Action potential

Question

In order for an action potential to be produced at the axon hillock, what has to first happen?

A. Sodium ion channels must be inactivated

B. ESPS(Excitatory postsynaptic potential) had to have summated to threshold by the time they reach the axon hillock.

C. Action potentials had to summate to threshold by the time they reach the axon hillock?

Answer 1

Let's go through this question going through each option:

Hi Mike,

This is a great question so let's go through this each option at a time.

In A, if you were inactivate the voltage gated sodium channels, the neuron would be preparing to go into the re-polarization phase by way of the calcium channels. With this in mind, we can eliminate this option because the inactivation of the Sodium channels would not be the first step in the creation of an action potential.

In C, you can eliminate this answer because action potentials cannot be summated.

B is the correct answer because in order to form an action potential at the neruon's axon hillock, the presynaptic neuron has to excite the postsynaptic neuron by way of EPSPs in order depolarize the post synaptic neuron. The summation is a factor here because you need to combine EPSPs from mutliple presynaptic neurons for the neuron of interest to get to threshold potential. This more specifically is a type of summation that is known as spatial summation.

Hopefully this answer helped you out!