Synapse

Synapses are specialized junctions between neurons where electrical or chemical signals are transmitted from one neuron to another or to an effector cell, such as a muscle or gland. They are the functional connections that enable communication within the nervous system. At a synapse, the transmitting neuron, known as the presynaptic neuron, releases neurotransmitter molecules into the synaptic cleft, a small gap between the presynaptic and postsynaptic neurons. These neurotransmitters bind to receptors on the postsynaptic neuron, initiating a cascade of events that either excite or inhibit the postsynaptic neuron, influencing whether an action potential is generated in the postsynaptic neuron. Synapses play a critical role in information processing, memory formation, and the coordination of physiological functions within the nervous system.

Neurotransmitter: 

Transmission of  an electrical impulse via synapse:

When an impulse reaches the end of the presynaptic neuron’s axon, it triggers the release of neurotransmitter molecules from synaptic vesicles into the synaptic gap.

The arrival of the impulse stimulates synaptic vesicles in the presynaptic neuron to release a small amount of neurotransmitter molecules into the synaptic cleft.

The neurotransmitter molecules quickly diffuse across the synaptic gap and bind with specific receptor proteins located on the membrane of the postsynaptic neuron’s cell body or dendrite.

The binding of neurotransmitter molecules to receptor proteins causes changes in the postsynaptic neuron, which may lead to the generation of a new electrical impulse in the postsynaptic neuron.

Sometimes, multiple impulses may need to arrive at the synapse to release enough neurotransmitter molecules to reach the threshold for firing an impulse in the postsynaptic neuron.

Impulses only travel in one direction across synapses. This directional control is maintained because neurotransmitter molecules are only synthesized on one side of the synapse, while receptor proteins are only present on the other side.

Synapses slightly slow down the speed of nerve impulses due to the time it takes for neurotransmitter molecules to diffuse across the synaptic gap. This delay helps regulate the timing and coordination of neural signals.