Figure 5.13  The generation of an EPSP.  (a) An impulse arriving in the presynaptic terminal causes the release of neurotransmitter.  (b) The molecules bind to transmitter-gated ion channels in the postsynaptic membrane.  If Na⁺ enters the postsynaptic cell through the open channels, the membrane will become depolarized.  (c) The resulting change in membrane potential (V_m), as recorded by a microelectrode in the cell, is the EPSP.