Podcast
Questions and Answers
What is the smallest muscle in the human body?
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?
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?
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?
What function does cardiac muscle primarily serve?
Which type of muscle tissue is controlled voluntarily?
Which type of muscle tissue is controlled voluntarily?
How many muscles are typically found in the human face?
How many muscles are typically found in the human face?
What characteristic of muscle tissue allows it to respond to stimuli?
What characteristic of muscle tissue allows it to respond to stimuli?
Which of the following statements about muscle control is false?
Which of the following statements about muscle control is false?
In which situation is temporal summation likely contributing to tetany?
In which situation is temporal summation likely contributing to tetany?
What could be a characteristic of Olympic medalist Hidilyn Diaz regarding her muscle contractions?
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?
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?
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 might differentiate Hidilyn Diaz's muscle attachments compared to an average individual?
What is the primary role of the diaphragm during respiration?
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 group is primarily responsible for flexing the leg at the knee?
Which muscle allows for the rotation of the forearm laterally during supination?
Which muscle allows for the rotation of the forearm laterally during supination?
What is the characteristic shape of a unipennate muscle?
What is the characteristic shape of a unipennate muscle?
Which muscle is involved in abducting the thigh and rotating it medially?
Which muscle is involved in abducting the thigh and rotating it medially?
What types of connective tissues attach muscles to bones?
What types of connective tissues attach muscles to bones?
Which muscle group primarily extends the leg at the knee?
Which muscle group primarily extends the leg at the knee?
Which skeletal muscle is responsible for closing the jaw?
Which skeletal muscle is responsible for closing the jaw?
Which term refers to the fleshy part of the muscle between the origin and insertion?
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?
What does a pennate arrangement of muscle fibers allow for?
Which type of muscle contraction is characterized by muscle length changing during contraction?
Which type of muscle contraction is characterized by muscle length changing during contraction?
What primarily contributes to cellular damage after exercise?
What primarily contributes to cellular damage after exercise?
What causes central fatigue in muscle performance?
What causes central fatigue in muscle performance?
Which method of energy production for muscle contraction utilizes the body’s stored glucose?
Which method of energy production for muscle contraction utilizes the body’s stored glucose?
What is the primary symptom associated with peripheral fatigue?
What is the primary symptom associated with peripheral fatigue?
Which process occurs during oxygen debt when skeletal muscles are used strenuously?
Which process occurs during oxygen debt when skeletal muscles are used strenuously?
What are the conditions causing muscle fatigue?
What are the conditions causing muscle fatigue?
What characterizes the process of muscle remodeling?
What characterizes the process of muscle remodeling?
What is the role of creatine phosphate in muscle energy production?
What is the role of creatine phosphate in muscle energy production?
Which of the following is NOT a type of muscle contraction?
Which of the following is NOT a type of muscle contraction?
What is the primary function of DHPR in heart 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 of the following proteins is involved in binding Ca+2 within the muscle cell?
Which channel blocker specifically affects heart muscle contraction?
Which channel blocker specifically affects heart muscle contraction?
What role does SERCA play during muscle relaxation?
What role does SERCA play during muscle relaxation?
How does RYR function in skeletal muscle compared to cardiac muscle?
How does RYR function in skeletal muscle compared to cardiac muscle?
Which statement accurately describes the sliding filament theory?
Which statement accurately describes the sliding filament theory?
What is observed in the latent period of a muscle twitch myogram?
What is observed in the latent period of a muscle twitch myogram?
What is the role of calsequestrin in muscle cells?
What is the role of calsequestrin in muscle cells?
What initiates the release of Ca+2 from the sarcoplasmic reticulum in muscle contraction?
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?
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?
What does elasticity refer to in the context of muscle function?
Which of the following describes the action of a depressor muscle?
Which of the following describes the action of a depressor muscle?
Which term best describes the action of an abductor muscle?
Which term best describes the action of an abductor muscle?
What is the naming basis for the muscle known as tibialis anterior?
What is the naming basis for the muscle known as tibialis anterior?
What action does a constrictor muscle perform?
What action does a constrictor muscle perform?
Which base pertains to the shape of the muscle known as serratus?
Which base pertains to the shape of the muscle known as serratus?
What does the term 'flexor' refer to in muscle classification?
What does the term 'flexor' refer to in muscle classification?
Which orientation is indicated by the muscle name 'deltoid'?
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?
What type of muscle contraction occurs when the muscle length remains constant while tension is developed?
How does fiber diameter influence muscle contraction?
How does fiber diameter influence muscle contraction?
What is the relationship between the number of active motor units and force produced?
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?
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?
What determines the amount of tension that a muscle fiber can develop?
Which muscle primarily compresses the abdominal wall?
Which muscle primarily compresses the abdominal wall?
What is the primary action of the gluteus maximus muscle?
What is the primary action of the gluteus maximus muscle?
Which muscle is involved in lateral rotation of the forearm?
Which muscle is involved in lateral rotation of the forearm?
How does the diaphragm contribute to respiration?
How does the diaphragm contribute to respiration?
What is a characteristic of the circular muscle arrangement?
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 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 term describes the connective tissue that connects muscle to bone?
Which muscle group is known for extending the leg at the knee?
Which muscle group is known for extending the leg at the knee?
What type of arrangement do muscles like the deltoid exhibit?
What type of arrangement do muscles like the deltoid exhibit?
Which muscle allows the lips to pucker?
Which muscle allows the lips to pucker?
What role does acetylcholinesterase play in muscle contraction?
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?
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?
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 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?
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 of the following statements about Ca+2 during muscle relaxation is accurate?
Which component primarily interacts with Ca+2 to facilitate muscle contraction?
Which component primarily interacts with Ca+2 to facilitate muscle contraction?
What initiates the release of Ca+2 from the sarcoplasmic reticulum?
What initiates the release of Ca+2 from the sarcoplasmic reticulum?
What is the role of the ryanodine receptor (RYR) in muscle contraction?
What is the role of the ryanodine receptor (RYR) in muscle contraction?
What occurs during the period of relaxation in muscle contraction?
What occurs during the period of relaxation in muscle contraction?
What characterizes complete (fused) tetanus?
What characterizes complete (fused) tetanus?
What is the primary function of extrafusal fibers?
What is the primary function of extrafusal fibers?
Which type of motor neuron innervates intrafusal fibers?
Which type of motor neuron innervates intrafusal fibers?
How does incomplete (unfused) tetanus differ from complete (fused) tetanus?
How does incomplete (unfused) tetanus differ from complete (fused) tetanus?
What is the definition of a motor unit?
What is the definition of a motor unit?
What leads to smooth and continuous muscle movement?
What leads to smooth and continuous muscle movement?
Which function is primarily associated with the lateral rectus muscle?
Which function is primarily associated with the lateral rectus muscle?
What happens to contractile force during the decline of active cross bridges?
What happens to contractile force during the decline of active cross bridges?
What type of muscle contraction occurs when a muscle lengthens while under tension?
What type of muscle contraction occurs when a muscle lengthens while under tension?
Which of the following contributes most to cellular damage after exercise?
Which of the following contributes most to cellular damage after exercise?
What is the primary cause of peripheral fatigue in muscle fibers?
What is the primary cause of peripheral fatigue in muscle fibers?
What is the primary effect of oxygen debt in muscle metabolism?
What is the primary effect of oxygen debt in muscle metabolism?
Which of the following is NOT a characteristic of muscle remodeling?
Which of the following is NOT a characteristic of muscle remodeling?
What is the primary function of skeletal muscle tissue?
What is the primary function of skeletal muscle tissue?
Which type of muscle tissue is characterized by multinucleated fibers?
Which type of muscle tissue is characterized by multinucleated fibers?
Which muscle is considered the longest muscle in the human body?
Which muscle is considered the longest muscle in the human body?
What characteristic of muscle tissue allows it to be stretched beyond its normal length?
What characteristic of muscle tissue allows it to be stretched beyond its normal length?
Which of the following describes the control mechanism of smooth muscle?
Which of the following describes the control mechanism of smooth muscle?
Which muscle is known as Ms. Mhin's favorite muscle in the body?
Which muscle is known as Ms. Mhin's favorite muscle in the body?
What is the primary role of cardiac muscle tissue?
What is the primary role of cardiac muscle tissue?
What is the biggest muscle in the human body?
What is the biggest muscle in the human body?
What is the primary function of the diaphragm during respiration?
What is the primary function of the diaphragm during respiration?
Which muscle is responsible for flexing the arm at the elbow?
Which muscle is responsible for flexing the arm at the elbow?
What type of muscle arrangement is described as strap-like?
What type of muscle arrangement is described as strap-like?
Which of the following muscle groups is primarily responsible for extending the leg at the knee?
Which of the following muscle groups is primarily responsible for extending the leg at the knee?
Which muscle allows for the rotation of the forearm medially during pronation?
Which muscle allows for the rotation of the forearm medially during pronation?
What do tendons connect?
What do tendons connect?
What is the primary role of the orbicularis oris muscle?
What is the primary role of the orbicularis oris muscle?
Which muscle group assists in compressing the abdominal wall?
Which muscle group assists in compressing the abdominal wall?
Which of the following muscles is part of the hamstring group?
Which of the following muscles is part of the hamstring group?
What is the action of the flexor digitorum profundus muscle?
What is the action of the flexor digitorum profundus muscle?
What type of contraction involves muscle length being held constant while tension is generated?
What type of contraction involves muscle length being held constant while tension is generated?
How does the diameter of a muscle fiber affect force production?
How does the diameter of a muscle fiber affect force production?
What determines the type of movement produced by muscle fibers per motor unit?
What determines the type of movement produced by muscle fibers per motor unit?
What happens to muscle fibers during isometric contraction?
What happens to muscle fibers during isometric contraction?
Which of the following factors contributes to the strength of contraction in muscles?
Which of the following factors contributes to the strength of contraction in muscles?
What characterizes an isotonic contraction?
What characterizes an isotonic contraction?
The force generated by a muscle fiber is affected by what relationship between fiber length and tension?
The force generated by a muscle fiber is affected by what relationship between fiber length and tension?
Which statement correctly describes the relationship between the number of active motor units and the force produced?
Which statement correctly describes the relationship between the number of active motor units and the force produced?
Which factor does NOT affect the threshold of a muscle fiber?
Which factor does NOT affect the threshold of a muscle fiber?
The active shortening of sarcomeres contributes to what type of muscle contraction?
The active shortening of sarcomeres contributes to what type of muscle contraction?
What initiates the release of Ca+2 from the sarcoplasmic reticulum?
What initiates the release of Ca+2 from the sarcoplasmic reticulum?
What is the role of acetylcholinesterase at the neuromuscular junction?
What is the role of acetylcholinesterase at the neuromuscular junction?
Which step follows the influx of Ca+2 into the muscle fiber?
Which step follows the influx of Ca+2 into the muscle fiber?
What primarily causes muscle relaxation after contraction?
What primarily causes muscle relaxation after contraction?
What is the primary function of dihydropyridine receptors (DHPR) in muscle contraction?
What is the primary function of dihydropyridine receptors (DHPR) in muscle contraction?
Which process follows the binding of acetylcholine to its receptor on the muscle membrane?
Which process follows the binding of acetylcholine to its receptor on the muscle membrane?
What structure facilitates the transmission of action potentials deep into muscle fibers?
What structure facilitates the transmission of action potentials deep into muscle fibers?
Which ions are primarily involved in the muscle contraction mechanism?
Which ions are primarily involved in the muscle contraction mechanism?
What occurs at the terminal cisternae during muscle contraction?
What occurs at the terminal cisternae during muscle contraction?
What is the term used for the process by which muscle fiber depolarization initiates contraction?
What is the term used for the process by which muscle fiber depolarization initiates contraction?
What does elasticity of a muscle refer to?
What does elasticity of a muscle refer to?
Which term describes a muscle that raises a body part?
Which term describes a muscle that raises a body part?
How is the muscle 'Deltoid' classified based on its shape?
How is the muscle 'Deltoid' classified based on its shape?
Which of the following muscles moves a part towards the midline of the body?
Which of the following muscles moves a part towards the midline of the body?
What is the primary action of a flexor muscle?
What is the primary action of a flexor muscle?
Which muscle is located on top of the temporal bone?
Which muscle is located on top of the temporal bone?
What type of muscle is described as 'constrictor'?
What type of muscle is described as 'constrictor'?
How is the muscle named 'Tibialis anterior' classified?
How is the muscle named 'Tibialis anterior' classified?
Which situation is most likely to contribute to temporal summation leading to tetany?
Which situation is most likely to contribute to temporal summation leading to tetany?
Which statement is likely true regarding Hidilyn Diaz's muscle activity while lifting?
Which statement is likely true regarding Hidilyn Diaz's muscle activity while lifting?
Which of the following statements about Hidilyn Diaz's muscles might be true?
Which of the following statements about Hidilyn Diaz's muscles might be true?
Which factor might influence the muscle contractions of an Olympic weightlifter?
Which factor might influence the muscle contractions of an Olympic weightlifter?
Which factor is less likely to be true about the muscle contractions of elite athletes?
Which factor is less likely to be true about the muscle contractions of elite athletes?
What initiates the opening of RYR in heart muscle contraction?
What initiates the opening of RYR in heart muscle contraction?
What role does SERCA play in muscle relaxation?
What role does SERCA play in muscle relaxation?
Which of the following proteins is responsible for binding Ca+2 in muscle cells?
Which of the following proteins is responsible for binding Ca+2 in muscle cells?
How does DHPR interact with RYR in skeletal muscle?
How does DHPR interact with RYR in skeletal muscle?
What is the significance of the latent period in a muscle twitch myogram?
What is the significance of the latent period in a muscle twitch myogram?
What happens to tropomyosin when Ca+2 levels decrease in muscle cells?
What happens to tropomyosin when Ca+2 levels decrease in muscle cells?
What is the primary action of calcium channel blocker drugs in heart muscle?
What is the primary action of calcium channel blocker drugs in heart muscle?
What is the primary function of DHP in muscle contraction?
What is the primary function of DHP in muscle contraction?
What anchors calsequestrin near RYR in muscle cells?
What anchors calsequestrin near RYR in muscle cells?
During muscle relaxation, how many Ca+2 ions does SERCA pump back into the terminal cisternae per ATP hydrolyzed?
During muscle relaxation, how many Ca+2 ions does SERCA pump back into the terminal cisternae per ATP hydrolyzed?
What is the primary role of the interaction between thick and thin filaments in a sarcomere?
What is the primary role of the interaction between thick and thin filaments in a sarcomere?
Which protein is responsible for binding to actin and regulating myosin binding?
Which protein is responsible for binding to actin and regulating myosin binding?
What component of a sarcomere is responsible for holding thick filaments together?
What component of a sarcomere is responsible for holding thick filaments together?
What distinguishes the I band from the A band in a sarcomere?
What distinguishes the I band from the A band in a sarcomere?
Which part of the sarcomere does the actin filament attach to?
Which part of the sarcomere does the actin filament attach to?
What is the function of calcium ions in muscle contraction?
What is the function of calcium ions in muscle contraction?
How many binding sites does a myosin head possess?
How many binding sites does a myosin head possess?
Which component of muscle cells prevents myosin from binding to actin in the absence of calcium?
Which component of muscle cells prevents myosin from binding to actin in the absence of calcium?
What is the H zone in a sarcomere?
What is the H zone in a sarcomere?
Which statement accurately describes myofibrils?
Which statement accurately describes myofibrils?
What occurs during the period of relaxation in muscle contraction?
What occurs during the period of relaxation in muscle contraction?
What characterizes incomplete (unfused) tetanus?
What characterizes incomplete (unfused) tetanus?
Which statement about motor units is true?
Which statement about motor units is true?
What happens to contractile force during the period of contraction?
What happens to contractile force during the period of contraction?
What type of muscle fiber is primarily responsible for generating the bulk of muscle force?
What type of muscle fiber is primarily responsible for generating the bulk of muscle force?
What is the primary characteristic of complete (fused) tetanus?
What is the primary characteristic of complete (fused) tetanus?
Which factor does NOT contribute to the diversity in contraction speed among different muscles?
Which factor does NOT contribute to the diversity in contraction speed among different muscles?
What is the result of decreasing intervals between successive stimuli in muscle contraction?
What is the result of decreasing intervals between successive stimuli in muscle contraction?
Which type of motor neuron innervates intrafusal fibers?
Which type of motor neuron innervates intrafusal fibers?
What allows for smooth and continuous movements in muscle function?
What allows for smooth and continuous movements in muscle function?
Which situation is most likely to involve temporal summation leading to tetany?
Which situation is most likely to involve temporal summation leading to tetany?
What is the primary contraction type employed by weightlifters during a clean and jerk maneuver?
What is the primary contraction type employed by weightlifters during a clean and jerk maneuver?
Which characteristic might differentiate an Olympic weightlifter's muscles from those of a typical individual?
Which characteristic might differentiate an Olympic weightlifter's muscles from those of a typical individual?
What could explain a reduced level of central fatigue in elite athletes like Hidilyn Diaz?
What could explain a reduced level of central fatigue in elite athletes like Hidilyn Diaz?
Which factor is most likely associated with the muscle adaptations of Olympic lifters compared to non-competitive individuals?
Which factor is most likely associated with the muscle adaptations of Olympic lifters compared to non-competitive individuals?
What does elasticity in muscle tissue specifically refer to?
What does elasticity in muscle tissue specifically refer to?
Which term describes a muscle that moves a body part away from the midline?
Which term describes a muscle that moves a body part away from the midline?
Which of the following muscles is named for its location on the cranial bone?
Which of the following muscles is named for its location on the cranial bone?
What does the term 'depressor' indicate about a muscle's action?
What does the term 'depressor' indicate about a muscle's action?
Which of the following best describes the action of a flexor muscle?
Which of the following best describes the action of a flexor muscle?
The muscle named 'Serratus' is best described by which characteristic?
The muscle named 'Serratus' is best described by which characteristic?
Which classification of muscle action is associated with opening spaces or widening openings?
Which classification of muscle action is associated with opening spaces or widening openings?
How is the Deltoid muscle primarily classified?
How is the Deltoid muscle primarily classified?
What type of injury is classified as a strain?
What type of injury is classified as a strain?
Which condition is characterized by the production of more muscle fibers?
Which condition is characterized by the production of more muscle fibers?
What does RICE stand for in the treatment of muscle strains and sprains?
What does RICE stand for in the treatment of muscle strains and sprains?
What is a common symptom of Myasthenia Gravis?
What is a common symptom of Myasthenia Gravis?
Which of the following is NOT a recommended practice for preventing muscle strains?
Which of the following is NOT a recommended practice for preventing muscle strains?
What is characterized by progressive weakness of muscle due to a mutated dystrophin-glycoprotein complex?
What is characterized by progressive weakness of muscle due to a mutated dystrophin-glycoprotein complex?
What role do assistive devices serve for aging individuals?
What role do assistive devices serve for aging individuals?
Which condition is related to the painful inflammation of a tendon?
Which condition is related to the painful inflammation of a tendon?
Which of the following is a common treatment for malignant hyperthermia?
Which of the following is a common treatment for malignant hyperthermia?
Which of the following conditions is known for causing chronic pain primarily in joints, muscles, and tendons?
Which of the following conditions is known for causing chronic pain primarily in joints, muscles, and tendons?
What occurs during the period of contraction in muscle fibers?
What occurs during the period of contraction in muscle fibers?
What characterizes complete (fused) tetanus?
What characterizes complete (fused) tetanus?
What type of muscle fiber is primarily responsible for generating force?
What type of muscle fiber is primarily responsible for generating force?
Which statement best describes incomplete (unfused) tetanus?
Which statement best describes incomplete (unfused) tetanus?
How is a motor unit defined?
How is a motor unit defined?
What happens to contractile force during the period of relaxation?
What happens to contractile force during the period of relaxation?
Which type of muscle fibers are innervated by gamma motor neurons?
Which type of muscle fibers are innervated by gamma motor neurons?
What leads to smooth, continuous movements in muscle contraction?
What leads to smooth, continuous movements in muscle contraction?
What is the primary role of calcium ions during muscle contraction?
What is the primary role of calcium ions during muscle contraction?
What distinguishes different types of skeletal muscle fibers?
What distinguishes different types of skeletal muscle fibers?
What is the primary characteristic of isometric contraction?
What is the primary characteristic of isometric contraction?
What primarily contributes to peripheral fatigue in muscles?
What primarily contributes to peripheral fatigue in muscles?
During oxygen debt, what happens to lactic acid produced in the muscles?
During oxygen debt, what happens to lactic acid produced in the muscles?
What is the primary cause of muscle fatigue during exercise?
What is the primary cause of muscle fatigue during exercise?
Which of the following describes the difference between hypertrophy and atrophy?
Which of the following describes the difference between hypertrophy and atrophy?
Which process is primarily involved in rapid energy production for muscles?
Which process is primarily involved in rapid energy production for muscles?
What role does central fatigue play in muscle performance?
What role does central fatigue play in muscle performance?
Which type of muscle contraction causes lengthening of the muscle under tension?
Which type of muscle contraction causes lengthening of the muscle under tension?
What is the immediate outcome when blood supply to a muscle is interrupted?
What is the immediate outcome when blood supply to a muscle is interrupted?
How does the body manage recovery from intense exercise?
How does the body manage recovery from intense exercise?
What type of contraction is characterized by muscle lengthening while contracting?
What type of contraction is characterized by muscle lengthening while contracting?
Which of the following is NOT a contributing factor to muscle fatigue?
Which of the following is NOT a contributing factor to muscle fatigue?
Which method of energy production is characterized by rapid energy release during muscle contractions?
Which method of energy production is characterized by rapid energy release during muscle contractions?
What condition is described as a muscle's inability to contract due to fatigue?
What condition is described as a muscle's inability to contract due to fatigue?
Which of the following is a common symptom of peripheral fatigue?
Which of the following is a common symptom of peripheral fatigue?
What is the role of the diaphragm during respiration?
What is the role of the diaphragm during respiration?
Which muscle group is responsible for flexing the arm at the elbow?
Which muscle group is responsible for flexing the arm at the elbow?
What type of muscle arrangement is exemplified by the deltoid?
What type of muscle arrangement is exemplified by the deltoid?
Which of the following muscles assists in rotating the forearm medially?
Which of the following muscles assists in rotating the forearm medially?
What is the function of the orbitalis oris muscle?
What is the function of the orbitalis oris muscle?
What does the term 'sartorius' refer to in the context of muscle arrangement?
What does the term 'sartorius' refer to in the context of muscle arrangement?
Which muscle is primarily responsible for extending the leg at the knee?
Which muscle is primarily responsible for extending the leg at the knee?
What does the flexor carpi radialis muscle primarily do?
What does the flexor carpi radialis muscle primarily do?
What is primarily responsible for muscle contraction within the sarcomere?
What is primarily responsible for muscle contraction within the sarcomere?
Which component of the sarcomere is responsible for anchoring thin filaments?
Which component of the sarcomere is responsible for anchoring thin filaments?
What is the role of tropomyosin in muscle contraction?
What is the role of tropomyosin in muscle contraction?
What is found in the H zone of the sarcomere?
What is found in the H zone of the sarcomere?
Which of the following proteins directly binds to calcium ions during muscle contraction?
Which of the following proteins directly binds to calcium ions during muscle contraction?
How many binding sites does a myosin molecule have?
How many binding sites does a myosin molecule have?
Which zone represents the area where myosin filaments do not overlap with actin filaments?
Which zone represents the area where myosin filaments do not overlap with actin filaments?
What function does the sarcoplasmic reticulum serve in muscle fibers?
What function does the sarcoplasmic reticulum serve in muscle fibers?
What do striations in muscle fibers represent?
What do striations in muscle fibers represent?
Which part of the sarcomere serves as the connection point for thick filaments?
Which part of the sarcomere serves as the connection point for thick filaments?
What triggers the release of Ca+2 from the sarcoplasmic reticulum during muscle contraction?
What triggers the release of Ca+2 from the sarcoplasmic reticulum during muscle contraction?
Which protein complex engages in the interaction that ultimately causes muscle contraction?
Which protein complex engages in the interaction that ultimately causes muscle contraction?
What role does acetylcholinesterase play in muscle contraction?
What role does acetylcholinesterase play in muscle contraction?
During what phase of muscle contraction is Ca+2 pumped back into the sarcoplasmic reticulum?
During what phase of muscle contraction is Ca+2 pumped back into the sarcoplasmic reticulum?
What initiates the action potential in a muscle fiber?
What initiates the action potential in a muscle fiber?
Which of the following correctly describes the role of T-tubules in muscle contraction?
Which of the following correctly describes the role of T-tubules in muscle contraction?
What is the primary effect of Ca+2 binding to troponin in muscle fibers?
What is the primary effect of Ca+2 binding to troponin in muscle fibers?
What is the role of dihydropyridine receptors in muscle contraction?
What is the role of dihydropyridine receptors in muscle contraction?
What results from the depolarization of the muscle fiber membrane?
What results from the depolarization of the muscle fiber membrane?
Which mechanism is responsible for muscle relaxation following contraction?
Which mechanism is responsible for muscle relaxation following contraction?
What type of muscle contraction involves a constant muscle length while generating tension?
What type of muscle contraction involves a constant muscle length while generating tension?
Which factor directly affects the amount of force produced by a muscle fiber?
Which factor directly affects the amount of force produced by a muscle fiber?
What happens to muscle tension when the number of active motor units increases?
What happens to muscle tension when the number of active motor units increases?
In terms of muscle fiber length, what is the relationship between length and tension development?
In terms of muscle fiber length, what is the relationship between length and tension development?
Which contraction type primarily represents a situation where muscle fibers shorten and produce external work?
Which contraction type primarily represents a situation where muscle fibers shorten and produce external work?
Which aspect is indirectly proportional to the threshold needed to activate muscle fibers?
Which aspect is indirectly proportional to the threshold needed to activate muscle fibers?
Which arrangement of fibers is typically associated with finer and more controlled movements?
Which arrangement of fibers is typically associated with finer and more controlled movements?
What does not occur during isometric contractions?
What does not occur during isometric contractions?
How does the tension relate to the contraction when the muscle fiber lengths are at an optimal state?
How does the tension relate to the contraction when the muscle fiber lengths are at an optimal state?
What effect does the muscle fiber diameter have on generated force?
What effect does the muscle fiber diameter have on generated force?
What is the primary function of axial muscles in the human body?
What is the primary function of axial muscles in the human body?
How are muscles classified based on their size?
How are muscles classified based on their size?
What percentage of skeletal muscles in the body are classified as appendicular muscles?
What percentage of skeletal muscles in the body are classified as appendicular muscles?
What are teres muscles characterized as?
What are teres muscles characterized as?
Which of the following describes the role of appendicular muscles?
Which of the following describes the role of appendicular muscles?
Which muscle is responsible for rotating the head and neck?
Which muscle is responsible for rotating the head and neck?
What is the primary action of the deltoid muscle?
What is the primary action of the deltoid muscle?
Which of the following muscles is involved in the extension of the leg at the knee?
Which of the following muscles is involved in the extension of the leg at the knee?
Which muscle group primarily facilitates shoulder abduction?
Which muscle group primarily facilitates shoulder abduction?
Which of the following muscles is located in the posterior compartment of the arm?
Which of the following muscles is located in the posterior compartment of the arm?
Which muscle assists in the flexion of the leg at the knee joint?
Which muscle assists in the flexion of the leg at the knee joint?
Which muscle is primarily responsible for dorsiflexing the foot?
Which muscle is primarily responsible for dorsiflexing the foot?
Which muscle is located in the lateral compartment of the thigh and assists in hip abduction?
Which muscle is located in the lateral compartment of the thigh and assists in hip abduction?
What do the terms indicating structural characteristics of a muscle often describe?
What do the terms indicating structural characteristics of a muscle often describe?
Which term is specifically used to indicate the muscle that raises a body part?
Which term is specifically used to indicate the muscle that raises a body part?
Which descriptive term would be appropriate for a muscle that moves away from the midline of the body?
Which descriptive term would be appropriate for a muscle that moves away from the midline of the body?
What does the prefix 'biceps' in muscle terminology indicate?
What does the prefix 'biceps' in muscle terminology indicate?
Which of the following terms describes the position of a muscle relative to the body's surface?
Which of the following terms describes the position of a muscle relative to the body's surface?
The term 'flexor' indicates which type of muscle action?
The term 'flexor' indicates which type of muscle action?
Which term identifies a muscle that performs the action of straightening a limb?
Which term identifies a muscle that performs the action of straightening a limb?
What does the term 'superficial' describe when referring to muscles?
What does the term 'superficial' describe when referring to muscles?
Which of the following muscle names indicates a circular muscle shape?
Which of the following muscle names indicates a circular muscle shape?
What unique characteristic is indicated by the term 'quadriceps' in muscle nomenclature?
What unique characteristic is indicated by the term 'quadriceps' in muscle nomenclature?
Which muscle is primarily responsible for elevating the shoulders?
Which muscle is primarily responsible for elevating the shoulders?
Which of the following muscles is not involved in the movement of the arm?
Which of the following muscles is not involved in the movement of the arm?
What is the primary function of the rectus abdominis muscle?
What is the primary function of the rectus abdominis muscle?
Which muscle is involved in breathing and separates the thoracic cavity from the abdominal cavity?
Which muscle is involved in breathing and separates the thoracic cavity from the abdominal cavity?
Which of the following muscles assists in flexing the forearm?
Which of the following muscles assists in flexing the forearm?
Which muscle is responsible for the abduction of the thigh?
Which muscle is responsible for the abduction of the thigh?
Which muscle is most associated with flexion of the knee?
Which muscle is most associated with flexion of the knee?
What role does the serratus anterior muscle play in shoulder movement?
What role does the serratus anterior muscle play in shoulder movement?
Which muscle is primarily responsible for extending the leg at the knee?
Which muscle is primarily responsible for extending the leg at the knee?
Which muscle acts to rotate the forearm medially?
Which muscle acts to rotate the forearm medially?
What is the primary characteristic of parallel muscles like the rectus abdominis?
What is the primary characteristic of parallel muscles like the rectus abdominis?
How much does a parallel muscle shorten when its fibers contract together?
How much does a parallel muscle shorten when its fibers contract together?
What factor is most crucial in determining the tension developed during a muscle contraction?
What factor is most crucial in determining the tension developed during a muscle contraction?
What is the impact of variations in muscle organization on movement?
What is the impact of variations in muscle organization on movement?
What is a key feature of muscle fibers in parallel arrangement?
What is a key feature of muscle fibers in parallel arrangement?
What happens to a 10 cm long parallel muscle when one end is held in place during contraction?
What happens to a 10 cm long parallel muscle when one end is held in place during contraction?
Which muscles serve as examples of parallel muscles?
Which muscles serve as examples of parallel muscles?
Which characteristic describes the gross anatomy of muscles?
Which characteristic describes the gross anatomy of muscles?
In terms of functional relationships, what should be noted about skeletal muscle fibers?
In terms of functional relationships, what should be noted about skeletal muscle fibers?
Which of the following factors does NOT affect the movement produced by muscle contractions?
Which of the following factors does NOT affect the movement produced by muscle contractions?
What is the primary action of the levator anguli oris?
What is the primary action of the levator anguli oris?
Which anatomical structure does the levator anguli oris originate from?
Which anatomical structure does the levator anguli oris originate from?
Which nerve innervates the levator anguli oris?
Which nerve innervates the levator anguli oris?
What is the insertion point for the levator anguli oris?
What is the insertion point for the levator anguli oris?
Which other muscle primarily works with the levator anguli oris to elevate parts of the mouth?
Which other muscle primarily works with the levator anguli oris to elevate parts of the mouth?
What is the arrangement of fascicles in a convergent muscle?
What is the arrangement of fascicles in a convergent muscle?
Which of the following is a characteristic of parallel muscles?
Which of the following is a characteristic of parallel muscles?
What is a primary functional difference between convergent muscles and parallel muscles?
What is a primary functional difference between convergent muscles and parallel muscles?
Which of the following statements about convergent muscles is true?
Which of the following statements about convergent muscles is true?
What occurs when the entire muscle of a convergent arrangement contracts?
What occurs when the entire muscle of a convergent arrangement contracts?
What type of attachment site can a convergent muscle pull on?
What type of attachment site can a convergent muscle pull on?
How does the arrangement of fascicles in muscles affect their function?
How does the arrangement of fascicles in muscles affect their function?
Which of the following muscles is an example of a convergent muscle?
Which of the following muscles is an example of a convergent muscle?
What is the primary function of the extensor carpi radialis longus muscle?
What is the primary function of the extensor carpi radialis longus muscle?
Which term describes muscles located entirely within an organ?
Which term describes muscles located entirely within an organ?
What does the name 'buccinator' primarily refer to in terms of muscle function?
What does the name 'buccinator' primarily refer to in terms of muscle function?
Which term indicates a muscle with fascicles that run parallel to the muscle's long axis?
Which term indicates a muscle with fascicles that run parallel to the muscle's long axis?
What is commonly suggested by the name 'risorius' muscle?
What is commonly suggested by the name 'risorius' muscle?
What distinguishing feature do rectus muscles share in terms of their anatomical structure?
What distinguishing feature do rectus muscles share in terms of their anatomical structure?
What is the primary action of the sartorius muscle?
What is the primary action of the sartorius muscle?
Which of the following terms refers to muscles that position or stabilize an organ?
Which of the following terms refers to muscles that position or stabilize an organ?
Which muscle name indicates its orientation as running across the body?
Which muscle name indicates its orientation as running across the body?
What type of muscle is described as serving a specific occupation or habit?
What type of muscle is described as serving a specific occupation or habit?
Which type of pennate muscle has fascicles on both sides of a central tendon?
Which type of pennate muscle has fascicles on both sides of a central tendon?
What arrangement of fascicles contributes to a muscle being classified as multipennate?
What arrangement of fascicles contributes to a muscle being classified as multipennate?
Which muscle is an example of a unipennate muscle?
Which muscle is an example of a unipennate muscle?
What is the function of circular muscles in the body?
What is the function of circular muscles in the body?
Which of the following muscles is bipennate?
Which of the following muscles is bipennate?
What occurs when a circular muscle contracts?
What occurs when a circular muscle contracts?
What is a key characteristic of a pennate muscle compared to a parallel muscle?
What is a key characteristic of a pennate muscle compared to a parallel muscle?
In the context of muscle anatomy, what does the term ‘fascicle’ refer to?
In the context of muscle anatomy, what does the term ‘fascicle’ refer to?
Which of the following describes the tension generation capabilities of pennate muscles?
Which of the following describes the tension generation capabilities of pennate muscles?
What is the primary role of the deltoid muscle in the context of fascicle arrangement?
What is the primary role of the deltoid muscle in the context of fascicle arrangement?
What is the primary function of the orbicularis oris muscle?
What is the primary function of the orbicularis oris muscle?
Which muscle is involved in moving food back across the teeth during chewing?
Which muscle is involved in moving food back across the teeth during chewing?
Which group of muscles is primarily responsible for facial expressions?
Which group of muscles is primarily responsible for facial expressions?
What action does the buccinator perform related to infant feeding?
What action does the buccinator perform related to infant feeding?
Which muscle group is primarily associated with movements of the eye, brows, and scalp?
Which muscle group is primarily associated with movements of the eye, brows, and scalp?
What is the role of the epicranium?
What is the role of the epicranium?
What type of movements are the axial muscles primarily involved in?
What type of movements are the axial muscles primarily involved in?
What is a key function of the buccinator muscle during chewing?
What is a key function of the buccinator muscle during chewing?
Which of the following statements correctly describes the function of facial muscles?
Which of the following statements correctly describes the function of facial muscles?
Which of the following is true about the groups of axial muscles?
Which of the following is true about the groups of axial muscles?
What does the term 'rectus' imply in muscle names such as rectus femoris?
What does the term 'rectus' imply in muscle names such as rectus femoris?
Which muscle name includes a reference to its origin and insertion?
Which muscle name includes a reference to its origin and insertion?
Which of the following is true about the naming of the biceps brachii?
Which of the following is true about the naming of the biceps brachii?
What characteristic is commonly included in the names of muscles?
What characteristic is commonly included in the names of muscles?
What does 'genioglossus' indicate about this muscle?
What does 'genioglossus' indicate about this muscle?
Which muscle is primarily involved in the abduction of the arm?
Which muscle is primarily involved in the abduction of the arm?
Which muscle group is considered part of the appendicular muscles?
Which muscle group is considered part of the appendicular muscles?
Which muscle is responsible for the flexion of the forearm?
Which muscle is responsible for the flexion of the forearm?
Which of the following muscles aids in lateral rotation of the arm?
Which of the following muscles aids in lateral rotation of the arm?
Which muscle is best known for its role in extending the knee?
Which muscle is best known for its role in extending the knee?
Which muscle is primarily responsible for knee flexion?
Which muscle is primarily responsible for knee flexion?
Which of the following muscles is involved in medial rotation of the arm?
Which of the following muscles is involved in medial rotation of the arm?
Which muscle helps in the stabilization of the shoulder joint?
Which muscle helps in the stabilization of the shoulder joint?
What characterizes a unipennate muscle?
What characterizes a unipennate muscle?
Which of the following muscles is an example of a bipennate muscle?
Which of the following muscles is an example of a bipennate muscle?
How do pennate muscles generate more tension compared to parallel muscles?
How do pennate muscles generate more tension compared to parallel muscles?
What is the function of circular muscles in the body?
What is the function of circular muscles in the body?
Which statement best describes a multipennate muscle?
Which statement best describes a multipennate muscle?
What type of muscle arrangement typically has the highest potential for force production?
What type of muscle arrangement typically has the highest potential for force production?
Which is NOT a characteristic of circular muscles?
Which is NOT a characteristic of circular muscles?
What structural feature distinguishes bipennate muscles from other types?
What structural feature distinguishes bipennate muscles from other types?
Which muscle type is characterized by fascicles concentrated on one side of a tendon?
Which muscle type is characterized by fascicles concentrated on one side of a tendon?
What term refers to muscles located in the arm region?
What term refers to muscles located in the arm region?
Which of the following terms indicates a muscle that is located towards the back of the body?
Which of the following terms indicates a muscle that is located towards the back of the body?
Which muscle term indicates a muscle that has three heads?
Which muscle term indicates a muscle that has three heads?
Which term describes a muscle that is located beneath another structure?
Which term describes a muscle that is located beneath another structure?
What does the term 'orbicularis' indicate about a muscle's shape?
What does the term 'orbicularis' indicate about a muscle's shape?
Which of the following muscles is specifically named for its location over the temporal bone of the skull?
Which of the following muscles is specifically named for its location over the temporal bone of the skull?
Which term signifies the action of moving a limb away from the midline of the body?
Which term signifies the action of moving a limb away from the midline of the body?
Which muscle type is indicated by the term 'latissimus'?
Which muscle type is indicated by the term 'latissimus'?
What descriptor is used for a muscle that runs straight along the body?
What descriptor is used for a muscle that runs straight along the body?
Which term refers to muscles that flex the limb toward the body?
Which term refers to muscles that flex the limb toward the body?
What happens to speed and distance traveled in a third-class lever compared to a second-class lever?
What happens to speed and distance traveled in a third-class lever compared to a second-class lever?
Which fascicle arrangement is likely found in a muscle that guards the anal opening?
Which fascicle arrangement is likely found in a muscle that guards the anal opening?
What is a characteristic of second-class levers in muscle function?
What is a characteristic of second-class levers in muscle function?
Why are skeletal muscles not effective in isolation?
Why are skeletal muscles not effective in isolation?
What is the primary trade-off when using a second-class lever?
What is the primary trade-off when using a second-class lever?
How do levers affect muscle efficiency?
How do levers affect muscle efficiency?
In which type of lever arrangement is the load positioned between the applied force and the fulcrum?
In which type of lever arrangement is the load positioned between the applied force and the fulcrum?
What defines the arrangement of forces in a third-class lever?
What defines the arrangement of forces in a third-class lever?
What is a common characteristic of third-class levers in the human body?
What is a common characteristic of third-class levers in the human body?
Which statement best describes the role of muscle connections to bones?
Which statement best describes the role of muscle connections to bones?
What is a benefit of understanding the arrangement of fascicles in muscles?
What is a benefit of understanding the arrangement of fascicles in muscles?
Which type of muscles is primarily associated with the axial skeleton?
Which type of muscles is primarily associated with the axial skeleton?
How do the appendicular muscles differ functionally from axial muscles?
How do the appendicular muscles differ functionally from axial muscles?
What can muscle names reveal about their characteristics?
What can muscle names reveal about their characteristics?
What is the significance of the origin and insertion of a muscle?
What is the significance of the origin and insertion of a muscle?
What role does exercise play in relation to the muscular system?
What role does exercise play in relation to the muscular system?
Which class of lever is most commonly found in the human body?
Which class of lever is most commonly found in the human body?
What is the difference between the upper and lower limb muscles?
What is the difference between the upper and lower limb muscles?
What is the primary action of the levator anguli oris muscle?
What is the primary action of the levator anguli oris muscle?
Where does the levator anguli oris originate?
Where does the levator anguli oris originate?
Which nerve innervates the levator anguli oris?
Which nerve innervates the levator anguli oris?
In addition to elevating the corner of the mouth, what is another function of the levator anguli oris?
In addition to elevating the corner of the mouth, what is another function of the levator anguli oris?
Which other muscle has a function that contrasts with that of the levator anguli oris?
Which other muscle has a function that contrasts with that of the levator anguli oris?
Which muscle is primarily responsible for shoulder abduction?
Which muscle is primarily responsible for shoulder abduction?
Which muscle helps in flexing the elbow?
Which muscle helps in flexing the elbow?
What is the primary function of the rectus abdominis?
What is the primary function of the rectus abdominis?
Which of the following muscles is involved in the movement of the thigh?
Which of the following muscles is involved in the movement of the thigh?
Which muscle acts primarily to extend the knee?
Which muscle acts primarily to extend the knee?
What is the function of the sternocleidomastoid muscle?
What is the function of the sternocleidomastoid muscle?
Which of the following muscles is NOT part of the rotator cuff?
Which of the following muscles is NOT part of the rotator cuff?
Which muscle is responsible for plantar flexion of the foot?
Which muscle is responsible for plantar flexion of the foot?
Which of the following muscles contributes to the movement of the arm toward the body?
Which of the following muscles contributes to the movement of the arm toward the body?
Which muscle is primarily responsible for the flexion of the wrist?
Which muscle is primarily responsible for the flexion of the wrist?
Which muscle is responsible for the rotation of the head and neck?
Which muscle is responsible for the rotation of the head and neck?
What is the primary function of the latissimus dorsi muscle?
What is the primary function of the latissimus dorsi muscle?
Which muscle assists in the flexion of the forearm at the elbow?
Which muscle assists in the flexion of the forearm at the elbow?
Which of the following muscles belongs to the appendicular group?
Which of the following muscles belongs to the appendicular group?
What is the main function of the gastrocnemius muscle?
What is the main function of the gastrocnemius muscle?
Which muscle is located on the posterior aspect of the upper limb?
Which muscle is located on the posterior aspect of the upper limb?
Which muscle is primarily responsible for adduction of the thigh?
Which muscle is primarily responsible for adduction of the thigh?
Which muscle primarily extends the leg at the knee?
Which muscle primarily extends the leg at the knee?
What is the function of the teres minor muscle?
What is the function of the teres minor muscle?
Which muscle contributes to the stabilization of the shoulder joint?
Which muscle contributes to the stabilization of the shoulder joint?
What action does the subscapularis muscle perform when it contracts?
What action does the subscapularis muscle perform when it contracts?
Where does the teres minor muscle cross in relation to the shoulder joint?
Where does the teres minor muscle cross in relation to the shoulder joint?
Which muscle is primarily responsible for lateral rotation of the shoulder?
Which muscle is primarily responsible for lateral rotation of the shoulder?
What is the naming basis for identifying muscles?
What is the naming basis for identifying muscles?
How many muscles are typically found in the human body?
How many muscles are typically found in the human body?
Which action does the subscapularis muscle NOT perform?
Which action does the subscapularis muscle NOT perform?
What aspect of the teres minor's action contributes to shoulder movement?
What aspect of the teres minor's action contributes to shoulder movement?
What factor does NOT influence the naming of a muscle?
What factor does NOT influence the naming of a muscle?
Which muscle is responsible for producing medial rotation at the shoulder joint?
Which muscle is responsible for producing medial rotation at the shoulder joint?
Which of the following statements is true regarding the teres minor?
Which of the following statements is true regarding the teres minor?
What term is used to describe a muscle that is found on the outside of the structure?
What term is used to describe a muscle that is found on the outside of the structure?
Which muscle name component indicates the number of heads it has?
Which muscle name component indicates the number of heads it has?
What does the term 'rectus' signify in muscle naming?
What does the term 'rectus' signify in muscle naming?
Which term indicates a muscle that is positioned toward the back of the body?
Which term indicates a muscle that is positioned toward the back of the body?
What does the term 'pectoralis' in muscle terminology reference?
What does the term 'pectoralis' in muscle terminology reference?
Which type of lever arrangement increases muscle efficiency by allowing a small force to move a larger weight?
Which type of lever arrangement increases muscle efficiency by allowing a small force to move a larger weight?
What is the effect of a second-class lever arrangement on speed and distance of movement?
What is the effect of a second-class lever arrangement on speed and distance of movement?
In a third-class lever, where is the applied force positioned in relation to the load and the fulcrum?
In a third-class lever, where is the applied force positioned in relation to the load and the fulcrum?
Which arrangement of muscle fibers provides a high range of motion at the expense of force?
Which arrangement of muscle fibers provides a high range of motion at the expense of force?
What characterizes the motion produced by skeletal muscles attached to bones?
What characterizes the motion produced by skeletal muscles attached to bones?
What is a key consequence of using a third-class lever system in the body?
What is a key consequence of using a third-class lever system in the body?
In the context of muscle action, what happens when a force moves the handle in a lever system?
In the context of muscle action, what happens when a force moves the handle in a lever system?
What type of lever would likely be used by a muscle guarding the anal opening?
What type of lever would likely be used by a muscle guarding the anal opening?
What defines an agonist muscle in relation to movement?
What defines an agonist muscle in relation to movement?
Which of the following muscles is described as an antagonist of the biceps brachii?
Which of the following muscles is described as an antagonist of the biceps brachii?
What is the primary action produced by the contraction of the subscapularis muscle?
What is the primary action produced by the contraction of the subscapularis muscle?
What is typically the point of origin for most muscles?
What is typically the point of origin for most muscles?
What term describes a muscle that produces flexion at the elbow?
What term describes a muscle that produces flexion at the elbow?
When the teres minor muscle contracts, what action does it primarily perform?
When the teres minor muscle contracts, what action does it primarily perform?
How does the presence of multiple origins affect muscle structure?
How does the presence of multiple origins affect muscle structure?
Where does the teres minor muscle cross in relation to the shoulder joint?
Where does the teres minor muscle cross in relation to the shoulder joint?
What role do antagonists play in muscle movement?
What role do antagonists play in muscle movement?
Which muscle is specifically identified as a medial rotator of the shoulder?
Which muscle is specifically identified as a medial rotator of the shoulder?
What defines a muscle's insertion point?
What defines a muscle's insertion point?
What characteristic is notably used in naming skeletal muscles?
What characteristic is notably used in naming skeletal muscles?
How many muscles are typically found in the human body?
How many muscles are typically found in the human body?
In muscle terminology, what does it mean if a muscle is described as having multiple origins?
In muscle terminology, what does it mean if a muscle is described as having multiple origins?
What is the primary function of the biceps brachii?
What is the primary function of the biceps brachii?
What region does the teres minor muscle primarily influence?
What region does the teres minor muscle primarily influence?
Which muscle crosses on the anterior side of the shoulder joint?
Which muscle crosses on the anterior side of the shoulder joint?
What is the relationship between agonists and antagonists during a muscle contraction?
What is the relationship between agonists and antagonists during a muscle contraction?
Which action does not occur when the teres minor contracts?
Which action does not occur when the teres minor contracts?
Which organizational feature is not commonly used to describe skeletal muscles?
Which organizational feature is not commonly used to describe skeletal muscles?
What is the arrangement of fascicles in a convergent muscle?
What is the arrangement of fascicles in a convergent muscle?
How do convergent muscles differ from parallel muscles in terms of force application?
How do convergent muscles differ from parallel muscles in terms of force application?
What is one advantage of convergent muscle arrangement?
What is one advantage of convergent muscle arrangement?
In a convergent muscle, how are muscle fibers arranged?
In a convergent muscle, how are muscle fibers arranged?
What is a potential disadvantage of convergent muscles compared to parallel muscles?
What is a potential disadvantage of convergent muscles compared to parallel muscles?
Which of the following is an example of a convergent muscle?
Which of the following is an example of a convergent muscle?
What characteristic helps distinguish convergent muscles from other muscle types?
What characteristic helps distinguish convergent muscles from other muscle types?
Why might a convergent muscle be preferable for certain activities?
Why might a convergent muscle be preferable for certain activities?
What type of connective tissue is often involved in the attachment of a convergent muscle?
What type of connective tissue is often involved in the attachment of a convergent muscle?
What defines the overall shape and function of convergent muscles?
What defines the overall shape and function of convergent muscles?
What does the name 'rectus femoris' indicate about the muscle?
What does the name 'rectus femoris' indicate about the muscle?
How does the origin and insertion naming convention work for muscles?
How does the origin and insertion naming convention work for muscles?
What distinctive feature is associated with the biceps brachii name?
What distinctive feature is associated with the biceps brachii name?
What does the term 'sartor' relate to in muscular terminology?
What does the term 'sartor' relate to in muscular terminology?
What can be inferred from the name 'flexor carpi radialis longus'?
What can be inferred from the name 'flexor carpi radialis longus'?
What is typically the origin point for most muscles?
What is typically the origin point for most muscles?
Which of the following describes the function of an antagonist muscle?
Which of the following describes the function of an antagonist muscle?
What role does the biceps brachii play during elbow flexion?
What role does the biceps brachii play during elbow flexion?
What defines a muscle with multiple origins and a single insertion?
What defines a muscle with multiple origins and a single insertion?
What defines a first-class lever in the human body?
What defines a first-class lever in the human body?
Which of the following pairs represents agonist and antagonist muscles?
Which of the following pairs represents agonist and antagonist muscles?
What occurs during a mechanical advantage situation?
What occurs during a mechanical advantage situation?
What structure is considered an origin for some muscles?
What structure is considered an origin for some muscles?
Which of the following is typically true about the origin of a muscle?
Which of the following is typically true about the origin of a muscle?
Which muscle produces extension at the elbow joint?
Which muscle produces extension at the elbow joint?
Which class of lever has the fulcrum located at one end with the applied force on the opposite side?
Which class of lever has the fulcrum located at one end with the applied force on the opposite side?
In biomechanical terms, what is referred to as a mechanical disadvantage?
In biomechanical terms, what is referred to as a mechanical disadvantage?
What do intermuscular septa represent?
What do intermuscular septa represent?
How do agonists and antagonists function in muscle movements?
How do agonists and antagonists function in muscle movements?
Which is a characteristic of the insertion of a muscle?
Which is a characteristic of the insertion of a muscle?
Which of the following statements about lever classification is accurate?
Which of the following statements about lever classification is accurate?
What is the relationship between the origin and insertion of a muscle?
What is the relationship between the origin and insertion of a muscle?
Which term is used to indicate a muscle located in the abdomen?
Which term is used to indicate a muscle located in the abdomen?
What does the term 'pectoralis' refer to in muscle terminology?
What does the term 'pectoralis' refer to in muscle terminology?
Which of the following terms indicates a muscle's position as located towards the front of the body?
Which of the following terms indicates a muscle's position as located towards the front of the body?
Which of the following terms indicates a muscle that originates with two heads?
Which of the following terms indicates a muscle that originates with two heads?
Which term is used to describe a muscle that is on the side of the body?
Which term is used to describe a muscle that is on the side of the body?
What does 'oblique' refer to regarding muscle arrangement?
What does 'oblique' refer to regarding muscle arrangement?
Which of the following describes a muscle that has a circular shape?
Which of the following describes a muscle that has a circular shape?
Which term indicates a muscle that is deeper in the body relative to other structures?
Which term indicates a muscle that is deeper in the body relative to other structures?
Which of the following actions is indicated by the term 'extensor'?
Which of the following actions is indicated by the term 'extensor'?
Which muscle name component refers to the number of heads it possesses?
Which muscle name component refers to the number of heads it possesses?
What is the key characteristic of a unipennate muscle?
What is the key characteristic of a unipennate muscle?
Which type of muscle is characterized by a converging pattern from multiple points to a single tendon?
Which type of muscle is characterized by a converging pattern from multiple points to a single tendon?
What is the primary function of circular muscles?
What is the primary function of circular muscles?
What distinguishes a multipennate muscle from other types of muscles?
What distinguishes a multipennate muscle from other types of muscles?
Which of the following is an example of a parallel muscle?
Which of the following is an example of a parallel muscle?
In what way do tendinous bands affect parallel muscles?
In what way do tendinous bands affect parallel muscles?
What is the characteristic feature of a bipennate muscle?
What is the characteristic feature of a bipennate muscle?
Which type of muscle is best described as having a long length with limited cross-sectional area?
Which type of muscle is best described as having a long length with limited cross-sectional area?
Which of the following is NOT a characteristic of pennate muscles?
Which of the following is NOT a characteristic of pennate muscles?
What is the primary advantage of the pennate arrangement of muscle fibers?
What is the primary advantage of the pennate arrangement of muscle fibers?
What term is used for muscles located entirely within an organ?
What term is used for muscles located entirely within an organ?
Which muscle is specifically known for compressing the cheeks?
Which muscle is specifically known for compressing the cheeks?
What is the primary function of the extensor carpi radialis longus?
What is the primary function of the extensor carpi radialis longus?
Which term describes the orientation of muscles that run at a slanting angle to the longitudinal axis of the body?
Which term describes the orientation of muscles that run at a slanting angle to the longitudinal axis of the body?
What does the term 'rectus' signify in muscle nomenclature?
What does the term 'rectus' signify in muscle nomenclature?
What is a lever in the context of the muscular and skeletal systems?
What is a lever in the context of the muscular and skeletal systems?
What is the role of muscles in the lever system of the body?
What is the role of muscles in the lever system of the body?
Which of the following changes can levers produce in the context of movement?
Which of the following changes can levers produce in the context of movement?
What is the significance of attaching muscles to levers in the body?
What is the significance of attaching muscles to levers in the body?
What is the fixed point on which a lever moves called?
What is the fixed point on which a lever moves called?
How do the origins and insertions of muscles influence their actions?
How do the origins and insertions of muscles influence their actions?
What is meant by the load in a lever-system context?
What is meant by the load in a lever-system context?
In which class of lever would the joint between the occipital bone of the skull and the first cervical vertebra (atlas) be classified?
In which class of lever would the joint between the occipital bone of the skull and the first cervical vertebra (atlas) be classified?
What did the nurse practitioner encourage Rick to try for improvement in his condition?
What did the nurse practitioner encourage Rick to try for improvement in his condition?
What sensation did Rick initially feel during his first yoga class?
What sensation did Rick initially feel during his first yoga class?
Which yoga pose was Rick preparing to attempt next?
Which yoga pose was Rick preparing to attempt next?
What was Rick’s improvement after practicing yoga for three months?
What was Rick’s improvement after practicing yoga for three months?
How many months after the initial class did the nurse practitioner suggest to return?
How many months after the initial class did the nurse practitioner suggest to return?
What was Rick's attitude toward practicing yoga as suggested by the nurse practitioner?
What was Rick's attitude toward practicing yoga as suggested by the nurse practitioner?
What specific yoga pose did Rick feel he might try after practicing other poses?
What specific yoga pose did Rick feel he might try after practicing other poses?
What role did the nurse practitioner play in Rick's yoga journey?
What role did the nurse practitioner play in Rick's yoga journey?
What was the reason for Rick to start attending yoga classes?
What was the reason for Rick to start attending yoga classes?
What kind of feedback did Rick receive about his yoga practice from the instructor?
What kind of feedback did Rick receive about his yoga practice from the instructor?
What is a characteristic of a first-class lever in the human body?
What is a characteristic of a first-class lever in the human body?
Where is the origin of a skeletal muscle typically located?
Where is the origin of a skeletal muscle typically located?
What happens during a contraction of a skeletal muscle?
What happens during a contraction of a skeletal muscle?
What defines mechanical advantage in the context of levers?
What defines mechanical advantage in the context of levers?
What is indicated by the positions L-F-AF in a lever?
What is indicated by the positions L-F-AF in a lever?
Which class of lever has the least number of examples in the human body?
Which class of lever has the least number of examples in the human body?
What is generally true about the insertion of a muscle?
What is generally true about the insertion of a muscle?
What does the term 'mechanical disadvantage' refer to?
What does the term 'mechanical disadvantage' refer to?
How are levers in the body categorized?
How are levers in the body categorized?
Which best describes the function of a lever in the human body?
Which best describes the function of a lever in the human body?
In a first-class lever, where is the fulcrum located in relation to the applied force and the load?
In a first-class lever, where is the fulcrum located in relation to the applied force and the load?
Which of the following is an example of a first-class lever?
Which of the following is an example of a first-class lever?
In a second-class lever, which component is positioned between the other two?
In a second-class lever, which component is positioned between the other two?
What role does the fulcrum play in a lever system?
What role does the fulcrum play in a lever system?
Which statement accurately describes the configuration of a second-class lever?
Which statement accurately describes the configuration of a second-class lever?
How does the position of the fulcrum influence the mechanical advantage of a lever?
How does the position of the fulcrum influence the mechanical advantage of a lever?
Which of the following could NOT be classified as a lever in human anatomy?
Which of the following could NOT be classified as a lever in human anatomy?
What is primarily used in the operation of a first-class lever?
What is primarily used in the operation of a first-class lever?
Which description would best illustrate the function of a pry bar?
Which description would best illustrate the function of a pry bar?
What key factor distinguishes first-class levers from second-class levers?
What key factor distinguishes first-class levers from second-class levers?
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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
- Action potential arrives at the neuromuscular junction, reaching the muscle fiber.
- Action potential travels along the sarcolemma, triggering release of calcium ions (Ca+2) from the sarcoplasmic reticulum (SR).
- Ca+2 initiates the interaction of myosin and actin, leading to muscle contraction.
- 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.
- Motor Unit: A motor neuron and all the muscle fibers it innervates.
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:
- Calcium Release: Calcium ions are released from the SR.
- Binding to Troponin: Calcium binds to Troponin C, causing a conformational change.
- Tropomyosin Movement: The conformational change in troponin moves tropomyosin away from the myosin binding sites on actin.
- Cross-Bridge Formation: Myosin heads bind to actin, forming cross-bridges.
- Power Stroke: Myosin heads pivot, pulling the actin filaments towards the center of the sarcomere.
- Detachment and Reattachment: Myosin detaches from actin and reattaches to a new binding site. This cycle repeats, pulling the actin filaments further.
- 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
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Question: In which of the following situations may temporal summation leading to tetany be occurring?
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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.
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Question: Which of the following might be true of Olympic medalist Hidilyn Diaz?
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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
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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.
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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
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The skeletal system's classification into axial and appendicular divisions helps categorize muscles.
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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.
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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.
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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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