a Where is the site of action potential initiation where the

a) Where is the site of action potential initiation (where the decision is made to fire an action potential)? (b) Why are action potentials most likely initiated at this site than in the soma? Consider pan-NaV antibody staining (green indicates staining of Nav channels).

Solution

a) The distal end of axon i.e. the unmyelinated initial segment of axon serves as site for decision making to fire an action potential. It is an \"all or none\" event and once the decision is made, the actiona potential is fired down the axon.
b) Soma is not the site for initiation of action potential. This is due to the fact that soma is the metabolic center of the neuron and has lower density of sodium channels. These channels are prerequisite for firing of action potential. So,higher density of these channels at the axon initial segment and comparative lower density in soma makes it not to fire the action potential at soma.