Muscle Functions Quiz

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Questions and Answers

Which of the following is NOT a function of muscles?

Storage of energy (correct)

Heat production

Protecting bones and internal organs

Movement

What characteristic allows muscle cells to respond to stimuli?

Excitability (correct)

Elasticity

Contractility

Extensibility

Which connective tissue layer surrounds a muscle fiber?

Endomysium (correct)

Perimysium

Epimysium

Sarcoplasm

What are the smallest contractile elements of a muscle unit?

Myofilaments Signup and view all the answers

Which term describes the functional unit of a muscle?

Sarcomere Signup and view all the answers

Which type of muscle is under voluntary control?

Skeletal muscle Signup and view all the answers

How do muscle fascicles contribute to the overall structure of skeletal muscle?

They hold muscle fibers together. Signup and view all the answers

What is the function of the sarcoplasmic reticulum in muscle cells?

Store calcium ions Signup and view all the answers

What is the primary source of ATP in the first 1-2 seconds of muscle contraction?

Creatine phosphate Signup and view all the answers

What process follows the breakdown of glucose into pyruvate during explosive power generation?

Krebs cycle Signup and view all the answers

How does the nervous system increase muscle contraction strength?

By stimulating additional motor units Signup and view all the answers

What characteristic is associated with small motor units?

They enable precise movements. Signup and view all the answers

What happens to muscle tension during repeated stimulation, leading to reduced performance?

Muscle fatigue occurs. Signup and view all the answers

Which factor does NOT affect muscle contraction strength?

The amount of oxygen available Signup and view all the answers

What is the motor unit size dependent on?

The number of muscle fibers it stimulates Signup and view all the answers

What happens to the rate of shortening and relaxation in fatigued muscle?

Both decrease. Signup and view all the answers

What is the primary function of tropomyosin in muscle contraction?

To cover the active binding sites on actin Signup and view all the answers

Which components are essential to form a triad in skeletal muscle?

1 T tubule and 2 Terminal Cisternae Signup and view all the answers

Which protein connects myosin to the Z line and prevents excessive stretching of the sarcomere?

Titin Signup and view all the answers

What role does dystrophin serve in muscle fibers?

Creating intracellular stability Signup and view all the answers

Which type of muscle protein is specifically responsible for linking actin to the Z line?

α-Actinin Signup and view all the answers

The region in a sarcomere that consists solely of thick myofilaments is known as the:

H zone Signup and view all the answers

What occurs when an action potential reaches the triad in skeletal muscle?

Calcium ions flow out of the sarcoplasmic reticulum Signup and view all the answers

What role does calcium play in muscle contraction?

It binds to troponin to initiate contraction. Signup and view all the answers

Which of the following statements about ATP usage in muscle contraction is true?

ATP is required to pump calcium back into the sarcoplasmic reticulum. Signup and view all the answers

What initiates the power stroke during muscle contraction?

The breakdown of ATP into ADP and phosphate. Signup and view all the answers

Which process occurs first during muscle relaxation?

Reuptake of calcium ions by the sarcoplasmic reticulum. Signup and view all the answers

What happens to the tropomyosin during the contraction cycle?

It undergoes a conformational change to expose actin's active sites. Signup and view all the answers

What is the primary function of acetylcholinesterase during muscle contraction?

To degrade acetylcholine in the synaptic cleft. Signup and view all the answers

How does the muscle fiber return to its resting length after contraction?

Through muscle elasticity and cross-bridge separation. Signup and view all the answers

What energy source is utilized immediately before ATP in muscle contraction?

Stored creatine phosphate. Signup and view all the answers

Study Notes

Skeletal Muscle Contraction

Skeletal muscles are responsible for movement, posture maintenance, and heat production.
Muscles protect bones and internal organs.
Key features of muscle cells include excitability (responding to stimuli), contractility (shortening and thickening to generate force), extensibility (extending without damage), and elasticity (returning to original shape).

Muscle Types

Skeletal muscle: Fibers are striated, tubular, and multinucleated. Voluntary.
Smooth muscle: Fibers are non-striated, spindle-shaped, and uninucleated. Involuntary.
Cardiac muscle: Fibers are striated, branched, and uninucleated. Involuntary.

Skeletal Muscle Structure

Organization: Actin (thin) and myosin (thick) filaments are the smallest contractile units, forming myofilaments. Myofilaments combine to form myofibrils, which in turn make up muscle fibers. Muscle fibers come together to form fascicles, ultimately creating skeletal muscle.
Connective tissue layers: Endomysium (surrounds individual muscle fibers), perimysium (surrounds fascicles), epimysium (surrounds entire muscle).
Sarcolemma: The membrane surrounding the muscle fiber,
Sarcoplasm: The cytoplasm of the muscle fiber,
Sarcoplasmic reticulum (SR): Endoplasmic reticulum of muscle cells, stores calcium.
Sarcomere: The functional unit of muscle contraction.
I band, A band, Z line, H zone: Regions within the sarcomere.

Neuromuscular Junction

The axon terminal of a motor neuron meets the muscle fiber at the motor end plate. This junction is called the neuromuscular junction.
Acetylcholine is released at the neuromuscular junction, and it binds to receptors on the muscle fiber, triggering a muscle action potential.
Acetylcholinesterase breaks down acetylcholine to stop the signal.

Molecular Mechanisms of Muscle Contraction

ATP is crucial for muscle contraction.
Myosin heads bind to actin, forming cross-bridges.
A power stroke occurs, and the filaments slide past each other.
The process repeats as long as calcium and ATP are available.
Calcium release is necessary for contraction.

Muscle Relaxation

Acetylcholinesterase breaks down acetylcholine.
Calcium is reabsorbed by the sarcoplasmic reticulum.
Myosin heads detach from actin.
The muscle returns to its resting length.

Energy Metabolism during Muscle Contraction

Stored ATP is the initial energy source.
Creatine phosphate is used to regenerate ATP.
Anaerobic glycolysis provides short-term energy.
Oxidative phosphorylation provides long-term energy.

Muscle Fatigue

Muscle fatigue results from repeated stimulation leading to decreased tension.
Factors contributing to fatigue: depletion of ATP, accumulation of metabolic byproducts (lactic acid), and changes in ion concentrations.

Skeletal Muscle Fiber Types

Slow-twitch fibers: Endurance activities; high oxidative capacity, lower force production and fatigue rate.
Fast-twitch fibers: High-intensity activities; Type 2a (fast oxidative-glycolytic); Type 2x/2b (fast glycolytic); higher force production, fatigue quickly.
Different fiber types contribute varying degrees of speed and power. Muscle hypertrophy involves increases in both the size and number of muscle fibers.

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Description

Test your knowledge on the various functions of muscles with this quiz. Identify which of the given options does not pertain to muscle functions. Enhance your understanding of anatomy and physiology through this engaging exercise.