Question 1

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

Accepted Answer

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

Question 2

A patient is exposed to botulinum toxin, which blocks acetylcholine (ACh) release at the neuromuscular junction. What is the most likely physiological effect?

Accepted Answer

Paralysis due to inability of skeletal muscle fibers to depolarize and contract.

Question 3

During the sliding filament theory of muscle contraction, which of the following occurs?

Accepted Answer

The $$I$$ bands and $$H$$ bands decrease in width as actin and myosin filaments slide past each other.

Question 4

Which connective tissue layer surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 5

A marathon runner relies heavily on slow oxidative muscle fibers. Which characteristic is most associated with these fibers?

Accepted Answer

High myoglobin content and resistance to fatigue

Question 6

Which of the following best explains why cardiac muscle can contract without neural stimulation?

Accepted Answer

It contains pacemaker cells that spontaneously depolarize.

Question 7

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

Accepted Answer

Depolarization of the T-tubule membrane by an action potential

Question 8

A muscle is stimulated at a frequency that does not allow complete relaxation between stimuli, resulting in a sustained, quivering contraction. What is this phenomenon called?

Accepted Answer

Incomplete (unfused) tetanus

Question 9

Which of the following best describes the role of creatine phosphate (CP) in muscle metabolism?

Accepted Answer

It donates a phosphate group to ADP to rapidly regenerate ATP during the initial seconds of intense activity.

Question 10

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

Accepted Answer

Calcium binds to calmodulin instead of troponin to initiate contraction.

Question 11

A patient with tetanus experiences sustained muscle contractions. What is the underlying cause of this condition?

Accepted Answer

Tetanus toxin blocks inhibitory neurotransmitter release, leading to continuous stimulation of muscles.

Question 12

Which of the following best explains why muscle fatigue occurs during prolonged, intense exercise?

Accepted Answer

Depletion of energy reserves (glycogen, ATP, CP) and accumulation of lactic acid lower pH.

Question 13

Which of the following statements about the neuromuscular junction is correct?

Accepted Answer

It is the site where a motor neuron releases acetylcholine to stimulate a muscle fiber.

Question 14

Which of the following best describes the 'all-or-none' principle of muscle fiber contraction?

Accepted Answer

A muscle fiber contracts completely or not at all in response to a threshold stimulus.

Question 15

Which of the following changes would you expect in skeletal muscle as a result of aging?

Accepted Answer

Decrease in muscle fiber thickness and elasticity, leading to reduced strength and endurance.

Question 16

Which of the following best explains why cardiac muscle cannot undergo tetanus?

Accepted Answer

Cardiac muscle cells have long refractory periods that prevent sustained contractions.

Question 17

During muscle relaxation, which of the following events occurs first?

Accepted Answer

Calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$are actively transported back into the sarcoplasmic reticulum.

Question 18

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 19

Which of the following is a characteristic of fast glycolytic (fast twitch) muscle fibers?

Accepted Answer

They fatigue quickly but generate powerful contractions.

Question 20

A muscle is producing tension but does not change in length. What type of contraction is this?

Accepted Answer

Isometric contraction

Muscle Tissue: Structure, Function, and Physiology (Chapter 10 Study Notes)

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