AUTONOMIC NERVOUS SYSTEM

DR NILESH KATE

MBBS,MDASSOCIATE 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

BRAINSPINAL CORD

CENTRALNERVOUSSYSTEM (CNS)

PERIPHERALNERVOUS SYSTEM

AFFERENT

NERVES

EFFERENT

NERVES

EXTERO-RECEPTORS

INTERO-RECEPTORS

SOMATIC AUTONOMIC

EFFECTORORGANS

SKELETALMUSCLES

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.

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.

C-2A-1

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 DIVISIONotherwise 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) nerve2. Facial (VII) nerve3. Glossopharyngeal (IX) nerve4. Vagus(X)nerve)3. Sacral outflow (sacral nerves)

PARASYMPATHETIC

SPINEEFFECTORORGAN

PARASYMPATHETICGANGLIA (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 Sympatheticand Parasympathetic Divisions

Comparison of some effects of sympathetic & parasympathetic branches

Sympathetic nervous Sympathetic nervous systemsystem

Parasympathetic nervous Parasympathetic nervous systemsystem

increases cardiac outputincreases cardiac output decreases cardiac outputdecreases cardiac output

increases blood pressureincreases blood pressure decreases blood pressuredecreases blood pressure

dilates bronchiolesdilates bronchioles constrict bronchiolesconstrict bronchioles

increases ventilation rateincreases ventilation rate decreases ventilation ratedecreases ventilation rate

dilates pupils dilates pupils constrict pupilconstrict pupil

Comparison of some effects of sympathetic & parasympathetic branches

Sympathetic nervous Sympathetic nervous systemsystem

Parasympathetic nervous Parasympathetic nervous systemsystem

contracts anal & bladder contracts anal & bladder sphincterssphincters

relaxes anal & bladder relaxes anal & bladder sphincterssphincters

contracts erector pili contracts erector pili musclesmuscles

no comparable effectno comparable effect

increases sweat productionincreases sweat production no comparable effectno comparable effect

no comparable effectno comparable effect increases secretion of tearsincreases secretion of tears

Autonomic ReflexesCardiovascular:

- 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.

SYMPATHETIC BLOCKERSSYMPATHETIC BLOCKERS 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

Disorders of the Autonomic Nervous System: Hypertension

Hypertension – high blood pressure Can result from overactive

sympathetic vasoconstriction

Disorders of the Autonomic Nervous System: Achalasia of the Cardia

Achalasia of the cardia Defect in the autonomic

innervation of the esophagus

Mass reflex reactionMass reflex reaction Uncontrolled activation of Uncontrolled activation of

autonomic and somatic motor autonomic and somatic motor neuronsneurons

Affects quadriplegics and Affects quadriplegics and paraplegicsparaplegics

Autonomic function tests. Cardiovascular Pupillary Sudomotor. Bladder.

Autonomic function tests. 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.

Autonomic function tests. Pupillary function.

Cocaine test.Normal pupil dilateHorner’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

Thank You

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