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Parasympathetic NS (craniosacral)Preganglionic neurons……………………….Cranial outflow…. - occulomotor (III) - facial (VII) - glossopharyngeal (IX) - vagus (X)Sacral outflow…..2nd, 3rd and 4th sacral segments

Post ganglionic neurons …. terminal ganglia

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The parasympathetic division often produces antagonistic effects to sympathetic division through the release of acetylcholine from its post ganglionic fibers

Functions of Parasympathetic Nervous SystemFunctions of Parasympathetic Nervous System

1- Head & Neck:

Occulomotor Nerve (3rd cranial nerve): → Pupil constriction (miosis) → increase power of lens necessary for

near vision

Facial nerve (7th cranial nerve): A- Secretomotor & vasodilator to the submandibular & sublingual salivary glands B- secretion of lacrimal & nasal glands.

Glossopharynqeal nerve (9th cranial nerve): Secretomotor & vasodilator to parotid

gland.

Functions of Parasympathetic Nervous SystemFunctions of Parasympathetic Nervous System

Thorax & Abdomen are supplied by Vagus nerve (10th cranial nerve )

2- Thorax:

Heart: → Inhibition of all atrial properties (NO vagal supply to ventricles)

→ Decrease coronary flow & 02

consumption

Lungs: → Bronchial constriction → Dilatation of pulmonary blood vessels → Increase bronchial secretion.

Functions of Parasympathetic Nervous SystemFunctions of Parasympathetic Nervous System

(3) Abdomen: GIT: → Motor to esophagus, stomach, small intestine, proximal part of large intestine → Inhibitory to sphincters

→ Secretory to glands of stomach, small intestine, liver, pancreas

Gall bladder: → Motor to wall → Inhibitory to sphincters i.e. Evacuation of gall bladder.

Functions of Parasympathetic Nervous SystemFunctions of Parasympathetic Nervous System

(4) Pelvis: sacral outflow a) Defecation ++

b) Micturition: ++

c) MaIe genitalia: → Erection → Secretory to seminal vesicle & prostate

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OrganParasympathetic Response

"Rest and Digest"Sympathetic Response

"Fight or Flight"

Heart Decreased heart rateCardiac output decreases

Increased rate and strength of contraction Cardiac output increases

Lung Bronchioles Constriction Dilation

Liver Glycogen No effectGlycogen breakdown

Blood glucose increases

Fat Tissue No effectBreakdown of fat

Blood fatty acids increase

Basal Metabolism No effect Increases ~ 2X

StomachIncreased secretion of HCl & digestive

enzymesIncreased motility

Decreased secretionDecreased motility

IntestineIncreased secretion of HCl & digestive

enzymesIncreased motility

Decreased secretionDecreased motility

Urinary bladderRelaxes sphincter

Detrusor muscle contractsUrination promoted

Constricts sphincterRelaxes detrusor

Urination inhibited

RectumRelaxes sphincter

Contracts wall musclesDefecation promoted

Constricts sphincterRelaxes wall musclesDefecation inhibited

EyePupils constrict

Adjusts for near visionPupils dilate

Adjusts for far vision

Male Sex Organs Promotes erection Promotes ejaculation 8

Chemical transmitters in autonomic nervous system

• Acetylcholine• Noradrenaline (Norepinephrine)

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Acetylcholine Sites of release of acetylcholine• All preganglionic autonomic fibers (sympathetic &para sympathetic )• preganglionic sympathetic fibers to suprarenal medulla• All postganglionic para sympathetic fibers• postganglionic sympathetic fibers to sweet glands and blood vessels

of skeletal muscle ( VD)Removal of acetylcholineIt is split into acetate & choline by acetylcholine esterase True acetylcholine esterase → cholinergic nerve endings Pseudo acetylcholine esterase → in plasma

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Cholinergic receptors

Nicotinic receptors -autonomic ganglia -skeletal muscles ( motor end plate) -suprarenal medulla

Muscarinic receptors -viscera supplied by postganglionic para sympathetic

fibers -sweet glands and blood vessels of skeletal muscle (

sympathetic cholinergic fibers)

Nor adrenaline (Norepinephrine)Sites of release of Noradrenaline All postganglionic sympathetic fibers except

fibers to sweet glands and blood vessels of skeletal muscle

Fate of Noradrenaline1. Re-uptake into the adrenergic nerve endings2. Diffusion away into the body fluids & plasma3. Destruction by• MAO ( monoamin oxidase) • COMT ( catechol-O –methyl transferase)

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Adrenergic receptors

Alpha receptorsAlpha 1 and alpha 2

Alpha 1 →Excitatory ( intracellular Ca++ )• Vasoconstriction • Contraction of sphincter of GIT, dilator pupillea ,

spleniccapsule, seminal vesicles and vas deferensAlpha 2 → inhibitory to intestinal wall ( c-AMP)

Beta receptorsBeta 1 → excitatory, heart & metabolic action

Bate 2 → inhibitory,smooth muscles of bronchi, urinary bladder, intestine, VD of skeletal muscle ( c-AMP)