Question 1

Which of the following best describes the role of acetylcholinesterase at the neuromuscular junction?

Accepted Answer

It breaks down acetylcholine, terminating its action at the synaptic cleft.

Question 2

During the excitation-contraction coupling process, what is the primary function of calcium ions ($$\mathrm{Ca$$^{2+}$$}$$)?

Accepted Answer

They bind to troponin, causing tropomyosin to shift and expose myosin-binding sites on actin.

Question 3

A patient is unable to relax their muscles after a contraction. Which of the following is the most likely cause?

Accepted Answer

Continued presence of acetylcholine in the synaptic cleft due to acetylcholinesterase inhibition.

Question 4

Which of the following best describes an isometric muscle contraction?

Accepted Answer

The muscle develops tension but does not change length.

Question 5

During a biceps curl, which type of contraction occurs as you slowly lower the weight back to the bench?

Accepted Answer

Eccentric isotonic contraction

Question 6

What is the correct sequence of events leading to skeletal muscle contraction?

Accepted Answer

Events at the neuromuscular junction → Muscle fiber excitation → Excitation-contraction coupling → Cross bridge cycle

Question 7

Which of the following best explains why eccentric contractions are important during activities such as walking down a steep hill?

Accepted Answer

They generate force as the muscle lengthens, helping to control and brake movement.

Question 8

A motor unit is defined as:

Accepted Answer

One motor neuron and all the muscle fibers it innervates.

Question 9

Which of the following events directly triggers the release of calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$from the sarcoplasmic reticulum?

Accepted Answer

Propagation of an action potential down the T-tubules

Question 10

Which phase of the action potential is primarily due to the exit of potassium ions ($$\mathrm{K^+}) $$from the muscle cell?

Accepted Answer

Repolarization

Question 11

In the cross-bridge cycle, what event immediately follows the power stroke?

Accepted Answer

ATP binds to the myosin head, causing cross-bridge detachment.

Question 12

Which of the following best explains why muscle soreness often occurs after eccentric contractions?

Accepted Answer

Eccentric contractions cause microtrauma to muscle fibers as they lengthen under tension.

Question 13

Which of the following is true regarding the sarcomere during muscle contraction?

Accepted Answer

The I band and H zone shorten, but the A band remains the same length.

Question 14

A person attempts to lift a heavy object but is unable to move it. Which type of muscle contraction is occurring?

Accepted Answer

Isometric contraction

Question 15

Which of the following best describes the function of T-tubules in skeletal muscle fibers?

Accepted Answer

They conduct action potentials deep into the muscle fiber to ensure simultaneous contraction.

Question 16

Which of the following is the correct formula for calculating muscle tension ($$T) if $$the force generated by the muscle is $$F$$ and the opposing load is $$L$$?

Accepted Answer

$$T = F - L$$

Question 17

Which of the following scenarios best illustrates an isometric contraction in daily life?

Accepted Answer

Holding a plank position during exercise.

Question 18

What would happen if the sarcolemma could not repolarize after an action potential?

Accepted Answer

The muscle fiber would remain in a depolarized state and be unable to generate new action potentials.

Question 19

Which of the following best explains why a single motor neuron can cause a strong muscle contraction?

Accepted Answer

A single motor neuron innervates multiple muscle fibers, causing them all to contract simultaneously.

Skeletal Muscle Physiology: Mechanisms of Muscle Contraction

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