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

This is an example of spatial summation. Because in spatial summation many neurons with excitory post synaptic potential reaches a particular post synaptic neuron at the same time. In temporal summation , many EPSPs are produced in specific intervals on the same postsynaptic cell. Here 14 neurons produces EPSP on the same postsynaptic simultaneously and hence spatial summation. Action potentials are produced when the resting membrane potential reaches 0mV. The threshold for action potential is -55mV . When the RMP reaches -55mV action potential is fired. Here the RMP is -50mV and hence action potential is fired.