(i) What are the two divisions of autonomic nervous system?
(ii) How are these autonomic in their actions? Explain with reference to any three organs in human body.
(i) Two divisions of autonomic nervous system are:
- Sympathetic nervous system
- Para-sympathetic nervous system.
(ii) All visceral motor nerve fibres make the autonomic nervous system which is responsible to bring about nervous co-ordination of internal organs. Autonomic pathways control unconscious involuntary behaviour via 2 sets of connections to each target. These are from sympathetic system and parasympathetic nervous system. Sympathetic connections rouse in preparation for high act but parasympathetic nervous system restore clam. Smooth muscles, cardiac muscle are directed by antagonistic command from nerve pairs of the autonomic nervous system. These are called thoracolumbar outflow and craniosacral outflow.
Antagonism: Sympathetic and para-sympathetic nervous system are antagonistic to each other. Nerve fibres SNS are main adrenergic since they release the hormone nor adrenaline. They increase working of various visceral organs. The nerve fibres of parasympathetic system are cholinergic since they produce acetylcholine. It inhibits the working of various visceral organs.
Example: Sympathetic nervous system accelerates rate of heart beat, enhances arterial blood pressure, constricts most of the blood vessels while on the other hand nerve fibre of parasympathetic nervous system decreases rate of heart beat, lower arterial blood pressure, dilates most of blood vessels etc.