Question 1

Which of the following statements best describes the difference between skeletal and cardiac muscle cells?

Accepted Answer

Skeletal muscle cells are multinucleated and voluntary, while cardiac muscle cells are single-nucleated and involuntary.

Question 2

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

Accepted Answer

Elasticity

Question 3

During the sliding-filament mechanism of contraction, which band remains unchanged as the sarcomere shortens?

Accepted Answer

A band

Question 4

What is the primary function of the sarcoplasmic reticulum (SR) in skeletal muscle fibers?

Accepted Answer

Storing and releasing calcium ions

Question 5

Which of the following best describes the role of creatine phosphate in muscle contraction?

Accepted Answer

It immediately regenerates ATP for about 10 seconds of maximum muscle activity.

Question 6

A patient is experiencing muscle fatigue after intense exercise. Which energy source is most likely depleted first?

Accepted Answer

Creatine phosphate

Question 7

Which of the following equations correctly represents the hydrolysis of ATP during muscle contraction?

Accepted Answer

$$ATP \rightarrow ADP + P_{i}$$

Question 8

Which of the following is true regarding the resting membrane potential of a skeletal muscle fiber?

Accepted Answer

It is approximately $$-85 mV $$and maintained by the Na$$^+/K$^+$$ pump.

Question 9

Which of the following best describes the function of ligand-gated channels at the neuromuscular junction?

Accepted Answer

They open in response to the binding of acetylcholine, allowing Na$$^+$$ ions to enter the muscle fiber.

Question 10

Which of the following events directly triggers the release of calcium ions from the sarcoplasmic reticulum during excitation-contraction coupling?

Accepted Answer

Propagation of action potentials down the T-tubules

Question 11

During muscle contraction, which protein binds calcium ions to initiate the crossbridge cycle?

Accepted Answer

Troponin

Question 12

Which of the following best explains why oxidative catabolism is the predominant energy source after one minute of exercise?

Accepted Answer

It requires oxygen and provides more ATP per molecule of glucose.

Question 13

A muscle fiber is exposed to a toxin that blocks voltage-gated K$$^+$$ channels. What is the most likely effect on the action potential?

Accepted Answer

Repolarization will be impaired, prolonging the action potential.

Question 14

Which of the following is a correct sequence of events in the crossbridge cycle?

Accepted Answer

Myosin binds actin, ATP is hydrolyzed, power stroke occurs, myosin releases actin.

Question 15

Which of the following best describes the role of acetylcholinesterase at the neuromuscular junction?

Accepted Answer

It degrades acetylcholine in the synaptic cleft, terminating the signal.

Question 16

Which of the following is true regarding the structure of the sarcomere?

Accepted Answer

The A band contains the zone of overlap where thick and thin filaments are found.

Question 17

A muscle cell is unable to contract even though ATP and calcium are present. Which protein is most likely malfunctioning?

Accepted Answer

Tropomyosin

Question 18

Which of the following is the correct formula for the resting membrane potential of a skeletal muscle fiber?

Accepted Answer

$$V_{rest} = -85\ \mathrm{mV}$$

Question 19

Which of the following best describes the function of elastic filaments in the sarcomere?

Accepted Answer

They stabilize the myofibril structure and resist excessive stretching.

Muscle Tissue: Structure, Function, and Contraction Mechanisms

Study Guide - Practice Questions