Excitory postsynaptic potential (EPSP) - Neurotransmitters open Na channels in the postsynaptic membrane causing an inflow of Na+ ions and depolarisation of the membrane.
If there are sufficient EPSPs, the positive charge in the post-synaptic membrane will exceed the threshold level and an action potential is set up.
Inhibitory postsynaptic potential (IPSP) - neurotransmitters open Cl and K channels causing Cl- ions to flow into the cell and K+ ions to flow out, resulting in hyperpolarisation of the membrane. IPSPs make the postsynaptic membrane less receptive to incoming signals.
If the EPSPs outnumber the IPSPs and the threshold potential is reached a new action potential is generated.
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