle strains?

Jumping right into intense activity Signup and view all the answers

What is characterized by progressive weakness of muscle due to a mutated dystrophin-glycoprotein complex?

Muscular Dystrophy Signup and view all the answers

What role do assistive devices serve for aging individuals?

Aid mobility Signup and view all the answers

Which condition is related to the painful inflammation of a tendon?

Tendonitis Signup and view all the answers

Which of the following is a common treatment for malignant hyperthermia?

Dantrolene Signup and view all the answers

Which of the following conditions is known for causing chronic pain primarily in joints, muscles, and tendons?

Fibromyalgia Signup and view all the answers

What occurs during the period of contraction in muscle fibers?

Cross bridges are active Signup and view all the answers

What characterizes complete (fused) tetanus?

Sustained smooth force Signup and view all the answers

What type of muscle fiber is primarily responsible for generating force?

Extrafusal fibers Signup and view all the answers

Which statement best describes incomplete (unfused) tetanus?

Twitches gradually increase but oscillate Signup and view all the answers

How is a motor unit defined?

A motor neuron and the muscle fibers it innervates Signup and view all the answers

What happens to contractile force during the period of relaxation?

It begins to decline Signup and view all the answers

Which type of muscle fibers are innervated by gamma motor neurons?

Intrafusal fibers Signup and view all the answers

What leads to smooth, continuous movements in muscle contraction?

Summation of individual twitches Signup and view all the answers

What is the primary role of calcium ions during muscle contraction?

Facilitate the binding of myosin and actin Signup and view all the answers

What distinguishes different types of skeletal muscle fibers?

The speed of contraction and force generation Signup and view all the answers

What is the primary characteristic of isometric contraction?

Muscle length remains unchanged Signup and view all the answers

What primarily contributes to peripheral fatigue in muscles?

Accumulation of metabolic waste Signup and view all the answers

During oxygen debt, what happens to lactic acid produced in the muscles?

It is converted to glucose in the liver Signup and view all the answers

What is the primary cause of muscle fatigue during exercise?

Accumulation of lactic acid Signup and view all the answers

Which of the following describes the difference between hypertrophy and atrophy?

Hypertrophy refers to increased muscle mass; atrophy to decreased muscle mass Signup and view all the answers

Which process is primarily involved in rapid energy production for muscles?

Creatine phosphate breakdown Signup and view all the answers

What role does central fatigue play in muscle performance?

It results from decreased efficiency of motor neuron activation Signup and view all the answers

Which type of muscle contraction causes lengthening of the muscle under tension?

Eccentric contraction Signup and view all the answers

What is the immediate outcome when blood supply to a muscle is interrupted?

Rapid muscle fatigue Signup and view all the answers

How does the body manage recovery from intense exercise?

By promoting rest and hydration Signup and view all the answers

What type of contraction is characterized by muscle lengthening while contracting?

Eccentric contraction Signup and view all the answers

Which of the following is NOT a contributing factor to muscle fatigue?

Enhanced release of adrenaline Signup and view all the answers

Which method of energy production is characterized by rapid energy release during muscle contractions?

Creatine phosphate Signup and view all the answers

What condition is described as a muscle's inability to contract due to fatigue?

Muscle fatigue Signup and view all the answers

Which of the following is a common symptom of peripheral fatigue?

Muscle soreness Signup and view all the answers

What is the role of the diaphragm during respiration?

Separates the abdominal cavity from the thoracic cavity Signup and view all the answers

Which muscle group is responsible for flexing the arm at the elbow?

Biceps brachii Signup and view all the answers

What type of muscle arrangement is exemplified by the deltoid?

Multipennate Signup and view all the answers

Which of the following muscles assists in rotating the forearm medially?

Pronator teres Signup and view all the answers

What is the function of the orbitalis oris muscle?

Puckers the lips Signup and view all the answers

What does the term 'sartorius' refer to in the context of muscle arrangement?

Parallel Signup and view all the answers

Which muscle is primarily responsible for extending the leg at the knee?

Rectus femoris Signup and view all the answers

What does the flexor carpi radialis muscle primarily do?

Flex and abduct the wrist Signup and view all the answers

What is primarily responsible for muscle contraction within the sarcomere?

Interaction between thick and thin filaments Signup and view all the answers

Which component of the sarcomere is responsible for anchoring thin filaments?

Z disc Signup and view all the answers

What is the role of tropomyosin in muscle contraction?

To prevent myosin from binding to actin Signup and view all the answers

What is found in the H zone of the sarcomere?

Only thick filaments Signup and view all the answers

Which of the following proteins directly binds to calcium ions during muscle contraction?

Troponin Signup and view all the answers

How many binding sites does a myosin molecule have?

Two, one for actin and one for ATP Signup and view all the answers

Which zone represents the area where myosin filaments do not overlap with actin filaments?

I band Signup and view all the answers

What function does the sarcoplasmic reticulum serve in muscle fibers?

Stores calcium ions necessary for contraction Signup and view all the answers

What do striations in muscle fibers represent?

The arrangement of actin and myosin filaments Signup and view all the answers

Which part of the sarcomere serves as the connection point for thick filaments?

M line Signup and view all the answers

What triggers the release of Ca+2 from the sarcoplasmic reticulum during muscle contraction?

The activation of dihydropyridine receptors Signup and view all the answers

Which protein complex engages in the interaction that ultimately causes muscle contraction?

Myosin and actin Signup and view all the answers

What role does acetylcholinesterase play in muscle contraction?

It degrades acetylcholine after contraction. Signup and view all the answers

During what phase of muscle contraction is Ca+2 pumped back into the sarcoplasmic reticulum?

Muscle relaxation Signup and view all the answers

What initiates the action potential in a muscle fiber?

The binding of Ach to its receptor Signup and view all the answers

Which of the following correctly describes the role of T-tubules in muscle contraction?

They propagate action potentials into the muscle fiber. Signup and view all the answers

What is the primary effect of Ca+2 binding to troponin in muscle fibers?

It allows actin and myosin to form a cross-bridge. Signup and view all the answers

What is the role of dihydropyridine receptors in muscle contraction?

They facilitate the release of calcium from the sarcoplasmic reticulum. Signup and view all the answers

What results from the depolarization of the muscle fiber membrane?

Action potential generation in muscle fibers Signup and view all the answers

Which mechanism is responsible for muscle relaxation following contraction?

Active transport of Ca+2 back into the sarcoplasmic reticulum Signup and view all the answers

What type of muscle contraction involves a constant muscle length while generating tension?

Isometric contraction Signup and view all the answers

Which factor directly affects the amount of force produced by a muscle fiber?

Diameter of the fiber Signup and view all the answers

What happens to muscle tension when the number of active motor units increases?

Force produced increases Signup and view all the answers

In terms of muscle fiber length, what is the relationship between length and tension development?

Optimal length allows maximum tension Signup and view all the answers

Which contraction type primarily represents a situation where muscle fibers shorten and produce external work?

Isotonic contraction Signup and view all the answers

Which aspect is indirectly proportional to the threshold needed to activate muscle fibers?

Fiber diameter Signup and view all the answers

Which arrangement of fibers is typically associated with finer and more controlled movements?

Fewer fibers per motor unit Signup and view all the answers

What does not occur during isometric contractions?

Change in muscle length Signup and view all the answers

How does the tension relate to the contraction when the muscle fiber lengths are at an optimal state?

Maximum tension is observed Signup and view all the answers

What effect does the muscle fiber diameter have on generated force?

Directly proportional Signup and view all the answers

What is the primary function of axial muscles in the human body?

Positioning the head and vertebral column Signup and view all the answers

How are muscles classified based on their size?

Sizes are denoted by terms like maximus, major, and minimus Signup and view all the answers

What percentage of skeletal muscles in the body are classified as appendicular muscles?

40 percent Signup and view all the answers

What are teres muscles characterized as?

Short and round Signup and view all the answers

Which of the following describes the role of appendicular muscles?

Moving and stabilizing structures of the upper and lower limbs Signup and view all the answers

Which muscle is responsible for rotating the head and neck?

Sternocleidomastoid Signup and view all the answers

What is the primary action of the deltoid muscle?

Abduction of the arm Signup and view all the answers

Which of the following muscles is involved in the extension of the leg at the knee?

Quadriceps femoris Signup and view all the answers

Which muscle group primarily facilitates shoulder abduction?

Deltoid Signup and view all the answers

Which of the following muscles is located in the posterior compartment of the arm?

Triceps brachii Signup and view all the answers

Which muscle assists in the flexion of the leg at the knee joint?

Semimembranosus Signup and view all the answers

Which muscle is primarily responsible for dorsiflexing the foot?

Tibialis anterior Signup and view all the answers

Which muscle is located in the lateral compartment of the thigh and assists in hip abduction?

Gluteus medius Signup and view all the answers

What do the terms indicating structural characteristics of a muscle often describe?

The size and shape of the muscle Signup and view all the answers

Which term is specifically used to indicate the muscle that raises a body part?

Levator Signup and view all the answers

Which descriptive term would be appropriate for a muscle that moves away from the midline of the body?

Abductor Signup and view all the answers

What does the prefix 'biceps' in muscle terminology indicate?

Two heads Signup and view all the answers

Which of the following terms describes the position of a muscle relative to the body's surface?

Anterior Signup and view all the answers

The term 'flexor' indicates which type of muscle action?

Bending movement Signup and view all the answers

Which term identifies a muscle that performs the action of straightening a limb?

Extensor Signup and view all the answers

What does the term 'superficial' describe when referring to muscles?

Muscles located toward the surface Signup and view all the answers

Which of the following muscle names indicates a circular muscle shape?

Orbicularis Signup and view all the answers

What unique characteristic is indicated by the term 'quadriceps' in muscle nomenclature?

Four heads Signup and view all the answers

Which muscle is primarily responsible for elevating the shoulders?

Trapezius Signup and view all the answers

Which of the following muscles is not involved in the movement of the arm?

Flexor digitorum superficialis Signup and view all the answers

What is the primary function of the rectus abdominis muscle?

Trunk flexion Signup and view all the answers

Which muscle is involved in breathing and separates the thoracic cavity from the abdominal cavity?

Diaphragm Signup and view all the answers

Which of the following muscles assists in flexing the forearm?

Brachioradialis Signup and view all the answers

Which muscle is responsible for the abduction of the thigh?

Gluteus medius Signup and view all the answers

Which muscle is most associated with flexion of the knee?

Gastrocnemius Signup and view all the answers

What role does the serratus anterior muscle play in shoulder movement?

Shoulder stabilization Signup and view all the answers

Which muscle is primarily responsible for extending the leg at the knee?

Vastus medialis Signup and view all the answers

Which muscle acts to rotate the forearm medially?

Pronator teres Signup and view all the answers

What is the primary characteristic of parallel muscles like the rectus abdominis?

They shorten significantly when contracting. Signup and view all the answers

How much does a parallel muscle shorten when its fibers contract together?

About 30 percent of its length. Signup and view all the answers

What factor is most crucial in determining the tension developed during a muscle contraction?

The total number of myofibrils present in the muscle. Signup and view all the answers

What is the impact of variations in muscle organization on movement?

It can dramatically affect power, range, and speed of movement. Signup and view all the answers

What is a key feature of muscle fibers in parallel arrangement?

They are aligned parallel to the muscle's long axis. Signup and view all the answers

What happens to a 10 cm long parallel muscle when one end is held in place during contraction?

It will move the held end 3 cm. Signup and view all the answers

Which muscles serve as examples of parallel muscles?

Rectus abdominis and supinator. Signup and view all the answers

Which characteristic describes the gross anatomy of muscles?

Muscles are made up of parallel, circular, or unipennate arrangements. Signup and view all the answers

In terms of functional relationships, what should be noted about skeletal muscle fibers?

They all contract at similar rates and shorten similarly. Signup and view all the answers

Which of the following factors does NOT affect the movement produced by muscle contractions?

Color of the muscle fibers. Signup and view all the answers

What is the primary action of the levator anguli oris?

Elevates the corner of the mouth Signup and view all the answers

Which anatomical structure does the levator anguli oris originate from?

Maxilla below the infra-orbital foramen Signup and view all the answers

Which nerve innervates the levator anguli oris?

Facial nerve (VII) Signup and view all the answers

What is the insertion point for the levator anguli oris?

Corner of mouth Signup and view all the answers

Which other muscle primarily works with the levator anguli oris to elevate parts of the mouth?

Zygomaticus major Signup and view all the answers

What is the arrangement of fascicles in a convergent muscle?

Fascicles extend over a broad area and converge at a single attachment. Signup and view all the answers

Which of the following is a characteristic of parallel muscles?

Fascicles are parallel to the long axis of the muscle. Signup and view all the answers

What is a primary functional difference between convergent muscles and parallel muscles?

Convergent muscles can pull in multiple directions. Signup and view all the answers

Which of the following statements about convergent muscles is true?

They typically pull on a tendon at the apex. Signup and view all the answers

What occurs when the entire muscle of a convergent arrangement contracts?

The overall pull is not as strong compared to a parallel muscle of the same size. Signup and view all the answers

What type of attachment site can a convergent muscle pull on?

Tendons, aponeurosis, or raphe. Signup and view all the answers

How does the arrangement of fascicles in muscles affect their function?

It affects how much force they can generate. Signup and view all the answers

Which of the following muscles is an example of a convergent muscle?

Pectoralis major Signup and view all the answers

What is the primary function of the extensor carpi radialis longus muscle?

Extension at the carpus Signup and view all the answers

Which term describes muscles located entirely within an organ?

Internus Signup and view all the answers

What does the name 'buccinator' primarily refer to in terms of muscle function?

Compresses the cheeks Signup and view all the answers

Which term indicates a muscle with fascicles that run parallel to the muscle's long axis?

Rectus Signup and view all the answers

What is commonly suggested by the name 'risorius' muscle?

One who laughs Signup and view all the answers

What distinguishing feature do rectus muscles share in terms of their anatomical structure?

They have straight fascicles Signup and view all the answers

What is the primary action of the sartorius muscle?

Crossing the legs Signup and view all the answers

Which of the following terms refers to muscles that position or stabilize an organ?

Extrinsics Signup and view all the answers

Which muscle name indicates its orientation as running across the body?

Transversus Signup and view all the answers

What type of muscle is described as serving a specific occupation or habit?

Extrinsic Signup and view all the answers

Which type of pennate muscle has fascicles on both sides of a central tendon?

Bipennate Signup and view all the answers

What arrangement of fascicles contributes to a muscle being classified as multipennate?

Fascicles branching off multiple tendons Signup and view all the answers

Which muscle is an example of a unipennate muscle?

Extensor digitorum Signup and view all the answers

What is the function of circular muscles in the body?

Surround body openings and act as valves Signup and view all the answers

Which of the following muscles is bipennate?

Rectus femoris Signup and view all the answers

What occurs when a circular muscle contracts?

The diameter of the opening becomes smaller Signup and view all the answers

What is a key characteristic of a pennate muscle compared to a parallel muscle?

Has a more complex fiber arrangement Signup and view all the answers

In the context of muscle anatomy, what does the term ‘fascicle’ refer to?

A grouping of muscle fibers Signup and view all the answers

Which of the following describes the tension generation capabilities of pennate muscles?

They can generate more tension relative to other muscle types. Signup and view all the answers

What is the primary role of the deltoid muscle in the context of fascicle arrangement?

To generate lifting force Signup and view all the answers

What is the primary function of the orbicularis oris muscle?

To constrict the opening of the mouth Signup and view all the answers

Which muscle is involved in moving food back across the teeth during chewing?

Buccinator Signup and view all the answers

Which group of muscles is primarily responsible for facial expressions?

Muscles of the head and neck Signup and view all the answers

What action does the buccinator perform related to infant feeding?

Provides suction for suckling Signup and view all the answers

Which muscle group is primarily associated with movements of the eye, brows, and scalp?

Muscles of facial expression Signup and view all the answers

What is the role of the epicranium?

To move the scalp Signup and view all the answers

What type of movements are the axial muscles primarily involved in?

Vertebral column extension Signup and view all the answers

What is a key function of the buccinator muscle during chewing?

Holding food between teeth Signup and view all the answers

Which of the following statements correctly describes the function of facial muscles?

They control movements of the mouth and are crucial for communication. Signup and view all the answers

Which of the following is true about the groups of axial muscles?

They can be grouped based on location and function. Signup and view all the answers

What does the term 'rectus' imply in muscle names such as rectus femoris?

It signifies that the muscle has straight fascicles. Signup and view all the answers

Which muscle name includes a reference to its origin and insertion?

Flexor carpi radialis longus Signup and view all the answers

Which of the following is true about the naming of the biceps brachii?

It indicates the number of tendons of origin. Signup and view all the answers

What characteristic is commonly included in the names of muscles?

Shape of the muscle Signup and view all the answers

What does 'genioglossus' indicate about this muscle?

It originates from the chin and inserts in the tongue. Signup and view all the answers

Which muscle is primarily involved in the abduction of the arm?

Deltoid Signup and view all the answers

Which muscle group is considered part of the appendicular muscles?

Gluteus maximus Signup and view all the answers

Which muscle is responsible for the flexion of the forearm?

Brachioradialis Signup and view all the answers

Which of the following muscles aids in lateral rotation of the arm?

Infraspinatus Signup and view all the answers

Which muscle is best known for its role in extending the knee?

Quadriceps femoris Signup and view all the answers

Which muscle is primarily responsible for knee flexion?

Gastrocnemius Signup and view all the answers

Which of the following muscles is involved in medial rotation of the arm?

Subscapularis Signup and view all the answers

Which muscle helps in the stabilization of the shoulder joint?

Infraspinatus Signup and view all the answers

What characterizes a unipennate muscle?

Fascicles arranged on the same side of a single tendon Signup and view all the answers

Which of the following muscles is an example of a bipennate muscle?

Rectus femoris Signup and view all the answers

How do pennate muscles generate more tension compared to parallel muscles?

They have more myofibrils for a given size Signup and view all the answers

What is the function of circular muscles in the body?

To surround openings and control their diameter Signup and view all the answers

Which statement best describes a multipennate muscle?

Fascicles arranged in multiple directions around a tendon Signup and view all the answers

What type of muscle arrangement typically has the highest potential for force production?

Pennate muscles Signup and view all the answers

Which is NOT a characteristic of circular muscles?

They perform linear muscle contractions Signup and view all the answers

What structural feature distinguishes bipennate muscles from other types?

Fascicles arranged symmetrically on both sides of a tendon Signup and view all the answers

Which muscle type is characterized by fascicles concentrated on one side of a tendon?

Unipennate muscle Signup and view all the answers

What term refers to muscles located in the arm region?

Brachial Signup and view all the answers

Which of the following terms indicates a muscle that is located towards the back of the body?

Posterior Signup and view all the answers

Which muscle term indicates a muscle that has three heads?

Triceps Signup and view all the answers

Which term describes a muscle that is located beneath another structure?

Profundus Signup and view all the answers

What does the term 'orbicularis' indicate about a muscle's shape?

Round Signup and view all the answers

Which of the following muscles is specifically named for its location over the temporal bone of the skull?

Temporal Signup and view all the answers

Which term signifies the action of moving a limb away from the midline of the body?

Abductor Signup and view all the answers

Which muscle type is indicated by the term 'latissimus'?

Largest Signup and view all the answers

What descriptor is used for a muscle that runs straight along the body?

Rectus Signup and view all the answers

Which term refers to muscles that flex the limb toward the body?

Adductor Signup and view all the answers

What happens to speed and distance traveled in a third-class lever compared to a second-class lever?

Speed and distance are increased at the expense of effective force. Signup and view all the answers

Which fascicle arrangement is likely found in a muscle that guards the anal opening?

Circular arrangement Signup and view all the answers

What is a characteristic of second-class levers in muscle function?

They can lift heavier weights with shorter muscle contractions. Signup and view all the answers

Why are skeletal muscles not effective in isolation?

Their effectiveness depends on the nature and site of their connections. Signup and view all the answers

What is the primary trade-off when using a second-class lever?

Greater effective force for less speed. Signup and view all the answers

How do levers affect muscle efficiency?

They reduce the overall amount of force required. Signup and view all the answers

In which type of lever arrangement is the load positioned between the applied force and the fulcrum?

Second-class lever Signup and view all the answers

What defines the arrangement of forces in a third-class lever?

Force is applied between the load and the fulcrum. Signup and view all the answers

What is a common characteristic of third-class levers in the human body?

They utilize a greater distance for action despite less force. Signup and view all the answers

Which statement best describes the role of muscle connections to bones?

They dictate the force, speed, and range of movement produced by muscles. Signup and view all the answers

What is a benefit of understanding the arrangement of fascicles in muscles?

It helps in predicting muscle actions. Signup and view all the answers

Which type of muscles is primarily associated with the axial skeleton?

Rectus abdominis Signup and view all the answers

How do the appendicular muscles differ functionally from axial muscles?

They facilitate limb movements. Signup and view all the answers

What can muscle names reveal about their characteristics?

Their location, function, or appearance. Signup and view all the answers

What is the significance of the origin and insertion of a muscle?

It provides insight into muscle interaction during movements. Signup and view all the answers

What role does exercise play in relation to the muscular system?

It enhances muscle interaction with other body systems. Signup and view all the answers

Which class of lever is most commonly found in the human body?

Third class levers. Signup and view all the answers

What is the difference between the upper and lower limb muscles?

Lower limb muscles support weight and balance compared to upper limb muscles. Signup and view all the answers

What is the primary action of the levator anguli oris muscle?

Elevates the corner of the mouth Signup and view all the answers

Where does the levator anguli oris originate?

Maxilla below the infra-orbital foramen Signup and view all the answers

Which nerve innervates the levator anguli oris?

Facial nerve (VII) Signup and view all the answers

In addition to elevating the corner of the mouth, what is another function of the levator anguli oris?

None of the above Signup and view all the answers

Which other muscle has a function that contrasts with that of the levator anguli oris?

Depressor anguli oris Signup and view all the answers

Which muscle is primarily responsible for shoulder abduction?

Deltoid Signup and view all the answers

Which muscle helps in flexing the elbow?

Brachialis Signup and view all the answers

What is the primary function of the rectus abdominis?

Spinal flexion Signup and view all the answers

Which of the following muscles is involved in the movement of the thigh?

Iliopsoas Signup and view all the answers

Which muscle acts primarily to extend the knee?

Vastus lateralis Signup and view all the answers

What is the function of the sternocleidomastoid muscle?

Lateral flexion of the neck Signup and view all the answers

Which of the following muscles is NOT part of the rotator cuff?

Teres major Signup and view all the answers

Which muscle is responsible for plantar flexion of the foot?

Gastrocnemius Signup and view all the answers

Which of the following muscles contributes to the movement of the arm toward the body?

Latissimus dorsi Signup and view all the answers

Which muscle is primarily responsible for the flexion of the wrist?

Palmaris longus Signup and view all the answers

Which muscle is responsible for the rotation of the head and neck?

Sternocleidomastoid Signup and view all the answers

What is the primary function of the latissimus dorsi muscle?

Extension and adduction of the arm Signup and view all the answers

Which muscle assists in the flexion of the forearm at the elbow?

Brachioradialis Signup and view all the answers

Which of the following muscles belongs to the appendicular group?

Gluteus maximus Signup and view all the answers

What is the main function of the gastrocnemius muscle?

Plantarflexion of the foot Signup and view all the answers

Which muscle is located on the posterior aspect of the upper limb?

Triceps brachii (long head) Signup and view all the answers

Which muscle is primarily responsible for adduction of the thigh?

Gracilis Signup and view all the answers

Which muscle primarily extends the leg at the knee?

Quadriceps femoris Signup and view all the answers

What is the function of the teres minor muscle?

Lateral rotation of the shoulder Signup and view all the answers

Which muscle contributes to the stabilization of the shoulder joint?

Infraspinatus Signup and view all the answers

What action does the subscapularis muscle perform when it contracts?

Medial rotation at the shoulder Signup and view all the answers

Where does the teres minor muscle cross in relation to the shoulder joint?

Posterior side of the shoulder joint Signup and view all the answers

Which muscle is primarily responsible for lateral rotation of the shoulder?

Teres minor Signup and view all the answers

What is the naming basis for identifying muscles?

Region of the body, position, and action Signup and view all the answers

How many muscles are typically found in the human body?

700 Signup and view all the answers

Which action does the subscapularis muscle NOT perform?

Lateral rotation of the shoulder Signup and view all the answers

What aspect of the teres minor's action contributes to shoulder movement?

Lateral rotation Signup and view all the answers

What factor does NOT influence the naming of a muscle?

Emotional significance of the muscle Signup and view all the answers

Which muscle is responsible for producing medial rotation at the shoulder joint?

Subscapularis Signup and view all the answers

Which of the following statements is true regarding the teres minor?

It crosses the shoulder joint posteriorly. Signup and view all the answers

What term is used to describe a muscle that is found on the outside of the structure?

Extrinsic Signup and view all the answers

Which muscle name component indicates the number of heads it has?

Biceps Signup and view all the answers

What does the term 'rectus' signify in muscle naming?

Straight Signup and view all the answers

Which term indicates a muscle that is positioned toward the back of the body?

Posterior Signup and view all the answers

What does the term 'pectoralis' in muscle terminology reference?

Chest Signup and view all the answers

Which type of lever arrangement increases muscle efficiency by allowing a small force to move a larger weight?

Second-class lever Signup and view all the answers

What is the effect of a second-class lever arrangement on speed and distance of movement?

Decreases speed and distance Signup and view all the answers

In a third-class lever, where is the applied force positioned in relation to the load and the fulcrum?

Between load and fulcrum Signup and view all the answers

Which arrangement of muscle fibers provides a high range of motion at the expense of force?

Parallel arrangement Signup and view all the answers

What characterizes the motion produced by skeletal muscles attached to bones?

Their effectiveness is determined by the nature and site of their connections Signup and view all the answers

What is a key consequence of using a third-class lever system in the body?

Wider range of motion and increased speed Signup and view all the answers

In the context of muscle action, what happens when a force moves the handle in a lever system?

The load moves more slowly and covers a shorter distance Signup and view all the answers

What type of lever would likely be used by a muscle guarding the anal opening?

Second-class lever Signup and view all the answers

What defines an agonist muscle in relation to movement?

A muscle that is primarily responsible for a specific movement. Signup and view all the answers

Which of the following muscles is described as an antagonist of the biceps brachii?

Triceps brachii Signup and view all the answers

What is the primary action produced by the contraction of the subscapularis muscle?

Medial rotation of the shoulder Signup and view all the answers

What is typically the point of origin for most muscles?

A bone. Signup and view all the answers

What term describes a muscle that produces flexion at the elbow?

Agonist Signup and view all the answers

When the teres minor muscle contracts, what action does it primarily perform?

Lateral rotation Signup and view all the answers

How does the presence of multiple origins affect muscle structure?

It enables more complex movements. Signup and view all the answers

Where does the teres minor muscle cross in relation to the shoulder joint?

Posterior side Signup and view all the answers

What role do antagonists play in muscle movement?

They oppose the action of the agonist. Signup and view all the answers

Which muscle is specifically identified as a medial rotator of the shoulder?

Subscapularis Signup and view all the answers

What defines a muscle's insertion point?

The point where the muscle attaches to the more movable bone. Signup and view all the answers

What characteristic is notably used in naming skeletal muscles?

Location, appearance, or function Signup and view all the answers

How many muscles are typically found in the human body?

Approximately 700 Signup and view all the answers

In muscle terminology, what does it mean if a muscle is described as having multiple origins?

It has only one insertion but several attachment points. Signup and view all the answers

What is the primary function of the biceps brachii?

To flex the elbow. Signup and view all the answers

What region does the teres minor muscle primarily influence?

Shoulder region Signup and view all the answers

Which muscle crosses on the anterior side of the shoulder joint?

Subscapularis Signup and view all the answers

What is the relationship between agonists and antagonists during a muscle contraction?

One contracts while the other relaxes. Signup and view all the answers

Which action does not occur when the teres minor contracts?

Medial rotation of the shoulder Signup and view all the answers

Which organizational feature is not commonly used to describe skeletal muscles?

Color of muscle fibers Signup and view all the answers

What is the arrangement of fascicles in a convergent muscle?

Fascicles converge on a common attachment site. Signup and view all the answers

How do convergent muscles differ from parallel muscles in terms of force application?

Parallel muscles have greater force application at the attachment site. Signup and view all the answers

What is one advantage of convergent muscle arrangement?

They allow stimulation of different portions for varying activities. Signup and view all the answers

In a convergent muscle, how are muscle fibers arranged?

In a fan-like shape spreading from a single point. Signup and view all the answers

What is a potential disadvantage of convergent muscles compared to parallel muscles?

They exert less overall force than parallel muscles of the same size. Signup and view all the answers

Which of the following is an example of a convergent muscle?

Pectoralis major Signup and view all the answers

What characteristic helps distinguish convergent muscles from other muscle types?

Fascicles spread out from one area to converge. Signup and view all the answers

Why might a convergent muscle be preferable for certain activities?

It allows for efficient fine motor control. Signup and view all the answers

What type of connective tissue is often involved in the attachment of a convergent muscle?

Aponeurosis Signup and view all the answers

What defines the overall shape and function of convergent muscles?

Their fascicles have a broader origin converging toward a single point. Signup and view all the answers

What does the name 'rectus femoris' indicate about the muscle?

It has a straight fiber arrangement along its length. Signup and view all the answers

How does the origin and insertion naming convention work for muscles?

The first part usually indicates the origin, while the second part indicates the insertion. Signup and view all the answers

What distinctive feature is associated with the biceps brachii name?

It indicates the number of tendons of origin. Signup and view all the answers

What does the term 'sartor' relate to in muscular terminology?

It means tailor in Latin. Signup and view all the answers

What can be inferred from the name 'flexor carpi radialis longus'?

It refers to a muscle that flexes the wrist and is long in length. Signup and view all the answers

What is typically the origin point for most muscles?

A bone Signup and view all the answers

Which of the following describes the function of an antagonist muscle?

It opposes the action of the agonist muscle. Signup and view all the answers

What role does the biceps brachii play during elbow flexion?

It functions as an agonist. Signup and view all the answers

What defines a muscle with multiple origins and a single insertion?

It has complex actions. Signup and view all the answers

What defines a first-class lever in the human body?

The fulcrum is between the applied force and the load. Signup and view all the answers

Which of the following pairs represents agonist and antagonist muscles?

Triceps brachii and biceps brachii Signup and view all the answers

What occurs during a mechanical advantage situation?

The applied force is farther from the fulcrum than the load. Signup and view all the answers

What structure is considered an origin for some muscles?

The aponeurosis Signup and view all the answers

Which of the following is typically true about the origin of a muscle?

It is usually less movable than the insertion. Signup and view all the answers

Which muscle produces extension at the elbow joint?

Triceps brachii Signup and view all the answers

Which class of lever has the fulcrum located at one end with the applied force on the opposite side?

Second-class lever Signup and view all the answers

In biomechanical terms, what is referred to as a mechanical disadvantage?

The applied force being closer to the fulcrum than the load. Signup and view all the answers

What do intermuscular septa represent?

A connective tissue sheath Signup and view all the answers

How do agonists and antagonists function in muscle movements?

They allow for movement and counteraction. Signup and view all the answers

Which is a characteristic of the insertion of a muscle?

It typically moves toward the origin during contraction. Signup and view all the answers

Which of the following statements about lever classification is accurate?

Levers are classified based on the position of applied force, fulcrum, and load. Signup and view all the answers

What is the relationship between the origin and insertion of a muscle?

The origin is generally proximal to the insertion. Signup and view all the answers

Which term is used to indicate a muscle located in the abdomen?

Abdominal Signup and view all the answers

What does the term 'pectoralis' refer to in muscle terminology?

A muscle of the chest Signup and view all the answers

Which of the following terms indicates a muscle's position as located towards the front of the body?

Anterior Signup and view all the answers

Which of the following terms indicates a muscle that originates with two heads?

Biceps Signup and view all the answers

Which term is used to describe a muscle that is on the side of the body?

Lateral Signup and view all the answers

What does 'oblique' refer to regarding muscle arrangement?

Slanting position Signup and view all the answers

Which of the following describes a muscle that has a circular shape?

Orbicularis Signup and view all the answers

Which term indicates a muscle that is deeper in the body relative to other structures?

Profundus Signup and view all the answers

Which of the following actions is indicated by the term 'extensor'?

Straightening Signup and view all the answers

Which muscle name component refers to the number of heads it possesses?

Biceps Signup and view all the answers

What is the key characteristic of a unipennate muscle?

It has all fibers oriented in one direction from a tendon. Signup and view all the answers

Which type of muscle is characterized by a converging pattern from multiple points to a single tendon?

Convergent muscle Signup and view all the answers

What is the primary function of circular muscles?

To regulate the passage of substances through openings. Signup and view all the answers

What distinguishes a multipennate muscle from other types of muscles?

It has multiple central tendons with fibers branching out. Signup and view all the answers

Which of the following is an example of a parallel muscle?

Biceps brachii Signup and view all the answers

In what way do tendinous bands affect parallel muscles?

They provide structural support and attachment points. Signup and view all the answers

What is the characteristic feature of a bipennate muscle?

It has fibers that attach at multiple angles to a single tendon. Signup and view all the answers

Which type of muscle is best described as having a long length with limited cross-sectional area?

Parallel muscle Signup and view all the answers

Which of the following is NOT a characteristic of pennate muscles?

Ability to contract over a large range of motion. Signup and view all the answers

What is the primary advantage of the pennate arrangement of muscle fibers?

Higher force generation. Signup and view all the answers

What term is used for muscles located entirely within an organ?

Internus Signup and view all the answers

Which muscle is specifically known for compressing the cheeks?

Buccinator Signup and view all the answers

What is the primary function of the extensor carpi radialis longus?

Extension at the carpus (wrist) Signup and view all the answers

Which term describes the orientation of muscles that run at a slanting angle to the longitudinal axis of the body?

Oblique Signup and view all the answers

What does the term 'rectus' signify in muscle nomenclature?

Straight Signup and view all the answers

What is a lever in the context of the muscular and skeletal systems?

A rigid structure that moves on a fixed point Signup and view all the answers

What is the role of muscles in the lever system of the body?

To provide the applied force Signup and view all the answers

Which of the following changes can levers produce in the context of movement?

Change the direction of an applied force Signup and view all the answers

What is the significance of attaching muscles to levers in the body?

It modifies the force and speed of movement Signup and view all the answers

What is the fixed point on which a lever moves called?

Fulcrum Signup and view all the answers

How do the origins and insertions of muscles influence their actions?

They influence the range and direction of movement Signup and view all the answers

What is meant by the load in a lever-system context?

The weight that must be overcome Signup and view all the answers

In which class of lever would the joint between the occipital bone of the skull and the first cervical vertebra (atlas) be classified?

First class lever Signup and view all the answers

What did the nurse practitioner encourage Rick to try for improvement in his condition?

Yoga Signup and view all the answers

What sensation did Rick initially feel during his first yoga class?

Locked up and stiff Signup and view all the answers

Which yoga pose was Rick preparing to attempt next?

Downward-Facing Dog Signup and view all the answers

What was Rick’s improvement after practicing yoga for three months?

Stronger leg muscles Signup and view all the answers

How many months after the initial class did the nurse practitioner suggest to return?

Three months Signup and view all the answers

What was Rick's attitude toward practicing yoga as suggested by the nurse practitioner?

Reluctant but willing Signup and view all the answers

What specific yoga pose did Rick feel he might try after practicing other poses?

Downward-Facing Dog Signup and view all the answers

What role did the nurse practitioner play in Rick's yoga journey?

His health guide Signup and view all the answers

What was the reason for Rick to start attending yoga classes?

To manage arthritis pain Signup and view all the answers

What kind of feedback did Rick receive about his yoga practice from the instructor?

He was making excellent progress Signup and view all the answers

What is a characteristic of a first-class lever in the human body?

The fulcrum lies between the load and the applied force. Signup and view all the answers

Where is the origin of a skeletal muscle typically located?

At an immovable attachment to a bone. Signup and view all the answers

What happens during a contraction of a skeletal muscle?

One end of the muscle moves while the other remains fixed. Signup and view all the answers

What defines mechanical advantage in the context of levers?

When the applied force is farther from the fulcrum than the load. Signup and view all the answers

What is indicated by the positions L-F-AF in a lever?

The order of the load, fulcrum, and applied force. Signup and view all the answers

Which class of lever has the least number of examples in the human body?

First-class lever Signup and view all the answers

What is generally true about the insertion of a muscle?

It is usually located more distally than the origin. Signup and view all the answers

What does the term 'mechanical disadvantage' refer to?

The applied force is closer to the load than the fulcrum. Signup and view all the answers

How are levers in the body categorized?

By the relative positions of force, fulcrum, and load. Signup and view all the answers

Which best describes the function of a lever in the human body?

To amplify the effect of applied forces in movement. Signup and view all the answers

In a first-class lever, where is the fulcrum located in relation to the applied force and the load?

The fulcrum is between the applied force and the load Signup and view all the answers

Which of the following is an example of a first-class lever?

A pry bar Signup and view all the answers

In a second-class lever, which component is positioned between the other two?

Load Signup and view all the answers

What role does the fulcrum play in a lever system?

It is the pivot point for rotation Signup and view all the answers

Which statement accurately describes the configuration of a second-class lever?

Load is positioned at one end with applied force in the middle Signup and view all the answers

How does the position of the fulcrum influence the mechanical advantage of a lever?

Positioning the fulcrum further from the load increases mechanical advantage Signup and view all the answers

Which of the following could NOT be classified as a lever in human anatomy?

Spine in a sitting position Signup and view all the answers

What is primarily used in the operation of a first-class lever?

Balance between load and force Signup and view all the answers

Which description would best illustrate the function of a pry bar?

It multiplies force to lift a load by increasing distance from the fulcrum Signup and view all the answers

What key factor distinguishes first-class levers from second-class levers?

The specific arrangement of the load, fulcrum, and applied force Signup and view all the answers

Study Notes

Trivia About Muscles

There are about 60 muscles in the face.
It takes 20 muscles to smile and over 40 to frown.
The Stapedius is the smallest muscle in the body.
The Gluteus Maximus is the biggest muscle in the body.
The longest muscle in the body is the Sartorius.

Types of Muscle Tissue

Skeletal muscle: attached to the skeleton, filamentous shape, voluntary control, striated, multinucleated, responsible for movement of the bone
Smooth muscle: found in the walls of hollow organs, spindle shaped, involuntary control, not striated, mononucleated, responsible for movement of internal organs
Cardiac muscle: located in the heart, branching filamentous shape, involuntary control, striated, mononucleated, responsible for beating of the heart

Skeletal Muscle Tissue

Excitability: ability to respond to a stimulus.
Contractility: ability to shorten and generate a pulling force.
Extensibility: ability to be stretched.

Movement of Muscles

Origin: the attachment of a muscle to the bone that remains stationary.
Insertion: the attachment of the muscle to the bone that moves.
Belly: the fleshy part of the muscle between the origin and the insertion.

Movement of Skeletal Muscle

Muscles work in pairs.
Contraction: shortening.
Extension: Lengthening.

Major Skeletal Muscles: The Head

Sternocleidomastoid: pulls the head to one side, pulls the head to the chest.
Splenius Capitis: rotates the head, allows the head to bend to the side.
Frontalis: raises the eyebrows.
Orbicularis Oris: allows the lips to pucker.
Orbicularis Oculi: allows the eyes to close.
Platysma: pulls the corners of the mouth down.
Zygomaticus: pulls the corners of the mouth up.
Masseter and Temporalis: close the jaw.

Major Skeletal Muscles: Upper Arm

Pectoralis Major: pulls the arm across the chest, rotates and adducts the arms.
Latissimus Dorsi: extends and adducts the arm, rotates the arm inwards.

Major Skeletal Muscles: Forearm

Biceps Brachii: flexes the arm at the elbow, rotates the hand laterally.
Brachialis: flexes the arm at the elbow.
Brachioradialis: flexes the forearm at the elbow.
Triceps Brachii: extends the arm at the elbow.
Supinator: rotates the forearm laterally (supination).
Pronator Teres: rotates the forearm medially (pronation).

Major Skeletal Muscles: Wrist, Hand, and Fingers

Flexor Carpi Radialis and Flexor Carpi Ulnaris: flex and abduct the wrist.
Extensor Carpi Radialis Longus and Brevis: extend the wrist and abduct the hand.
Palmaris Longus: flexes the wrist.
Flexor Digitorum Profundus: flexes the distal joints of the fingers, but not the thumb.
Extensor Carpi Ulnaris: extends the wrist.
Extensor Digitorum: extends the fingers, but not the thumb.

Major Skeletal Muscles: Respiratory

Diaphragm: separates the thoracic cavity from the abdominal cavity, contraction causes inspiration.
External and Internal Intercostals: expand and lower the ribs during breathing.

Major Skeletal Muscles: Abdominal

External and Internal Obliques: compress the abdominal wall
Transverse Abdominis: compresses the abdominal wall.
Rectus Abdominis: flexes the vertebral column, compresses the abdominal wall.

Major Skeletal Muscles: Pectoral Girdle

Trapezius: raises the arms, pulls the shoulders downwards.
Pectoralis Minor: pulls the scapula downwards.

Major Skeletal Muscles: Leg

Psoas Major and Iliacus: flexes the thigh.
Gluteus Maximus: extends the thigh.
Gluteus Medius and Minimus: abduct the thighs, rotates them medially.
Adductor Longus and Magnus: adduct the thighs, rotate them laterally.
Biceps Femoris, Semitendinosus, and Semimembranosus: known as the hamstring group, flex the leg at the knee.

Major Skeletal Muscles: Leg

Rectus Femoris, Vastus Lateralis, Vastus Medialis, and Vastus Intermedius: extend the leg at the knee.
Sartorius: flexes the leg at the knee and thigh, abducts the thigh, rotates the thigh laterally but rotates the lower leg medially.

Major Skeletal Muscles: Ankle, Foot, and Toes

Tibialis Anterior: inverts the foot, points the foot up (dorsiflexion).
Soleus: flexes the foot.
Flexor Digitorum Longus: flexes the foot and toes.
Extensor Digitorum Longus: extends the toes and point the foot up.
Gastrocnemius: flexes the foot and flexes the leg at the knee.

Muscle Naming Conventions

Size: Maximus (largest), Minimus (smallest), Longus (longest), Brevis (short), Major (large).
Direction of fibers: Rectus (straight), Transverse (perpendicular to long axis), Oblique (diagonal).
Number of Origins: Biceps (2), Triceps (3), Quadriceps (4).
Origin and Insertion: Sternocleidomastoid (originates from sternum and clavicle, inserts on mastoid process of temporal bone), Flexor Carpi Radialis (flexes wrist), Abductor Pollicis Brevis (flexes thumb), Abductor Magnus (abducts thigh), Extensor Digitorum (extends fingers).

Arrangement of Fascicles

Parallel: strap-like (example: Sartorius).
Fusiform: spindle-shaped (example: Biceps Femoris).
Pennate: feather shaped.
Unipennate: example: Extensor Digitorum Longus.
Bipennate: example: Rectus Femoris.
Multipennate: example: Deltoid.
Convergent: example: Pectoralis Major.
Circular: sphincters (example: Orbicularis Oris).

Organization Level of Muscles

Skeletal muscles are made of muscle fibers, nerves, blood vessels, and connective tissues.
Each muscle is served by one nerve, one artery, and one or more veins.

Attachments of Muscles

Tendons: narrow bands of connective tissue that connect muscles to bone.
Ligaments: bands of connective tissue that join bone to bone.
Aponeuroses: bands of connective tissue that attach flat muscle to another muscle or to several bones.

Structure of Skeletal Muscle

Composed of striated muscle cells and connective tissue.

Muscle Contraction

Terminal Cisternae: several Ca+2 binding proteins.
Calsequestrin: a Ca+2 binding protein.
Histidine-rich calcium-binding protein (HRC): a Ca+2 binding protein.
Sarcalumenin: a Ca+2 binding protein.
Triadin: anchors calsequestrin near RYR.
SERCA (Sarcoplasmic or ER calcium ATPase): pumps Ca+2 into SR.
DHPR and RYR Interaction: In heart muscle, DHPR opens, causing Ca+2 influx, then Ca+2 influx causes RYR to open. In skeletal muscle, DHPR is mechanically attached to RYR. When DHPR changes shape, RYR opens.
Calcium Channel Blocker Drugs: work on heart muscles, not on skeletal muscles.

Sliding Filament Theory

The myosin head binds to actin, forming a cross bridge, pulling the actin towards the center of the sarcomere, shortening the sarcomere.
The myosin head detaches from the actin, binds to another actin, and pulls again.

Muscle Relaxation

SERCA pumps 2 Ca+2 back into the terminal cisternae per ATP hydrolyzed.
Lowered Ca+2 allows tropomyosin to block actin binding sites again, decreasing the actin-myosin interaction.

The Muscle Twitch

Myogram: a recording of electrical activity during muscle contraction.
Latent Period: Cross bridges begin to cycle, but muscle tension is not yet measurable.

Types of Muscle Contraction

Isotonic Contraction: length changes while contracting.
Concentric: shortening (muscle contracts).
Eccentric: lengthening (muscle is being stretched).
Isometric Contraction: muscle contracts but does not change in length (load is too heavy or immovable).

Types of Fatigue

Peripheral Fatigue: occurs in muscle fibers.
Causes: accumulation of metabolic waste (lactate, hydrogen ions).
Symptoms: muscle soreness, weakness, cramping.
Recovery: rest, hydration, nutrition.
Central Fatigue: occurs in the central nervous system (brain and spinal cord).
Causes: decreased ability of the central nervous system to activate motor neurons.
Symptoms: feeling tired, difficulty concentrating, reduced motivation.
Recovery: rest, sleep, stress management.

Production of Energy for Muscle

ATP (adenosine triphosphate): A type of chemical energy needed for sustained or repeated muscle contractions.
Creatine phosphate: rapid production of energy.
Aerobic respiration: uses the body’s store of glucose.
Lactic Acid Production: a byproduct of anaerobic respiration.

Production of Energy: Oxygen Debt

Occurs when skeletal muscles are used strenuously for several minutes, and cells are low in oxygen.
Pyruvic Acid: converts to lactic acid which builds up.
Lactic Acid: taken to the liver for conversion to glucose, requiring more energy.

Production of Energy: Muscle Fatigue

Muscle has lost its ability to contract.
Causes: accumulation of lactic acid, interruption of blood supply to the muscle, a motor neuron loses its ability to release acetylcholine onto muscle fiber.

Muscle Remodeling

Hypertrophy: increase in mass.
Atrophy: decrease in mass.

Questions

Temporal summation leading to tetany might be occurring when standing at attention or carrying a very heavy load (E).
Olympic medalist Hidilyn Diaz might experience less central fatigue compared to most people because she has trained extensively and her body is accustomed to strenuous exercise (C).

Elasticity

Muscles have the ability to recoil to their original resting length after being stretched.

Naming Skeletal Muscles

Location: Muscles are named based on their proximity to bones and body parts.
Shape: The shape of the muscle can also be used for naming (e.g., deltoid - triangle shaped).
Size: Size descriptors like "maximus" (largest), "minimus" (smallest), "longus" (longest), and "brevis" (short) are used.
Direction: Muscle fiber orientation influences names - "rectus" (straight), "transverse", and "oblique".
Number of Origins: The number of points of attachment, like biceps (2), triceps (3), and quadriceps (4).
Attachments: Names can reflect the origin and insertion points (e.g., sternocleidomastoid - originates from sternum and clavicle, inserts on mastoid process).
Action: Describes the function, like flexor, extensor, abductor, adductor, etc.

Classification of Muscles by Action

Flexor: Bends a body part closer to the joint.
Extensor: Straightens a body part away from the joint.
Abductor: Moves a body part away from the midline of the body.
Adductor: Moves a body part toward the midline of the body.
Dilator: Opens spaces or widens openings.
Constrictor: Closes or compresses openings.
Levator: Raises a body part.
Depressor: Lowers a body part.

Muscle Named by Location

Tibialis Anterior: Located in front of the tibia.
Frontalis: Found on top of the frontal bone.
Temporalis: Situated on top of the temporal bone.
Epicranius: Located around the cranium.

Movement of Muscles

Origin: The fixed attachment of the muscle to the bone that remains stationary.
Insertion: The attachment of the muscle to the bone that moves.
Belly: The fleshy part of the muscle between the origin and insertion points.

Movement of Skeletal Muscle

Skeletal muscles contract upon receiving signals from the brain.
Muscles operate in pairs to produce coordinated movements.
Two primary movements of skeletal muscles:
- Contraction: Shortening of muscle fibers.
- Extension: Lengthening of muscle fibers

Major Skeletal Muscles: The Head

Sternocleidomastoid: Pulls the head to one side, pulls the head to the chest.
Splenius Capitis: Rotates the head, bends it to the side.
Orbicularis Oris: Allows the lips to pucker.
Frontalis: Raises the eyebrows.
Orbicularis Oculi: Allows the eyes to close.
Platysma: Pulls down the corners of the mouth.
Zygomaticus: Pulls the corners of the mouth upwards.
Masseter and Temporalis: Close the jaw.

Major Skeletal Muscles: Upper Arm

Pectoralis Major: Pulls the arm across the chest, rotates and adducts the arm.
Latissimus Dorsi: Extends and adducts the arm, rotates it inwards.

Major Skeletal Muscles: Forearm

Biceps Brachii: Flexes the arm at the elbow, rotates the hand laterally.
Brachialis: Flexes the arm at the elbow.
Brachioradialis: Flexes the forearm at the elbow.
Triceps Brachii: Extends the arm at the elbow.
Supinator: Rotates the forearm laterally (supination).
Pronator Teres: Rotates the forearm medially (pronation).

Major Skeletal Muscles: Wrist, Hand, and Fingers

Flexor Carpi Radialis and Flexor Carpi Ulnaris: Flex and abduct the wrist.
Extensor Carpi Radialis Longus and Brevis: Extend the wrist and abduct the hand.
Palmaris Longus: Flexes the wrist.
Flexor Digitorum Profundus: Flexes the distal joints of the fingers, but not the thumb.
Extensor Carpi Ulnaris: Extends the wrist.
Extensor Digitorum: Extends the fingers, but not the thumb.

Major Skeletal Muscles: Respiratory

Diaphragm: Separates the thoracic cavity from the abdominal cavity, contraction causes inspiration.
External and Internal Intercostals: Expand and lower the ribs during breathing.

Major Skeletal Muscles: Abdominal

External and Internal Obliques: Compress the abdominal wall.
Transverse Abdominis: Also compresses the abdominal wall.
Rectus Abdominis: Flexes the vertebral column, compresses the abdominal wall.

Major Skeletal Muscles: Pectoral Girdle

Trapezius: Raises the arms, pulls the shoulders downward.
Pectoralis Minor: Pulls the scapula downward.

Major Skeletal Muscles: Leg

Psoas Major and Iliacus: Flexes the thigh.
Gluteus Maximus: Extends the thigh.
Gluteus Medius and Minimus: Abduct the thighs, rotate them medially.
Adductor Longus and Magnus: Adduct the thighs, rotate them laterally.
Biceps Femoris, Semitendinosus, and Semimembranosus: Known as the hamstring group, flex the leg at the knee.
Rectus Femoris, Vastus Lateralis, Vastus Medialis, and Vastus Intermedius: Extend the leg at the knee.
Sartorius: Flexes the leg at the knee and thigh, abducts the thigh, rotates the thigh laterally, and rotates the lower leg medially.

Major Skeletal Muscles: Ankle, Foot, and Toes

Tibialis Anterior: Inverts the foot and points it upwards (dorsiflexion).
Soleus: Flexes the foot.
Extensor Digitorum Longus: Extends the toes and points the foot upwards.
Flexor Digitorum Longus: Flexes the foot and toes.
Gastrocnemius: Flexes the foot and flexes the leg at the knee.

Muscle Named By Size

Maximus: Largest.
Minimus: Smallest.
Longus: Longest.
Brevis: Shortest.
Major: Large.

Muscle Named By Direction of Fibers

Rectus: Straight, parallel to the long axis.
Transverse: Perpendicular to the long axis.
Oblique: Diagonal to the long axis.

Muscle Named For: Number of Origins, Origin and Insertion, Action

Biceps (2), Triceps (3), Quadriceps (4): Refer to the number origins.
Sternocleidomastoid: Originates from the sternum and clavicle, inserts on the mastoid process of the temporal bone.
Flexor Carpi Radialis, Extensor Carpi Radialis: Flexors and extensors of the wrist, respectively.
Abductor Pollicis Brevis, Adductor Pollicis: Abduct and adduct the thumb, respectively.
Abductor Magnus: Abducts the thigh.
Extensor Digitorum: Extends the fingers.

Arrangement of Fascicles

Parallel: Strap-like (e.g., Sartorius).
Fusiform: Spindle shaped (e.g., Biceps femoris).
Pennate: Feather shaped, classified as:
- Unipennate: (e.g., Extensor digitorum longus).
- Bipennate: (e.g., Rectus femoris).
- Multipennate: (e.g., Deltoid).
Convergent: (e.g., Pectoralis major).
Circular: Sphincters, encircle openings (e.g., Orbicularis oris).

Organization Levels of Muscles

Skeletal muscles are composed of muscle fibers, nerves, blood vessels, and connective tissues.
Each muscle is served by one nerve, one artery, and one or more veins.
Skeletal muscle fibers can only contract under nerve stimulation, unlike cardiac and smooth muscle.

Attachments of Muscles

Tendons: Narrow connective tissue bands that connect muscles to bone.
Ligaments: Connective tissue bands joining bones to bones.
Aponeuroses: Flat connective tissue bands attaching flat muscles to other muscles or bones.

Structure of Skeletal Muscle

Skeletal muscles are composed of striated muscle cells and connective tissue.

Neuromuscular Junction

The junction where a motor neuron communicates with a muscle fiber.
This is the site where nerve impulses are transmitted to muscle fibers, triggering contraction.

Muscle Contraction

Excitation-Contraction Coupling
1. Action potential arrives at the neuromuscular junction, reaching the muscle fiber.
2. Action potential travels along the sarcolemma, triggering release of calcium ions (Ca+2) from the sarcoplasmic reticulum (SR).
3. Ca+2 initiates the interaction of myosin and actin, leading to muscle contraction.
4. Ca+2 is pumped back into the SR, causing muscle relaxation.

Step 1: Neuromuscular Junction

Action potential reaches the end of the motor neuron, increasing calcium influx and releasing acetylcholine (Ach).
Ach binds to receptors on the muscle membrane, allowing sodium (Na+) influx which generates a local potential.
This activates voltage-gated sodium channels, triggering an action potential.
Acetylcholinesterase degrades Ach.

Step 2: Sarcolemma and SR

Action potential travels through T-tubules, activating dihydropyridine receptors (DHPR).
DHPR activates ryanodine receptors (RYR) in the terminal cisternae of the SR.
This triggers the release of Ca+2 into the myofibril.

Types of Skeletal Muscle Fibers

Different skeletal muscles contract at varying speeds due to different types of muscle fibers.

Tetanus

Fusion of muscle twitches that occurs with high-frequency stimulations, resulting in smooth, continuous movements.
Incomplete (Unfused) Tetanus: Individual contractions are observed, brief relaxation periods between contractions, peak tension increases but oscillates.
Complete (Fused) Tetanus: Individual contractions are indistinguishable, sustained, smooth, high force generated.

Motor Unit

The smallest functional unit of a muscle, consisting of a motor neuron and the muscle fibers it innervates.
The basic unit of movement.
Extrafusal fibers: Primary muscle fibers that contract, innervated by alpha motor neurons.
Intrafusal fibers: Sensory fibers embedded within the muscle, detect stretch, innervated by gamma motor neurons.

Fiber Length (Length-Tension Relation)

Tension generated during contraction is affected by muscle fiber length.
Isometric contraction: Muscle length remains constant while tension increases.
Isotonic contraction: Force is constant, but muscle length changes.

Factors Determining Muscle Tension

Fiber Diameter:
- Larger diameter fibers generate greater force and have higher thresholds.
- Smaller diameter fibers generate lower force and have lower thresholds.
Number of Active Fibers:
- Number of fibers per motor unit: Fewer fibers = finer movements, more fibers = gross movements.
- Number of active motor units: More activated units = stronger force produced.

Types of Muscle Contraction

Isometric Contraction: Muscle length remains constant, tension increases, no external work done.
Isotonic Contraction: Muscle length changes, tension is constant, external work is done.

Trivia about muscles

There are approximately 60 muscles in the human face.
Smiling requires 20 muscles, while frowning requires over 40.
The longest muscle in the body is the Sartorius.
The smallest muscle in the body is the Stapedius.
The largest muscle in the body is the Gluteus Maximus.

Types of Muscle Tissue

There are three types of muscle tissue: skeletal, smooth, and cardiac.
Skeletal muscle is attached to the skeleton and is responsible for movement.
Smooth muscle is found in the walls of hollow organs and is responsible for involuntary movement.
Cardiac muscle is found in the heart and is responsible for the beating of the heart.

Characteristics of Muscle Tissue

Muscle tissue is excitable, meaning it can respond to a stimulus.
Muscle tissue is contractile, meaning it can shorten and generate a pulling force.
Muscle tissue is extensible, meaning it can be stretched to its normal resting length and beyond.

Movement of Muscles

Origin: The point of attachment of a muscle to a bone that remains stationary during contraction.
Insertion: The point of attachment of a muscle to a bone that moves during contraction.
Belly: The fleshy portion of a muscle between the origin and insertion.
Muscles work in pairs to produce movement: Contraction (shortening) and Extension (lengthening).

Major Skeletal Muscles of the Head

Sternocleidomastoid: Pulls the head to one side, pulls the head toward the chest.
Splenius Capitis: Rotates the head and allows it to bend to the side.
Frontalis: Raises the eyebrows.
Orbicularis Oris: Allows the lips to pucker.
Orbicularis Oculi: Allows the eyes to close.
Platysma: Pulls the corners of the mouth down.
Zygomaticus: Pulls the corners of the mouth up.
Masseter and Temporalis: Muscles responsible for closing the jaw.

Major Skeletal Muscles of the Upper Arm

Pectoralis major: Pulls the arm across the chest, rotates and adducts the arms.
Latissimus Dorsi: Extends and adducts the arm, rotates the arm inwardly.

Major Skeletal Muscles of the Forearm

Biceps Brachii: Flexes the arm at the elbow, rotates the hand laterally.
Brachialis: Flexes the arm at the elbow.
Brachioradialis: Flexes the forearm at the elbow.
Triceps Brachii: Extends the arm at the elbow.
Supinator: Rotates the forearm laterally (supination).
Pronator Teres: Rotates the forearm medially (pronation).

Major Skeletal Muscles of the Wrist, Hand, and Fingers

Flexor Carpi Radialis and Flexor Carpi Ulnaris: Flex and abduct the wrist.
Palmaris Longus: Flexes the wrist.
Flexor Digitorum Profundus: Flexes the distal joints of the fingers (not the thumb).
Extensor Carpi Radialis Longus and Brevis: Extends the wrist and abducts the hand.
Extensor Carpi Ulnaris: Extends the wrist.
Extensor Digitorum: Extends the fingers (not the thumb).

Major Skeletal Muscles of Respiration

Diaphragm: Separates the thoracic cavity from the abdominal cavity. Contraction aids in inspiration (breathing in).
External and Internal Intercostals: Expand and lower the ribs during breathing.

Major Skeletal Muscles of the Abdomen

External and Internal Obliques: Compress the abdominal wall.
Transverse Abdominis: Compresses the abdominal wall.
Rectus Abdominis: Flexes the vertebral column, compresses the abdominal wall.

Major Skeletal Muscles of the Pectoral Girdle

Trapezius: Raises the arms, pulls the shoulders downward.
Pectoralis Minor: Pulls the scapula downward.

Major Skeletal Muscles of the Leg

Psoas Major and Iliacus: Flexes the thigh.
Gluteus Maximus: Extends the thigh.
Gluteus Medius and Minimus: Abducts the thighs, rotates them medially.
Adductor Longus and Magnus: Adducts the thighs, rotates them laterally.
Biceps Femoris, Semitendinosus, and Semimembranosus (Hamstring Group): Flexes the leg at the knee.
Rectus Femoris, Vastus Lateralis, Vastus Medialis, and Vastus Intermedius (Quadriceps): Extend the leg at the knee.
Sartorius: Flexes the leg at the knee and thigh, abducts the thigh, rotates thigh laterally, rotates lower leg medially.

Major Skeletal Muscles of the Ankle, Foot, and Toes

Tibialis Anterior: Inverts the foot and points the foot up (dorsiflexion).
Extensor Digitorum Longus: Extends the toes and points the foot up.
Soleus: Flexes the foot.
Flexor Digitorum Longus: Flexes the foot and toes.
Gastrocnemius: Flexes the foot and flexes the leg at the knee.

Muscle Naming Conventions

Size: Maximus (largest), Minimus (smallest), Longus (longest), Brevis (shortest), Major (large).
Direction of Fibers: Rectus (straight, parallel to the long axis), Transverse (perpendicular to the long axis), Oblique (diagonal to the long axis).
Number of Origins: Biceps (two), Triceps (three), Quadriceps (four).
Origin and Insertion: Sternocleidomastoid (originates from sternum and clavicle, inserts on mastoid process of temporal bone).
Action: Flexor Carpi Radialis (flexes the wrist), Abductor Pollicis Brevis (abducts the thumb), Abductor Magnus (abducts the thigh), Extensor Digitorum (extends the fingers).

Arrangement of Fascicles

Parallel: Strap-like (Sartorius).
Fusiform: Spindle-shaped (Biceps Femoris).
Pennate: Feather-shaped.
- Unipennate: Extensor Digitorum Longus.
- Bipennate: Rectus Femoris.
- Multipennate: Deltoid.
Convergent: Pectoralis Major.
Circular: Sphincters (Orbicularis Oris).

Organization Level of Muscles

Skeletal muscles are composed of muscle fibers, nerves, blood vessels, and connective tissues.
Each muscle is served by one nerve, one artery, and one or more veins.

Attachments of Muscles

Tendons: Narrow bands of connective tissue that attach muscles to bones.
Ligaments: Bands of connective tissue that join bone to bone.
Aponeuroses: Bands of connective tissue that attach flat muscles to other muscles or to several bones.

Structure of Skeletal Muscle

Composed of striated muscle cells and connective tissue.

Neuromuscular Junction

The site where a motor neuron communicates with a muscle fiber.

Muscle Contraction (Excitation-Contraction Coupling)

The process by which depolarization of a muscle fiber initiates contraction.
Steps:
- Action potential travels to the neuromuscular junction and reaches the muscle fiber.
- Action potential travels along the sarcolemma (muscle fiber membrane), causing the release of calcium ions (Ca+2) from the sarcoplasmic reticulum.
- Ca+2 initiates the interaction of myosin and actin, causing muscle contraction.
- Ca+2 is pumped back into the sarcoplasmic reticulum, causing muscle relaxation.

Muscle Contraction: Step 1 (Neuromuscular Junction)

Action potential reaches the end of the motor neuron, increasing calcium influx.
This triggers the release of acetylcholine (Ach).
Ach binds to Ach receptors on the muscle membrane, causing sodium (Na+) influx.
This generates a local potential which opens voltage-gated Na+ channels and initiates an action potential.
Ach is then degraded by acetylcholinesterase.

Muscle Contraction: Step 2 (Sarcolemma and SR)

The action potential travels through T-tubules and activates dihydropyridine receptors (DHPR).
Activated DHPRs activate ryanodine receptors (RYR) in the terminal cisternae, leading to the release of Ca+2 into the myofibril.

Factors Determining Muscle Tension

Fiber Length (Length-Tension Relation): The effect of muscle fiber length on the amount of tension it can develop.
- Tension is generated when a muscle contracts and decreases its length.
- Types of Contraction:
  - Isometric: Muscle length is held constant while tension is generated.
  - Isotonic: Force or tone is held constant, but there is a change in muscle length.
Fiber Diameter:
- Larger diameter = Greater force produced.
- Smaller diameter = Lower threshold.
Number of Active Fibers:
- Motor Unit: A motor neuron and all the muscle fibers it innervates.
  - Fewer fibers per motor unit = Finer movement.
  - More fibers per motor unit = Grosser movement.
- Number of Active Motor Units:
  - More motor units activated = Stronger force produced.

Types of Muscle Contraction

Isotonic:
- Muscle length changes during contraction.
- Concentric: Muscle shortens.
- Eccentric: Muscle lengthens (contributes most to cellular damage after exercise).
Isometric:
- Muscle contracts but does not change in length.
- Load is too heavy or immovable.

Types of Fatigue

Peripheral Fatigue:
- Location: Muscle fibers.
- Cause: Accumulation of metabolic waste (lactate, hydrogen ions).
- Symptoms: Muscle soreness, weakness, cramping.
- Recovery: Rest, hydration, nutrition.
Central Fatigue:
- Location: Central nervous system (brain and spinal cord).
- Cause: Decreased ability of the central nervous system to activate motor neurons.
- Symptoms: Feeling tired, difficulty concentrating, reduced motivation.
- Recovery: Rest, sleep, stress management.

Production of Energy for Muscle Contraction

ATP (adenosine triphosphate): A type of chemical energy needed for sustained or repeated muscle contractions.
Muscles have three ways to store or make ATP:
- Creatine Phosphate: Rapid production of energy.
- Aerobic Respiration: Uses the body’s store of glucose.
- Lactic Acid Production:

Production of Energy: Oxygen Debt

Occurs when skeletal muscles are used strenuously for several minutes and cells are low in oxygen.
Lactic acid builds up, leading to muscle fatigue.

Production of Energy: Muscle Fatigue

A condition in which a muscle has lost its ability to contract.
Causes:
- Accumulation of lactic acid.
- Interruption of blood supply to a muscle.
- A motor neuron loses its ability to release acetylcholine onto muscle fibers.

Muscle Remodeling

Muscles undergo continuous remodeling.
Hypertrophy: Increase in muscle mass.
Atrophy: Decrease in muscle mass.
Remodeling involves adjustments in the number of contractile proteins, energy-supplying enzymes, and other factors within the muscle.

Elasticity

The ability of a muscle to recoil to original resting length after being stretched.

Naming Skeletal Muscles

Location: The location of the muscle is often used to name it (e.g., Tibialis anterior - muscle in front of the tibia).
Shape: The shape of the muscle can also be a part of its name (e.g., Deltoid - triangular shaped, Serratus - saw-toothed).
Relative Size: Relating the size of the muscle to surrounding structures or other muscles (e.g., Pectoralis major - larger than Pectoralis minor).
Direction/Orientation of Fibers: The direction in which the fibers run can influence its name (e.g., Rectus - straight, Oblique - diagonal).
Number of Origins: The number of origins (where a muscle attaches to a bone) can be included in the name (e.g., Biceps, Triceps).
Location of Attachments: Where the muscle attaches to bones, both origin and insertion (e.g., Sternocleidomastoid - attaches to the sternum, clavicle, and mastoid process).
Action: The primary function of the muscle is often part of its name (e.g., Flexor, Extensor, Abductor, Adductor, Dilator, Constrictor, Levator, Depressor).

Muscle Classification by Action

Flexor: Bends a part near the joint.
Extensor: Straightens a part near the joint.
Abductor: Moves a part away from the midline of the body.
Adductor: Moves a part towards the midline of the body.
Dilator: Opens spaces or widens openings.
Constrictor: Closes or compresses openings.
Levator: Raises a body part.
Depressor: Lowers a body part.

Sarcomere

The smallest functional unit of a muscle fiber.
Made up of repeating units within myofibrils.
Interaction between thick (myosin) and thin (actin) filaments within the sarcomere are responsible for muscle contraction.

Parts of a Sarcomere

A band: The area where myosin (thick) filaments are present, including regions with overlapping actin filaments.
I band: The area between thick filaments where only thin filaments are present.
Z disc: Protein to which actin (thin) filaments are connected.
M line: Protein to which myosin (thick) filaments are connected.
H zone: The area surrounding the M line where only myosin filaments are present (actin filaments don't reach this area).

Myofilaments

Thick filaments: Composed of the protein myosin.
Thin filaments: Composed of the protein actin.

Molecular Composition of Myofilaments

Actin: Protein of the thin filament. Has binding sites for myosin.
Myosin Head: Myosin molecule consists of 2 myosin heads facing outwards. Binds to active sites on actin to form cross bridges. Has motor functions and binding sites for actin and ATP.
Tropomyosin: A protein that wraps around actin and prevents myosin from grabbing it. Involved in skeletal muscle contraction.
Troponin: A protein complex with three subunits:
- Troponin I: Binds to actin and helps inhibit myosin binding.
- Troponin T: Binds to tropomyosin.
- Troponin C: Has binding sites for calcium ions.

Sarcoplasmic Reticulum

A network of endoplasmic reticulum that stores calcium ions, essential for muscle contraction.

Muscle Contraction

DHPR (Dihydropyridine Receptor): Acts as a voltage sensor in the T-tubules.
RYR (Ryanodine Receptor): A calcium release channel located on the sarcoplasmic reticulum.
Calcium Channel Blockers: These drugs (e.g. amlodipine, nifedipine) work on heart muscles, not skeletal muscles.
Terminal Cisternae: Areas of the SR that store large amounts of calcium.
Calcium Binding Proteins: Several proteins help bind calcium in the SR:
- Calsequestrin:
- Histidine-rich Calcium-binding Protein (HRC):
- Sarcalumenin:
Triadin: Anchors calsequestrin near RYR.
SERCA (Sarcoplasmic or ER calcium ATPase): Pumps calcium back into the SR.

Sliding Filament Theory

This theory explains how muscle contraction occurs:
1. Calcium Release: Calcium ions are released from the SR.
2. Binding to Troponin: Calcium binds to Troponin C, causing a conformational change.
3. Tropomyosin Movement: The conformational change in troponin moves tropomyosin away from the myosin binding sites on actin.
4. Cross-Bridge Formation: Myosin heads bind to actin, forming cross-bridges.
5. Power Stroke: Myosin heads pivot, pulling the actin filaments towards the center of the sarcomere.
6. Detachment and Reattachment: Myosin detaches from actin and reattaches to a new binding site. This cycle repeats, pulling the actin filaments further.
7. Sarcomere Shortening: The sarcomere shortens as the actin filaments slide past the myosin filaments, resulting in muscle contraction.

Muscle Relaxation

Calcium Removal: SERCA pumps calcium back into the SR, decreasing calcium levels in the cytosol.
Tropmyosin Block: Tropomyosin returns to its blocking position over the myosin binding sites on actin.
Muscle Lengthening: The sarcomere lengthens, returning to its resting length, and muscle relaxation occurs.

The Muscle Twitch

Myogram: A recording of electrical activity during muscle contraction.
Latent Period: Cross-bridges begin to cycle, but muscle tension is not measurable yet.
Period of Contraction: Cross-bridges are active leading to an increase in tension.
Period of Relaxation: Calcium is pumped back into the SR, and tension decreases.

Types of Skeletal Muscle Fibers

Different muscles contract at different speeds, due to the presence of different types of muscle fibers.

Tetanus

Summation of twitches that occur at high frequency stimulations.
Incomplete (Unfused) Tetanus: Individual contractions are observed, brief relaxation between contractions, and peak tension increases, but oscillates.
Complete (Fused) Tetanus: Individual contractions are indistinguishable, resulting in a sustained, smooth contraction with higher force.

Motor Unit

The smallest functional unit of a muscle; the basic unit of movement.
Consists of a motor neuron and the muscle fibers it innervates.

Muscle Fiber Types

Extrafusal Fibers: Innervated by alpha motor neurons, comprise the bulk of the muscle and are responsible for force generation.
Intrafusal Fibers: Innervated by gamma motor neurons, involved in proprioception (sensing the position and movement of the body).

Questions and Answers

Question: In which of the following situations may temporal summation leading to tetany be occurring?
Answer: E. B and D only. Temporal summation leading to tetany is more likely to occur in situations where there is a sustained muscle contraction, like standing at attention or carrying a heavy load.
Question: Which of the following might be true of Olympic medalist Hidilyn Diaz?
Answer: E. B and C are true. A weightlifter like Hidilyn Diaz likely has muscles that insert closer to the fulcrum (the joint), providing a mechanical advantage for lifting heavy weights. She also likely experiences less central fatigue, which refers to the brain's ability to sustain effort and coordination over extended periods.

Muscle Properties

Elasticity is a muscle's ability to return to its original resting length after being stretched

Naming Skeletal Muscles

Location: Muscles are named based on their location in relation to specific bones.
Shape: Muscles are often named after their shape (e.g., Deltoid, trapezius).
Relative Size: Size relative to other muscles (e.g., Teres minor, Teres major).
Direction of Muscle Fibers: The orientation of muscle fibers (e.g., Rectus abdominis, Oblique).
Number of Origins: The number of attachment points.
Location of Attachments: The origins and insertions of muscles.
Action: The movement the muscle causes (e.g., Flexor, Extensor).

Muscle Actions

Flexor: Bends a part near a joint.
Extensor: Straightens a part near a joint.
Abductor: Moves a part away from the midline of the body.
Adductor: Moves a part towards the midline of the body.
Dilator: Opens spaces or widens openings
Constrictor: Closes or compresses openings.
Levator: Raises a body part.
Depressor: Lowers a body part.

Muscle Named by Location

Tibialis Anterior: Located in front of the tibia.
Frontalis: Muscle on top of the frontal bone.
Temporalis: Muscle on top of the temporal bone.
Epicranius: Located around the cranium.

Muscle Contraction

Period of contraction: Cross bridges are active, generating tension.
Period of relaxation: Calcium is pumped back into the sarcoplasmic reticulum (SR), reducing cross-bridge formation and muscle tension.

Muscle Fiber Types

Skeletal muscle fibers differ in their speed of contraction due to the different types of fibers present.
Fast-twitch fibers: Contract rapidly and generate high force, but fatigue quickly.
Slow-twitch fibers: Contract slowly and generate less force, but are fatigue-resistant.

Tetanus

Summation of twitches: Repeated stimulation of a muscle fiber at high frequency leads to a sustained contraction called tetanus.
Incomplete (Unfused Tetanus): Muscle fibers relax briefly between stimulations; peak tension increases but oscillates.
Complete (Fused Tetanus): Muscle fiber contractions fuse together, resulting in a smooth, sustained contraction at high force.

Motor Unit

The smallest functional unit of a muscle: Consists of a motor neuron and all the muscle fibers it innervates.
Smallest amount of muscle that can be activated voluntarily.
Extrafusal fibers: The bulk of muscle fibers, generating force; innervated by alpha motor neurons
Intrafusal fibers: Specialized sensory fibers within muscle spindles; innervated by gamma motor neurons.

Types of Muscle Contraction

Isotonic Contraction: Muscle changes length while contracting.
- Concentric: Muscle shortens.
- Eccentric: Muscle lengthens, often resulting in muscle damage after exercise.
Isometric Contraction Muscle contracts but does not change length; load is too heavy or immovable.

Muscle Fatigue

Central Fatigue: Results from the central nervous system (brain and spinal cord) being unable to effectively activate motor neurons.
Peripheral Fatigue: Occurs in muscle fibers, due to the accumulation of metabolic waste, such as lactate and hydrogen ions.

Production of Energy for Muscle Contraction

ATP (adenosine triphosphate): The primary energy source for muscle contraction.
Creatine Phosphate: Provides a rapid source of energy for muscle contraction.
Aerobic Respiration: Uses glucose and oxygen to produce ATP, providing a sustained energy source for muscle activity.
Lactic Acid Production: A byproduct of anaerobic respiration, which can lead to muscle fatigue.

Oxygen Debt

Muscle cells require oxygen to perform aerobic respiration.
During intense exercise, oxygen demand exceeds supply.
Oxygen debt: The amount of oxygen needed to restore muscle cells to their resting state after exercise.
Lactic acid buildup: Can contribute to muscle fatigue during intense exercise.

Muscle Fatigue

A condition where a muscle loses its ability to contract.
Causes:
- Lactic acid buildup
- Interruption of blood supply to the muscle
- Motor neurons losing the ability to release acetylcholine (neurotransmitter crucial for muscle contraction).

Muscle Remodeling

Muscles undergo continuous remodeling in response to activity and inactivity.
Hypertrophy: Increase in muscle mass due to increased contractile proteins, energy-supplying enzymes, and sarcomere number.
Atrophy: Decrease in muscle mass due to inactivity or nerve damage.
Hyperplasia: Increase in muscle fiber number; rare phenomenon, usually occurring under extreme conditions.

Muscle Strains and Sprains

Strains: Injuries caused by overstretched muscles or tendons.
Sprains: More serious injuries involving tears to tendons, ligaments, and cartilage of joints.
RICE treatment: Rest, Ice, Compression, Elevation.

Muscle Strain and Sprain Prevention

Warm-up: Prepares muscles for activity, increasing temperature and flexibility.
Stretching: Improves muscle performance; perform after warming up or exercising.
Cool-down: Slowing down gradually helps to remove lactic acid and prevent blood pooling.

Aging and Muscles

Decreased strength and speed of contraction: Muscle fibers become slower and weaker with age.
Reduced dexterity and gripping ability:
Potential decrease in mobility:
Exercise and assistive devices: Regular exercise, like swimming, and assistive devices can help maintain muscle health in older adults.

Diseases and Disorders of the Muscular System

Botulism: A bacterial infection that affects nerve function, leading to muscle weakness.
Fibromyalgia: Chronic pain condition affecting joints, muscles, and tendons.
Muscular Dystrophy: Inherited disorder characterized by progressive muscle weakness and loss of muscle tissue.
Myasthenia Gravis: Autoimmune disorder that causes muscle weakness.
Rhabdomyolysis: Damage to kidney function due to severe muscle injury and release of muscle proteins into the bloodstream.
Tendonitis: Painful inflammation of a tendon and its attachment to bone.
Torticollis (Wryneck): A condition where the head is tilted to one side due to a spasm or shortening of the sternocleidomastoid muscle.

Clinical Applications

Muscular Dystrophy: Caused by mutations in the dystrophin-glycoprotein complex, leading to progressive muscle weakness.
Malignant Hyperthermia: A rare condition where certain anesthetics trigger a release of calcium in susceptible individuals.
Dantrolene: Used to treat malignant hyperthermia.

Types of Muscles

Rhomboideus major: A muscle that pulls the shoulder blade toward the spine.
Trapezius: A large muscle in the back that helps move the shoulder blade and extends the neck.
Orbicularis A muscle that closes the mouth or eyes.

Muscle Movements

Origin: The attachment of a muscle to a bone that stays stationary.
Insertion: The attachment of a muscle to a bone that moves.
Belly: The fleshy part of the muscle between the tendons of origin and insertion.
Contraction: Shortening the length of a muscle fiber.
Extension: Lengthening the length of a muscle fiber.

Major Head Muscles

Sternocleidomastoid: A muscle in the neck extends the neck forward.
Splenius capitis: A neck muscle that rotates the head.
Orbicularis Oris: A muscle surrounding the mouth that controls puckering and closing of the mouth.
Frontalis: A muscle that raises the eyebrows.
Orbicularis Oculi: A muscle that closes the eyes.
Platysma: A muscle that moves the corners of the mouth downward.
Zygomaticus: A muscle that pulls the corners of the mouth upward.
Masseter and Temporalis: A set of jaw muscles that closes the jaw.

Major Arm Muscles

Pectoralis major: A muscle that pulls the arm across the chest, rotates and adducts the arms.
Latissimus dorsi: A muscle that extends and adducts the arm, rotates the arm inwardly.
Biceps brachii: A muscle that flexes the arm at the elbow and rotates the hand.
Brachialis: A muscle that flexes the arm at the elbow.
Brachioradialis: A muscle that flexes the forearm at the elbow.
Triceps brachii: A muscle that extends the arm at the elbow.
Supinator: A muscle that rotates the forearm laterally.
Pronator teres: A muscle that rotates the forearm medially.

Major Wrist, Hand, and Finger Muscles

Flexor carpi radialis and flexor carpi ulnaris: Muscles that flex and abduct the wrist.
Palmaris longus: This muscle flexes the wrist.
Flexor digitorum profundus: This muscle flexes the distal joints of the fingers, but not the thumb.
Extensor carpi radialis longus and brevis: Muscles that extend the wrist and abduct the hand.
Extensor carpi ulnaris: A muscle that extends the wrist.
Extensor digitorum: A muscle that extends the fingers, but not the thumb.

Major Respiratory Muscles

Diaphragm: A dome-shaped muscle that separates the thoracic and abdominal cavities and contracts to inspire (breathe in).
External and internal intercostals: These muscles expand and lower the ribs during breathing.

Major Abdominal Muscles

External and internal obliques: These muscles compress the abdominal wall.
Transverse abdominis: This muscle compresses the abdominal wall.
Rectus abdominis: A muscle that flexes the vertebral column and compresses the abdominal wall.

Major Pectoral Girdle Muscles

Trapezius: A muscle that raises the arms and pulls the shoulders downward.
Pectoralis minor: This muscle pulls the scapula downward.

Major Leg Muscles

Psoas major and iliacus: Muscles that flex the thigh.
Gluteus maximus: A muscle that extends the thigh.
Gluteus medius and minimus: Muscles that abduct and rotate the thighs medially.
Adductor longus and magnus: Muscles that adduct and rotate the thighs laterally.
Biceps femoris, semitendinosus, and semimembranosus: These muscles make up the hamstring group, which flexes the leg at the knee.
Rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius: These muscles are part of the quadriceps muscle group and extend the leg at the knee.
Sartorius A muscle that flexes the leg at the knee and thigh. It abducts the thigh, rotating it laterally, but rotates the lower leg medially.

Major Ankle, Foot, and Toe Muscles

Tibialis anterior: This muscle inverts the foot and points the foot up.
Extensor digitorum longus: A muscle that extends the toes and points the foot up.
Soleus: A muscle that flexes the foot.
Flexor digitorum longus: A muscle that flexes the foot and toes.
Gastrocnemius: A muscle that flexes the foot and flexes the leg at the knee.

Naming Muscles

Maximus, minimis, longus, brevis, major: refer to the size of the muscle.
Rectus, transverse, oblique: refer to the direction of muscle fibers.
Biceps, triceps, quadriceps: refer to the number of origins.
Origin and Insertion: Muscles can be named for their points of attachment.
Action: Some muscles are named for their actions.

Arrangement of Fascicles

Parallel: A muscle that is strap-like. Example: Sartorius.
Fusiform: A muscle that is spindle shaped. Example: Biceps femoris.
Pennate: A muscle that is feather shaped:
- Unipennate: Example: Extensor digitorum longus.
- Bipennate: Example: Rectus femoris.
- Multipennate: Example: Deltoid.
Convergent: A muscle with fibers that converge at a single point. Example: Pectoralis major.
Circular: A muscle that encircles an opening. Example: Orbicularis oris.

Muscle Structure

Muscle fibers: Individual muscle cells.
Myofibrils: Within a muscle fiber are a bundle of long protein filaments called myofibrils. They are the contractile elements of muscle cells.
Sarcomere: The basic functional unit of a myofibril. Contains protein filaments called myosin and actin.
Sarcoplasmic reticulum: A network of membranes that stores calcium ions, essential for muscle contraction.

Composition of Myofilaments

Myosin: Thick filaments composed of the protein myosin.
Actin: Thin filaments composed of the protein actin.
Tropomyosin: A protein associated with actin, preventing myosin from interacting with actin.
Troponin: A protein complex attached to tropomyosin, It can bind calcium ions and regulate muscle contraction.

Neuromuscular Junction

The point where a motor neuron communicates with a muscle fiber.
Acetylcholine (Ach) is released from the motor neuron, triggering the muscle to contract.

Muscle Contraction

Excitation-contraction coupling: The process by which a nerve impulse triggers a muscle contraction.
Steps of Muscle Contraction:
- Action Potential: A nerve impulse travels down a motor neuron, triggering the release of acetylcholine at the neuromuscular junction.
- Sarcolemma and SR: The action potential spreads across the muscle fiber membrane and travels into the muscle fiber via T-tubules, stimulating the release of calcium ions from the sarcoplasmic reticulum.
- Myosin and Actin: The presence of calcium ions allows myosin to bind to actin and initiate the sliding filament mechanism of muscle contraction.

Muscle Tension

Length-Tension Relation: The amount of tension a muscle can generate is influenced by its length.
Isometric Contraction: Muscle contracts, but its length remains the same.
Isotonic Contraction: Muscle contracts, and there is a change in its length.
- Concentric: Muscle shortens.
- Eccentric: Muscle lengthens.

Muscle Tension: Factors

Fiber diameter: Larger fibers produce more force.
Number of active fibers: More fibers produce more force.
Number of active motor units: More motor units activated produce more force.

Muscle Fatigue

Peripheral fatigue: Fatigue resulting from the build-up of metabolites in the muscle fibers.
Central fatigue: Fatigue resulting from changes in the central nervous system.

Muscle Remodeling

Hypertrophy: Muscle growth in size, due to an increase in the number of contractile proteins and other components in muscle cells.
Atrophy: Muscle shrinkage, caused by a decrease in the number of contractile proteins.

Production of Energy

ATP: The primary source of energy for muscle contraction.
Creatine Phosphate: A molecule in muscles that quickly provides energy for short bursts of activity.
Aerobic Respiration: The long-term process of using glucose and oxygen to make ATP.
Lactic Acid Production: Anaerobic process that occurs when oxygen is limited, producing lactic acid.

Oxygen Debt

The accumulation of lactic acid during intense exercise. Requires additional oxygen to convert the lactic acid back to glucose in the liver.

Muscle Fatigue

The inability of a muscle to contract.
Causes:
- Accumulation of lactic acid:
- Interruption of blood supply:
- Motor neuron failure:

Anatomical Terms

Understanding anatomical terms is crucial for identifying and remembering muscles.

Muscle Shape and Size

Muscle shape often reflects its name.
- Trapezius resembles a trapezoid.
- Deltoid looks like a triangle (similar to the Greek letter delta, ∆).
- Rhomboid resembles a rhomboid shape.
- Orbicularis is circular.
Muscle size is indicated by certain terms:
- Longus or longissimus refer to long muscles.
- Teres muscles are both long and round.
- Brevis designates short muscles.
- Magnus (big), major (bigger), or maximus (biggest) denote large muscles.
- Minor (smaller) or minimus (smallest) refer to small muscles.

Axial and Appendicular Muscles

The skeletal system's classification into axial and appendicular divisions helps categorize muscles.
Axial muscles arise on the axial skeleton (skull, vertebral column, ribs, and sternum).
- They comprise approximately 60% of skeletal muscles.
- Their roles include:
  - Positioning the head and vertebral column.
  - Moving the rib cage, aiding in breathing.
  - Forming the pelvic floor.
Appendicular muscles stabilize or move structures of the appendicular skeleton (bones of the limbs).
- They constitute 40% of skeletal muscles.
- They are responsible for:
  - Moving and supporting the pectoral (shoulder) and pelvic girdles.
  - Moving the upper and lower limbs.
Superficial muscles are generally large and located on the body's surface.

Muscle Fascicle Arrangement

Parallel Muscles: Fascicles run parallel to the long axis of the muscle.
Convergent Muscles: Fascicles converge on a common attachment site.
Pennate Muscles: Fascicles arranged at an angle to the tendon.
- Unipennate: Fascicles on one side of the tendon.
- Bipennate: Fascicles on both sides of the central tendon.
- Multipennate: Several tendon branches within the muscle.
Circular Muscles: (aka Sphincters) Fascicles concentrically arranged around an opening.

Muscle Names

Externus/Superficialis: Muscles visible at the surface of the body.
Internus/Profundus: Deeper muscles.
Extrinsic Muscles: Muscles that position or stabilize an organ.
Intrinsic Muscles: Muscles located entirely within an organ.
Names based on direction:
- Transversus: Across the body.
- Oblique: Slanting angle.
Names based on fascicle orientation:
- Rectus: Straight, fascicles run parallel to the long axis of the muscle

Axial Muscles

Function: Movement of the face, tongue, and larynx.
Muscles of Facial Expression:
- Buccinator: Compresses cheeks, moves food back across teeth during chewing, assists with suckling in infants.
- Depressor Labii Inferioris: Depresses lower lip.
- Levator Labii Superioris: Elevates upper lip.
- Levator Anguli Oris: Elevates corner of mouth.
- Mentalis: Elevates and protrudes lower lip.
- Orbicularis Oris: Compresses and purses lips.
- Risorius: Draws corner of mouth to the side.
- Depressor Anguli Oris: Depresses corner of mouth.
- Zygomaticus Major: Retracts and elevates corner of mouth.
- Zygomaticus Minor: Retracts and elevates upper lip.
- Corrugator Supercilii: Wrinkles brow.
- Levator Palpebrae Superioris: Elevates upper eyelid.
- Orbicularis Oculi: Closes the eye.
- Procerus: Moves the nose, changes position and shape of nostrils.
- Nasalis: Moves the nose.

Muscle Terminology

Axial Muscles: These muscles are involved in the movement of the head, neck, and trunk.
Appendicular Muscles: These muscles support and move the limbs.
Muscle names can be descriptive of features including:
- Region of the body: For example, "abdominis" refers to the abdomen.
- Position, direction, or fascicle arrangement: For example, "rectus" indicates straight fascicles.
- Structural characteristics: For example, "biceps" indicates two heads of origin.
- Actions: For example, "flexor" indicates that the muscle bends a joint.

Classification of Skeletal Muscles Based on Fascicle Arrangement

Parallel Muscles: Fascicles run parallel to the long axis of the muscle.
Convergent Muscles: Fascicles converge toward a single tendon.
Pennate Muscles: Fascicles are short and attach to a tendon that runs along the length of the muscle.
- Unipennate: Fascicles are on one side of the tendon.
- Bipennate: Fascicles are on both sides of the tendon.
- Multipennate: Tendon branches within the muscle.
Circular Muscles: Fascicles are arranged concentrically around an opening.

Muscle Classification Based on Lever Action

First-Class Lever: Fulcrum is located between the load and the applied force.
Second-Class Lever: Load is located between the fulcrum and the applied force.
Third-Class Lever: Applied force is located between the load and the fulcrum. This is the most common type of lever in the body.

Examples of Muscles

Temporalis: An axial muscle located in the head.
Brachialis: An appendicular muscle located in the arm.
Rectus abdominis: An axial muscle with straight fascicles that run along its long axis.
Biceps brachii: An appendicular muscle with two tendons of origin.
Triceps brachii: An appendicular muscle with three tendons of origin
Quadriceps femoris: An appendicular muscle with four tendons of origin.
Genioglossus: An axial muscle that originates at the chin and inserts in the tongue.
Extensor digitorum: An appendicular muscle that extends the finger joints.
Rectus femoris: An appendicular muscle that extends the knee.
Deltoid: An appendicular muscle that is multipennate, meaning the tendon branches within the muscle.
Orbicularis oris: An axial muscle that surrounds the mouth.
Flexor carpi radialis longus: An appendicular muscle that flexes the wrist.
Plantaris: An appendicular muscle that is involved in ankle extension.
Sartorius: An appendicular muscle named after the Latin word for "tailor."

Chapter 11: The Muscular System

This chapter describes the human muscular system and its functions.
The chapter includes the following learning outcomes:
- Describe the formation of fascicles in different muscle types and their resulting functions.
- Explain how leverage works and how it makes muscles more efficient.
- Predict a muscle's action based on its origin and insertion, and explain how muscles interact to produce or oppose movements.
- Explain how muscle names can tell us information about their location, appearance, or function.
- Compare and contrast axial and appendicular muscles.
- Identify the main axial muscles, including their origins, insertions, actions, and innervation.
- Identify the main appendicular muscles, including their origins, insertions, actions, and innervation, comparing the functional differences between upper and lower limbs.
- Explain the functional relationship between the muscular system and other organ systems, and the role of exercise on these other organ systems.

Muscle Names

Muscle names often include descriptive information about:
- Region of the body
- Position, direction, and fascicle arrangement
- Structural characteristics
- Action
There are approximately 700 muscles in the human body.
You don't need to learn all their names, but you should familiarize yourself with many of them.

Examples of Muscle Names

Subscapularis: This muscle is located under the scapula (shoulder blade), and its action is medial rotation at the shoulder joint.
Teres Minor: This muscle is small (teres means round) and is located on the posterior side of the shoulder joint. Its action is lateral rotation at the shoulder joint.

The Levator Anguli Oris

The levator anguli oris is a facial muscle that elevates the corner of the mouth.
It originates from the maxilla, below the infraorbital foramen.
It inserts into the corner of the mouth.
The levator anguli oris is innervated by the facial nerve (VII).
This action helps create the expression of a smile.

Lever Systems

A lever is a rigid object that rotates around a fixed point, called a fulcrum
In the body, bones serve as levers and joints act as fulcrums
Muscle contractions provide the force necessary to move the lever
Muscle efficiency can be described by the class of lever they form
First Class Lever Fulcrum is in the middle, force and load on either side
Second Class Lever Load is in the middle, force and fulcrum on either side
Third Class Lever Force is in the middle, load and fulcrum on either side
Most muscles in the body act as third-class levers, sacrificing power for speed and range of motion

Fascicle Arrangements

Muscle fibers in a skeletal muscle form bundles called fascicles
Fascicle arrangement determines a muscle's functional properties
Parallel Muscles Fascicles are parallel to the long axis of muscle, generate strong force in one direction
Convergent Muscles Muscle fibers spread out broadly, converging at a common attachment site, can pull in different directions, generating less force than a parallel muscle of the same size
Pennate Muscles Fascicles are short and attach to a tendon at an angle, allowing for increased muscle force in one direction
Circular Muscles Fascicles are arranged in a circle, closing openings when contracted

Muscle Names

Muscle names often provide clues to their location, appearance, or function
Regional Terms Refer to the body region where the muscle is located (e.g., temporalis, brachialis)
Descriptive Terms Information about the muscle's position, direction, or fascicle arrangement (e.g., biceps, triceps, rectus)
Structural Characteristics Include information about the muscle's shape (e.g., deltoid, trapezius), origin (e.g., biceps), or size (e.g., major, minor)
Action Terms Describe what the muscle does (e.g., flexor, extensor, abductor)

Agonists and Antagonists

An agonist is a muscle that produces a specific movement
An antagonist is a muscle that opposes the action of an agonist
Agonists and antagonists work together to control movement, ensuring smooth and coordinated action

Summary of Muscle Terminology

Descriptive terms used to determine muscle location, position, fascicle arrangement, function, etc.
Examples of terms:
- Region : Abdominal, Ancon, Auricular, Brachial etc...
- Position : Anterior, External, Inferior, Internal etc...
- Structural Characteristics : Biceps (two heads), Triceps (three heads), Deltoid (triangle), Trapezius (trapezoid)
- Action : Abductor, Adductor, Depressor, Extensor, Flexor, Levator, Pronator, Supinator, Tensor, etc...

Lever Systems and Muscle Actions

A lever is a rigid structure that utilizes a fixed point called a fulcrum to produce movement.
Applied force is the pressure exerted on a lever.
Load is the resistance to the applied force.
Levers can alter the direction, distance, speed, and strength of an applied force.
Three classes of levers:
- First-class lever: Fulcrum is between the applied force and the load. (e.g., neck extension)
- Second-class lever: Load is between the applied force and the fulcrum. (e.g., calf muscle raising the heel)
- Third-class lever: Applied force is between the load and the fulcrum. (e.g., biceps flexing the elbow)
Mechanical advantage: Lever amplifies force when the applied force is further from the fulcrum than the load.
Mechanical disadvantage: Lever reduces force when the applied force is closer to the load than the fulcrum.

Muscle Origins and Insertions

Origin: Less movable end of a muscle; typically fixed and proximal to insertion.
Insertion: More movable end of a muscle; moves towards the origin during contraction.
Muscle actions are determined by the relative positions of the origin and insertion.
Muscle interactions are crucial for producing or opposing movements.
Extrinsic muscles: Superficial muscles that position or stabilize organs.
Intrinsic muscles: Muscles located entirely within an organ.

Muscle Naming Conventions

Externus/superficialis: Muscles visible at the body surface.
Internus/profundus: Deeper muscles.
Transversus: Muscles that run across the longitudinal body axis.
Oblique: Muscles that run at a slanting angle to the longitudinal body axis.
Rectus: Muscles with fascicles running along the longitudinal axis.
Directional descriptors: Names may indicate the muscle's location or function.

Examples of Descriptive Muscle Names

Biceps brachii: Located on the anterior surface of the arm.
Splenius capitis and semispinalis capitis: Muscles responsible for neck extension and head lifting.
Extensor carpi radialis longus: Muscle extending the wrist.
Buccinator: Compresses the cheeks, used in blowing.
Risorius: Facial muscle associated with grimacing.
Sartorius: Longest muscle in the body, active when crossing legs.

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Muscle Anatomy and Functions Quiz

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Questions and Answers

What is the smallest muscle in the human body?

Which of the following muscles is considered the biggest in the human body?

Skeletal muscle tissue can be characterized by which of the following features?

What function does cardiac muscle primarily serve?

Which type of muscle tissue is controlled voluntarily?

How many muscles are typically found in the human face?

What characteristic of muscle tissue allows it to respond to stimuli?

Which of the following statements about muscle control is false?

In which situation is temporal summation likely contributing to tetany?

What could be a characteristic of Olympic medalist Hidilyn Diaz regarding her muscle contractions?

Which statement about muscle hypertrophy in Olympic weightlifters is most likely accurate?

When would central fatigue likely be reduced in an athlete like Hidilyn Diaz?

What might differentiate Hidilyn Diaz's muscle attachments compared to an average individual?

What is the primary role of the diaphragm during respiration?

Which muscle group is primarily responsible for flexing the leg at the knee?

Which muscle allows for the rotation of the forearm laterally during supination?

What is the characteristic shape of a unipennate muscle?

Which muscle is involved in abducting the thigh and rotating it medially?

What types of connective tissues attach muscles to bones?

Which muscle group primarily extends the leg at the knee?

Which skeletal muscle is responsible for closing the jaw?

Which term refers to the fleshy part of the muscle between the origin and insertion?

What does a pennate arrangement of muscle fibers allow for?

Which type of muscle contraction is characterized by muscle length changing during contraction?

What primarily contributes to cellular damage after exercise?

What causes central fatigue in muscle performance?

Which method of energy production for muscle contraction utilizes the body’s stored glucose?

What is the primary symptom associated with peripheral fatigue?

Which process occurs during oxygen debt when skeletal muscles are used strenuously?

What are the conditions causing muscle fatigue?

What characterizes the process of muscle remodeling?

What is the role of creatine phosphate in muscle energy production?

Which of the following is NOT a type of muscle contraction?

What is the primary function of DHPR in heart muscle contraction?

Which of the following proteins is involved in binding Ca+2 within the muscle cell?

Which channel blocker specifically affects heart muscle contraction?

What role does SERCA play during muscle relaxation?

How does RYR function in skeletal muscle compared to cardiac muscle?

Which statement accurately describes the sliding filament theory?

What is observed in the latent period of a muscle twitch myogram?

What is the role of calsequestrin in muscle cells?

What initiates the release of Ca+2 from the sarcoplasmic reticulum in muscle contraction?

Which process is affected by the decrease in Ca+2 levels in muscle cells?

What does elasticity refer to in the context of muscle function?

Which of the following describes the action of a depressor muscle?

Which term best describes the action of an abductor muscle?

What is the naming basis for the muscle known as tibialis anterior?

What action does a constrictor muscle perform?

Which base pertains to the shape of the muscle known as serratus?

What does the term 'flexor' refer to in muscle classification?

Which orientation is indicated by the muscle name 'deltoid'?

What type of muscle contraction occurs when the muscle length remains constant while tension is developed?

How does fiber diameter influence muscle contraction?

What is the relationship between the number of active motor units and force produced?

Which type of contraction occurs when the muscle fibers shorten while generating external work?

What determines the amount of tension that a muscle fiber can develop?

Which muscle primarily compresses the abdominal wall?

What is the primary action of the gluteus maximus muscle?

Which muscle is involved in lateral rotation of the forearm?

How does the diaphragm contribute to respiration?

What is a characteristic of the circular muscle arrangement?

Which muscle group flexes the arm at the elbow and simultaneously rotates the hand laterally?

Which term describes the connective tissue that connects muscle to bone?

Which muscle group is known for extending the leg at the knee?

What type of arrangement do muscles like the deltoid exhibit?

Which muscle allows the lips to pucker?

What role does acetylcholinesterase play in muscle contraction?

Which channel is primarily responsible for propagating the action potential in muscle fibers after acetylcholine binds to its receptors?

How does Ca+2 contribute to muscle contraction during excitation-contraction coupling?

What is the primary action that takes place at the neuromuscular junction to trigger muscle contraction?

What occurs after the action potential travels along the sarcolemma and into the T-tubules?

Which of the following statements about Ca+2 during muscle relaxation is accurate?

Which component primarily interacts with Ca+2 to facilitate muscle contraction?

What initiates the release of Ca+2 from the sarcoplasmic reticulum?

What is the role of the ryanodine receptor (RYR) in muscle contraction?

What occurs during the period of relaxation in muscle contraction?