Question

One of the side effects of Drug X is that muscle tone can become exaggerated, and muscle activity can increase. Which of the following is the most likely way that Drug X is producing these side effects at the neuromuscular junction?
Enhances activity of acetylcholinesterase
Binds and activates Ach receptors (AchRs)
Prevents presynaptic Ach release
None of these would cause increased muscular activity
Blocks/inhibits AchRs

Answer 1

Answer: Binds and activates acetylcholine receptors (AchR)

Explanation: If drug X is increasing muscle tone and activity, it must be stimulating the Ach receptor present on motor end plate of skeletal muscle. Ach is the neurotransmitter normally responsible for contraction of muscle.

Other options stand incorrect because:

Enhancing Achase activity would decrease Ach which means less muscle stimulation

Less presynaptic Ach release means less postsynaptic stimulation ie, less stimulation of muscle.

Blocking Ach receptor would again results in no stimulation of muscle.