What does depolarization of a neuron have to do with sending a signal to another neuron?

Question

I know that dendrites of a neuron receive a chemical "code" that produces an electrical current of either excitatory or inhibitory signals inside the neuron. This electrical current gets sent down the axon. If there is enough energy to reach the requirement for the threshold, then the action potential is reached. Once that happens, Sodium floods back into the neuron. The vesicles then send out neurotransmitters (chemical signals) through the synapse to the next neuron. I just don't get what the depolarization of the neuron (which happens when the sodium flows back inside) has to do with the signal being sent.

Geoff · Accepted Answer

An action potential is actually a self-propagating wave of depolarization, so the depolarization IS the signal.  In the cell membrane of the axon, there are special sodium and potassium channels called voltage-gated ion channels, which are sensitive to how depolarized the membrane is.  If the membrane is depolarized enough, then the voltage-gated sodium channels open, which further depolarizes the cell, causing an action potential.  This large depolarization causes nearby voltage-gated sodium channels to open as well, which then spreads the depolarization further, which causes more voltage-gated sodium channels to open, and so on. This is how the action potential to propagates down the axon; not as a direct electric current within the axon (which can only travel a short distance before it is attenuated), but as a self-sustaining wave of membrane depolarization.

I hope that helps.

AnnaMaria · Answer

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What does depolarization of a neuron have to do with sending a signal to another neuron?

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