Look at the diagram of three nerve cells on the right. At the bottom, there is a postsynaptic cell, which receives chemical synapses from two presynaptic cells, which are shown at the top of the diagram. One of the presynaptic cells is labeled excitatory and the other is labeled inhibitory. Assume that a single action potential in a presynaptic cell does not produce an action potential in the postsynaptic cell. Show (by drawing a graph of membrane potential against time) how the membrane potential of the postsynaptic cell changes if there is one action potential in:
a.only the excitatory presynaptic cell.
b.only the inhibitory presynaptic cell.
c.both the inhibitory and the excitatory presynaptic cells.