august 14, 2015ans 1 autonomic nervous system organization sympathetic parasympathetic functional...

April 19, 2023ANS 1

AUTONOMIC NERVOUS SYSTEM

OrganizationSympathetic

ParasympatheticFunctional Anatomy

Functional Anatomy

ANS control the activity of Smooth muscles of all organs Cardiac muscles Secretions of glands

Mediates the neural control of internal environment Blood pressure, GIT motility and

secretions, urinary output, sweating and temperature control

April 19, 2023ANS 2

Functional Anatomy

Activated by centers located in the Spinal cord Brain stem Hypothalamus Cerebral cortex

April 19, 2023ANS 3

Functional Anatomy

Customarily subdivided into Sympathetic Parasympathetic

Sympathetic was thought to act In sympathy with emotions

Fear, rage Parasympathetic was thought to

Restrain sympathetic promoting calmness

April 19, 2023ANS 4

Sympathetic System

Cell bodies of the pre-ganglionic nerves Located in the lateral horns of

Thoracic and lumbar spinal cord segments

Pre-ganglionic fibres leave the spinal cord via the ventral root Join the spinal nerve They then leave the spinal nerve via white

ramus communicantes Join the sympathetic ganglia where

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Sympathetic System

Either synapse with post-ganglionic nerve Rejoins the spinal nerve via gray ramus

communicantes Innervate effector organs

Or pass directly to a collateral ganglia to synapse with postganglionic nerve

April 19, 2023ANS 6

April 19, 2023ANS 7

Dorsal root ganglia

Ventral root

Ganglia chain

Collateral ganglia

White ramus

Gray ramus

Spinal nerve

Pre-ganglionic

Post-ganglionic

April 19, 2023ANS 8

Somatic nervous system

Effector organs

Parasympathetic ganglia

Sympathetic

gangliaPre-ganglionic

Post-ganglionic

Post-

Pre-ganglionic

Adrenal Medulla

catecholamine

Somatic N .S (voluntary)

Autonomic N .S (involuntary)

1) Innervate skeletal muscles 1 (Supply smooth muscles, Cardiac and Glands

2) One neurone between C.N.S and effector organ

2 (Has 2 neurons connected by synapse between C.N.S & organ

3) Efferent arises from ventral horn cell.

3 (Efferent preganglionic arises from lateral horn cells.

4) Chemical transmitter Acetyl choline

4 (Either acetyl cholin or norepinephrine.

Adrenal Medulla

Cells of adrenal medulla are derived from nervous tissue

Analogous to postganglionic nerves Preganglionic fibres

Pass through symp. Chain of ganglia Synapse with adrenal medulla cells

Cells secrete adrenalin, Nor adrenalin and dopamine

April 19, 2023ANS 10

Parasympathetic System

Cell bodies of the pre-ganglionic neurons found Nuclei of cranial nerves in midbrain and

medulla Give origin to cranial parasympathetic

outflow

From the sacral segment of spinal cord Cell bodies of pre-ganglionic nerves give

rise to sacral parasympathetic outflow



Parasympathetic system

Nucleus

Either Or Pre-ganglionic

fibre

Post- ganglionic fibre

ganglion

Effector organ

The Parasympathetic ganglia is

•Either in the viscera (effector organ)

•Or close to the viscera (effector organ)

Parasympathetic

Midbrain From Edinger Westphal nucleus

Pre-ganglionic nerve join the occulomotor nerve

Synapse with post-ganglionic nerve in ciliary ganglia

Innervate the ciliary and pupillary muscles of the eye


E W Nucleus

occulomotor

Ciliary ganglia

Ciliary muscle

Pupillary constrictor

Parasympathetic

Pons From Lacrimal and Salivatory nucleus

Preganglionic fibres join the facial nerve to The sphenopalatine ganglia

Synapse with post-ganglionic fibres Innervate the lacrimal glands

Submandibular ganglion Synapse with post-ganglionic fibres Innervate submandibular and sublingual glands



Pons

Facial Nerve

Sphenopalatine ganglia

Submandibular ganglia

Lacrimal gland

Submandibular and sublingual glands

Parotid gland

Otic ganglia

IX

Inferior salivatory Nucleus

Medulla

Parasympathetic

From the inferior salivatory nucleus Pre-ganglionic fibres join IX to Otic ganglia Innervate parotid glands

From dorsal motor nucleus of VAGUS Preganglionic fibres join the vagus

nerve Synapse with post ganglionic nerves in

various effector organs in thorax and abdomen



Dorsal motor nucleus of vagus

vagus Heart

Lungs

Oesophagus

Stomach

Small intestines

Colon

Liver, gall bladder, Pancreas, ureters

Sacral Parasympathetic Outflow From lateral horns of grey matter Sacral segment 2,3,4 Preganglionic fibres leave to join nerve

eregentes to sacral plexus Synapse with post synaptic nerves Innervate effector organs

Descending colon Rectum Urinary bladder Lower potions of ureters External genitalia


ANS Transmission

Chemical transmission Acetylcholine (Ach) Nor adrenalin Dopamine GnRH Co-transmitters

VIP released with ach ATP and neuropeptide Y released with Nor

adrenalin


Chemical Division of ANS

Cholinergic All pre-ganglionic neurons Also included

Parasympathetic post-ganglionic neurons Sympathetic neurons which innervate sweat

glands Sympathetic neurons which end on blood vessel to

skeletal muscles causing vasodilatation

Noradrenergic Remaining sympathetic postganglionic

nerves


Chemical Division of ANS

Adrenal medulla Essentially sympathetic ganglia Post-ganglionic nerves have lost the

axons Secretes into blood

Adrenalin Nor adrenalin Dopamine



ANS Neurotransmitters

At the ganglia

Acetylcholine

Both sympathetic and Parasympathetic release Acetylcholine as the neurotransmiter

Postganglionic

Parasympathetic Release Acetylcholine which can

cause both Excitation Inhibition

Excitation occur Smooth muscle of stomach, intestines,

bladder, bronchi On glands


Mechanisms of Ach Action

Ach bind to receptors Cause depolarization

Ach increase the concentration of ca++ in ICF Increase ca++ conductance Ca++ initiate contraction

Acetylcholine bind to membrane receptors Activate membrane bound G-protein

Guanosine triphosphate (GTP)


Mechanism of Ach Actions

Activation of G-protein Stimulation of Phospholipase C

Breakdown of Phosphatidylinostol bisphosphate (PIP2) into DAG & IP3 which then Initiate membrane and intracellular events

leading to muscle contraction



Ach

receptor G-Protein Membrane bound Lipase

Diacylglycerol

Protein Kinase

Opening Ionic channels

Sarcoplasmic Reticulum

Inositol Triphosphate

Ca++

Ca++

ICFMuscle contraction

PIP2DAG + IP3


Inhibitory effect of acetylcholine

Ach

K+

K+

K+

K+

K+

Pr -Pr -

On the heart SAN, AVN

Ach bind to receptor

Activation of ionic channels

K+ ion efflux

Hyperpolarization

Decrease Pacemaker activityK+

K+

K+


Sympathetic

Ach

Dopamineβ

αNor-epinephrine

(ATP, Neuropeptide Y)

Nor-adrenalin

Has got both Excitatory and Inhibitory effects

Noradrenalin

Binding to β receptors Activates Gs protein

Adenylate cyclase ATP cAMP Increase in cAMP

Activation of protein Kinase A variety of physiological activities



Noradrenalin

β-receptor

Gs-Protein Adenylate CyclaseOpening Ionic channels

ATP cAMP

Inactive Protein Kinase

Active Protein Kinanse

Variety of Physiological Functions

Binding to β receptors

On the heart The activated protein Kinase

Phosphorylate Ca++ channels Increase of Ca++ entry into the cell Increase in contractility Increase in force of contraction


Binding to β receptors

On bronchial smooth muscles Activated protein Kinase

Phosphorylate Ca++ channels on sarcoplasmic reticulum

Increase of Ca++ entry into the sarcoplasmic reticulum

Decrease in [Ca++ ] in cytoplasm Decrease force of contraction


Noradrenalin binding to α-Receptors Two types : α1 and α2

Binding to α1 receptors Activation of Gs Protein system

Stimulation of Phospholipase C Breakdown of Phosphatidylinostol

bisphosphate (PIP2) into DAG & IP3 which then

Initiate variety of physiological activities


Noradrenalin on α2

Activation of Gi Protein Aadenylate cyclase is inhibited Decreased concentration of cAMP Inhibition of variety of Physiologic

effects


Actions of Autonomic Nervous System on Organs Dual innervations The eyes, salivary glands, heart,

digestive system, pelvic viscera Receive both sympathetic and

parasympathetic innervations The two system occasionally act

antagonistically However, in most organs one system is

dominant Under physiological condition

Parasympathetic activity predominates


Dual innervations

Sweat gland , adrenal medulla, pilo-erectors and majority of blood vessels Receive sympathetic innervation only



The EYE The Pupil

Radial Muscles

•Sympathetic

•Contraction

•Pupillary dilatation

Circular muscles

•Parasympathetic

•Contraction

•Pupillary constriction


Lens

Ciliary muscles

Suspensory ligaments

Lens

Parasympathetic

Stimulate ciliary muscles

Contraction

Ligaments loosen

Lens focuses for Near Vision

Sympathetic

Inhibition of the Muscle

Relaxation

Suspensory ligaments tighten

Lens focuses for far vision

ANS Effects On Glands

Nasal, lacrimal, salivary, GIT glands Strongly stimulated by parasympathetic

Leads to increased amounts of secretions by the glands

Sympathetic Little direct effect Causes vasoconstriction

Decreases blood flow Hence decrease in the rate of secretion


ANS Effects On Glands

Sweat glands Stimulated by sympathetic nerves

Which are mostly cholinergic Primarily stimulated by centers in

the hypothalamus considered parasympathetic

Apocrine glands Sympathetic stimulation

Produce thick odoriferous secretion


ANS Effects

GIT Intramural plexuses

Myenteric (Auerbachs) Meissners (Submucosal plexus)

Parasympathetic nerves end on Myenteric and Meissners plexuses Stimulation causes

Excitation of intestinal smooth muscles Relaxation of sphincters (excitation of dilator

components)


ANS Effects

Leads to increased in overall activity Increased peristalsis Decrease in gastric and intestinal

emptying time Increase in gastrin and gastric glands

secretions


ANS Effects

Sympathetic nerves terminate on Postganglionic cholinergic nerves

Presynaptic inhibition of Acetylcholine release

Blood vessels Cause vasoconstriction

Smooth muscles Increase tone of sphincters Inhibit motility of GIT


ANS Effects on the Heart

Both sympathetic and parasympathetic Sympathetic

Accelerates the pace maker Increases speed of conduction (positive

chronotropic) Increases the force of contraction (positive

ionotropic) Overall effect

Increase the effectiveness of the heart


ANS Effects on the Heart

Parasympathetic Retards the depolarization of pacemaker

cells Slows conduction of cardiac impulse

(negative chronotropic) Decreases the strength of contraction

(negative inotropic) Overall effect

Decrease the effectiveness of the heart


august 14, 2015ans 1 autonomic nervous system organization sympathetic parasympathetic functional...

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