Assume a hypothetical postsynaptic neuron has three presynaptic inputs, X, Y, and Z.When presynaptic neurons X and Y are stimulated simultaneously, the postsynaptic neuron reaches threshold and undergoes an action potential.Yet, when presynaptic neurons X and Z are stimulated simultaneously, there is no change in potential of the postsynaptic neuron.Which of these statements describes the presynaptic neurons Y and Z
A)Presynaptic neurons Y and Z are both excitatory.
B)Presynaptic neurons Y and Z are both inhibitory.
C)Presynaptic neuron Y is excitatory, and presynaptic neuron Z is inhibitory.
D)Presynaptic neuron Y is inhibitory, and presynaptic neuron Z is excitatory.

Question

Quizplus · Accepted Answer

Since presynaptic neurons X and Y together can reach threshold and generate an action potential, we can assume that X and Y are excitatory. If the postsynaptic neuron does not change its potential when X and Z are stimulated together, it is likely that Z is inhibitory. Therefore, presynaptic neuron Y must be excitatory and presynaptic neuron Z must be inhibitory.

Assume a Hypothetical Postsynaptic Neuron Has Three Presynaptic Inputs, X