Podcast
Questions and Answers
What primarily determines the number of motor units activated during muscle contraction?
What primarily determines the number of motor units activated during muscle contraction?
Which muscle fiber type has densely packed myofibrils and large glycogen reserves?
Which muscle fiber type has densely packed myofibrils and large glycogen reserves?
Slow muscle fibers are characterized by which of the following?
Slow muscle fibers are characterized by which of the following?
What contributes to the red appearance of slow twitch muscle fibers?
What contributes to the red appearance of slow twitch muscle fibers?
Signup and view all the answers
Slow muscle fibers primarily utilize which substrates for energy during contraction?
Slow muscle fibers primarily utilize which substrates for energy during contraction?
Signup and view all the answers
What type of muscle fibers are likely more prevalent in a very good sprinter?
What type of muscle fibers are likely more prevalent in a very good sprinter?
Signup and view all the answers
Most skeletal muscle fibers in the body are classified as which type based on contraction duration?
Most skeletal muscle fibers in the body are classified as which type based on contraction duration?
Signup and view all the answers
What is a characteristic feature of slow muscle fibers?
What is a characteristic feature of slow muscle fibers?
Signup and view all the answers
What aspect does the term 'flexor' in the flexor carpi radialis indicate?
What aspect does the term 'flexor' in the flexor carpi radialis indicate?
Signup and view all the answers
Which naming convention explains the term 'latissimus' in muscle anatomy?
Which naming convention explains the term 'latissimus' in muscle anatomy?
Signup and view all the answers
What does the name 'piriformis' indicate about the shape of the muscle?
What does the name 'piriformis' indicate about the shape of the muscle?
Signup and view all the answers
In muscle anatomy, which term best describes a muscle that is slender?
In muscle anatomy, which term best describes a muscle that is slender?
Signup and view all the answers
Where is the insertion of a muscle typically located in relation to its origin?
Where is the insertion of a muscle typically located in relation to its origin?
Signup and view all the answers
Which type of lever includes the load between the fulcrum and the applied force?
Which type of lever includes the load between the fulcrum and the applied force?
Signup and view all the answers
Which of the following is NOT a property of a lever?
Which of the following is NOT a property of a lever?
Signup and view all the answers
How does the term 'lateralis' differ from 'latissimus' in muscle classification?
How does the term 'lateralis' differ from 'latissimus' in muscle classification?
Signup and view all the answers
What is the primary function of T tubules in muscle contraction?
What is the primary function of T tubules in muscle contraction?
Signup and view all the answers
Which molecule assists in the exposure of active sites on thin filaments during muscle contraction?
Which molecule assists in the exposure of active sites on thin filaments during muscle contraction?
Signup and view all the answers
What leads to rigor mortis in muscles postmortem?
What leads to rigor mortis in muscles postmortem?
Signup and view all the answers
The sliding mechanism of myofilaments involves which of the following actions?
The sliding mechanism of myofilaments involves which of the following actions?
Signup and view all the answers
During muscle contraction, what happens to the I band?
During muscle contraction, what happens to the I band?
Signup and view all the answers
Which statement about the A band during contraction is true?
Which statement about the A band during contraction is true?
Signup and view all the answers
How does calcium influence muscle contraction?
How does calcium influence muscle contraction?
Signup and view all the answers
What role does acetylcholine play in muscle contraction?
What role does acetylcholine play in muscle contraction?
Signup and view all the answers
What components are part of the triad in muscle fibers?
What components are part of the triad in muscle fibers?
Signup and view all the answers
Which of the following correctly describes the sarcoplasmic reticulum?
Which of the following correctly describes the sarcoplasmic reticulum?
Signup and view all the answers
In a sarcomere, which region contains the M line, H band, and zone of overlap?
In a sarcomere, which region contains the M line, H band, and zone of overlap?
Signup and view all the answers
What is the primary structure that shortens during skeletal muscle contraction?
What is the primary structure that shortens during skeletal muscle contraction?
Signup and view all the answers
What causes delayed-onset muscle soreness related to muscle fibers?
What causes delayed-onset muscle soreness related to muscle fibers?
Signup and view all the answers
Which area has no actin filaments in a myofibril?
Which area has no actin filaments in a myofibril?
Signup and view all the answers
Which symptoms are typically associated with fibromyalgia?
Which symptoms are typically associated with fibromyalgia?
Signup and view all the answers
What is the primary cause of muscle fiber breakdown during muscular activity?
What is the primary cause of muscle fiber breakdown during muscular activity?
Signup and view all the answers
Which connective tissue layer surrounds the entire muscle?
Which connective tissue layer surrounds the entire muscle?
Signup and view all the answers
What is the function of perimysium in muscle tissue?
What is the function of perimysium in muscle tissue?
Signup and view all the answers
What connects a muscle to a bone?
What connects a muscle to a bone?
Signup and view all the answers
Which structure is the largest in diameter among the following?
Which structure is the largest in diameter among the following?
Signup and view all the answers
Actinin molecules are found at which of the following structures?
Actinin molecules are found at which of the following structures?
Signup and view all the answers
From what type of embryonic cells do skeletal muscle fibers develop?
From what type of embryonic cells do skeletal muscle fibers develop?
Signup and view all the answers
Why do skeletal muscle fibers contain multiple nuclei?
Why do skeletal muscle fibers contain multiple nuclei?
Signup and view all the answers
Which sequence correctly orders structures from smallest to largest?
Which sequence correctly orders structures from smallest to largest?
Signup and view all the answers
What is the muscle tone?
What is the muscle tone?
Signup and view all the answers
When all of the motor units of a muscle contract at the maximal rate of stimulation, it leads to the production of ________.
When all of the motor units of a muscle contract at the maximal rate of stimulation, it leads to the production of ________.
Signup and view all the answers
While wearing a cast due to a broken bone, muscles shrink due to the process of ________.
While wearing a cast due to a broken bone, muscles shrink due to the process of ________.
Signup and view all the answers
In muscles that have been repeatedly stimulated to produce near-maximal tension, the net effect is ________.
In muscles that have been repeatedly stimulated to produce near-maximal tension, the net effect is ________.
Signup and view all the answers
By varying the ________ at any one time, the nervous system provides precise control over the pull exerted by the muscle.
By varying the ________ at any one time, the nervous system provides precise control over the pull exerted by the muscle.
Signup and view all the answers
The muscle fiber type that contains densely packed myofibrils, large glycogen reserves, and relatively few mitochondria, is called ________.
The muscle fiber type that contains densely packed myofibrils, large glycogen reserves, and relatively few mitochondria, is called ________.
Signup and view all the answers
Slow muscle fibers ________.
Slow muscle fibers ________.
Signup and view all the answers
Slow twitch fibers appear red due to the intracellular storage of ________.
Slow twitch fibers appear red due to the intracellular storage of ________.
Signup and view all the answers
Slow fibers primarily use which of the following substrates for energy?
Slow fibers primarily use which of the following substrates for energy?
Signup and view all the answers
A very good sprinter is likely to have ________.
A very good sprinter is likely to have ________.
Signup and view all the answers
Most of the skeletal muscle fibers in the body are called ________ fibers, in reference to their duration of contraction following stimulation.
Most of the skeletal muscle fibers in the body are called ________ fibers, in reference to their duration of contraction following stimulation.
Signup and view all the answers
Slow muscle fibers contain large amounts of the oxygen-binding protein ________.
Slow muscle fibers contain large amounts of the oxygen-binding protein ________.
Signup and view all the answers
An intermediate fiber contracts fast, but it has more ________ and greater resistance to fatigue than a fast fiber.
An intermediate fiber contracts fast, but it has more ________ and greater resistance to fatigue than a fast fiber.
Signup and view all the answers
Two factors that are used to determine the classification of a skeletal muscle are ________.
Two factors that are used to determine the classification of a skeletal muscle are ________.
Signup and view all the answers
The most powerful muscle fiber arrangement, in which more tension is generated during contraction, is called ________.
The most powerful muscle fiber arrangement, in which more tension is generated during contraction, is called ________.
Signup and view all the answers
The muscles surrounding the entrances of the digestive and urinary tracts are classified as ________.
The muscles surrounding the entrances of the digestive and urinary tracts are classified as ________.
Signup and view all the answers
A bundle of muscle fibers within a skeletal muscle body is called a ________.
A bundle of muscle fibers within a skeletal muscle body is called a ________.
Signup and view all the answers
If a muscle has a tendon that branches within the muscle tissue, it is a ________.
If a muscle has a tendon that branches within the muscle tissue, it is a ________.
Signup and view all the answers
The biceps brachii is an example of a muscle with its fascicle oriented in a ________ fashion.
The biceps brachii is an example of a muscle with its fascicle oriented in a ________ fashion.
Signup and view all the answers
In a ________ muscle, the muscle fibers are based over a broad area, but all the fibers come together at a common attachment site.
In a ________ muscle, the muscle fibers are based over a broad area, but all the fibers come together at a common attachment site.
Signup and view all the answers
In the case of the triceps brachii, the shoulder is the ________; the olecranon is the ________.
In the case of the triceps brachii, the shoulder is the ________; the olecranon is the ________.
Signup and view all the answers
Regarding a typical muscle insertion, which of the following is true?
Regarding a typical muscle insertion, which of the following is true?
Signup and view all the answers
A muscle whose contraction is mostly responsible for a movement is said to be the ________ for that movement.
A muscle whose contraction is mostly responsible for a movement is said to be the ________ for that movement.
Signup and view all the answers
The triceps brachii and biceps brachii are good examples of ________.
The triceps brachii and biceps brachii are good examples of ________.
Signup and view all the answers
The adductor magnus muscle is so named, partially due to the ________.
The adductor magnus muscle is so named, partially due to the ________.
Signup and view all the answers
What does the term longissimus in a muscle name primarily indicate about that muscle?
What does the term longissimus in a muscle name primarily indicate about that muscle?
Signup and view all the answers
What does the name flexor carpi radialis most likely mean?
What does the name flexor carpi radialis most likely mean?
Signup and view all the answers
How does a muscle named lateralis differ from one named latissimus?
How does a muscle named lateralis differ from one named latissimus?
Signup and view all the answers
A word in a muscle name that indicates it is a pear-shaped muscle might be ________.
A word in a muscle name that indicates it is a pear-shaped muscle might be ________.
Signup and view all the answers
Which of the following words means slender?
Which of the following words means slender?
Signup and view all the answers
Typically, the insertion of a muscle is ________ to its origin.
Typically, the insertion of a muscle is ________ to its origin.
Signup and view all the answers
A lever in which the load is between the fulcrum and the applied force is a ________.
A lever in which the load is between the fulcrum and the applied force is a ________.
Signup and view all the answers
Which of the following is/are properties of a lever?
Which of the following is/are properties of a lever?
Signup and view all the answers
Flexion of the forearm at the elbow involves the use of the principle of (a) ________ lever(s).
Flexion of the forearm at the elbow involves the use of the principle of (a) ________ lever(s).
Signup and view all the answers
Aging skeletal muscles develop increasing amounts of ________.
Aging skeletal muscles develop increasing amounts of ________.
Signup and view all the answers
The M line is located at the end of a sarcomere.
The M line is located at the end of a sarcomere.
Signup and view all the answers
At the zone of overlap, each thin filament sits in a triangle formed by three thick filaments.
At the zone of overlap, each thin filament sits in a triangle formed by three thick filaments.
Signup and view all the answers
When viewed under polarized light, the dark staining bands are the A bands.
When viewed under polarized light, the dark staining bands are the A bands.
Signup and view all the answers
The Z line is comprised of thick filaments attached to interconnecting proteins, delineating the ends of the sarcomere.
The Z line is comprised of thick filaments attached to interconnecting proteins, delineating the ends of the sarcomere.
Signup and view all the answers
Light staining areas of a muscle fiber viewed under polarized light are called I bands.
Light staining areas of a muscle fiber viewed under polarized light are called I bands.
Signup and view all the answers
The expanded portion of the axonal branch that faces a region of the sarcolemma is called an axon terminal.
The expanded portion of the axonal branch that faces a region of the sarcolemma is called an axon terminal.
Signup and view all the answers
A space that separates the expanded tip of the axon at the neuromuscular synapse from the motor end plate is the synaptic vesicle.
A space that separates the expanded tip of the axon at the neuromuscular synapse from the motor end plate is the synaptic vesicle.
Signup and view all the answers
The sarcoplasmic reticulum conducts action potentials that spread across the sarcolemma into the cell.
The sarcoplasmic reticulum conducts action potentials that spread across the sarcolemma into the cell.
Signup and view all the answers
A muscle that opposes the action of a prime mover is a synergist.
A muscle that opposes the action of a prime mover is a synergist.
Signup and view all the answers
A muscle that assists a prime mover is an agonist.
A muscle that assists a prime mover is an agonist.
Signup and view all the answers
The fulcrum lies between the applied force and the resistance in a first-class lever.
The fulcrum lies between the applied force and the resistance in a first-class lever.
Signup and view all the answers
Which of the following is the type of muscle that pushes blood through the blood vessels of the cardiovascular system?
Which of the following is the type of muscle that pushes blood through the blood vessels of the cardiovascular system?
Signup and view all the answers
Smooth muscles are primarily used to ________.
Smooth muscles are primarily used to ________.
Signup and view all the answers
How many skeletal muscles are there in the muscular system?
How many skeletal muscles are there in the muscular system?
Signup and view all the answers
Which of the following features is NOT characteristic of muscle tissues?
Which of the following features is NOT characteristic of muscle tissues?
Signup and view all the answers
What characteristic of muscle tissue allows it to respond to stimulation by the nervous system?
What characteristic of muscle tissue allows it to respond to stimulation by the nervous system?
Signup and view all the answers
Which of the following is a function of skeletal muscle?
Which of the following is a function of skeletal muscle?
Signup and view all the answers
Why are skeletal muscles called voluntary?
Why are skeletal muscles called voluntary?
Signup and view all the answers
The layers of connective tissue surrounding a skeletal muscle from the inside to the outside in correct order are ________.
The layers of connective tissue surrounding a skeletal muscle from the inside to the outside in correct order are ________.
Signup and view all the answers
The epimysium, which separates the muscle from surrounding tissues and organs, is connected to the ________.
The epimysium, which separates the muscle from surrounding tissues and organs, is connected to the ________.
Signup and view all the answers
The connective tissue surrounding a fascicle is called ________.
The connective tissue surrounding a fascicle is called ________.
Signup and view all the answers
The attachment of a muscle to a bone is called ________.
The attachment of a muscle to a bone is called ________.
Signup and view all the answers
Which of these orders of functional muscle structures progresses from the smallest to largest in diameter?
Which of these orders of functional muscle structures progresses from the smallest to largest in diameter?
Signup and view all the answers
Actinin molecules form an open meshwork at the ________.
Actinin molecules form an open meshwork at the ________.
Signup and view all the answers
Skeletal muscle fibers arise from embryonic cells called ________.
Skeletal muscle fibers arise from embryonic cells called ________.
Signup and view all the answers
Why does a skeletal muscle fiber have more than one nucleus?
Why does a skeletal muscle fiber have more than one nucleus?
Signup and view all the answers
The complex known as the triad consists of ________.
The complex known as the triad consists of ________.
Signup and view all the answers
The sarcoplasmic reticulum is (the) ________.
The sarcoplasmic reticulum is (the) ________.
Signup and view all the answers
The portion of a sarcomere that contains the M line, H band and the zone of overlap is the ________.
The portion of a sarcomere that contains the M line, H band and the zone of overlap is the ________.
Signup and view all the answers
The structures within the muscle fiber that shorten to cause skeletal muscle fiber contraction are (the) ________.
The structures within the muscle fiber that shorten to cause skeletal muscle fiber contraction are (the) ________.
Signup and view all the answers
Delayed-onset muscle soreness is potentially caused by microscopic ruptures at the ________ of the sarcomeres.
Delayed-onset muscle soreness is potentially caused by microscopic ruptures at the ________ of the sarcomeres.
Signup and view all the answers
The area of a myofibril where there are no actin filaments is the ________.
The area of a myofibril where there are no actin filaments is the ________.
Signup and view all the answers
What symptoms accompany fibromyalgia?
What symptoms accompany fibromyalgia?
Signup and view all the answers
Tropomyosin and troponin are which of the following types of molecules?
Tropomyosin and troponin are which of the following types of molecules?
Signup and view all the answers
The ________ is a dense irregular connective tissue layer that surrounds the entire skeletal muscle.
The ________ is a dense irregular connective tissue layer that surrounds the entire skeletal muscle.
Signup and view all the answers
A skeletal muscle is divided into a series of internal compartments, each of which contains a bundle of muscle fibers called a ________.
A skeletal muscle is divided into a series of internal compartments, each of which contains a bundle of muscle fibers called a ________.
Signup and view all the answers
The connective tissue that surrounds each skeletal muscle fiber and binds each muscle fiber to its neighbor is the ________.
The connective tissue that surrounds each skeletal muscle fiber and binds each muscle fiber to its neighbor is the ________.
Signup and view all the answers
Between the endomysium and the muscle fibers lie a number of stem cells that aid in the repair of damaged muscle tissues. These are the ________ cells.
Between the endomysium and the muscle fibers lie a number of stem cells that aid in the repair of damaged muscle tissues. These are the ________ cells.
Signup and view all the answers
Thick (myosin) and thin (actin) filaments together form ________.
Thick (myosin) and thin (actin) filaments together form ________.
Signup and view all the answers
The smallest functional units of the muscle fibers are the ________.
The smallest functional units of the muscle fibers are the ________.
Signup and view all the answers
The sarcoplasmic reticulum stores ________.
The sarcoplasmic reticulum stores ________.
Signup and view all the answers
Which of the following ions is the trigger for a muscle contraction?
Which of the following ions is the trigger for a muscle contraction?
Signup and view all the answers
The function of T tubules is to ________.
The function of T tubules is to ________.
Signup and view all the answers
Troponin assists in controlling the interaction between myosin heads and thin filaments by ________.
Troponin assists in controlling the interaction between myosin heads and thin filaments by ________.
Signup and view all the answers
Which of the following molecules or ions are absent following death and leads to rigor mortis?
Which of the following molecules or ions are absent following death and leads to rigor mortis?
Signup and view all the answers
The sliding mechanism of myofilaments works when ________.
The sliding mechanism of myofilaments works when ________.
Signup and view all the answers
When contraction occurs, ________.
When contraction occurs, ________.
Signup and view all the answers
Regarding the effect of sarcomere length on tension production, a very highly stretched muscle (increased sarcomere length above normal 3.1 µm) will produce a contraction (% maximum tension) that is ________.
Regarding the effect of sarcomere length on tension production, a very highly stretched muscle (increased sarcomere length above normal 3.1 µm) will produce a contraction (% maximum tension) that is ________.
Signup and view all the answers
Each skeletal muscle fiber is controlled by a single ________.
Each skeletal muscle fiber is controlled by a single ________.
Signup and view all the answers
The motor neuron releases acetylcholine, which then binds to receptors sites on a special region of the sarcolemma called ________.
The motor neuron releases acetylcholine, which then binds to receptors sites on a special region of the sarcolemma called ________.
Signup and view all the answers
The neurotransmitter involved in the process of contraction in skeletal muscles is ________.
The neurotransmitter involved in the process of contraction in skeletal muscles is ________.
Signup and view all the answers
The enzyme that is partly responsible for shutting down a muscle contraction is ________.
The enzyme that is partly responsible for shutting down a muscle contraction is ________.
Signup and view all the answers
Which of the following events occurs in a muscle that is relaxing?
Which of the following events occurs in a muscle that is relaxing?
Signup and view all the answers
What is the significance of the change in membrane potential of the T tubules within the sarcolemma?
What is the significance of the change in membrane potential of the T tubules within the sarcolemma?
Signup and view all the answers
Which of the following events occurs first?
Which of the following events occurs first?
Signup and view all the answers
Skeletal muscle fiber contractions are caused by the interaction between the ________ and the ________ filaments of the sarcomeres.
Skeletal muscle fiber contractions are caused by the interaction between the ________ and the ________ filaments of the sarcomeres.
Signup and view all the answers
When acetylcholine binds to receptors on the motor end plate, ________ occurs immediately.
When acetylcholine binds to receptors on the motor end plate, ________ occurs immediately.
Signup and view all the answers
The steady increase in muscular tension produced by increasing the number of active motor units is called ________.
The steady increase in muscular tension produced by increasing the number of active motor units is called ________.
Signup and view all the answers
What type of muscular activity is present in a muscle at rest?
What type of muscular activity is present in a muscle at rest?
Signup and view all the answers
When one motor neuron fires a single action potential the result affects one ________.
When one motor neuron fires a single action potential the result affects one ________.
Signup and view all the answers
The number of cells per motor unit in the leg muscles can reach up to ________.
The number of cells per motor unit in the leg muscles can reach up to ________.
Signup and view all the answers
When a single motor neuron controls a greater number of muscle fibers in a motor unit, ________.
When a single motor neuron controls a greater number of muscle fibers in a motor unit, ________.
Signup and view all the answers
When a resting muscle contracts only enough to produce tension without movement, this is an example of ________.
When a resting muscle contracts only enough to produce tension without movement, this is an example of ________.
Signup and view all the answers
Study Notes
Muscle Structure
- Endomysium surrounds individual muscle fibers
- Perimysium surrounds groups of muscle fibers called fascicles
- Epimysium surrounds the entire muscle and connects to the deep fascia
- Tendon attaches muscle to bone
- Aponeurosis is a broad sheet of connective tissue that attaches muscle to bone or other tissues
- Muscle fiber is a single muscle cell
- Myofibril is a cylindrical bundle of protein filaments within a muscle fiber
- Sarcomere is the basic functional unit of a muscle fiber
- Z line anchors thin filaments
- M line anchors thick filaments
- A band is the entire length of the thick filament
- I band is the region where only thin filaments are present
- H band is the region where only thick filaments are present
Muscle Contraction
- Sarcoplasmic reticulum stores and releases calcium ions
- Transverse tubules (T tubules) carry electrical impulses deep into the muscle fiber
- Triad is a complex of one T tubule and two terminal cisternae of the sarcoplasmic reticulum
- Troponin binds calcium ions and controls the interaction between myosin and actin
- Tropomyosin covers the active sites on actin filaments
- Actin is a thin filament protein that binds to myosin
- Myosin is a thick filament protein that forms cross-bridges with actin
- Sliding filament theory explains how muscle fibers contract when thin filaments slide over thick filaments
- Rigor mortis occurs when ATP is depleted and the myosin heads remain bound to actin
Muscle Fiber Types
- Fast fibers are large, powerful, and fatigue quickly
- Slow fibers are small, fatigue resistant, and use aerobic metabolism
- Intermediate fibers have characteristics of both fast and slow fibers
Muscle Naming
- Lateralis means located on the side
- Latissimus means wide
- Piriformis means pear-shaped
- Gracilis means slender
Muscle Function
- Flexion is a decrease in the angle between two bones
- Extension is an increase in the angle between two bones
- Abduction is movement away from the midline
- Adduction is movement toward the midline
- Rotation is movement around a longitudinal axis
- Circumduction is a circular movement
Muscle Levers
- First-class lever has the fulcrum between the effort and the load
- Second-class lever has the load between the fulcrum and the effort
- Third-class lever has the effort between the fulcrum and the load
Muscular System: Skeletal Muscle Tissue and Muscle Organization
- Cardiac muscle is responsible for pushing blood through the circulatory system.
- Smooth muscle is primarily used for pushing fluids and solids through the digestive tract.
- The muscular system is comprised of over 700 skeletal muscles.
- Muscle tissue is characterized by excitability, contractility, extensibility, and elasticity.
- Muscle tissue responds to stimulation by nerve cells due to its excitability.
- Skeletal muscle functions include producing skeletal movement, maintaining posture, supporting soft tissues, and regulating body temperature.
- Skeletal muscles are considered voluntary because their contractions can be consciously controlled.
- The layers of connective tissue surrounding a skeletal muscle from the inside to the outside are: endomysium, perimysium, and epimysium.
- The epimysium connects to the deep fascia.
- Perimysium surrounds fascicles.
- The attachment of a muscle to bone is called a tendon or an aponeurosis.
- The order of structural components in a muscle, from smallest to largest, is myofibril, muscle fiber, fascicle, muscle.
- The Z line is where actinin molecules form an open meshwork.
- Skeletal muscle fibers develop from embryonic cells called myoblasts.
- Skeletal muscle fibers have multiple nuclei because groups of embryonic cells (myoblasts) fuse together during development.
- The triad consists of one transverse tubule and two terminal cisternae.
- The sarcoplasmic reticulum is a membrane complex in skeletal muscle similar to smooth endoplasmic reticulum.
- The A band of a sarcomere contains the M line, H band, and the zone of overlap.
- Myofibrils shorten to cause skeletal muscle fiber contraction.
- Delayed-onset muscle soreness may be caused by microscopic ruptures at the Z lines of sarcomeres.
- The H band of a sarcomere contains no actin filaments.
- Fibromyalgia symptoms include temporomandibular joint disorder, irritable bowel syndrome, anxiety, and tension headaches.
- Tropomyosin and troponin are regulatory proteins.
- The epimysium is a dense irregular connective tissue layer that surrounds the entire skeletal muscle.
- A fascicle is a bundle of muscle fibers within a skeletal muscle compartment.
- The endomysium surrounds each skeletal muscle fiber and binds fibers together.
- Myosatellite cells are stem cells that aid in the repair of damaged muscle tissues.
- Thick and thin filaments, together, form myofibrils.
- The smallest functional unit of a muscle fiber is the sarcomere.
- The sarcoplasmic reticulum stores calcium ions.
- Calcium ions trigger muscle contraction.
- T tubules help distribute the electrical impulse that causes the sarcoplasmic reticulum to release calcium ions.
- Troponin binds to calcium ions, leading to a change in the orientation of the troponin-tropomyosin complex.
- Rigor mortis occurs due to the lack of ATP following death.
- During muscle contraction, myosin heads bind to active sites on actin molecules.
- The sarcomere shortens during contraction, causing the following:
- A band remains constant.
- H band gets smaller.
- I band begins to disappear.
- Z lines move closer together.
- A highly stretched muscle (above 3.1 µm sarcomere length) produces only 20-40% maximum tension.
- Each skeletal muscle fiber is controlled by a single motor neuron.
- The motor end plate is a specialized region of the sarcolemma.
- Acetylcholine is the neurotransmitter involved in skeletal muscle contraction.
- Acetylcholinesterase helps to shut down muscle contractions.
- During muscle relaxation, acetylcholine is broken down by acetylcholinesterase.
- The change in the membrane potential of the T tubules causes the release of calcium ions from the sarcoplasmic reticulum.
- The following occur during a muscle contraction in sequence:
- Calcium ions are released from the sarcoplasmic reticulum.
- Calcium binds to troponin.
- Myosin cross-bridges attach to actin.
- The myosin head pivots toward the M line.
- The myosin head binds ATP and detaches from actin.
- Skeletal muscle contraction is caused by the interaction between the thin and thick filaments of the sarcomeres.
- Acetylcholine binding to receptors on the motor end plate causes an action potential.
- Recruitment is the steady increase in muscular tension produced by increasing the number of active motor units.
- Some activity in motor units causes slight, constant tension in a muscle at rest, known as muscle tone.
- A motor unit consists of one motor neuron and all the muscle fibers it controls.
- The number of muscle fibers in a single motor unit in leg muscles can reach thousands.
- A larger motor unit has less precise control.
- Contracting a muscle without movement is called muscle tone.
- Muscle hypertrophy occurs due to repeated stimulation resulting in near-maximal tension.
- Muscle atrophy occurs when muscles are not used and shrink.
- Muscle fibers contract more forcefully and rapidly when the number of activated motor units increases.
- Muscle fiber types:
- Fast fibers contain densely packed myofibrils, large glycogen reserves, and relatively few mitochondria.
- Slow fibers are specialized for aerobic respiration.
- Intermediate fibers have characteristics in between fast and slow fibers.
- Slow muscle fibers are:
- Red in color due to myoglobin content.
- Specialized for aerobic metabolism.
- Resistant to fatigue.
- Used for posture.
- Found in muscles that contract slowly but sustain contractions over long periods.
Skeletal Muscle Fiber Types
- Slow twitch fibers are supported by aerobic metabolism and can contract for a long period
- Slow twitch fibers are red due to the intracellular storage of myoglobin
- Slow twitch fibers use carbohydrates, lipids, and amino acids through the aerobic pathway for energy
- Fast twitch fibers are more common in the body
- Fast twitch fibers have less myoglobin compared to slow twitch fibers
- Intermediate fibers are fast-contracting but have more mitochondria and greater resistance to fatigue than fast twitch fibers
Skeletal Muscle Structure
- Skeletal muscle fibers can be arranged in different ways for various functions
- The most powerful arrangement is pennate, generating more tension during contraction
- Circular muscles surround body openings, such as the digestive and urinary tracts
- A muscle with a tendon that branches within the muscle tissue is a multipennate muscle
- Convergent muscles have fibers that converge at a common attachment site
Skeletal Muscle Function
- The origin of a muscle is the fixed or less movable end, while the insertion is the movable end
- Agonists are the prime movers for a specific motion, examples include biceps brachii and triceps brachii
- Antagonists oppose the action of the agonists
- Muscles are named based on their location, size, shape, fiber orientation, and actions
- The biceps brachii is a parallel muscle with two heads, and its name indicates its location and function
- The triceps brachii has three heads and its name indicates its location and function
- The adductor magnus is named for its size
- Words like "longissimus" indicate muscle length, "lateralis" indicates its side of the body, and "piriformis" indicates a pear-shaped muscle
Lever Systems
- A first-class lever has the fulcrum in between the load (resistance) and applied force
- A second-class lever has the load in between the fulcrum and the applied force
- A third-class lever has the applied force in between the fulcrum and the load
Skeletal Muscle Aging and Performance
- As muscles age, they develop increasing amounts of fibrous connective tissue, leading to decreased muscle mass and flexibility.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
This quiz covers essential concepts related to muscle structure and the mechanisms of muscle contraction. It includes key terms like endomysium, sarcomere, and the roles of different muscle components. Test your understanding of how muscles function and their structural organization.
