Synapses

The synaptic knob, the space between neurons (Synaptic cleft) and the portion of the cell to which, the impulse is being transmitted constitute the synapses. According to the change in target cell; the synapse can be differentiated like neuron to neuron synapse or neuron to muscle (or gland) synapse.

As a message travels down the neuron, it reaches a synapse that it must cross to the neuron; it reaches a synapse that it must cross to “jump” to the next neuron. According to this “jumping” process the synapses can be classified into two types

1. An electrical synapse

2. A chemical synapse

In an electrical synapse, the electrical nerve impulses of two cells cross directly through a very small separation (called gap junction or nexus) from the presynaptic to the postsynaptic cells; this type of synapses is found in smooth and cardiac muscles.

In chemical synapses, the chemical substances called neuro transmitters are discharged into the space (cleft) between two neurons and proposal the message onto the next neurotic presynaptic neurons to post synaptic neuron. The neuro transmitter excites, inhibits or modifies signals to the second neuron by interacting with the receptors on its membrane .More than 100 neuro transmitters have been identified. Important one’s are

1. Acetylcholine

2. Serotonine

3. Dopamine

4. Nor-epinephrine

5. Gamma amino butyric acid

Category: Physiology Notes