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What triggers the opening of sodium channels in a neuronal membrane? Is it acetylcholine that activates sodium channels in the postsynaptic membrane?

Are sodium channels like receptors that have to bind to something (like a protein or an ion) to open? If so, what is the substance that forces Na+ channels to open?

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Sodium channels are primarily voltage-gated - these are the channels responsible for action potentials.

Many other receptors are ligand-gated, and these are typically the signal that causes the initial voltage change that opens the voltage-gated sodium channels; however, these channels are less selective cation channels and are permeable to ions like potassium as well as sodium. Still, their permeability to sodium is quite important and so they may also be thought of as sodium channels sometimes.

These include neurotransmitter gated channels like nicotinic acetylcholine receptors and AMPA (glutamate) receptors, and transient receptor potential channels like the TRPV1 receptor that is sensitive to painful heat and the chemical capsaicin which makes chili peppers "hot."

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  • $\begingroup$ Thanks for the answer but I'm still confused. The Wikipedia link says that a change in the cell's membrane causes a change in the state of nearby Na+ channels and opens them. But I thought that a change in the membrane's electric potential (i.e. action potential?) is possible after the sodium channels have opened already and not before it. So, how can the cell's membrane potential change if no sodium ions have entered the cell yet? Do you see what I'm trying to say? I'm afraid that I'm not explaining myself well. $\endgroup$ – stressed out Sep 24 at 19:24
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    $\begingroup$ @stressedout Action potentials are driven by a positive feedback loop among voltage-gated sodium channels once a cell is depolarized enough. The initial depolarization is not an action potential and comes from someplace else, usually the ligand-gated channels I described. I recommend a basic textbook on neurobiology like Purves' "Neuroscience" or Kandel's "Principles of Neural Science" - both will explain this in detail. $\endgroup$ – Bryan Krause Sep 24 at 19:46

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