Autonomic Autonomic nervous nervous

systemsystemBy By

Pak Int’l Med Pak Int’l Med CollegeCollege

Peshawar::::Peshawar::::

The Autonomic nervous system is the portion of The Autonomic nervous system is the portion of the nervous system that controls most visceral the nervous system that controls most visceral functions of the bodyfunctions of the body

It is primarily concerned with the regulation of It is primarily concerned with the regulation of visceral or vegetative functions of the body, so it is visceral or vegetative functions of the body, so it is called vegetative or involuntary nervous systemcalled vegetative or involuntary nervous system

This system helps to control arterial pressure, This system helps to control arterial pressure, gastrointestinal motility, sweating, body gastrointestinal motility, sweating, body temperature and many other activities some of temperature and many other activities some of which are controlled almost entirely and some only which are controlled almost entirely and some only particularly by the autonomic nervous system.particularly by the autonomic nervous system.

One of the most striking characteristic of the One of the most striking characteristic of the autonomic nervous system is the rapidity and autonomic nervous system is the rapidity and intensity with which it can change visceral intensity with which it can change visceral functions.functions.

General organization of General organization of autonomic nervous system.autonomic nervous system.

The autonomic nervous system is The autonomic nervous system is activated mainly by centers located in activated mainly by centers located in the spinal cord, brainstem and the spinal cord, brainstem and hypothalamus. Also portions of the hypothalamus. Also portions of the cerebral cortex especially of the limbic cerebral cortex especially of the limbic cortex, can transmit signal to the lower cortex, can transmit signal to the lower centers and in this way influence centers and in this way influence autonomic controls.autonomic controls.

The autonomic nervous system also The autonomic nervous system also often operates through visceral reflexes.often operates through visceral reflexes.

Division of ANSDivision of ANSFrom anatomical and physiological From anatomical and physiological

point of view, the autonomic nervous point of view, the autonomic nervous system is divided into two divisions.system is divided into two divisions.

1.Sympathetic division1.Sympathetic division

2. Parasympathetic division.2. Parasympathetic division.

It is otherwise called It is otherwise called thoracolumber outflow thoracolumber outflow because the preganglionic because the preganglionic neurons are situated in lateral neurons are situated in lateral gray horns of 12 thoracic and gray horns of 12 thoracic and first two lumber segments of first two lumber segments of spinal cord. The fibers arising spinal cord. The fibers arising from here are known as from here are known as preganglionic fibers. The preganglionic fibers. The preganglionic fibers leave the preganglionic fibers leave the spinal cord through anterior spinal cord through anterior nerve root and white rami nerve root and white rami communicants and terminates communicants and terminates in the postganglionic neurons, in the postganglionic neurons, which are situated in the which are situated in the sympathetic ganglia.sympathetic ganglia.

Sympathetic division supplies Sympathetic division supplies smooth muscles fibers of all smooth muscles fibers of all the visceral organs such as the visceral organs such as blood vessels, heart, lungs, blood vessels, heart, lungs, glands, GIT etcglands, GIT etc

Sympathetic gangliaSympathetic ganglia

The ganglia of The ganglia of sympathetic division sympathetic division are classified into are classified into three groups.three groups.

1. Paravertebral or 1. Paravertebral or sympathetic chain sympathetic chain gangliaganglia

2. Prevertebral or 2. Prevertebral or collateral gangliacollateral ganglia

3. Terminal or 3. Terminal or peripheral gangliaperipheral ganglia

Paravertebral or Paravertebral or sympathetic chain gangliasympathetic chain ganglia

Paravertebral or sympathetic chain ganglia are Paravertebral or sympathetic chain ganglia are arranged in a segmental fashion along the arranged in a segmental fashion along the anterolateral surface of vertebral column.anterolateral surface of vertebral column.

The ganglia on either side of the spinal cord are The ganglia on either side of the spinal cord are connected with each other by longitudinal fibers to connected with each other by longitudinal fibers to form the sympathetic chains.form the sympathetic chains.

Both the chains extend from skull to coccyx Both the chains extend from skull to coccyx Ganglia of the sympathetic chain (trunk) on each Ganglia of the sympathetic chain (trunk) on each

side are divided into four groups.side are divided into four groups. 1. Cervical ganglia.1. Cervical ganglia. 2. Thoracic ganglia.2. Thoracic ganglia. 3. Lumber ganglia.3. Lumber ganglia. 4. Sacral ganglia.4. Sacral ganglia.

Prevertebral or collateral Prevertebral or collateral gangliaganglia

Prevertebral ganglia are situated in thorax, Prevertebral ganglia are situated in thorax, abdomen and pelvis in relation to aorta and its abdomen and pelvis in relation to aorta and its branchesbranches

The Prevertebral ganglia areThe Prevertebral ganglia are 1. Celiac ganglion1. Celiac ganglion 2. Superior mesenteric ganglion2. Superior mesenteric ganglion 3. Inferior mesenteric ganglion3. Inferior mesenteric ganglion The Prevertebral ganglia receives preganglionic The Prevertebral ganglia receives preganglionic

fibers from Tfibers from T5 5 to L to L2 2 segments. segments. The postganglionic fibers from these ganglia The postganglionic fibers from these ganglia

supply the visceral organs of thorax, abdomen supply the visceral organs of thorax, abdomen and pelvis. and pelvis.

Terminal or peripheral Terminal or peripheral ganglia.ganglia.

Terminal ganglia are situated within Terminal ganglia are situated within or close to structures innervated by or close to structures innervated by them.them.

Heart, bronchi, pancreas and urinary Heart, bronchi, pancreas and urinary bladder are innervated by the bladder are innervated by the terminal gangliaterminal ganglia

Segmental distribution Segmental distribution of the SNFof the SNF

The sympathetic fiber The sympathetic fiber from cord segment from cord segment are fromare from

TT11 generally passes generally passes up the chain to the up the chain to the headhead

TT22 in the neck in the neck TT33 ,T ,T44 ,T ,T5 5 and Tand T66 into into

the thoraxthe thorax TT77 ,T ,T88 ,T ,T99 ,T ,T1010 and and

TT1111 into the abdomen into the abdomen TT1212 ,L ,L11 ,L ,L22 into the into the

legs.legs.

Sympathoadrenergic Sympathoadrenergic systemsystem

Sympathoadrenergic system is a functional Sympathoadrenergic system is a functional phylogenetics unit that includes sympathetic phylogenetics unit that includes sympathetic division and adrenal medulladivision and adrenal medulla

Adrenal medulla is a modified sympathetic Adrenal medulla is a modified sympathetic ganglion.ganglion.

Since adrenal medulla and sympathetic Since adrenal medulla and sympathetic division develop from same neural crest, their division develop from same neural crest, their secretion and functions are almost the samesecretion and functions are almost the same

Any increase in sympathetic activity Any increase in sympathetic activity increases the secretion of Catecholamine increases the secretion of Catecholamine from adrenal medullafrom adrenal medulla

The parasympathetic division The parasympathetic division of ANS is otherwise called of ANS is otherwise called craniosacral outflow because, craniosacral outflow because, the fibers of this division arise the fibers of this division arise from brain and sacral from brain and sacral segments of spinal cord.segments of spinal cord.

The cranial portion of The cranial portion of parasympathetic division in parasympathetic division in brainstem innervates the brainstem innervates the blood vessels of the head and blood vessels of the head and neck and many neck and many thoracoabdominal visceral thoracoabdominal visceral organs.organs.

The sacral portion in sacral The sacral portion in sacral segments of the spinal cord segments of the spinal cord innervates the smooth innervates the smooth muscles forming the walls of muscles forming the walls of viscera and the glands such viscera and the glands such as large intestines, liver, as large intestines, liver, spleen, kidneys, bladder, spleen, kidneys, bladder, genitalia etcgenitalia etc

Cranial nerves of Cranial nerves of Parasympathetic divisionParasympathetic division

The cranial nerve of the parasympathetic division are.The cranial nerve of the parasympathetic division are. 1. Oculomotor (iii) nerve1. Oculomotor (iii) nerve 2. Facial (vii) nerve2. Facial (vii) nerve 3. Glossopharyngeal (ix) nerve3. Glossopharyngeal (ix) nerve 4. Vagus (x) nerve4. Vagus (x) nerve The fibers of sacral outflow arise from second to fourth The fibers of sacral outflow arise from second to fourth

sacral (ssacral (s11 to s to s22 ) segments of spinal cord and occasionally ) segments of spinal cord and occasionally the first and fourth sacral nervesthe first and fourth sacral nerves

Thus the preganglionic fibers of parasympathetic division Thus the preganglionic fibers of parasympathetic division arise from the neurons situated at three different levels arise from the neurons situated at three different levels

1. Tectal or midbrain level (iii cranial nerve)1. Tectal or midbrain level (iii cranial nerve) 2. Bulbar level or bulbar outflow (vii, ix, x cranial nerve)2. Bulbar level or bulbar outflow (vii, ix, x cranial nerve) 3. Sacral outflow (sacral nerves)3. Sacral outflow (sacral nerves)

Tectal or midbrain level.Tectal or midbrain level. In ciliary's ganglionIn ciliary's ganglion Bulbar level or bulbar outflow.Bulbar level or bulbar outflow.Fibers of vii cranial nerve supply the lacrimal, nasal, Fibers of vii cranial nerve supply the lacrimal, nasal,

sub maxillary and sublingual glands sub maxillary and sublingual glands Fibers of ix cranial nerve supply the parotid gland Fibers of ix cranial nerve supply the parotid gland

Fibers of x cranial nerve supply visceral Fibers of x cranial nerve supply visceral organs of the bodyorgans of the body

About 75 % of all parasympathetic nerve About 75 % of all parasympathetic nerve fibers are in Vagus nerves passing entire fibers are in Vagus nerves passing entire thoracic and abdominal regions of the bodythoracic and abdominal regions of the body

Sacral outflowSacral outflow

The preganglionic fibers arise from The preganglionic fibers arise from anterior gray horn cells of 2anterior gray horn cells of 2ndnd, 3, 3rdrd and 4 and 4thth sacral segments of spinal cord and form sacral segments of spinal cord and form the pelvic nerve.the pelvic nerve.

The fibers end on the postganglionic The fibers end on the postganglionic neurons which are situated on or near the neurons which are situated on or near the visceral organs.visceral organs.

The sacral parasympathetic fibers supply The sacral parasympathetic fibers supply those visceral organs which are not those visceral organs which are not supplied by Vagus.supplied by Vagus.

Neurotransmitter of ANSNeurotransmitter of ANS

The different nerve fibers of ANS execute The different nerve fibers of ANS execute the functions by releasing some the functions by releasing some neurotransmitter substanceneurotransmitter substance

Neurotransmitter Neurotransmitter substancesubstance

Those fibers that secrete Those fibers that secrete acetylcholine are said to be acetylcholine are said to be cholinergic.cholinergic.

Those that secrete nor epinephrine Those that secrete nor epinephrine are said to be adrenergic, a term are said to be adrenergic, a term derived from adrenaline, which is an derived from adrenaline, which is an alternate name for epinephrinealternate name for epinephrine

Sympathetic fibersSympathetic fibers

Preganglionic fibers: Acetylcholine Preganglionic fibers: Acetylcholine (ach)(ach)

Postganglionic noradrenergic fibers: Postganglionic noradrenergic fibers: Nor adrenalineNor adrenaline

Postganglionic cholinergic fibers: AchPostganglionic cholinergic fibers: Ach The postganglionic sympathetic The postganglionic sympathetic

cholinergic nerve fibers supply sweat cholinergic nerve fibers supply sweat gland and blood vessels in heart and gland and blood vessels in heart and in skeletal muscle.in skeletal muscle.

Parasympathetic fibersParasympathetic fibers

Preganglionic fibers: ACHPreganglionic fibers: ACH Postganglionic fibers: ACHPostganglionic fibers: ACH

Types of acetylcholine Types of acetylcholine receptorsreceptors

Acetylcholine activates mainly two types of Acetylcholine activates mainly two types of receptors.receptors.

They are calledThey are called Muscarinic and nicotinic receptors.Muscarinic and nicotinic receptors. The reason for these names is that muscarine, The reason for these names is that muscarine,

a poison from toadstools, activates only a poison from toadstools, activates only Muscarinic receptors and will not activate Muscarinic receptors and will not activate nicotinic receptor, whereas nicotine activates nicotinic receptor, whereas nicotine activates only nicotinic receptor ;Acetylcholine activates only nicotinic receptor ;Acetylcholine activates both of themboth of them

Adrenergic receptors.Adrenergic receptors.

These are also two major types of These are also two major types of adrenergic receptors,adrenergic receptors,

ALPHA and BETA receptors.ALPHA and BETA receptors. Alpha: alphaAlpha: alpha11 and alpha and alpha22

Beta: betaBeta: beta11 beta beta22 and beta and beta33

Adrenergic receptors Adrenergic receptors and functionand function

ALPHAALPHA1.1. VasoconstrictionVasoconstriction2.2. Iris dilationIris dilation3.3. Intestinal relaxationIntestinal relaxation4.4. Intestinal sphincter Intestinal sphincter

contractioncontraction5.5. Pilomotor Pilomotor

contractioncontraction6.6. Bladder sphincter Bladder sphincter

contractioncontraction7.7. Inhibits Inhibits

neurotransmitter neurotransmitter releaserelease

BETABETA1.1. VasodilatationVasodilatation2.2. CardioaccelerationCardioacceleration3.3. Increased Increased

myocardial myocardial strengthstrength

4.4. Intestinal Intestinal relaxationrelaxation

5.5. BronchodilatorBronchodilator6.6. CalorigenesisCalorigenesis7.7. GlycogenolysisGlycogenolysis