[orgo814]

One of the answers to a HW question tells me that the influx of positive charges causes the membrane potential to increase. Question was: "how would the Na+ flow through the acetylcholine ion channel change the membrane potential?"

2 questions: first off, acetylcholine is positively charged so why would this be selective for sodium ion (another positively charged ion)?

Also, when they say increase membrane potential, does this mean the difference in potential is greater or that it becomes less negative (since in the context of the problem it is being flowed into a muscle cell where their concentration is low)

Thanks for any help I can get

[Babcock_Hall]

I don't know how selective the channel is for acetylcholine versus sodium ions, but the question is worded as a hypothetical, so perhaps it does not matter.  From the context of the question, I suspect that "greater" means less negative.

[Yggdrasil]

Acetylcholine ion channels (aka nicotinic acetylcholine receptors) are not channels for acetylcholine, they are channels for sodium and potassium ions.  They are gated by acetylcholine, meaning that they open only when they bind to acetylcholine or related molecules.

When they say that opening the nAChRs increases the membrane potential, they mean that the membrane potential becomes less negative (i.e. channel opening depolarizes the cell).