The full form of EPSP is excitatory postsynaptic potential. Postsynaptic potentials (PSPs) are graded potentials whose function is to inhibit or initiate action potentials. Here, let us explore the meaning, properties and significance of EPSP, which is a type of PSP.
Table of Contents
EPSP – Meaning
The primary role of the synapse is to transfer impulses or action potentials from one neuron to another. Depending on their functions, synapses are divided into 2 types:
- Synapses with inhibitory property
- Synapses with excitatory property
Excitatory Function
The non-propagated electrical potential that emerges during synaptic transmission is known as the excitatory postsynaptic potential (EPSP). The binding of excitatory neurotransmitters, that are released from the presynaptic membrane, results in the formation of EPSP. The presynaptic nerve’s vesicles contain the excitatory neurotransmitters that are released to generate an action potential.
The common excitatory neurotransmitter is acetylcholine. At the neuromuscular junction, acetylcholine acts by attaching to receptors and activating ligand-gated channels. As a result, sodium ions with positive charges start to enter the postsynaptic cell. An action potential is produced on the postsynaptic nerve by the depolarization of the postsynaptic membrane.
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Excitatory Neurotransmitters |
Excitatory and Inhibitory Neurotransmitters |
Inhibitory Neurotransmitters |
|
Acetylcholine Glutamate Aspartate |
Adrenalin Noradrenalin |
Serotonin Dopamine Glycine |
Properties of EPSP
EPSP is restricted to the synapse only. It typically increases the neurons’ membrane potential. Like IPSPs, EPSPs are graded (have an additive effect). The combined effect of multiple EPSPs on a single region of the postsynaptic membrane equals the sum of the individual EPSPs. EPSP possesses 2 main qualities:
1. It is non-propagated.
2. It disobeys the all-or-none law.
All-or-none or all-or-nothing law states that the degree to which a muscle or nerve fibre reacts to a stimulus is unrelated to the stimulus’s intensity. When a stimulus is greater than a threshold potential, the nerve fibre either responds fully or there is no response.
See more: Difference between Electrical and Chemical Synapse
Significance of EPSP
Fast EPSP plays a crucial role in the quick transformation of neurally encoded information between neuronal cell bodies and axons as well as the dendrites that make up the enteric microcircuitry.
EPSP does not enter the axon of a postsynaptic neuron. However, it results in the axon’s development of an action potential. The initial segment of the axon opens voltage-gated sodium channels when EPSP is strong enough to do so. Now that sodium ions have entered the cell, the action potential begins to form as the first segment of the axon depolarizes. The action potential then spreads to other axonal segments from this point.
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