Question 1

Which enzyme is responsible for breaking down acetylcholine (ACh) at the neuromuscular junction, and what are the resulting products?

Accepted Answer

Acetylcholinesterase (AChE); acetic acid and choline

Question 2

After acetylcholine is broken down by acetylcholinesterase, what happens to the choline produced?

Accepted Answer

It is recycled and used to synthesize new acetylcholine

Question 3

What is the fate of acetic acid produced from acetylcholine breakdown at the neuromuscular junction?

Accepted Answer

It enters the Krebs cycle as acetyl-CoA

Question 4

Which of the following best describes the role of acetylcholinesterase (AChE) in muscle fiber relaxation?

Accepted Answer

AChE breaks down acetylcholine, terminating the signal and allowing muscle relaxation

Question 5

If acetylcholinesterase is inhibited, what would be the most likely effect on skeletal muscle?

Accepted Answer

Continuous muscle contraction due to persistent acetylcholine signaling

Question 6

Which clinical condition is treated by inhibiting acetylcholinesterase, and why?

Accepted Answer

Myasthenia gravis; to increase acetylcholine availability at the neuromuscular junction

Question 7

Which equation correctly represents the breakdown of acetylcholine by acetylcholinesterase?

Accepted Answer

$$\mathrm{ACh} \xrightarrow{\mathrm{AChE}} \mathrm{acetic\ acid} + \mathrm{choline}$$

Question 8

During muscle fiber relaxation, which process is directly dependent on ATP?

Accepted Answer

Active transport of Ca$$^{2+}$$ into the sarcoplasmic reticulum

Question 9

Which of the following would most likely result from a mutation that prevents choline recycling at the neuromuscular junction?

Accepted Answer

Reduced synthesis of acetylcholine and impaired muscle contraction

Question 10

A patient is exposed to a drug that mimics acetylcholine but is not broken down by acetylcholinesterase. What is the most likely outcome?

Accepted Answer

Prolonged muscle contraction and possible muscle spasms

Question 11

Which of the following best explains why acetylcholine must be rapidly broken down at the neuromuscular junction?

Accepted Answer

To prevent continuous stimulation and allow controlled muscle contraction and relaxation

Question 12

Which of the following is a direct consequence of acetylcholine breakdown at the motor end plate?

Accepted Answer

Termination of the muscle contraction signal

Question 13

Which step in muscle fiber relaxation is directly facilitated by acetylcholinesterase?

Accepted Answer

Breakdown of acetylcholine at the motor end plate

Question 14

Which of the following would most likely occur if acetylcholine is not broken down at the neuromuscular junction?

Accepted Answer

Sustained depolarization and continuous muscle contraction

Question 15

Which of the following is NOT a product of acetylcholine breakdown by acetylcholinesterase?

Accepted Answer

Lactic acid

Question 16

Which pathway does acetic acid, produced from acetylcholine breakdown, enter in the cell?

Accepted Answer

Krebs cycle as acetyl-CoA

Question 17

Which of the following best describes the recycling of choline at the neuromuscular junction?

Accepted Answer

Choline is taken up by the presynaptic neuron and used to synthesize new acetylcholine

Question 18

Which of the following would most likely be observed in a patient with a genetic deficiency in acetylcholinesterase?

Accepted Answer

Muscle spasms and difficulty relaxing muscles

Question 19

Which of the following is a correct summary of the fate of acetylcholine at the neuromuscular junction?

Accepted Answer

Acetylcholine is broken down by acetylcholinesterase into acetic acid and choline; acetic acid enters the Krebs cycle, and choline is recycled

Skeletal Muscle Physiology: Structure, Function, and Clinical Applications

Study Guide - Practice Questions