Question

Create diagrams (of the cells) and graphs (of the potentials) to illustrate the two different situations described below in a multipolar neuron with a threshold voltage of 15 mV above resting potential. In each, indicate decrease over distance of graded potentials (by drawing the same graded potential at different points as it spreads along the neuron), as well as summation of excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs). Your answer should be included on this page only.

Situation 1: There are three simultaneously active synapses on the multipolar neuron, two producing EPSPs and one an IPSP. At least one of the EPSPs is larger than 15 mV at the synapse. The neuron does NOT generate an action potential.

Situation 2: There are two simultaneously active synapses, one producing an EPSP and the other an IPSP. The neuron generates an action potential.

Answer 1

An action potential is generated when,

the summated EPSP- the summated IPSP in an area of cell membrane reaches the threshold potential of that cell.

Situation 1: It represents that there are 3 simultaneously active synapses on a multipolar neuron ,two are producing EPSP and one is producing IPSP.

It is shown that according to spatial summation of 3 stimulus applied simultaneously the threshold potential is not reached and therefore,the action potential is not generated, despite being the fact that one of the EPSP is larger than 15mV.

Situation 2: It is represented that there are two simultaneously active synapses, one producing EPSP and another producing IPSP.

It is shown that according to spatial summation of two simultaneously applied stimulus,the threshold potential is reached and an action potential is generated.