Question

Acetylcholine stimulates an action potential in the muscle cell membrane by:

a) Opening chloride channels in the muscle cell membrane

b) Opening channels in the neuromuscular junction which allow sodium to move out of the cell

c) Opening channels in the neuromuscular junction which allow potassium to move out of the cell

d) Opening channels in the neuromuscular junction which allow sodium to move in and potassium to move out, though sodium moves faster than potassium because both chemical and electrical gradients drive sodium into the cell

e) Opening channels in the neuromuscular junction which allow sodium to move in and potassium to move out, though potassium moves faster than sodium because potassium is closer to equilibrium

Please provide an explanation. Thank you.

Answer 1

The acetylcholine a neurotransmitter in a muscle stimulate an action potential by opening channels in the neuromuscular junction which allow sodium to move in and potassium to move out, though sodium moves in faster than potassium Because both chemical and electrical gradient move sodium into the cell. The answer is d. Because the cell needs to be positively charged where the depolarization occurs and the influx of sodium ion increases and the out of potassium ion continues.

a)Acetylcholine do not open chloride channels in the muscle cell to stimulate an action potential. SO it's not suitable answer.

b) The sodium will not move out of the cell because for an depolarization the sodium influx should be more into the cell to be positively charged. So it's not suitable answer.

c) The opening of neuromuscular junction not only move out potassium ion and also influx the sodium ion into the cell to stimulate an action potential. So it's not suitable answer.

e)The sodium ions moves faster than the potassium ions because the cell need to be positively charged both electrically and as a chemical gradient to stimulate an action potential so potassium will continue to move out but not fastly for equilibrium so it's not suitable answer.