Autonomic nervous system ANS

ANS

 Autonomic nervous system consist of peripheral nerve that nerve is embedded in organs such as heart, lungs, digestive tract and other visceral organ. Higher nerve center of brain is regulated autonomic nervous system. 

Autonomic nervous system is divided into two

1. Sympathetic nervous system
2. Parasympathetic nervous system
   

Physiological changes brought about by sympathetic will be opposed by parasympathetic nervous system or vice-versa.

Each of these systems possesses three parts

1. Pre ganglionic fibers
2. Post ganglionic fibers
3. Ganglia

Sympathetic nervous system

There are 21 pairs of sympathetic ganglia, which are embedded on both side of vertebral column. These sympathetic ganglia form a chain called sympathetic trunk or lateral chain ganglia or sympathetic chain. 

The pre-ganglionic fibers comes from the gray matter of spinal cord. 

The spinal nerve has 3 parts:

1. Ramus dorsalis
2. Ramus ventralis
3. Ramus communicans
   

Pre-ganlionic sympathetic fiber secretes acetylcholine (Ach), which work as a neurotransmitter. Pre-ganlionic sympathetic fibers are short.

Post-ganlionic sympathetic fiber secretes adrenaline and nor- adrenaline on all the target organs. Post-ganlionic sympathetic fibers are long.

This system is also known as adrenergic system.

 

Parasympathetic nervous system

Parasympathetic ganglia are present near and/or within the wall of organ. They cannot form a chain as sympathetic ganglia. They are distinctly present as per target organ.

Pre-ganlionic parasympathetic fibers are arise from brain and sacral region of spinal cord. 

Cranial nerve from brain

III – Occulomotor
VII – Facial
IX – Glassopharyngeal
X – Vagus

The 4 pair of cranial nerves and 3 pair of sacral spinal nerve gives out pre-ganlionic parasympathetic fibers.

Pre and post ganlionic parasympathetic fibers both secretes acetylcholine (Ach) as neurotransmitter.

This system is also known as cholinergic system.

Functions of autonomic nervous system

Sympathetic system is utilizes energy and parasympathetic system conserve energy. 

Sympathetic nervous system gets activated on following condition-

1. Fear
2. Fight
3. Flight – Run away from situation