A postsynaptic neuron has three presynaptic inputs - from neurons X,Y and Z.When X and Y are stimulated simultaneously and repeatedly,the postsynaptic neuron reaches threshold and undergoes an action potential.When X and Z are stimulated simultaneously,however,there is no change in the membrane potential of the postsynaptic neuron.What can you tell about presynaptic neurons Y and Z?
A)They are probably both excitatory
B)They are probably both inhibitory
C)Y is probably excitatory and Z is probably inhibitory
D)Z is probably excitatory and Y is probably inhibitory

Question

Quizplus · Accepted Answer

If the postsynaptic neuron reaches threshold and undergoes an action potential when X and Y are stimulated together, it suggests that both X and Y are excitatory inputs. On the other hand, if there is no change in the membrane potential of the postsynaptic neuron when X and Z are stimulated together, it suggests that Z is an inhibitory input. Therefore, Y is probably excitatory and Z is probably inhibitory, making choice C the best option.

A Postsynaptic Neuron Has Three Presynaptic Inputs - from Neurons