Question

acetylcholine binds to a membrane bound receptor and causes ligand-gated sodium channels to open and results in:
a there is not enough information to predict the outcome
b hypoplarization
c no change in membrane potential
d depolarization
e hyperpolarization

Explanation:

When acetylcholine binds to its receptor and opens ligand - gated sodium channels, sodium ions ($Na^+$) flow into the cell. Since sodium ions are positively charged, the influx of $Na^+$ makes the inside of the cell less negative (or more positive) relative to the outside. Depolarization is defined as a change in the membrane potential towards a less negative (more positive) value. Hypopolarization is not a standard term in this context. Hyperpolarization would be if the inside became more negative (e.g., due to $K^+$ outflow or $Cl^-$ inflow). And since we know the ion movement (sodium influx) and its charge, we can predict the outcome, so option A is incorrect. Also, a change in ion distribution (sodium influx) will change the membrane potential, so option C is wrong.

Answer:

D. depolarization