Difference Between Presynaptic Neuron and Postsynaptic Neuron

The key difference between presynaptic neuron and postsynaptic neuron is that the presynaptic neuron is involved in releasing the neurotransmitter while the postsynaptic neuron is involved in receiving the neurotransmitter.

Neurotransmission is the transmission of nerve impulses. This process is a well-coordinated process that takes place through neurons. The synapse is the gap between nerve endings that are physiologically developed for efficient nerve impulse transmission. Most synapses are chemical and others are electrical; chemical synapses communicate using chemical messengers, and electrical synapses communicate through ions flowing directly between cells. At a chemical synapse, the postsynaptic neuron releases neurotransmitters when an action potential is triggered. These molecules then bind to the receptors on postsynaptic cells to fire an action potential.

CONTENTS

1. Overview and Key Difference
2. What is Presynaptic Neuron 
3. What is Postsynaptic Neuron
4. Similarities – Presynaptic Neuron and Postsynaptic Neuron
5. Presynaptic Neuron vs Postsynaptic Neuron in Tabular Form
6. Summary

What is a Presynaptic Neuron?

The presynaptic neuron is the neuron that opens the synapse and mainly functions in releasing the neurotransmitters. Acetylcholine is the main neurotransmitter released to the synapse from the presynaptic neuron. The release of the neurotransmitter from the presynaptic neuron ending takes place in response to the action potential reaching the end of the axon. Thus, the presynaptic neuron’s primary function is to conduct and transmit the incoming nerve impulse to the synapse.

Figure 01: Presynaptic Neuron

The release of the neurotransmitter from the presynaptic neuron takes place via exocytosis. Presynaptic knobs are formed at the terminal of the presynaptic neuron. The presynaptic knobs or vesicles then release the neurotransmitter to the synapse. The release of the neurotransmitter thus activates the opening of the calcium channel. This, in turn, activates the transmission of the nerve impulse from the presynaptic neuron to the synapse. Following this, the postsynaptic neuron takes part in receiving the signal.

What is a Postsynaptic Neuron?

Postsynaptic neuron is the neuron that takes part in receiving the neurotransmitter during the nerve impulse transmission. The postsynaptic neuron receives the neurotransmitter at the synapse to facilitate the transmission of the action potential.

Figure 02: Postsynaptic Neuron

This physiological mechanism takes place through the activation of the postsynaptic receptors. Following this action, the nerve impulse transmits to the postsynaptic neuron through the synapse. Then the ligand gates channels or the G protein receptors are activated, and the signal transmission is complete. Upon the completion of the nerve impulse transmission, depolarization takes place, and the Calcium channels close.

Similarities Between Presynaptic Neuron and Postsynaptic Neuron

  1. Both presynaptic and postsynaptic neurons are essential in nerve impulse transmission.
  2. They are sensitive to neurotransmitters.
  3. Both presynaptic and postsynaptic neurons border the synapse
  4. These neurons have special endings or knobs.

Difference Between Presynaptic Neuron and Postsynaptic Neuron

The key difference between presynaptic neuron and postsynaptic neuron is the direction of neurotransmitter activity. While the presynaptic neuron releases the neurotransmitter, the postsynaptic neuron receives the neurotransmitter to facilitate nerve impulse transmission. The presynaptic neuron undergoes exocytosis to release the neurotransmitter, while the postsynaptic neuron undergoes endocytosis to receive the neurotransmitter. Thus, this is another significant difference between presynaptic neuron and postsynaptic neuron.

The below infographic tabulates the differences between presynaptic neuron and postsynaptic neuron for side by side comparison.

Summary – Presynaptic Neuron vs Postsynaptic Neuron

Nerve impulse transmission at the synapse is mediated by neurotransmitters. The release of neurotransmitters is important in order to maintain the continuity of the transmission signal. Thus, the presynaptic neuron takes part in releasing the neurotransmitter to the synapse. The release of the neurotransmitter from the presynaptic neuron ending takes place in response to the action potential reaching the end of the axon. Upon this, polarization is activated, and the calcium gated channels open. Acetylycholine is the main neurotransmitter that releases to the synapse from the presynaptic neuron. The postsynaptic neuron takes part in receiving the neurotransmitter to complete the nerve impulse transmission across the synapse. Then, depolarization is activated as the postsynaptic neuron is activated. Thus, this is the summary of difference between presynaptic neuron and postsynaptic neuron.