AUTONOMIC NERVOUS SYSTEM

IT IS USEFULL FOR THE B.PHARM AND PHARM D STUDENTS AND ALSO FOR DIPLOMA IN PHARMACY AND ALSO NURSING AND MEDICAL STUDENTS

1. AUTONOMIC NERVOUS SYSTEM (ANS) SURESH BABU EMANDI M.Pharm Vikas Institute of Pharmaceutical Sciences Near Air Port, Rajahmundry, Andhrapradesh-533102.

2. Autonomic nervous system (ANS) is primarily concerned with regulation of visceral or vegetative functions of the body. So , it is also called vegetative or involuntary nervous system.

3. DIVISIONS OF ANS From anatomical and physiological point of view, ANS is divided into two divisions. Sympathetic division. 2 . Parasympathetic division.

4. DIVISIONS OF ANS

5. SYMPATHETIC DIVISION Sympathetic division is otherwise called thoracolumbar outflow because, the preganglionic neurons are situated in lateral gray horns of 12 thoracic and first two lumbar segments of spinal cord. Fibers arising from here are known as preganglionic fibers. Preganglionic fibers leave the spinal cord through anterior nerve root and white rami communicantes and terminate in the postganglionic neurons, which are situated in the sympathetic ganglia. Sympathetic division supplies smooth muscle fibers of all the visceral organs such as blood vessels, heart, lungs, glands, gastrointestinal organs, etc.

6. SYMPATHETIC GANGLIA Ganglia of sympathetic division are classified into three groups. P aravertebral or sympathetic chain ganglia B . Prevertebral or collateral ganglia C . Terminal or peripheral ganglia.

7. Paravertebral or Sympathetic Chain Ganglia Paravertebral or sympathetic chain ganglia are arranged in a segmental fashion along the anterolateral surface of vertebral column. Ganglia on either side of the spinal cord are connected with each other by longitudinal fibers, to form the sympathetic chains.

8. Classical comparison of sympathetic and parasympathetic divisions of autonomic nervous system

9. Prevertebral or Collateral Ganglia Prevertebral ganglia are situated in thorax, abdomen and pelvis, in relation to aorta and its branches. Prevertebral ganglia are: 1. Celiac ganglion 2. Superior mesenteric ganglion 3. Inferior mesenteric ganglion. Prevertebral ganglia receive preganglionic fibers from T5 to L2 segments. Postganglionic fibers from these ganglia supply the visceral organs of thorax, abdomen and pelvis.

10. Terminal or Peripheral Ganglia Terminal ganglia are situated within or close to structures innervated by them. Heart , bronchi, pancreas and urinary bladder are innervated by the terminal ganglia

11. PARASYMPATHETIC DIVISION Parasympathetic division of ANS is otherwise called the cranio -sacral outflow because, the fibers of this division arise from brain and sacral segments of spinal cord.

12. CRANIAL OUTFLOW OR CRANIAL PORTION OF PARASYMPATHETIC DIVISION Cranial outflow or cranial portion of parasympathetic division arises from brainstem. It innervates the blood vessels of head and neck and many thoraco -abdominal visceral organs.

13. Cranial outflow includes the following cranial nerves: 1 . Oculomotor (III) nerve 2 . Facial (VII) nerve 3 . Glossopharyngeal (IX) nerve 4 . Vagus (X) nerve .

14. Preganglionic fibers of these cranial nerves arise from neurons situated at two different levels: Tectal or midbrain outflow (III cranial nerve) 2 . Bulbar level or bulbar outflow (VII, IX and X cranial nerves). Preganglionic fibers are longer and reach the postganglionic neurons, which are situated within the organs or close to the organs innervated by these nerves. Preganglionic fibers are myelinated , but the postganglionic fibers are non- myelinated .

15. FUNCTIONS OF ANS Autonomic nervous system is concerned with the regulation of functions, which are beyond voluntary control. By controlling the various vegetative functions, ANS plays an important role in maintaining constant internal environment (homeostasis). Almost all the visceral organs are supplied by both sympathetic and parasympathetic divisions of ANS and the two divisions produce antagonistic effects on each organ . When the fibers of one division supplying to an organ is sectioned or affected by lesion, the effects of fibers from other division on the organ become more prominent.

16. NEUROTRANSMITTERS OF ANS Different nerve fibers of ANS execute the functions by releasing some neurotransmitter substances. SYMPATHETIC FIBERS Preganglionic fibers: Acetylcholine (Ach) 2 . Postganglionic noradrenergic fibers: Noradrenaline 3 . Postganglionic cholinergic fibers: Ach Postganglionic sympathetic cholinergic nerve fibers supply sweat glands and blood vessels in heart and in skeletal muscle. „ PARASYMPATHETIC FIBERS Preganglionic fibers: Ach 2 . Postganglionic fibers: Ach