Function autonomic nervous system

8/13/2019 Function autonomic nervous system

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AUTONOMIC NERVOUS

SYSTEM

Dr.P.Sasikala,

Assistant Professor


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Divisions of Nervous system

Nervoussystem

CentralN.S

Brain

Spinalcord

PeripheralN.S

CerebrospinalN.S

12 pairs ofcranialnerves

31 pairs ofspinal nerves

PeripheralautonomicN.S

Sympathetic N.S

ParasympatheticN.S


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AUTONOMIC NERVOUS

SYSTEMThe autonomic nervous system is thesubdivision of the peripheral nervous systemthat regulates involuntary body activities(that are generally not under conscious

control)Autonomic nervous system innervate

smooth muscle (eg, blood vessels, gut wall,

bronchial tree, pupil, urinary bladder) cardiac muscle

Arrector pili muscles of the hair

glands (eg, sweat glands, salivary glands)


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Autonomic nervous system

Called visceral system

Made up of afferent and efferent pathways

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Somatic

nervous system

Autonomic nervous system

Afferent f ibres

Efferent fib res Pass directly from

CNS to the

skeletal muscle

Do not pass directly from CNS.

First relay in autonomic ganglia

outside CNS, then

postganglionic fibres supply the

effector organs.

Made up of two neurons

1. Preganglionic and

2. Postganglionic


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Pre and post ganglionic neuron

Somatic division: Cell bodies of motor neurons reside in CNS (brain or

spinal cord)

Their axons (sheathed in spinal nerves) extend all the

way to their skeletal muscles Autonomic system: chains of two motor neurons

1st= preganglionic neuron (in brain or cord)

2nd= gangionic neuron (cell body in ganglion outsideCNS)

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Pre and postganglionic fiber

Axon of 1st(preganglionic) neuron leaves CNS to

synapse with the 2nd(ganglionic) neuron

Axon of 2nd(postganglionic) neuron extends to

the organ it serves

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DIVISION OF ANS

Parasysmpathetic:routine maintenance

rest &digest

Sympathetic:mobilization & increased

metabolism i.e during acuteemergencies

fight, flight or fright

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WHERE THEY COME FROM

Parasympathetic:

Craniosacral

outflowarises from

brain (GVE nuclei

of brainstem) and

S2-4 segments of

spinal cord

Sympathetic:Thoracolumbar

outflow arises

from lateral

horn cells ofthoracic and

upper two

lumbar

segments

(T1 to L2)


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Sympathetic and

parasympathetic gangliaSympathetic ganglia

Many lie close to spinal cord(Paravertebral or lateral)

Others lie approximately midway between spinal cord

and effector organ(Prevertebral or collateral)

Terminal ganglia- located within suprarenal medullaas chromaffin cells

Postganglionic sympathetic fibres are longer in length

Parasympathetic ganglia

Lie close to or

within the walls

of effector organ

Postganglionic

fibres are shorter


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Parasympathetic

system

Sympathetic

system


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SYMPATHETIC OUTFLOWfight, flight or fright

Also called thoraco lumbarsystem: all its neuronsare in lateral horn of gray matter from T1-L2

Lead to every part of the body (unlike parasymp.) Easy to remember that when nervous, you sweat; when

afraid, hair stands on end; when excited blood pressurerises (vasoconstriction): these sympathetic only

Also causes: dry mouth, pupils to dilate, increased heart& respiratory rates to increase O2 to skeletal muscles,and liver to release glucose


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Anatomy of the sympathetic

system Consists of

1. Pair of ganglionated sympathetic trunks,

2. their rami of communications,3. branches,

4. plexuses and

5. subsidiary ganglia

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Sympathetic trunk(lateral ganglia)

Two ganglionated chains of nerve fibres

Paravertebral in position

Extends from atlas vertebra above to first coccygeal vertebra

Ganglion impar- both trunks unite at the coccyx

Each sympathetic chain possesses 22 sympathetic ganglia

1) 3 in cervical region

2) 11- thoracic

3) 4 - lumbar

4) 4- sacral

Prevertebral ganglia 3 in no. coeliac, superior mesenteric and

inferior mesenteric ganglion.

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Sympathetic trunk

Each thoracic and upper two lumbar sympatheticganglion connected to corresponding spinal nerve byboth white and grey rami communicantes

Rest of sympathetic ganglia connected to

corresponding spinal nerves only by grey ramicommunicantes

White rami- convey preganglionic fibres from T1-L2segments and sensory sympathetic fibres from viscera

Grey rami convey post-ganglionic fibres from lateral

ganglia to all 31 pairs of spinal nerves and their limbplexuses to supply sudomotor, pilomotor andvasoconstictor of all blood vessels

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S th ti

2 Wid i f


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Figure 8-2

Sympathetic

nervous

system4.Secretion of sweatglands

5.Motor for arrector pili

muscles

6.Vasoconstriction of

blood vessels7.Stimulation of heart

8.Bronchodilatation and

inhibition of secretion from

bronchial glands

9.Inhibition of

gastrointestinal motilityand secretions

10.Sensory for pain from

most of the viscera

11.Contraction of

sphincters of the bladder

and bowl

2.Widening of

palpebral fissure

3.Stop the

Secretion of saliva

7.Stimulation of heart

8.Bronchodilatation and

inhibition of secretion

from bronchial glands

1.

12.Motor for

ejaculation


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Parasympathetic

nervous system

Cranio sacral

outflow

Arises from brainstem

nuclei of 3rd,7th,9th

and 10thcranial nerve

S2-S4 segments of

spinal cord

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PARASYMPATHETIC OUTFLOW

Cranial outflow

III - pupils constrict

VII - tears, nasal mucus, saliva

IXparotid salivary gland

X (Vagus n)visceral organs of thorax & abdomen: Stimulates digestive glands

Increases motility of smooth muscle of digestive tract

Decreases heart rate

Causes bronchial constriction

Sacral outflow (S2-4): form pelvic splanchnic nerves

Supply 2ndhalf of large intestine

Supply all the pelvic (genitourinary) organs


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Pupils constrict

Decreases heart

rate

Causes bronchial

constriction

Secrete saliva


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Stimulates digestive glandsIncreases

motility of

Smoothmuscle of

digestive tract


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IMPORTANT

NEUROTRANSMITTERS

Acetylcholine =Cholinergic

Fibers that release acetylcholine are

known as chol inergic fibers All preganglionic neurons of the autonomic

division and all postganglionic neurons of

the parasympathetic division arecholinergic


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Norepinephrine = Adrenergic

Neurotransmitter between the sympatheticpostganglionic fiber and the effector cell

Fibers that release norepinephrine are

adrenergicfibers

Most postganglionic neurons of the

sympathetic division are adrenergic Few are cholinergic(sweat gland,some blood

vessels in skeletal muscle)


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ADRENAL GLAND IS

EXCEPTION

On top of kidneys

Adrenal medulla(inside part) is a

major organ of

the sympatheticnervous system


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Adrenal gland is exception

Synapse in gland

Can cause body-widerelease of epinephrine

and norepinephrine


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Central control of the

Autonomic NSAmygdala:main limbic

region for emotions

Hypothalamus: mainintegration center

Posterior part-sympathetic activity

Anterior part-parasympatheticactivity

Reticu lar form ation :most direct influenceover autonomicfunction


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Difference between Sympathetic

and Parasympathetic systems

Sympathetic system Parasympathetic system

Efferents:

Pre-ganglionic

neurons

Thoraco-lumbar outflow

Lateral horn cells of T1-L2

segments of spinal cord

Cranio-sacral outflow

In cranial part

Edinger-Westphal nucleus of 3rdcranial

nerve

Superior salivatory nucleus of 7thnerve

Inferior salivatory nucleus of 9thnerve

Dorsal nucleus of 10thnerve

In sacral part

Lateral horn cells of S2-S4 segments

Ganglia Lateral, collateral andterminal

Collateral and terminal

Pre-ganglionic

neuron synapse

20 or more post-ganglionic

neurons

Only one-or a few

Pre-ganglionic

fibre

Shorter, Post-ganglionic

fibres are longer

Longer than post-ganglionic fibre


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and Parasympathetic systemsSympathetic system Parasympathetic system

Action Produces mass reaction

mobilising resources of the

body (catabolic in function;

works for to-day)

Cutaneous blood vesselsconstricted, coronary and

skeletal vessels dilate, heart

rate is increased, BP raised,

pupils dilate, intestinal

peristalsis diminished and

sphincters of the gut closed

Produces localised and

isolated effects, conserving

resources of the body

(anabolic in function; works for

to-morrow)HR slowed, pupils

constricted,

Digestion and absorption

promoted by increased

intestinal secretion and

enhanced peristalsis,bladder and rectum

evacuated

Nerve of emergency, works

during stress and strain for

fight or flight

Nerve of transquility

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and Parasympathetic systemsSympathetic system Parasympathetic

system

Neurotransmitters All post-ganglionic fibres

are adrenagic except

sweat glands and most

of the blood vessels ofskeletal muscles

All post-ganglionic fibres

are cholinergic

Afferents Convey mostly visceral

pain sensation

Convey general visceral

sensation

Central control Posterior part of

hypothalamus

Anterior part of

hypothalamus

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Thank you

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Function autonomic nervous system