Question 1

Which of the following best describes the sequence of structures from largest to smallest in skeletal muscle organization?

Accepted Answer

Muscle \u003e Fascicle \u003e Fibre \u003e Myofibril \u003e Myofilament

Question 2

At the neuromuscular junction, which enzyme is responsible for breaking down acetylcholine in the synaptic cleft?

Accepted Answer

Acetylcholinesterase

Question 3

Which ion is primarily responsible for triggering the release of acetylcholine from the motor neuron at the neuromuscular junction?

Accepted Answer

Ca$$^{2+}$$

Question 4

During muscle contraction, which protein binds to calcium to initiate the movement of tropomyosin and expose myosin binding sites on actin?

Accepted Answer

Troponin

Question 5

Which of the following best explains the role of ATP in the cross-bridge cycle of muscle contraction?

Accepted Answer

ATP binds to myosin, causing it to detach from actin after the power stroke.

Question 6

A patient is exposed to a toxin that blocks voltage-gated Na$$^{+}$$ channels on the muscle cell membrane. What is the most likely effect?

Accepted Answer

The muscle cell will not generate an action potential, preventing contraction.

Question 7

Which of the following is the correct formula for calculating the force generated by a muscle, given the cross-sectional area ($$A) $$and the specific tension ($$	au$$)?

Accepted Answer

$$F = A 	imes 	au$$

Question 8

Which structural protein provides elasticity and helps anchor thick filaments to the Z line in the sarcomere?

Accepted Answer

Titin

Question 9

A muscle is damaged during eccentric contraction. Which of the following best describes eccentric contraction?

Accepted Answer

The muscle lengthens while generating force.

Question 10

Which of the following events occurs FIRST during excitation-contraction coupling in skeletal muscle?

Accepted Answer

An action potential arrives at the motor neuron terminal.

Question 11

If the acetylcholine receptors on the muscle cell membrane are blocked, which of the following will most likely occur?

Accepted Answer

The muscle cell will not depolarize, and contraction will not occur.

Question 12

Which of the following best describes the function of the perimysium in skeletal muscle?

Accepted Answer

It surrounds and separates fascicles within the muscle.

Question 13

During the cross-bridge cycle, what directly causes the power stroke that moves actin filaments?

Accepted Answer

Release of ADP and Pi from the myosin head

Question 14

Which of the following is a unique characteristic of skeletal muscle compared to other muscle types?

Accepted Answer

It is striated and under voluntary control.

Question 15

A patient with myasthenia gravis has antibodies against acetylcholine receptors. Which step in muscle contraction is most directly affected?

Accepted Answer

Depolarization of the muscle cell membrane

Question 16

Which of the following best describes the role of the sarcoplasmic reticulum in muscle contraction?

Accepted Answer

It stores and releases Ca$$^{2+}$$ ions to trigger contraction.

Question 17

Which of the following is the correct sequence of events in excitation-contraction coupling?

Accepted Answer

Action potential in neuron → Acetylcholine release → Muscle cell depolarization → Ca$$^{2+}$$ release → Cross-bridge formation

Question 18

Which of the following proteins forms the thick filament in the sarcomere?

Accepted Answer

Myosin

Question 19

If a mutation prevents the binding of Ca$$^{2+} to $$troponin, what is the most likely consequence for muscle contraction?

Accepted Answer

Tropomyosin will not move, and myosin binding sites on actin will remain covered.

Skeletal Muscle Structure and Neuromuscular Junction: Anatomy & Physiology Study Notes

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