Fifteen different presynaptic neurons synapse on a single po

Fifteen different presynaptic neurons synapse on a single postsynaptic neuron. The postsynaptic neuron has a RMP of -70 mV. At the trigger zone, 14 of the presynaptic neurons produce excitatory postsynaptic potentials of 2 mV each, and the other one produces an inhibitory postsynaptic potential of 9 mV. The threshold for the postsynaptic neuron is -50 mV. Will action potentials be produced in the postsynaptic neuron? Is this an example of temporal summation or spatial summation? Explain your answers.

Solution

RMP OF POSTSYNAPTIC NEURON=-70mV

TOTAL POSTSYNAPTIC POTENTIAL BY PRESYNAPTIC NEURONS= (2mV*14)+ (-9mV)=28mV-9mV=19 mV

So,the postsynaptic neuron would depolarize and action potentials would be produced.

This is an example of spatial summation. The effect produced by a particular neuron to be able to achieve an action potential is referred to temporal summation whereas, spatial summation is the method of achieving an action potential in a neuron which receives input from several cells. In this case involvement of 15 presynaptic neurons makes it an example of spatial summation.