Question 1

Which of the following best describes the role of the sarcoplasmic reticulum (SR) in skeletal muscle contraction?

Accepted Answer

It stores and releases $$\mathrm{Ca$$^{2+}$$}$$ ions, which are necessary for muscle contraction.

Question 2

A patient is exposed to a toxin that inhibits acetylcholinesterase at the neuromuscular junction. What is the most likely effect on skeletal muscle contraction?

Accepted Answer

Prolonged muscle contraction due to continued presence of acetylcholine in the synaptic cleft.

Question 3

Which of the following correctly matches the muscle tissue type with its characteristic?

Accepted Answer

Cardiac muscle – striated and involuntary

Question 4

During the sliding filament model of contraction, which event occurs as a direct result of ATP binding to the myosin head?

Accepted Answer

The myosin head detaches from the actin filament.

Question 5

A muscle fiber is unable to relax after contraction. Which of the following is the most likely cause?

Accepted Answer

Failure to pump $$\mathrm{Ca$$^{2+}$$}$$ back into the sarcoplasmic reticulum.

Question 6

Which structure in a skeletal muscle fiber is responsible for conducting impulses deep into the muscle, ensuring every sarcomere receives the signal to contract?

Accepted Answer

T tubules

Question 7

What is the primary function of troponin in skeletal muscle contraction?

Accepted Answer

It binds $$\mathrm{Ca$$^{2+}$$}$$ and moves tropomyosin away from actin's binding sites.

Question 8

Which of the following best explains why rigor mortis occurs after death?

Accepted Answer

ATP is no longer produced, so cross bridges cannot detach from actin.

Question 9

Which connective tissue sheath surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 10

A researcher measures the resting membrane potential of a skeletal muscle fiber and finds it to be more negative than usual. Which of the following could account for this observation?

Accepted Answer

Increased activity of the $$\mathrm{Na^+}$$/$$\mathrm{K^+}$$ pump

Question 11

Which of the following events occurs first during excitation-contraction (E-C) coupling in skeletal muscle?

Accepted Answer

An action potential propagates along the sarcolemma and down the T tubules.

Question 12

Which of the following best describes the function of the perimysium?

Accepted Answer

It surrounds fascicles, which are groups of muscle fibers.

Question 13

A patient with a genetic defect in the protein dystrophin would most likely experience which of the following?

Accepted Answer

Progressive muscle weakness due to impaired linkage between myofibrils and the sarcolemma.

Question 14

Which of the following is true regarding the arrangement of thick and thin filaments in a sarcomere?

Accepted Answer

Thick filaments are anchored at the M line and extend the length of the A band.

Question 15

During muscle contraction, which of the following changes occur in the sarcomere?

Accepted Answer

The I bands shorten, and the H zones disappear.

Question 16

Which of the following best explains why smooth muscle can contract without nervous system stimulation?

Accepted Answer

It is capable of spontaneous depolarization (automaticity).

Question 17

A drug blocks voltage-gated $$\mathrm{Na^+}$$ channels in the sarcolemma. What is the most immediate effect on muscle function?

Accepted Answer

Action potentials cannot be generated, so muscle contraction is inhibited.

Question 18

Which of the following best describes the 'power stroke' in the cross bridge cycle?

Accepted Answer

The myosin head pivots and pulls the thin filament toward the M line.

Question 19

Which of the following is a function of skeletal muscle tissue that is NOT shared by cardiac or smooth muscle?

Accepted Answer

Voluntary movement of the body

Question 20

A muscle fiber is stimulated by a motor neuron, but no contraction occurs. Which of the following is the most likely explanation?

Accepted Answer

The sarcolemma lacks functional acetylcholine receptors.

Muscle Tissue: Structure, Function, and Physiology

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