Answer:
<h2>Excitatory postsynaptic potential (EPSP): brings the postsynaptic membrane potential closer to threshold
.</h2><h2>Inhibitory postsynaptic potential (IPSP): it moves the postsynaptic membrane potential farther away from threshold
.</h2><h2>In both cases: it is a graded potential in both.</h2>
Explanation:
Excitatory postsynaptic potential (EPSP):
i) EPSP brings the postsynaptic membrane potential closer to threshold
ii) it depolarizes the postsynaptic membrane
; and
iii) it results from the movement of Na+ ions into postsynaptic cell
.
Inhibitory postsynaptic potential (IPSP):
i) it moves the postsynaptic membrane potential farther away from threshold
;
ii) it hyper-polarizes the postsynaptic membrane
;
iii) it results from the movement of K+ ions out of the postsynaptic cell
In both cases: it is a graded potential
.
Excitatory postsynaptic potentials (EPSPs) are excitatory because they make the postsynaptic neuron to generate an action potential by depolarizing the membrane and bringing the membrane potential closer to threshold where new action can generate . This happens by opening ligand-gated Na+ channels in the postsynaptic membrane, which then allows Na+ ions to enter the cell.
Inhibitory postsynaptic potentials make it more difficult for the postsynaptic neuron to produce an action potential by hyper-polarizing the membrane and moving the membrane potential farther from threshold. This happens by opening ligand-gated K+ channels, which allows K+ ions to move out of the cell.
Regardless of as they are excitatory or inhibitory, all postsynaptic potentials are graded. And because a postsynaptic potential is not propagated like an action potential, its magnitude decreases with distance from the synapse along with the cell body.