Ans

ANS: •The nervous system is made up of CNS (Central Nervous System) & PNS (Peripheral nervous System). The CNS is made up of brain and spinal cord. And the PNS is made up of SNS & ANS.

•Autonomic nervous system (ANS) is mostly innervates visceral organs of the body. Two neurons are present in the ANS pathway. One is called as preganglionic neuron and other is called as post ganglionic neuron. The junction beween two neurons is called as ganglion or synapse.

Preganglionic neurons: Its cell body is present in the brain or spinal cord and its axon is elongated from inside to outside of CNS. The axon is myelinated. Actually, the cell body is present in the lateral horn of gray matter in thoracolumbar division (sympathetic). And cell body of cranio-sacral division is presence in the cranial nerves. Postganglionic neurons: It is the second neuron present after the ganglia. Its cell body and dendrites are located in the autonomic ganglion. It is unmyelinated. Ganglia: it is the junction between the preganglionic neuron and postganglionic neuron. By positioning of ganglia in to the body, they are sympathetic trunk, prevertebral and terminal ganglia SYMPATHETIC TRUNK GANGLIA: It is also known as paravertebral ganglia because located parallel on the either side of spinal cord. Mostly, the postganglionic neurons from

sympathetic trunk innervate the organs above the diaphragm like heart, lungs, salivary glands, special senses etc. PREVERTEBRAL GANGLIA: They are collateral ganglia located outside the line of paravertebral ganglia. The postganglionic neurons from vertebral ganglia innervate the organ below the diaphragm like stomach, intestine, pancreas, kidney, reproductive organs etc. It is also sympathetic type of ganglia. TERMINAL GANGLIA: The axons and cell bodies synapse in to terminal ganglia are from the parasympathetic division. It is also called as intramural ganglia. It is presence near the walls of visceral organs. It innervates most of the visceral. •ANS is broadly divided in to two: sympathetic & parasympathetic. •Sympathetic division:

Ø It is also known as thoracolumbar Ø Cell bodies of preganglionic neurons are presence in to lateral horn of gray matter in all thoracic and two lumbar region of the spinal cord. Ø The preganglionic neurons axons are shorter than the postsynaptic axons. Ø The preganglionic axons leave the spinal cord through anterior root of spinal nerve. After that the preganglionic neurons enter a short pathway called as white ramus before passing to sympathetic trunk, containing myelinated neurons.

Ø The sympathetic trunk subdivided in to superior, middle, inferior ganglia. Ø Postganglionic axons from lumbar & sacral site enter a short pathway called as gray ramus and merge with spinal cord or enter in to visceral. Ø The preganglionic neuron releases acetylcholine (Ach) as neurotransmitter in to ganglia. Where as postganglionic neuron releases NA (nor-adrenaline) or Ach as neurotransmitter in the visceral organs. o Parasympathetic division:

Ø It is also called as cranio-sacral division. Ø Cell bodies of presynaptic neurons are located in the nuclei of brain stem (cranial nerve) and in lateral horn of gray matter in to sacral region.

Ø The preganglionic neurons are longer than postganglionic neurons & the ganglia located near to the effector organs or in to the wall of effector organ. Ø The ganglion is known as terminal ganglia which is of four type: ciliary ganglia, pterygopalatine ganglia, submandibular ganglia, otic ganglia. Ø Both preganglionic & postganglionic neurons release Ach as neurotransmitter