Question

The binding of neurotransmitter to ligand-gated ion channels in the postsynaptic membrane causes these channels to open. As soon as the neurotransmitter is removed from the synaptic cleft, the ligand-gated ion channels close. In the brief time these channels are open, ions are able to diffuse across the postsynaptic membrane down their electrochemical gradient. The result is a postsynaptic potential, a brief change in the membrane potential of the dendrites and cell body of the postsynaptic cell. There are two types of postsynaptic potentials: excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs). An EPSP is excitatory because it makes it more likely that the axon of the postsynaptic cell will trigger an action potential. Conversely, an IPSP is inhibitory because it makes it less likely that the axon of the postsynaptic cell will trigger an action potential. Sort the phrases into the appropriate bins depending on which type of postsynaptic potential they describe. If a phrase describes both types of potentials, drag it to the "both" bin.

Answer 1

Answer:

Excitatory postsynaptic potential (EPSP)

a) it  brings the postsynaptic membrane potential closer or nearer to threshold

b) it depolarizes the postsynaptic membrane ; and  

c) it results from the movement of Na+ ions into postsynaptic cell . .

Inhibitory postsynaptic potential (IPSP):

a)  it moves the postsynaptic membrane potential farther away from threshold .

b) it hyper-polarizes the postsynaptic membrane ;

c) it results from the movement of K+ ions out of the postsynaptic cell

In both cases:  it is a graded potential  in both.

Explanation:

Excitatory postsynaptic potentials 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 .It 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 occurs 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 by this , its magnitude decreases with distance from the synapse along with the cell body.