Question

__________ is triggered if the membrane threshold at the axon hillock is depolarized to threshold.

A.) Summation
B.) Neuropeptides
C.) Action Potential
D.) Neurotransmitter

Answer 1

An Action Potential is initiated at the axon hillock when graded potentials summate, reaching a threshold that opens voltage-gated Na+ channels, starting the depolarization.

Step-by-step explanation:

An Action Potential is triggered if the membrane threshold at the axon hillock is depolarized to threshold. This depolarization occurs when graded potentials, which can be either excitatory postsynaptic potentials (EPSPs) or inhibitory postsynaptic potentials (IPSPs), summate, or add together, either spatially or temporally, to reach a particular threshold. When this threshold is reached, a high density of voltage-gated Na+ channels at the initial segment of the axon or the axon hillock open, initiating the depolarizing phase of the action potential that then propagates along the axon.