What happens at the synapse between two neurons?

At a synapse, which is the junction between two neurons (nerve cells), information is transmitted from one neuron to another. The synapse is a critical site for communication in the nervous system, and the process involves a series of events. Here’s an overview of what happens at the synapse:

1. Presynaptic Neuron:
» The neuron that sends the signal is called the presynaptic neuron. When an action potential (electrical signal) reaches the end of the axon (the long, fiber-like extension of a neuron), it triggers the release of neurotransmitters.

2. Release of Neurotransmitters:
» The action potential arriving at the presynaptic terminal causes the synaptic vesicles (small sacs containing neurotransmitters) to fuse with the cell membrane.

» This fusion releases neurotransmitters into the synaptic cleft, a tiny gap between the presynaptic neuron’s axon terminal and the postsynaptic neuron’s dendrites.

3. Synaptic Cleft:
» The synaptic cleft is the extracellular fluid-filled space between the presynaptic and postsynaptic neurons. Neurotransmitters traverse this gap to transmit the signal.

4. Neurotransmitter Binding:
» The neurotransmitters released into the synaptic cleft bind to specific receptor sites on the postsynaptic neuron’s membrane. The postsynaptic membrane is usually on the dendrites or the cell body of the neuron.

5. Postsynaptic Response:
» The binding of neurotransmitters to receptors on the postsynaptic neuron’s membrane triggers a response. This response can be excitatory or inhibitory, depending on the type of neurotransmitter and its receptor.

» Excitatory: If the neurotransmitter promotes the generation of an action potential in the postsynaptic neuron, it is excitatory. This typically involves the opening of ion channels that depolarize the postsynaptic membrane.
» Inhibitory: If the neurotransmitter inhibits the generation of an action potential, it is inhibitory. This may involve the opening of ion channels that hyperpolarize the postsynaptic membrane, making it less likely to generate an action potential.

6. Reuptake or Enzymatic Breakdown:
» After neurotransmitters transmit the signal, they can be removed from the synaptic cleft through reuptake by the presynaptic neuron or broken down by enzymes in the synaptic cleft.

7. Termination of Signal:
» The termination of the signal is crucial to prevent continuous stimulation. The removal of neurotransmitters from the synaptic cleft ends the postsynaptic response.
This process of synaptic transmission allows information to be transmitted from one neuron to another, enabling communication within the nervous system. The specificity of neurotransmitter-receptor interactions contributes to the precision and complexity of neural signaling.