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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)
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 ¶ 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)