Difference Between Presynaptic Neuron and Postsynaptic Neuron

Difference Between Presynaptic Neurons and Postsynaptic Neurons: Presynaptic Neurons and Postsynaptic Neurons are two neurons that are involved in forming chemical synapses for the transmission of impulses between two neurons. The major difference between a presynaptic neuron and a postsynaptic neuron is that the presynaptic neuron is involved in transmitting a message to the synaptic cleft by releasing neurotransmitters while the postsynaptic neuron is involved in receiving the message from the synaptic cleft by taking up neurotransmitters from the cleft.

In this article, you will study the Difference between Presynaptic Neuron and Postsynaptic Neuron, along with their similarities.

What is a Synapse?

The synapse is a junction between two neurons that helps in nerve impulse transmission. The presynaptic neuron, synaptic cleft, and post-synaptic neuron collectively form a chemical synapse. Synapse is of two types- chemical synapse and electrical synapse.

• ​Chemical synapse –  In the Chemical synapse, two neurons are not in direct contact, and thus for transmission, chemical messengers, also known as neurotransmitters are needed. This type of transmission is slow.
• Electrical synapse- In the Electrical synapse, two neurons are in direct contact with the help of gap junctions, and thus ions flow directly between neurons. Transmission is quick in this type of synapse.

What is a Presynaptic Neuron?

The presynaptic neuron is the neuron that is involved in transmitting the message to the synaptic cleft by releasing neurotransmitters such as Acetylcholine (Ach). It is present before the synaptic cleft. Its function is to send the information.
When the wave of depolarization reaches the axon ending of the presynaptic neuron, calcium channels present on the presynaptic membrane open, and the influx of calcium ions occurs. Calcium ions bind with synaptic vesicles present in synaptic knobs or terminal knobs of axons. After this, synaptic vesicles containing neurotransmitters fuses with the presynaptic membrane and release neurotransmitters in the synaptic cleft. The process involved is exocytosis. After this, the postsynaptic neuron will receive the message.

What is a Postsynaptic Neuron?

The postsynaptic neuron is the neuron that is involved in receiving the message by taking up the neurotransmitters from the synaptic cleft during nerve impulse transmission. It is present after the synaptic cleft. Its function is to receive the information.
On the membrane of the dendrite of the postsynaptic neuron, receptors for neurotransmitters such as Ach receptors are present. The neurotransmitters in the synaptic cleft released by presynaptic neuron binds with their receptors on postsynaptic neuron and this way the wave of depolarization is transferred to other neuron. The process involved is endocytosis.

Difference Between Presynaptic Neuron and Postsynaptic Neuron

Here’s the Tabular Difference between Presynaptic Neuron and Postsynaptic Neuron with their definition, location, functions, effects etc.

Features	Presynaptic Neuron	Postsynaptic Neuron
Definition	The presynaptic neuron is the neuron that is involved in transmitting the message to the synaptic cleft by releasing neurotransmitters	The postsynaptic neuron is the neuron that is involved in receiving the message by taking up the neurotransmitters from the synaptic cleft during nerve impulse transmission.
Location	Occurs before synaptic cleft	Occurs after synaptic cleft
Function	Sends Information	Receives Information
Effects	Opening of calcium channels	Closing of calcium channels
Result	The nerve impulse is transmitted to the synapse	The nerve impulse is transmitted from the synapse to another neuron.
Process Involved	Exocytosis	Endocytosis
Type of knobs that mediate transmission	Presynaptic knobs	Postsynaptic receptors

Similarities Between Presynaptic Neuron and Postsynaptic Neuron

As Presynaptic Neurons and Postsynaptic Neurons are different from each other, still they have a lot of common things. Here’s some of the similarities between Presynaptic Neurons and Postsynaptic Neurons:

1. Both presynaptic and postsynaptic neurons rely on neurotransmitters for communication. The presynaptic neuron releases neurotransmitters into the synaptic cleft, while the postsynaptic neuron receives these neurotransmitters.
2. Both presynaptic and postsynaptic neurons collectively form a chemical synapse, where information is transmitted from one neuron to another through neurotransmitter release and reception.
3. Both presynaptic and postsynaptic neurons play essential roles in nerve impulse transmission. The presynaptic neuron initiates the transmission by releasing neurotransmitters, and the postsynaptic neuron receives the message by binding to these neurotransmitters.
4. Both presynaptic and postsynaptic neurons are affected by the opening and closing of calcium channels. In the presynaptic neuron, calcium channels open upon depolarization, leading to neurotransmitter release. In the postsynaptic neuron, calcium channels are involved in depolarization upon binding of neurotransmitters.
5. Both presynaptic and postsynaptic neurons possess specific receptors on their membranes that interact with neurotransmitters during the transmission process.

FAQs on Difference Between Presynaptic Neuron and Postsynaptic Neuron

1. What are the functions of presynaptic and postsynaptic neurons?

The function of the presynaptic neuron is to transmit messages to the synaptic cleft by releasing neurotransmitters. On the other hand, the postsynaptic neuron receives messages by taking up neurotransmitters from the synaptic cleft during nerve impulse transmission.

2. What is the location of a presynaptic neuron compared to a postsynaptic neuron?

The presynaptic neuron occurs before the synaptic cleft, while the postsynaptic neuron occurs after the synaptic cleft.

3. How do presynaptic and postsynaptic neurons affect calcium channels during transmission?

In the presynaptic neuron, the opening of calcium channels occurs upon depolarization, facilitating the release of neurotransmitters. In contrast, the postsynaptic neuron experiences the closing of calcium channels upon binding of neurotransmitters during the reception process.

4. What process is involved in transmitting messages in a presynaptic neuron?

The presynaptic neuron employs exocytosis, where synaptic vesicles fuse with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft.

5. How does a postsynaptic neuron receive messages from the synaptic cleft?

The postsynaptic neuron utilizes endocytosis to take up neurotransmitters from the synaptic cleft, leading to depolarization and nerve impulse transmission.