THE BRAIN SYSTEM-INTRODUCTORY
Central Nervous System which is originating from the Big Brain known as the Cerebrum is the major nervous system of our body. Unlike Autonomic Nervous System the CNS has many nerve transmitters, synapses, and a large array of inhibitory neurons.
The major nerve transmitters and their characters are as follows:-
1.Acetylcholine-Excitatory
2.Norepinephrine-Excitatory
3.Dopamine-Excitatory
4.Serotonin-Excitatory
5.Gamma Amino Butyric Acid (GABA), a neutral amino acid-Inhibitory
6.Glycine, an amino acetic acid, neutral,-Inhibitory
7.Aspartic Acid, an acidic amino acid-Excitatory
8.Glutamic Acid, an acidic aminoacid-Excitatory
Unlike in ANS which contains mostly G-coupled receptors, in CNS most of the receptors are ion gated receptors of sodium, potassium, calcium and chloride ions, like Na+, K+, Ca++, and Cl- respectively.
Excitation of a nerve initiated by the binding of an excitatory neurotransmitter at its receptors and opening the depolarizing ion gates of Na+or K+ or Ca++ to initiate an Excitatory Post Synaptic Potential(EPSP) when the nerve depolarize sufficiently to reach the threshold in order to stimulate an action potential to return to quick repolarization.
Inhibition of a nerve initiated by the action of an inhibitory neurotransmitter at its receptor and opening polarizing ion gates of Cl- to initiate an Inhibitory Post Synaptic Potential (IPSP) and the nerve depolarize insufficiently to reach the threshold in order to inhibit an action potential to delay the repolarization and the nerve becomes relaxed.
Drugs acting on CNS are affecting the production, storage, release, or metabolism of a neurotransmitter. Some drugs affect the postsynaptic receptors as mimics or blockers.
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