Question

Describe EPSP’s and IPSP’s and how spatial and temporal summation relate to EPSP’s and IPSP’s. Include a discussion of how EPSP’s lead to an action potential.

Answer 1

EPSP is excitatory postsynaptic potential. This is a temporary depolarization(loss of difference in charge between inside and outside of nerve cell)of the postsynaptic membrane which is nerve cell caused by the flow of positively charged ions into postsynaptic cell. This will result in the opening of ligand-sensitive channels. So this makes a postsynaptic neuron to fire an action potential when connected to a dendrite.

How EPSP lead to action potential:

The EPSP signal is first transmitted to a dendrite and this is connected with other inputs at the axon hilllock(the part of the cell body of neuron that connects axon) The EPSP increases membrane potential to the neuron and when it reaches the threshold then the cell produces an action potential. This sends the information down the axon to communicate with postsynaptic cells.

IPSP is inhibitory postsynaptic potentials. This is just the opposite of EPSP which is a temporary hyperpolarization of the postsynaptic membrane caused by the flow of negatively charged ions into the postsynaptic cell. So to fire an action potential the same mechanism that occurs in EPSP happens in IPSP.

How spatial and temporal summation is related to EPSP and IPSP:

A EPSP may not generate action potential but several EPSPs can produce. And this is done by spatial and temporal summation. The spatial summation occurs when several EPSPs are produced simultaneously at different synapses that are located on different regions of a cell. Whereas temporal summation means summation of many EPSPs at a same synapse generated by high frequencies of action potentials.

IPSP also undergo spatial and temporal summation. The spatial and temporal summation in Ipsp occurs just as it occured in Epsp. But in Ipsp it results in greater membrane hyperpolarization and whereas in Epsp greater membrane depolarization.