Question 1

Which of the following best describes the role of the sodium-potassium pump in maintaining the resting membrane potential of a skeletal muscle cell?

Accepted Answer

It actively transports 3 Na+ ions out of the cell and 2 K+ ions into the cell, maintaining a negative resting membrane potential.

Question 2

A patient is given a drug that blocks acetylcholinesterase (AChE) at the neuromuscular junction. What is the most likely effect on skeletal muscle contraction?

Accepted Answer

Muscle contraction will become sustained and spastic due to prolonged presence of acetylcholine.

Question 3

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

Accepted Answer

They are formed by the fusion of multiple myoblasts during embryogenesis.

Question 4

During the sliding filament mechanism of muscle contraction, what event directly triggers the power stroke of the myosin head?

Accepted Answer

Release of ADP and Pi from the myosin head

Question 5

Which of the following is TRUE regarding the difference between isotonic and isometric muscle contractions?

Accepted Answer

Isotonic contractions involve a change in muscle length, while isometric contractions do not.

Question 6

A muscle cell is placed in a hypotonic solution. What is the most likely outcome?

Accepted Answer

The cell will gain water and may undergo cytolysis.

Question 7

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

Accepted Answer

It stores and releases calcium ions necessary for muscle contraction.

Question 8

Which of the following statements about fast (Type II-B) and slow (Type I) skeletal muscle fibers is correct?

Accepted Answer

Fast fibers contract rapidly and fatigue quickly, while slow fibers contract slowly and are fatigue-resistant.

Question 9

Which of the following best explains the effect of increasing the frequency of stimulation on muscle tension, as shown in the incomplete tetanus graph?

Accepted Answer

Tension rises to a peak with brief periods of relaxation between contractions.

Question 10

Which of the following is a direct result of ATP binding to the myosin head during the muscle contraction cycle?

Accepted Answer

The myosin head detaches from actin, breaking the cross-bridge.

Question 11

Which of the following best describes the role of troponin in skeletal muscle contraction?

Accepted Answer

Troponin binds calcium ions, causing a conformational change that moves tropomyosin and exposes actin active sites.

Question 12

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

Accepted Answer

Inability to actively transport calcium ions back into the sarcoplasmic reticulum

Question 13

Which of the following is TRUE regarding the length-tension relationship in skeletal muscle?

Accepted Answer

Tension is greatest when there is optimal overlap between thick and thin filaments, allowing maximum cross-bridge formation.

Question 14

Which of the following best explains why lactic acid accumulates in muscle cells during intense exercise?

Accepted Answer

Aerobic metabolism is unable to meet ATP demands, so anaerobic glycolysis produces ATP and lactic acid as a byproduct.

Question 15

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

Accepted Answer

Ability to contract without neural stimulation (automaticity)

Question 16

Which of the following best describes the function of gap junctions in cardiac and smooth muscle?

Accepted Answer

They allow direct electrical and chemical communication between adjacent cells.

Question 17

A patient with myasthenia gravis experiences muscle weakness because:

Accepted Answer

Their acetylcholine receptors are destroyed by the immune system, reducing muscle cell activation.

Question 18

Which of the following best explains the concept of asynchronous motor unit summation?

Accepted Answer

Motor units take turns contracting to sustain tension and prevent fatigue.

Question 19

Which of the following is a primary effect of aging on the muscular system?

Accepted Answer

Decrease in muscle mass, strength, and endurance (sarcopenia)

Membrane Transport, Muscle Structure, and Muscle Contraction: Study Notes for Anatomy & Physiology

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