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 necessary for muscle contraction.

Question 2

A patient presents with muscle weakness and drooping eyelids. Laboratory tests reveal antibodies against acetylcholine (ACh) receptors. Which disease is most likely responsible for these symptoms?

Accepted Answer

Myasthenia gravis

Question 3

During the cross bridge cycle, what event directly causes the detachment of the myosin head from actin?

Accepted Answer

Binding of ATP to the myosin head

Question 4

Which of the following is a characteristic unique to cardiac muscle tissue?

Accepted Answer

It is striated and involuntary.

Question 5

A muscle fiber is stimulated by a series of rapid stimuli such that it does not have time to relax between stimuli, resulting in a smooth, sustained contraction. What is this phenomenon called?

Accepted Answer

Fused (complete) tetanus

Question 6

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

Accepted Answer

ATP is no longer produced, so myosin heads cannot detach from actin.

Question 7

Which connective tissue sheath surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 8

Which of the following statements about the sliding filament model of contraction is correct?

Accepted Answer

Thin filaments slide past thick filaments, increasing their overlap without changing the length of either filament.

Question 9

Which energy system provides the fastest way to regenerate ATP during the first few seconds of intense muscle activity?

Accepted Answer

Direct phosphorylation of ADP by creatine phosphate

Question 10

A marathon runner relies primarily on which type of muscle fibers during a race?

Accepted Answer

Slow oxidative fibers

Question 11

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

Accepted Answer

It links thin filaments to proteins of the sarcolemma, stabilizing the muscle cell membrane.

Question 12

Which of the following is NOT a function of muscle tissue?

Accepted Answer

Producing hormones

Question 13

During isometric contraction, which of the following occurs?

Accepted Answer

Muscle tension increases but the muscle does not change length.

Question 14

Which of the following best explains the 'size principle' of motor unit recruitment?

Accepted Answer

Smaller motor units are recruited first, followed by larger ones as stimulus intensity increases.

Question 15

Which of the following is a distinguishing feature of smooth muscle compared to skeletal muscle?

Accepted Answer

Smooth muscle cells have a single nucleus and lack striations.

Question 16

A patient is unable to perform rapid, powerful movements but can maintain posture for long periods. Which muscle fiber type is most likely deficient?

Accepted Answer

Fast glycolytic fibers

Question 17

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

Accepted Answer

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

Question 18

Which of the following best describes the role of calcium ions ($$\mathrm{Ca$$^{2+}$$}) in $$muscle contraction?

Accepted Answer

They bind to troponin, causing a conformational change that moves tropomyosin and exposes myosin-binding sites on actin.

Question 19

Which of the following is a real-life example of an eccentric isotonic contraction?

Accepted Answer

Slowly lowering a heavy box to the ground

Question 20

Which of the following best explains why muscle fatigue occurs during prolonged, high-intensity exercise?

Accepted Answer

Ionic imbalances and accumulation of inorganic phosphate interfere with calcium release and cross bridge cycling.

Muscles and Muscle Tissue: Structure, Function, and Physiology

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