Muscle Tissue Characteristics Quiz

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Questions and Answers

Which of the following is NOT a universal characteristic of muscle tissue?

Digestion (correct)

Excitability

Contractility

Conductivity

Skeletal muscle is involuntary and striated.

False (B)

What is the name for a muscle cell?

Muscle fiber or myofiber

The connective tissue layer surrounding muscle tissue is continuous with the ______ of tendons.

collagen fibers Signup and view all the answers

Match the following muscle characteristics with their descriptions:

Excitability = Ability to shorten when stimulated Conductivity = Ability to return to its original length after being stretched Contractility = Ability to be stretched Extensibility = Ability to respond to stimuli, such as chemical signals or electrical changes Elasticity = Ability to transmit electrical impulses along the muscle fiber Signup and view all the answers

What is the primary function of tendons in skeletal muscle?

To attach muscle to bone (C) Signup and view all the answers

What are the two main reasons for the striated appearance of skeletal muscle?

Alternating light and dark bands due to the arrangement of actin and myosin filaments. Signup and view all the answers

The elasticity of collagen fibers in tendons helps prevent muscle injury by resisting excessive stretching.

True (A) Signup and view all the answers

What is the outermost layer of connective tissue surrounding a muscle called?

Epimysium (B) Signup and view all the answers

Muscle fibers are individual cells that are elongated and slender.

True (A) Signup and view all the answers

What is the function of the sarcoplasmic reticulum in a muscle fiber?

The sarcoplasmic reticulum stores and releases calcium ions, which are essential for muscle contraction. Signup and view all the answers

A bundle of muscle fibers within a muscle is called a ______.

fascicle Signup and view all the answers

Match the following structural components of a skeletal muscle with their descriptions:

Fascicle = A single muscle cell, containing myofibrils and multiple nuclei Muscle fiber = A bundle of muscle fibers surrounded by perimysium Endomysium = A thin fibrous sleeve surrounding a muscle fiber Epimysium = A fibrous sheath surrounding the entire muscle, separating it from neighboring muscles Signup and view all the answers

The functional, contractile unit of the muscle fibre is called a ______.

sarcomere Signup and view all the answers

Myofilaments are composed of only one type of protein.

False (B) Signup and view all the answers

Which of the following is NOT a characteristic of a sarcomere?

It is composed of hundreds of myofibrils end to end. (A) Signup and view all the answers

What are the two main types of myofilaments and their respective protein compositions?

Thick filaments are mainly composed of myosin, while thin filaments are mainly composed of actin. Signup and view all the answers

Match the following structural components of a muscle fiber with their descriptions:

Sarcomere = The functional, contractile unit of the muscle fiber. Myofilaments = Fibrous protein strands that carry out the contraction process. Sarcoplasmic reticulum = A network of membranes that stores and releases calcium ions, essential for muscle contraction. Mitochondria = Organelles responsible for providing energy (ATP) for muscle contraction. Signup and view all the answers

Which of the following is NOT a characteristic feature of skeletal muscle cells?

Presence of a single, centrally located nucleus (A) Signup and view all the answers

Myoglobin, a red pigment found in muscle fibers, helps store and transport oxygen needed for muscle activity.

True (A) Signup and view all the answers

What are satellite cells and what is their role in muscle tissue?

Satellite cells are unspecialized myoblasts located between the muscle fiber and the endomysium. They play a crucial role in regeneration of damaged skeletal muscle tissue by differentiating into new muscle fibers. Signup and view all the answers

The ______ is a network of smooth ER that surrounds each myofibril in a muscle fiber.

sarcoplasmic reticulum Signup and view all the answers

Match the following structures with their descriptions:

Sarcolemma = The plasma membrane of a muscle fiber. T tubules = Tubular infoldings of the sarcolemma that penetrate the muscle fiber. Terminal cisterns = Dilated end-sacs of the SR that cross the muscle fiber. Triad = A T tubule and two terminal cisterns associated with it. Signup and view all the answers

Which of the following statements is TRUE about sarcomeres?

All of the above (D) Signup and view all the answers

What is the function of the M line in a sarcomere?

The M line is a protein structure that connects neighboring thick filaments in the center of the sarcomere. Signup and view all the answers

The ______ is the region of a sarcomere that contains only thick filaments.

H band Signup and view all the answers

Tropomyosin is a protein that binds to actin and blocks the active sites on G actin subunits.

True (A) Signup and view all the answers

What is the function of dystrophin in muscle fibers?

Dystrophin is a protein that links actin in the outermost myofilaments to membrane proteins that connect to the endomysium. It transfers the forces of muscle contraction to the connective tissue, ultimately leading to the tendon. Signup and view all the answers

Which of the following structures shortens during skeletal muscle contraction?

Sarcomeres (A), I bands (B), H bands (D) Signup and view all the answers

The width of the A band remains constant during skeletal muscle contraction.

True (A) Signup and view all the answers

What protein links the thin filaments to the sarcolemma and helps transfer muscle tension to the extracellular tissue?

Dystrophin Signup and view all the answers

A single motor neuron and all the muscle fibers it innervates are collectively called a ______.

motor unit Signup and view all the answers

Which of the following is NOT a feature of a small motor unit?

Found in muscles responsible for powerful contractions (B) Signup and view all the answers

The neuromuscular junction is a synapse where a nerve fiber meets a target cell.

True (A) Signup and view all the answers

What is the name of the neurotransmitter released at the neuromuscular junction?

Acetylcholine (ACh) Signup and view all the answers

The ______ of the sarcolemma beneath the axon terminal increase surface area for ACh receptors.

junctional folds Signup and view all the answers

Which of the following enzymes breaks down ACh in the synaptic cleft?

Acetylcholinesterase (B) Signup and view all the answers

Muscle fibers and neurons are electrically excitable cells, meaning they can generate action potentials.

True (A) Signup and view all the answers

What is the resting membrane potential (RMP) of a skeletal muscle cell?

Approximately -90 mV Signup and view all the answers

The influx of ______ ions into the cell during depolarization makes the inside of the plasma membrane positive.

sodium (Na+) Signup and view all the answers

Which of the following occurs during repolarization?

Potassium gates open (A) Signup and view all the answers

An action potential is a quick event that travels down the length of a cell membrane as a wave of excitation.

True (A) Signup and view all the answers

Match the following toxins with their effects on neuromuscular function:

Cholinesterase inhibitors = Spastic paralysis due to continuous muscle contraction Tetanus toxin = Spastic paralysis due to blocking glycine release Botulism toxin = Flaccid paralysis due to blocking ACh release Signup and view all the answers

What is the process called where nerve action potentials lead to muscle action potentials?

Excitation (A) Signup and view all the answers

The events that link action potentials on the sarcolemma to the activation of myofilaments are known as contraction.

False (B) Signup and view all the answers

What is the name of the process that involves the muscle fiber developing tension and potentially shortening?

Contraction Signup and view all the answers

When stimulation ends, the muscle fiber ______ and returns to its resting length.

relaxes Signup and view all the answers

Which of the following is NOT a stage involved in the excitation of a muscle fiber?

Formation of cross-bridges between actin and myosin (D) Signup and view all the answers

Calcium ions bind to troponin, causing it to change shape and move tropomyosin away from the active sites on thin filaments.

True (A) Signup and view all the answers

What is the name of the structure that releases calcium ions into the sarcoplasm during muscle contraction?

Sarcoplasmic reticulum Signup and view all the answers

The ______ heads bind to the active sites on F-actin, forming cross-bridges and initiating the contraction cycle.

myosin Signup and view all the answers

Match the following events with the corresponding stage of the excitation-contraction coupling process:

Action potential arrives at the neuromuscular junction = Excitation Acetylcholine is released from the synaptic terminal = Excitation Acetylcholine binds to receptors on the sarcolemma = Excitation Action potential spreads along the sarcolemma and down the T tubules = Excitation-contraction coupling Calcium ions are released from the sarcoplasmic reticulum = Excitation-contraction coupling Calcium ions bind to troponin = Excitation-contraction coupling Tropomyosin moves away from the active sites on thin filaments = Excitation-contraction coupling Signup and view all the answers

The power stroke, where the myosin head pivots towards the M line, requires energy from ATP.

True (A) Signup and view all the answers

What is the term for the stiffening of muscles and body that happens after death?

Rigor mortis Signup and view all the answers

The minimum voltage necessary to generate an action potential in a muscle fiber and produce contraction is called the ______.

threshold Signup and view all the answers

What is the term for a single contraction and relaxation cycle in response to a single stimulus?

Twitch (D) Signup and view all the answers

Increasing the frequency of stimulus delivery can increase the tension output of a muscle.

True (A) Signup and view all the answers

Explain what happens in wave summation.

Wave summation occurs when multiple stimuli arrive before the relaxation phase of the previous twitch has ended, resulting in a stronger contraction because the contractions are summed together. Signup and view all the answers

The phenomenon where muscle tension increases with successive stimulations, even if the same voltage is delivered, is called ______.

treppe Signup and view all the answers

Study Notes

Muscle Physiology Lecture Notes

Muscle physiology lecture covers skeletal muscle.
Learning outcomes include listing skeletal muscle characteristics, describing muscle fiber structures, identifying and explaining the functions of major muscle proteins, explaining stimulation and contraction processes in skeletal muscle fibers, and describing muscle twitch stages.
Universal characteristics of muscle include excitability (responding to stimuli), conductivity (transmitting electrical signals), contractility (shortening), extensibility (stretching), and elasticity (returning to resting length).
Skeletal muscle is attached to bone by tendons via a continuous external connective tissue layer. Contractions cause movement at joints. Collagen is extensible and elastic, stretching under tension and recoiling. It resists overstretching and protects muscle from injury, returning the muscle to its resting length. It contributes to power output and muscle efficiency.
Skeletal muscle is voluntary and striated.
Voluntary - under conscious control.
Striated - alternating light & dark bands due to internal contractile proteins.
A muscle cell is a muscle fiber (myofibre) up to 30 cm in length.
A muscle fiber has many nuclei, mitochondria positioned between myofibrils, glycogen (carbohydrate energy storage), and myoglobin (red pigment for oxygen delivery).

Structural Hierarchy of Skeletal Muscle

A muscle is a contractile organ composed of bundles of muscle fibers (fascicles).
Each fascicle is a bundle of muscle fibers enclosed by perimysium.
A muscle fiber is a single muscle cell, elongated enclosed in a specialized plasma membrane (sarcolemma). It contains bundles of myofibrils.
Myofibrils contain myofilaments – thin filaments (actin) and thick filaments (myosin). Interactions of thick and thin filaments lead to muscle contraction.
Myofibrils are organized into repeating functional units called sarcomeres.

Myofilaments

Myofilaments are the protein filaments found within myofibrils.
Actin, arranged in thin filaments:
- fibrous (F) actin: two intertwined strands
- globular (G) actin subunits with active sites for myosin binding.
- tropomyosin - an actin-binding protein that blocks active sites on G actin
- troponin - calcium-binding protein on tropomyosin.
Myosin, arranged in thick filaments:
- Two headed club-shaped myosin molecules.
- A myosin molecule has a tail and globular head.
- Heads are arranged in a helix around the myosin bundle.
Dystrophin: important protein linking actin in myofilaments to endomysium, transfers contractile force to connective tissue. Defects can cause muscular dystrophy.
Titin or connectin: large protein, runs through myosin filament, stabilizing and positioning the thick filament. Prevents overstretching. Prevents overstretching and provides recoil).

Sarcomeres: Contractile Units

Sarcomeres are repeating subunits within myofibrils.
Sarcomere sections are demarcated by Z lines.
Thick filaments are found in the A band, with the M line in the center.
Thin filaments, called I bands, are on both sides of the A band.
The H band contains only thick filaments.
The zone of overlap is where thin and thick filaments overlap

The Neuromuscular Junction

Synapse: where a nerve fiber meets a target cell, or in a motor neuron meeting a muscle fiber.
Neuromuscular junction (NMJ): the synapse where a motor neuron stimulates a muscle fiber.
Acetylcholine (ACh): neurotransmitter releases at the NMJ, stimulating muscle contraction.
The NMJ includes terminal branches of nerve fibers, synaptic cleft, and acetylcholine receptors.
The axon terminal has synaptic vesicles containing ACh.
Basal lamina - thin layer of collagen and glycoproteins separating nerve and muscle tissue.

Electrically Excitable Cells

Muscle fibers and neurons are electrically excitable.
Membrane voltage changes in response to stimulation
Voltage or electrical potential: difference in electrical charge between points.
Resting membrane potential: ± -90 mV in skeletal muscles.
Maintained by sodium-potassium pump.

Excitation-Contraction Coupling

Action potential travels along the T tubules.
Calcium released from terminal cisterns of the sarcoplasmic reticulum.
Calcium binds to troponin, causing tropomyosin to move, revealing active sites on actin.

Contraction Cycle

Energized myosin heads bind to active sites on F-actin.
Myosin head pivots toward the M line (power stroke).
ATP binds to myosin and breaks the link to actin.
Active site exposed again ready for new cycle/cross-bridge.
Myosin head pivots toward the M line, pulling the actin filament.

Muscle Relaxation

Cessation of nervous stimulation
ACh breakdown by acetylcholinesterase (AChE).
Calcium ions are reabsorbed into the sarcoplasmic reticulum.
Tropomyosin returns to its blocking position, actin and myosin detach.

The Length-Tension Relationship

Amount of tension generated depends on how stretched or shortened the muscle was before stimulation.
Optimal resting length produces the greatest force during contraction.
Nervous system maintains resting muscle tone near optimal length.

Rigor Mortis

Happens after death.
Deterioration of sarcoplasmic reticulum releases calcium ions.
Muscle activation leads to contraction but unable to relax.

Threshold, Latent Period, and Twitch

Threshold: minimum voltage necessary to generate an action potential in muscle cells for contraction.
Twitch: single contraction-relaxation cycle.
Latent period: delay between stimulation and contraction (excitation, excitation-contraction coupling, and tensing).
Contraction phase: tension generation.
Relaxation phase: tension declines (calcium reabsorption).
Contraction strength of twitches varies due to: muscle starting length, fatigue, temperature, and hydration.

Stimulation of Muscle

Treppe: increase in tension in successive stimuli.
Wave summation: increased tension with successive stimuli.
Incomplete tetanus: only partial relaxation between stimuli.
Complete tetanus: no relaxation between stimuli, maximum tension.

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Test your knowledge on the characteristics and functions of muscle tissue with this comprehensive quiz. You will explore topics such as muscle fibers, tendons, and connective tissue. Answers to questions about muscle structure and function await you!

Muscle Tissue Characteristics Quiz

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Questions and Answers

Which of the following is NOT a universal characteristic of muscle tissue?

Skeletal muscle is involuntary and striated.

What is the name for a muscle cell?

The connective tissue layer surrounding muscle tissue is continuous with the ______ of tendons.

Match the following muscle characteristics with their descriptions:

What is the primary function of tendons in skeletal muscle?

What are the two main reasons for the striated appearance of skeletal muscle?

The elasticity of collagen fibers in tendons helps prevent muscle injury by resisting excessive stretching.

What is the outermost layer of connective tissue surrounding a muscle called?

Muscle fibers are individual cells that are elongated and slender.

What is the function of the sarcoplasmic reticulum in a muscle fiber?

A bundle of muscle fibers within a muscle is called a ______.

Match the following structural components of a skeletal muscle with their descriptions:

The functional, contractile unit of the muscle fibre is called a ______.

Myofilaments are composed of only one type of protein.

Which of the following is NOT a characteristic of a sarcomere?

What are the two main types of myofilaments and their respective protein compositions?

Match the following structural components of a muscle fiber with their descriptions:

Which of the following is NOT a characteristic feature of skeletal muscle cells?

Myoglobin, a red pigment found in muscle fibers, helps store and transport oxygen needed for muscle activity.

What are satellite cells and what is their role in muscle tissue?

The ______ is a network of smooth ER that surrounds each myofibril in a muscle fiber.

Match the following structures with their descriptions:

Which of the following statements is TRUE about sarcomeres?

What is the function of the M line in a sarcomere?

The ______ is the region of a sarcomere that contains only thick filaments.

Tropomyosin is a protein that binds to actin and blocks the active sites on G actin subunits.

What is the function of dystrophin in muscle fibers?

Which of the following structures shortens during skeletal muscle contraction?

The width of the A band remains constant during skeletal muscle contraction.

What protein links the thin filaments to the sarcolemma and helps transfer muscle tension to the extracellular tissue?

A single motor neuron and all the muscle fibers it innervates are collectively called a ______.

Which of the following is NOT a feature of a small motor unit?

The neuromuscular junction is a synapse where a nerve fiber meets a target cell.

What is the name of the neurotransmitter released at the neuromuscular junction?

The ______ of the sarcolemma beneath the axon terminal increase surface area for ACh receptors.

Which of the following enzymes breaks down ACh in the synaptic cleft?

Muscle fibers and neurons are electrically excitable cells, meaning they can generate action potentials.

What is the resting membrane potential (RMP) of a skeletal muscle cell?

The influx of ______ ions into the cell during depolarization makes the inside of the plasma membrane positive.

Which of the following occurs during repolarization?

An action potential is a quick event that travels down the length of a cell membrane as a wave of excitation.

Match the following toxins with their effects on neuromuscular function:

What is the process called where nerve action potentials lead to muscle action potentials?

The events that link action potentials on the sarcolemma to the activation of myofilaments are known as contraction.

What is the name of the process that involves the muscle fiber developing tension and potentially shortening?

When stimulation ends, the muscle fiber ______ and returns to its resting length.

Which of the following is NOT a stage involved in the excitation of a muscle fiber?

Calcium ions bind to troponin, causing it to change shape and move tropomyosin away from the active sites on thin filaments.

What is the name of the structure that releases calcium ions into the sarcoplasm during muscle contraction?

The ______ heads bind to the active sites on F-actin, forming cross-bridges and initiating the contraction cycle.

Match the following events with the corresponding stage of the excitation-contraction coupling process:

The power stroke, where the myosin head pivots towards the M line, requires energy from ATP.

What is the term for the stiffening of muscles and body that happens after death?

The minimum voltage necessary to generate an action potential in a muscle fiber and produce contraction is called the ______.

What is the term for a single contraction and relaxation cycle in response to a single stimulus?

Increasing the frequency of stimulus delivery can increase the tension output of a muscle.

Explain what happens in wave summation.

The phenomenon where muscle tension increases with successive stimulations, even if the same voltage is delivered, is called ______.

Study Notes

Muscle Physiology Lecture Notes

Structural Hierarchy of Skeletal Muscle

Myofilaments

Sarcomeres: Contractile Units

The Neuromuscular Junction

Electrically Excitable Cells

Excitation-Contraction Coupling

Contraction Cycle

Muscle Relaxation

The Length-Tension Relationship

Rigor Mortis

Threshold, Latent Period, and Twitch

Stimulation of Muscle

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