$$\text{CP} + \text{ADP} \rightarrow \text{ATP} + \text{creatine}$$

Question 1

Which of the following best describes the role of acetylcholine (ACh) at the neuromuscular junction?

Accepted Answer

ACh acts as a neurotransmitter that initiates muscle excitation by binding to ligand-gated Na+ channels on the motor end plate.

Question 2

During the depolarization phase of an action potential in a muscle cell, which ion moves into the cell and what is the effect on membrane potential?

Accepted Answer

Na+ enters the cell, causing the membrane potential to become more positive.

Question 3

What is the primary function of T-tubules in skeletal muscle fibers?

Accepted Answer

Conduct action potential deep into the muscle fiber to trigger calcium release.

Question 4

Which equation represents the immediate energy source reaction in muscle cells involving creatine phosphate?

Accepted Answer

$$	ext{CP} + 	ext{ADP} ightarrow 	ext{ATP} + 	ext{creatine}$$

Question 5

Which event directly triggers the release of calcium from the sarcoplasmic reticulum during muscle contraction?

Accepted Answer

Depolarization of T-tubules by the action potential.

Question 6

What is the role of troponin and tropomyosin in muscle contraction?

Accepted Answer

Regulate access to actin binding sites by responding to Ca2+.

Question 7

Which step in the cross-bridge cycle is responsible for the power stroke that pulls actin toward the M line?

Accepted Answer

Release of ADP and P from myosin after binding to actin.

Question 8

Which enzyme is responsible for muscle relaxation by degrading acetylcholine in the synaptic cleft?

Accepted Answer

Acetylcholinesterase

Question 9

A patient is experiencing muscle weakness due to a defect in the Na+/K+ pump. Which of the following best explains the effect on muscle function?

Accepted Answer

The resting membrane potential cannot be restored, impairing action potential generation.

Question 10

Which of the following is a correct sequence of events during excitation-contraction coupling?

Accepted Answer

Action potential travels down T-tubules → Ca2+ released from SR → Ca2+ binds to troponin → Tropomyosin moves → Myosin binds to actin

Question 11

Which process allows muscle fibers to continue contracting for more than a few seconds when immediate ATP stores are depleted?

Accepted Answer

Anaerobic glycolysis, which converts glucose to pyruvate and produces ATP.

Question 12

If a muscle fiber is deprived of oxygen, which pathway will it primarily use to generate ATP?

Accepted Answer

Anaerobic glycolysis

Question 13

Which of the following best explains why ATP is required for muscle relaxation?

Accepted Answer

ATP powers calcium ion pumps that return Ca2+ to the sarcoplasmic reticulum.

Question 14

Which of the following would most likely result in sustained muscle contraction (tetany)?

Accepted Answer

Continuous presence of acetylcholine in the synaptic cleft due to inhibition of acetylcholinesterase.

Question 15

Which of the following is TRUE regarding the role of myoglobin in muscle cells?

Accepted Answer

Myoglobin stores oxygen to support aerobic ATP production during prolonged activity.

Question 16

A muscle cell is exposed to a toxin that blocks voltage-gated Ca2+ channels in the sarcoplasmic reticulum. What is the most immediate effect?

Accepted Answer

Ca2+ cannot be released, preventing troponin activation and muscle contraction.

Question 17

Which of the following best describes the relationship between ATP and the cross-bridge cycle?

Accepted Answer

ATP is required to detach myosin from actin and reset the myosin head for another cycle.

Question 18

Which of the following equations represents the net ATP yield from aerobic glucose catabolism?

Accepted Answer

$$	ext{Glucose} + 	ext{O}_2 ightarrow 36 	ext{ATP}$$

Question 19

Which of the following would most likely occur if tropomyosin failed to move away from actin's active sites?

Accepted Answer

Myosin would be unable to bind to actin, preventing muscle contraction.

Muscle Tissue II: Action Potentials, Neuromuscular Junction, Excitation-Contraction Coupling, and Muscle Energy

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