Q: Which of the following best describes the role of the Na\textsuperscript{+}/K\textsuperscript{+} pump in maintaining the resting membrane potential of a muscle cell?

It moves 3 Na\textsuperscript{+} ions out of the cell and 2 K\textsuperscript{+} ions in, using ATP.

Q: During the depolarization phase of muscle contraction, which ion primarily moves into the muscle cell, and through which type of channel?

Na\textsuperscript{+} through voltage-gated channels

Q: Which of the following is the correct sequence of events in excitation-contraction coupling in skeletal muscle?

ACh release → ACh binds to receptor → Na\textsuperscript{+} influx → action potential → Ca\textsuperscript{2+} release → muscle contraction

Question 1

Which of the following best describes the role of the Na	extsuperscript{+}/K	extsuperscript{+} pump in maintaining the resting membrane potential of a muscle cell?

Accepted Answer

It moves 3 Na	extsuperscript{+} ions out of the cell and 2 K	extsuperscript{+} ions in, using ATP.

Question 2

A patient is given a drug that blocks acetylcholine (ACh) receptors on the muscle fiber. What is the most likely physiological consequence?

Accepted Answer

Muscle paralysis because the muscle fiber cannot be stimulated to contract.

Question 3

During the depolarization phase of muscle contraction, which ion primarily moves into the muscle cell, and through which type of channel?

Accepted Answer

Na	extsuperscript{+} through voltage-gated channels

Question 4

Which equation correctly represents the ATP-generating reaction catalyzed by creatine kinase in muscle cells?

Accepted Answer

$$\mathrm{ADP} + \mathrm{CP} \rightarrow \mathrm{ATP} + \mathrm{Creatine}$$

Question 5

A person dies of a drug overdose and is found three days later with their muscles stiffened. What is the physiological explanation for this postmortem rigidity?

Accepted Answer

Lack of ATP prevents myosin heads from detaching from actin, resulting in rigor mortis.

Question 6

Which of the following pathways produces the highest yield of ATP per glucose molecule in muscle cells?

Accepted Answer

Aerobic respiration

Question 7

What would happen to muscle contraction if acetylcholinesterase is inhibited at the neuromuscular junction?

Accepted Answer

Muscle fibers would remain contracted due to persistent stimulation.

Question 8

Which of the following best explains the sliding filament model of muscle contraction?

Accepted Answer

Myosin heads pull actin filaments toward the center of the sarcomere, shortening the muscle.

Question 9

Which of the following is a direct result of calcium binding to troponin during muscle contraction?

Accepted Answer

Tropomyosin moves, exposing myosin-binding sites on actin.

Question 10

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

Accepted Answer

ACh release → ACh binds to receptor → Na	extsuperscript{+} influx → action potential → Ca	extsuperscript{2+} release → muscle contraction

Question 11

Which muscle energy source is most important during a marathon?

Accepted Answer

Aerobic respiration

Question 12

A mutation in a gene related to thin filament proteins (such as actin or troponin) is most likely to cause which clinical manifestation?

Accepted Answer

Muscle weakness due to impaired crossbridge formation

Question 13

Which of the following is a consequence of anaerobic glycolysis in muscle cells?

Accepted Answer

Production of lactic acid

Question 14

In malignant hyperthermia, a mutation affects calcium storage in the sarcoplasmic reticulum. What is the most dangerous effect if all calcium is released during anesthesia?

Accepted Answer

Sustained muscle contraction and dangerous increase in body temperature

Question 15

Which of the following best describes muscle fatigue?

Accepted Answer

A state in which the muscle cannot contract even when stimulated

Question 16

Which of the following is true regarding the crossbridge cycle in muscle contraction?

Accepted Answer

Release of ADP and P	extsubscript{i} from myosin triggers the power stroke.

Question 17

Which of the following would most likely occur if a muscle cell did not produce enough ATP during contraction?

Accepted Answer

Myosin heads would remain attached to actin, preventing relaxation.

Question 18

Which of the following is a function of the sarcoplasmic reticulum in skeletal muscle cells?

Accepted Answer

Storing and releasing calcium ions during contraction

Question 19

Which of the following statements about ligand-gated and voltage-gated ion channels in muscle fibers is correct?

Accepted Answer

Voltage-gated channels open in response to electrical changes across the membrane.

Muscle Physiology: How Muscle Cells Contract 8.2

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