Consecutive neurons are so arranged that the axon endings of one neuron are connected to the dendrites of the next neurons. There is no cytoplasmic connected between the two neurons and Microscopic gaps are left between them. Each of these contact points is known as synapse.
A single neurons may form synapses with many incoming fibres of different neurons.
A neurons impulse is passed from one neurons to the other through the synapse, but a single impulse does not necessary get across the synapse. It may take two or three impulse arriving in rapid succession or perhaps simultaneously from two or more fiber to start an impulse in the next neurons.
The action potential cannot jump from one neurons to the next in line; rather the massage is transmission across synapse in the form of chemical messenger called neurotransmitter.
When an impulse reached a synapse knob, synapse vesicles within fuse with the presynaptic membrane, causing the release of neurons litter molecular into the synapse cleft. The neurotransmitter molecular bind to the reception , on the postsynaptic , triggering , an action potential in the postsynaptic neurons, by causing changes in its permeability to certain ions.
Neurotransmitters are chemical which are released at the axon ending of the neurons, at synapse . Many different types of neurotransmitter are known. These are; acetylcholine, adrenaline,nor- epinephrine, serotonin and dopamine.
Acetylcholine is the main transmitter for synapse that lie outside the central nervous system.
Others are mostly involved in synapses transmitter within the brain and spinal cord.