Question 1

Which property of muscle cells allows them to return to their original shape after being stretched?

Accepted Answer

Elasticity

Question 2

During the sliding filament mechanism, which proteins interact to produce muscle contraction?

Accepted Answer

Myosin and Actin

Question 3

What is the role of troponin in muscle contraction?

Accepted Answer

It acts as a clip, keeping tropomyosin on the actin until calcium binds.

Question 4

Which structure is the plasma membrane of a muscle fiber?

Accepted Answer

Sarcolemma

Question 5

A patient is experiencing muscle weakness due to a defect in titin. Which function is most likely impaired?

Accepted Answer

Anchoring and stabilizing myofilaments within the sarcomere

Question 6

Which equation best represents the resting membrane potential of a muscle cell?

Accepted Answer

$$V_{rest} \approx -90\ \mathrm{mV}$$

Question 7

During depolarization of the sarcolemma, which ion primarily enters the muscle cell?

Accepted Answer

Sodium ($$Na^+)$$

Question 8

Which type of ion channel opens in response to a chemical binding, such as acetylcholine at the motor end plate?

Accepted Answer

Ligand-gated channel

Question 9

What is the correct sequence of events for muscle contraction after an action potential reaches the neuromuscular junction?

Accepted Answer

Release of calcium from sarcoplasmic reticulum → Troponin binds calcium → Tropomyosin moves → Myosin binds actin

Question 10

Which connective tissue layer surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 11

A toxin blocks acetylcholine release at the neuromuscular junction. What is the most immediate effect on muscle contraction?

Accepted Answer

Muscle contraction is prevented

Question 12

Which of the following best describes the function of myoglobin in muscle cells?

Accepted Answer

Stores oxygen for aerobic metabolism

Question 13

Which type of muscle fiber is most resistant to fatigue and has high myosin-ATPase activity?

Accepted Answer

Type 1 (slow oxidative)

Question 14

If a muscle cell is unable to regenerate ATP via creatine phosphate, which process will be most affected during short, intense activity?

Accepted Answer

Immediate energy supply for contraction

Question 15

Which equation represents the net ATP yield from anaerobic glycolysis of one glucose molecule?

Accepted Answer

$$C_6H_{12}O_6$ \rightarrow 2\ ATP + 2\ lactic\ acid$$

Question 16

Which event directly triggers the exposure of myosin binding sites on actin?

Accepted Answer

Release of calcium ions from the sarcoplasmic reticulum

Question 17

A marathon runner's muscle fibers are likely to have which characteristics?

Accepted Answer

Many mitochondria, high myoglobin, slow contraction

Question 18

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

Accepted Answer

It facilitates rapid transmission of action potentials and calcium release.

Question 19

During repolarization of the muscle cell membrane, which ion channel opens to restore the resting potential?

Accepted Answer

Voltage-gated potassium channel

Question 20

Which process is responsible for the propagation of action potentials along the entire sarcolemma?

Accepted Answer

Opening of voltage-gated sodium channels throughout the membrane

Muscle Cell Structure, Function, and Physiology: Study Notes for Anatomy & Physiology

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