Question 1

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

Accepted Answer

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

Question 2

A patient presents with muscle weakness and elevated levels of creatine phosphokinase (CPK) in the blood. Which of the following best explains the significance of elevated CPK?

Accepted Answer

It suggests muscle damage, as CPK leaks out of damaged muscle cells.

Question 3

During a muscle contraction, which of the following changes occur in the sarcomere?

Accepted Answer

The H zone narrows, and the Z lines move closer together.

Question 4

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

Accepted Answer

It stores and releases calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$that trigger contraction.

Question 5

A sprinter experiences muscle fatigue after a short, intense race. Which metabolic process is primarily responsible for ATP production during this activity, and what byproduct accumulates as a result?

Accepted Answer

Anaerobic glycolysis; lactic acid

Question 6

Which of the following best explains why muscle tension is greatest at an optimal sarcomere length?

Accepted Answer

There is maximal overlap between thick and thin filaments, allowing the greatest number of cross-bridges to form.

Question 7

Which of the following events occurs first during excitation-contraction coupling at the neuromuscular junction?

Accepted Answer

Arrival of an action potential at the synaptic terminal

Question 8

A person attempts to lift a heavy object but cannot move it. Which type of muscle contraction is occurring, and what happens at the sarcomere level?

Accepted Answer

Isometric contraction; sarcomeres shorten but the muscle does not change length

Question 9

Which of the following best describes the difference between fast-twitch (Type II-A) and slow-twitch (Type I) muscle fibers?

Accepted Answer

Slow-twitch fibers are more resistant to fatigue due to higher mitochondrial content and capillary density.

Question 10

Which of the following is a direct result of acetylcholine (ACh) binding to receptors on the motor end plate?

Accepted Answer

Opening of chemically gated sodium channels, leading to depolarization

Question 11

Which of the following best explains why external tension in a muscle builds more slowly than internal tension during contraction?

Accepted Answer

Elastic elements such as tendons must first be stretched before they transmit force.

Question 12

Which of the following statements about the Cori cycle is correct?

Accepted Answer

It describes the conversion of lactic acid to pyruvic acid in the liver, which is then used to synthesize glucose.

Question 13

Which of the following is a function of muscle tone?

Accepted Answer

It maintains posture and stabilizes bones and joints even when the muscle is not actively contracting.

Question 14

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

Accepted Answer

It donates a phosphate group to ADP to rapidly regenerate ATP during the initial phase of contraction.

Question 15

Which of the following is true regarding the relationship between resistance and speed of muscle contraction?

Accepted Answer

As resistance increases, the speed of contraction decreases.

Question 16

A muscle fiber is stimulated repeatedly at a high frequency such that the relaxation phase disappears and contraction is continuous. What is this phenomenon called?

Accepted Answer

Complete tetanus

Question 17

Which of the following best explains why you continue to breathe heavily after intense exercise?

Accepted Answer

To replenish oxygen debt and restore ATP and creatine phosphate levels in muscle and other tissues.

Question 18

Which of the following is a training effect that increases the endurance of skeletal muscle?

Accepted Answer

Increase in the number of mitochondria within muscle fibers

Question 19

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

Accepted Answer

It binds calcium ions, causing a conformational change that moves tropomyosin and exposes myosin binding sites on actin.

Question 20

Which of the following best explains why fast-twitch muscle fibers fatigue more quickly than slow-twitch fibers?

Accepted Answer

They have fewer mitochondria and rely more on anaerobic glycolysis, which produces less ATP and more lactic acid.

Skeletal Muscle Tissue: Structure, Function, and Physiology

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