Question 1

Which of the following best describes the function of the sarcoplasmic reticulum (SR) in skeletal muscle fibers?

Accepted Answer

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

Question 2

During the sliding filament model of muscle contraction, which event occurs immediately after $$\mathrm{Ca$$^{2+}$$}$$ binds to troponin?

Accepted Answer

Tropomyosin shifts to expose myosin-binding sites on actin.

Question 3

Which connective tissue sheath surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 4

A patient is diagnosed with a disorder that prevents the reuptake of acetylcholine (ACh) at the neuromuscular junction. What is the most likely effect on muscle contraction?

Accepted Answer

Prolonged muscle contraction due to continued stimulation.

Question 5

Which of the following is TRUE regarding the structure of a sarcomere?

Accepted Answer

The A band contains thick (myosin) filaments.

Question 6

What is the role of titin in the sarcomere?

Accepted Answer

It anchors and centers the thick filament between Z discs, providing elasticity.

Question 7

Which of the following best explains why skeletal muscle fibers are multinucleated?

Accepted Answer

They are formed by the fusion of multiple embryonic myoblasts.

Question 8

A muscle fiber is unable to relax after contraction. Which process is most likely impaired?

Accepted Answer

Reuptake of $$\mathrm{Ca$$^{2+}$$}$$ into the sarcoplasmic reticulum

Question 9

Which of the following is a property shared by all three types of muscle tissue (skeletal, cardiac, and smooth)?

Accepted Answer

Excitability

Question 10

Which event directly triggers the release of $$\mathrm{Ca$$^{2+}$$}$$ from the sarcoplasmic reticulum during muscle contraction?

Accepted Answer

Propagation of an action potential along the T-tubules

Question 11

Which of the following best describes the function of myoglobin in skeletal muscle fibers?

Accepted Answer

It stores oxygen for use during muscle contraction.

Question 12

A toxin blocks the voltage-gated sodium channels in the sarcolemma. What is the most immediate effect on muscle function?

Accepted Answer

Action potentials cannot propagate, preventing muscle contraction.

Question 13

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

Accepted Answer

Action potential → $$\mathrm{Ca$$^{2+}$$}$$ release → cross-bridge formation → power stroke

Question 14

Which protein covers the myosin-binding sites on actin in a relaxed muscle fiber?

Accepted Answer

Tropomyosin

Question 15

A muscle biopsy reveals fibers with a single central nucleus, no striations, and spindle-shaped cells. Which type of muscle is this?

Accepted Answer

Smooth muscle

Question 16

Which of the following best explains why the A band remains the same length during muscle contraction?

Accepted Answer

The length of the thick (myosin) filaments does not change.

Question 17

Which of the following is a function of the perimysium in skeletal muscle?

Accepted Answer

It surrounds and bundles fascicles.

Question 18

Which of the following events occurs during the power stroke of cross-bridge cycling?

Accepted Answer

The myosin head pivots, pulling the actin filament toward the M line.

Question 19

Which of the following best describes the 'all-or-none' principle of action potentials in muscle fibers?

Accepted Answer

Once threshold is reached, the action potential is generated and spreads along the entire sarcolemma.

Question 20

A patient has a genetic mutation that prevents the formation of functional troponin. What is the most likely consequence for muscle contraction?

Accepted Answer

The muscle cannot contract because tropomyosin cannot be moved to expose myosin-binding sites.

Muscle Tissue: Structure, Function, and Physiology

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