AUTONOMIC NERVOUS SYSTEM

AUTONOMIC
NERVOUS
SYSTEM
DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
ESIC MEDICAL COLLEGE, GULBARGA.
DEPT. OF PHYSIOLOGY

OBJECTIVES
 Anatomical consideration.
 Divisions.
 General organization.
 The Sympathetic Division
 The Parasympathetic Division.
 Physiological consideration.
 Neurotransmitters & receptors.
 Functions of ANS.
 Relationships Between the Sympathetic and
Parasympathetic Divisions
 Applied physiology

ORGANIZATION OF THE NERVOUS
SYSTEM
BRAIN
SPINAL CORD
CENTRAL
NERVOUS
SYSTEM (CNS)
PERIPHERAL
NERVOUS
SYSTEM
AFFERENT
NERVES
EFFERENT
NERVES
EXTERO-RECEPTORS
INTERO-RECEPTORS
SOMATIC AUTONOMIC
EFFECTOR
ORGANS
SKELETAL
MUSCLES
SMOOTH AND
CARDIAC MUSCLES
AND GLANDS

Autonomic Nervous System (ANS)
 Derived from Greek word “autos – self &
nomos – control”
 An involuntary nervous system that modulates
and controls the function of visceral organs.
 Since it controls vegetative functions also
called as vegetative system.

Divisions of the ANS
 2 divisions:
 Sympathetic :
 (fight or flight)
 Parasympathetic :
 Controls daily body
functions
 Both divisions are
constantly “counteracting”
or acting together in
“autonomic tone”

Autonomic Nervous System (ANS)
Thursday, December 11, 2014

SOMATIC & AUTONOMIC NERVOUS
SYSTEM.
SOMATIC
 Afferent neuron terminate in
dorsal horn.
 Interneuron terminates in
ventral horn.
 Efferent neuron cell body in
ventral horn.
 Single efferent neuron
 Innervates skeletal muscles.
 Neurotransmitter – Ach
 Activity – excitation.
 Always voluntary.
ANS
 Afferent neuron terminate in
intermediolateral horn.
 Interneuron terminates in
autonomic ganglia.
 Efferent neuron cell body in
autonomic ganglia.
 2 efferent neurons.
 Innervates smooth muscle,
cardiac muscle , secretory glands.
 Neurotransmitter – Ach & NE.
 Activity – Excitation & inhibition.
 Usually Involuntary.

GENERAL ORGANIZATION.
 Autonomic areas in cerebral hemisphere.
 Autonomic centers in brain stem.
 Autonomic centers in spinal cord.
 Peripheral part of ANS.

Autonomic areas in cerebral
hemisphere.
 Limbic system.
 Prefrontal cortex.
 Hypothalamus.
 Integration of somatic, autonomic & endocrine
functions.
 Main ganglion of ANS.
 LIMBIC CORTEX equally important.
 Thalamus.

Autonomic centers in brain
stem.
 Reticular formation.
 Gigantocellular nucleus.
 Parvocellular nuclei.
 Visceral nuclei of cranial nerves.

Visceral nuclei of cranial
nerves.
 Afferent nucleus.
 Nucleus of solitary
tract in medulla.
 Receives through IX &
X.
 Along with reticular
formation reflex
control of RS & CVS
function.
 Efferent nucleus.
 Preganglionic fibres of
parasympathetic
craniosacral outflow.
 Includes- (DES).
 Dorsal nucleus of vagus.
 Edinger-vestphal N.
 Salivary nucleus.

Autonomic centers in spinal
cord.
 Intermediolateral
grey column of
spinal cord.
 2 levels.
 Sympathetic – T-1
to L-3
 Parasympathetic –
cranial part
- S-2
to S-4.

Peripheral part of ANS.
 All autonomic nerves & ganglia.
 No nerve in the body is totally autonomic.

Neurons of ANS
 PREGANGLIONIC NEURON
 cell body in brain or spinal cord
 axon is myelinated type B fiber that extends to
autonomic ganglion
 POSTGANGLIONIC NEURON
 cell body lies outside the CNS in an autonomic
ganglion
 axon is unmyelinated type C fiber that terminates in a
visceral effector

Physiological Effects of the ANS
Hypothalamus
 only sympathetic
innervations
 sweat glands, adrenal
medulla, erector pili &
many blood vessels
 controlled by regulation
of the “tone” of the
sympathetic system
 Rest receive dual
innervations
 Hypothalamus .

Sympathetic motor ANS
 Thoracolumber outflow
 3 destinations.
 Terminate in the
ganglia.
 Travel up & down &
then terminate.
 Pass without
synapsing &
terminate in
prevertebral ganglia.

SYMPATHETIC GANGLIA
 The ganglia of
sympathetic division are
classified into three
groups.
Para vertebral or
sympathetic chain ganglia
Prevertebral or collateral
ganglia
Terminal or peripheral
ganglia

SYMPATHEIC GANGLIA.
A
B
C-4
C-1
A-1 C-2
A-2
A-3
B-1
B-2
B-3
C-3

Sympathetic motor NS
 Lateral horn 
paravertebral ganglia 
spinal nerve = white
communicating ramus
(myelinated)
 Signals from the ganglion
(to the target tissue)
travel along unmyelinated
fibers = grey
communicating ramus
 Signals between ganglia
along the sympathetic
trunk

PARASYMPATHETIC DIVISION
otherwise called
craniosacral outflow because,
the fibers of this division arise
from brain and sacral
segments of spinal cord
The cranial nerves of the
parasympathetic division are:
1. Oculomotor (III) nerve
2. Facial (VII) nerve
3. Glossopharyngeal (IX) nerve
4. Vagus(X)nerve)
3. Sacral outflow (sacral nerves)

PARASYMPATHETIC
SPINE EFFECTOR
ORGAN
PARASYMPATHETIC
GANGLIA (NEAR
EFFECTOR ORGAN)

TECTAL OR MIDBRAIN LEVEL
 The group of cells forming Edinger-Westphal
nucleus of Ill cranial nerve gives rise to tectal
fibers.
 The fibers from this nucleus end in the ciliary
ganglion.
 The postganglionic fibers from here supply the
sphincter pupillae and ciliary muscIe

MIDBRAIN OR TECTAL OUTFLOW.
& BULBAR OUTFLOW.

Autonomic neurotransmitters.

Cholinergic receptors.

Adrenergic receptors.
Alpha receptors.(α)
 α - 1 (VGR)
 Vascular smooth
muscles of skin &
splanchnic region
 GIT & bladder
sphincters
 Radial muscles of Iris.
 α -- 2 ( PPFW)
 Presynaptic nerve
terminal
 Platelets
 Fat cells
 Walls of GIT.

Adrenergic receptors.
Beta receptors.(β)
 β -- 1 ( SAV)
 SA node
 AV node
 Ventricular
muscles of heart.
 β – 2 (VBWB)
 Vascular smooth
muscles of skeletal
muscles
 Bronchial smooth
muscle
 Walls of GIT
 Bladder.
 β – 3

Differences in Sympathetic
and Parasympathetic Divisions

Comparison of some effects of sympathetic &
parasympathetic branches
SSyymmppaatthheettiicc nneerrvvoouuss
ssyysstteemm
PPaarraassyymmppaatthheettiicc nneerrvvoouuss
ssyysstteemm
iinnccrreeaasseess ccaarrddiiaacc oouuttppuutt ddeeccrreeaasseess ccaarrddiiaacc oouuttppuutt
iinnccrreeaasseess bblloooodd pprreessssuurree ddeeccrreeaasseess bblloooodd pprreessssuurree
ddiillaatteess bbrroonncchhiioolleess ccoonnssttrriicctt bbrroonncchhiioolleess
iinnccrreeaasseess vveennttiillaattiioonn rraattee ddeeccrreeaasseess vveennttiillaattiioonn rraattee
ddiillaatteess ppuuppiillss ccoonnssttrriicctt ppuuppiill

Comparison of some effects of sympathetic
& parasympathetic branches
SSyymmppaatthheettiicc nneerrvvoouuss
ssyysstteemm
PPaarraassyymmppaatthheettiicc nneerrvvoouuss
ssyysstteemm
ccoonnttrraaccttss aannaall && bbllaaddddeerr
sspphhiinncctteerrss
rreellaaxxeess aannaall && bbllaaddddeerr
sspphhiinncctteerrss
ccoonnttrraaccttss eerreeccttoorr ppiillii
mmuusscclleess
nnoo ccoommppaarraabbllee eeffffeecctt
iinnccrreeaasseess sswweeaatt pprroodduuccttiioonn nnoo ccoommppaarraabbllee eeffffeecctt
nnoo ccoommppaarraabbllee eeffffeecctt iinnccrreeaasseess sseeccrreettiioonn ooff tteeaarrss

Autonomic Reflexes
Cardiovascular:
- baroreceptor reflex:
It is stretch reflex in the main arteries such
as carotid artery to detect the blood
pressure
 Gastrointestinal:
The receptors in the nose and mouth send
a signal to parasympathetic to notify the
glands of mouth & stomach to secrete the
digestive juices

Autonomic Reflexes
 Urinary Bladder:
- Initiate the micturation by
parasympathetic innervations
 Sexual reflexes:
- erection by parasympathetic
- ejaculation by sympathetic
 The sympathetic activation often occurs in a
mass discharge such as in fright or severe
pain “fight or fright”(sympathetic stress
response)

Functions of ANS
 Mediate neuronal regulation of internal
environment
 Coordinate bodily function necessary for
survival
 Regulate removal of waste products from the
body
 Prepare the body for normal and life-threatening
stress
 Effected via control over smooth and heart M.
and glands
 “autonomic” = self-governing

The Race Horse and the Cow
Sympathetic
Parasympathetic

Sympathetic Nervous System (SNS)
 Operates continuously to modulate the
functions of many organ systems e.g; heart,
blood vessels, GIT, bronchi and sweat glands
 Stressful stimulation activates SNS leads to a
response known as “fight or flight”: increased
arterial pressure, blood flow, blood glucose,
metabolic rate and mental activity

Applied aspects.
 Autonomic drugs.
 Autonomic failure.
 Autonomic function tests.

Autonomic drugs.
 Mimetic
 Lytic or Blockers.
 So……………..
 Sympathomimetic
 Sympatholytic
 Parasympathomimetic
 Parasympatholytic.

SYMPATHOMIMETIC DRUGS
 Directly acting.
 Act directly on alpha &
beta adrenergic
receptors.
 E.g.—
 Adrenaline
 Nor adrenaline
 Phenylnephrine.
 Indirectly acting.
(enhancing action of
NE)
 displacing NE from
storage sites. –
amphetamine.
 Inhibiting reuptake. –
imipramine.
 MAO inhibitors.

SSYYMMPPAATTHHEETTIICC BBLLOOCCKKEERRSS
 Prevention of synthesis & storage of NE. –
Reserpine.
 Prevention of release of NE. – Guanethidine.
 Blockage of receptors.
 Alpha -- Phentolamine
 Beta – Propranolol, Metoprolol.
 Blockage of transmission of nerve impulse. –
Hexamethonium.

Parasympathomimetic drugs.
 Drugs acting on muscarinic receptors. –
Pilocarpine, Methacholine.
 Prolonging action of Ach –Neostigmine,
Physostigmine.

Parasympathetic blockers.
 Drugs blocking Muscarinic receptors.
 Atropine
 Homatropine
 Scopolamine.

Autonomic failure.
 Primary
 Cause not known.
 Autonomic
neuronal
degeneration.
 Secondary
 Secondary to
some cause.
 Most common
cause.--Diabetes
mellitus.

Autonomic failure.
 Features.
 CVS – Orthostatic hypotension , tachycardia.
 Sudomotor – anhidrosis, heat intolerance.
 GIT – constipation , diarrhea & dysphagia.
 Urinary – nocturia, frequency, urgency,
incontinence & retention.
 Reproductive – erectile & ejaculation failure.

Disorders of the Autonomic Nervous
System: Raynaud’s Disease
 Raynaud’s disease – characterized by
constriction of blood vessels
 Provoked by exposure to cold or by
emotional stress

System: Hypertension
 Hypertension – high blood pressure
Can result from overactive
sympathetic vasoconstriction

System: Achalasia of the Cardia
MMaassss rreefflleexx rreeaaccttiioonn
 UUnnccoonnttrroolllleedd aaccttiivvaattiioonn ooff
aauuttoonnoommiicc aanndd ssoommaattiicc mmoottoorr
nneeuurroonnss
 AAffffeeccttss qquuaaddrriipplleeggiiccss aanndd
ppaarraapplleeggiiccss
 Achalasia of the cardia
 Defect in the autonomic
innervation of the esophagus

Autonomic function tests.
 Cardiovascular
 Pupillary
 Sudomotor.
 Bladder.

 Cardiovascular.
 Valsalva manoeuvre.
 Heart rate variation
during deep breathing.
 Heart rate response to
standing.
 blood pressure
response to standing.
 Blood pressure
response to sustained
handgrip.
 Sudomotor.
 Evaluation of sweating
response to increased
body temperature.

 Pupillary function.
 Cocaine test.
Normal pupil dilate
Horner’s pupil – not
 Adrenaline test.
Horner’s pupil dilate
more than normal.
 Bladder function
 Absense of
accommodation.
 Absense or poor
voluntary bladder
contraction.

RECAP
 Anatomical consideration.
 Divisions.
 General organization.
 The Sympathetic Division
 The Parasympathetic Division.
 Physiological consideration.
 Neurotransmitters & receptors.
 Functions of ANS.
 Relationships Between the Sympathetic and
Parasympathetic Divisions
 Applied physiology

AUTONOMIC NERVOUS SYSTEM

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