Question

Compare and contrast excitatory and inhibitory post-synaptic potentials. In your answer, address the following:

1. How are they generated?
2. What is the outcome?
3. How might their size or strength be increased or decreased?
4. Why might you want to modify synaptic strength? Provide a mechanism.

Answer 1

Excitatory postsynaptic potential (EPSP) is a postsynaptic potential that makes the postsynaptic neuron more likely to fire an action potential, while Inhibitory post-synaptic potential is a post synaptic potential that makes the postsynaptic neurone less likely to fire an action potential

An EPSP is generated when there is  change in the membrane voltage of a postsynaptic cell following the influx of positively charged ions like sodium into a cell as a result of the activation of ligand-sensitive channels. This causes depolarization of the postsynaptic cell, thus increasing the likelihood of action potential propagation. An IPSP is generated when there is influx of negative ions like chlorine  into the cell or the efflux of positive ions like potassium ions out of the postsynaptic cell. This results in cell hyperpolarization and thus decreases the likelihood of action potential propagation

The size of the EPSP produced by a given amount of neurotransmitter increases with the size of the membrane potential of the postsynaptic cell. EPSPs are larger when the postsynaptic membrane is highly polarized than when it is relatively depolarized, simlarily size of IPSP decreases when the amount of neurotransmitter released is less

The size and strength of EPSP and IPSP can be increased or decreased based on the process of summation,  Synaptic potentials summate; that is, they add with each other in moving the membrane potential closer to or farther from the threshold of the nerve impulse in the process of summation. If two EPSP are added together or summated than the size or strength will be increased, on the other hand if tow IPSP are summated the size or srength can be decreased. Summation can be of two types Spatial summation which is the integration of postsynaptic potential that occurs in different location but at the same time, while Temporal summation is the integration of postsynaptic potential that occur in the same place but at different times (one after other)

d)  Changes in synaptic strength is thought to contribute to learning and memory.  the ability of synapses to strengthen or weaken over time is known as synaptic plasticity, Synaptic plasticity in both excitatory and inhibitory synapses has been found to be dependent upon postsynaptic calcium release.

Similarities between IPSP and EPSP.

Both are graded potentials; they increase in size as a function of the amount of neurotransmitter released. Both have similar durations, and both show synaptic delay