The microscopic gap present between the axon ending of one neuron to the dendrite of the other neuron is called synapse.
· It is not a cytoplasmic connection it is only a gap.
· A synapse may be formed by the single neuron with many other incoming neurons.
· Through synapse, a nerve impulse is transferred from one neuron to another.
· To get through the synapse, it is necessary to pass three or more impulses in rapid succession because a single impulse cannot get across a synapse.
Neurotransmitters
· A chemical messenger through which message containing by impulse is transferred from one neuron to another is called neurotransmitters.
· These chemical messengers are present because action potential cannot pass through neuron in line.
Types of neurotransmitters
ü Acetylcholine
ü Serotonin
ü Dopamine
ü Adrenaline
ü Nor epinephrine
The neurotransmitter which is responsible for synapse outside the central nervous system is acetylcholine.
Dopamine, nor epinephrine, serotonin and adrenaline are responsible for synapse transmission within the brain and spinal cord.
Communication across synapse
When impulse reaches at synaptic knob, its message goes into synaptic vesicles which contains neurotransmitters, these vesicles fuse with pre-synaptic membrane and neurotransmitters are released at synapse cleft. Post synaptic membrane is the membrane of next neuron which contains receptors and cause change to permeability to certain ions.
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