Question 1

Which of the following statements best describes the structural difference between skeletal and smooth muscle fibers?

Accepted Answer

Skeletal muscle fibers are multinucleated and contain striations, while smooth muscle fibers are uninucleated and lack striations.

Question 2

During muscle contraction, which protein directly binds calcium to initiate the conformational change that exposes myosin binding sites on actin?

Accepted Answer

Troponin

Question 3

A patient is experiencing muscle fatigue after prolonged low-intensity aerobic exercise. What is the most likely physiological cause?

Accepted Answer

Depletion of glycogen stores

Question 4

Which of the following best explains why fast twitch muscle fibers contract more rapidly than slow twitch fibers?

Accepted Answer

Fast twitch fibers contain myosin that hydrolyzes ATP to ADP and P faster, resulting in quicker myosin head cocking.

Question 5

Which of the following equations correctly represents the hydrolysis of ATP during the crossbridge cycle?

Accepted Answer

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

Question 6

A muscle is generating force but does not shorten because the load is greater than the muscle tension. What type of twitch is this?

Accepted Answer

Isometric twitch

Question 7

Which of the following changes would you expect in skeletal muscle fibers after several weeks of high-intensity exercise?

Accepted Answer

Increase in glycolysis enzymes and fiber diameter, decrease in mitochondria size and number

Question 8

Which of the following is a key difference in the source of calcium for contraction between skeletal and smooth muscle?

Accepted Answer

Skeletal muscle uses internal Ca$$^{2+}$$ from the sarcoplasmic reticulum, while smooth muscle uses mostly external Ca$$^{2+}$$ entering the cell.

Question 9

Which process is responsible for terminating skeletal muscle contraction?

Accepted Answer

Active calcium uptake through SERCA pumps on the sarcoplasmic reticulum

Question 10

Which of the following best describes the role of tropomyosin in muscle contraction?

Accepted Answer

It masks the myosin binding site on actin in the absence of calcium.

Question 11

A marathon runner trains with low-intensity exercise over several months. Which adaptation is most likely to occur in their skeletal muscle fibers?

Accepted Answer

Increase in oxidative capacity and conversion of some glycolytic fibers into oxidative fibers

Question 12

Which of the following is true regarding the arrangement of actin and myosin in smooth muscle compared to skeletal muscle?

Accepted Answer

Actin and myosin in smooth muscle run parallel in several axes and connect to dense bodies, while in skeletal muscle they are organized into sarcomeres.

Question 13

Which of the following best describes the mechanical response of a muscle fiber to a single action potential?

Accepted Answer

A twitch

Question 14

Which of the following is a characteristic of oxidative (aerobic) muscle fibers?

Accepted Answer

High myoglobin content and many mitochondria

Question 15

Which of the following steps occurs first in the excitation-contraction coupling of skeletal muscle?

Accepted Answer

Motor neuron action potential

Question 16

Which enzyme is responsible for inactivating myosin and shutting off smooth muscle contraction?

Accepted Answer

Phosphatase

Question 17

During high-intensity exercise, muscle fatigue is primarily caused by which of the following?

Accepted Answer

Lactic acid buildup

Question 18

Which of the following best describes the function of the SERCA pump in skeletal muscle physiology?

Accepted Answer

It actively transports Ca$$^{2+}$$ back into the sarcoplasmic reticulum to terminate contraction.

Question 19

Which of the following is true regarding the conversion of muscle fiber types with different exercise intensities?

Accepted Answer

Low-intensity exercise can convert some glycolytic fibers into oxidative fibers, while high-intensity exercise can convert some oxidative fibers into glycolytic fibers.

Muscle Physiology: Structure, Function, and Types of Muscle

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