When acetylcholine binds to receptors at the motor end plate, the muscle membrane becomes?

Question

a. more permeable to sodium ions
b. less permeable to sodium ions
c. more permeable to potassium ions
d. less permeable to potassium ions

Answer 1

Acetylecholine open the sodium ion channels. Thus the answer is A (more permeable to sodium ions).

When flood of Na+ get into the cell, the cell generate action potential which runs to the T-tubules of the muscle cell and open the Sarcoplastic Reticulum and release calcium for muscle contraction to occur.

Answer 2

B is the best answers of those you have presented. The sodium influx causes a graded potential. If the membrane voltage reaches approximately -55 milivolt it will cause an action potential (the falling dominos you describe). Technically the nicotinic receptor activates an adjacent sodium gated channel, but not the same type are you find on the axon that causes the action potential.

Answer 3

Strictly speaking, the answer is both A and C, because acetylcholine opens the non-specific cation channel in the nicotinic receptor. Because both sodium and potassium are cations, both can move through the channel. However, the answer the teacher is probably looking for is A. More sodium does move through the channel than potassium, because sodium is further away from its equilibrium potential, so there is more driving force on it to move.

Answer 4

A