Question 1

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

Accepted Answer

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

Question 2

A patient presents with muscle weakness and is diagnosed with McArdle’s disease. Which metabolic pathway is directly affected in this disorder?

Accepted Answer

Conversion of glycogen to glucose 6-phosphate

Question 3

During the contraction-relaxation cycle of skeletal muscle, what is the primary event that leads to muscle relaxation?

Accepted Answer

Pumping of $$\mathrm{Ca$$^{2+}$$}$$ back into the sarcoplasmic reticulum by $$\mathrm{Ca$$^{2+}$$}-$$ATPase

Question 4

Which protein is responsible for aligning actin filaments within the sarcomere?

Accepted Answer

Nebulin

Question 5

A muscle is stimulated repeatedly before it has fully relaxed, resulting in a stronger contraction. What is this phenomenon called?

Accepted Answer

Summation

Question 6

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

Accepted Answer

They have fewer mitochondria and rely primarily on anaerobic glycolysis.

Question 7

In the sliding filament theory, what happens to the I band and H zone during muscle contraction?

Accepted Answer

The I band and H zone decrease in width as actin and myosin filaments slide past each other.

Question 8

Which of the following is TRUE regarding the role of ATP in the crossbridge cycle?

Accepted Answer

ATP binding to myosin causes myosin to detach from actin.

Question 9

A person is performing a bicep curl. Which type of muscle contraction occurs as the biceps shorten to lift the weight?

Accepted Answer

Concentric isotonic contraction

Question 10

Which of the following best describes the difference between single-unit and multiunit smooth muscle?

Accepted Answer

Single-unit smooth muscle cells are electrically connected via gap junctions, while multiunit cells are not.

Question 11

Which equation correctly represents the breakdown of phosphocreatine to regenerate ATP during intense muscle activity?

Accepted Answer

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

Question 12

Which of the following muscle types is striated, contains sarcomeres, and is under involuntary control?

Accepted Answer

Cardiac muscle

Question 13

A muscle cramp is best described as:

Accepted Answer

A sustained, painful contraction of muscle fibers.

Question 14

Which of the following events occurs FIRST during excitation-contraction coupling in skeletal muscle?

Accepted Answer

Binding of acetylcholine to receptors on the sarcolemma

Question 15

Which protein provides elasticity and stabilizes the position of contractile elements in the sarcomere?

Accepted Answer

Titin

Question 16

During maximal exercise, which ion imbalance is most likely to contribute to muscle fatigue?

Accepted Answer

Increased extracellular $$\mathrm{K^+}$$

Question 17

Which of the following is a correct statement about the latent period in a muscle twitch?

Accepted Answer

It is the short delay between the muscle action potential and the beginning of muscle tension development.

Question 18

Which of the following is TRUE regarding the mechanics of body movement?

Accepted Answer

Isotonic contractions result in muscle shortening and movement of the load.

Question 19

Which of the following is a function of myoglobin in muscle fibers?

Accepted Answer

It binds oxygen, making it readily available for aerobic processes.

Question 20

Which of the following best describes the effect of histamine on smooth muscle in the airways?

Accepted Answer

It constricts smooth muscle, decreasing airflow.

Muscle Physiology: Structure, Function, and Types

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