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The autonomic nervous system I


Sympathetic
Parasympathetic
Action
Prepares body for an emergency
Conserves & restore energy
Outflow
T1 – L2 spinal segments (Lateral grey column)
Cranial nerves III, VII, IX, X and S2,3,4
Pre – ganglionic fibers
Myelinated
Ganglia Para vertebral (Sympathetic trunks)
Pre vertebral (Celiac, Superior & inferior mesenteric)
Small ganglia close to viscera (Ciliary, Otic)
Ganglion cells in plexus (Cardiac, pulmonary)
Neurotransmitter within the ganglia
Acetylcholine
Ganglion blocking agent
Hexamethonium & Tetraethyl ammonium (Compete with Ach)
Post – ganglionic fibers Long
Non myelinated
Short
Non myelinated
Characteristic activity Widespread due to many post ganglionic fibers
Liberation of epinephrine & nor epinephrine from supra renal medulla
Discrete action with few post ganglionic fibers
Neurotransmitter at post ganglionic endings Nor epinephrine at most endings
Ach in few endings (Sweat glands)
Ach at all ends
Blocking agents on receptors of effector cells Alpha adrenergic receptors – Phenoxybenzamine
Beta adrenergic receptors – Propranolol
Atropine
Scopolamine
Agents inhibiting synthesis & storage of neurotransmitter at post ganglionic endings
Reserpine

Agents inhibiting hydrolysis of neurotransmitter at sites of effector cells

Acetylcholine esterase blockers (Neostigmine)
Drugs which mimic autonomic activity  Sympathomimetic drugs
α receptors – Phenylephrine 
β receptors – Isoproterenol
Parasympathomimetic drugs
Pilocarpine
Methacholine 
Higher control
Hypothalamus


Autonomic innervations





Organ Sympathetic action Parasympathetic action
Eye Pupil Dilates Contracts
Ciliary muscles Relaxes Contracts
Glands Lacrimal, Parotid, Submandibular, Sublingual & Nasal Reduce secretions (By vasoconstriction of blood vessels) Increase secretions
Sweat  Increase secretions
Heart Cardiac muscles Increase force of contraction Decrease force of contraction
Coronary arteries α receptors – Constricts
β receptors – Dilates
Lungs Bronchial muscles Relaxes (Dilates bronchi) Contracts (Constricts bronchi)
Bronchial secretions Increase secretions
Bronchial arteries Constricts Dilates
GIT Muscles in walls Decrease peristalsis Increase peristalsis
Muscles in sphincters Contracts Relaxes
Glands Reduce secretions (By vasoconstriction of blood vessels) Increase secretions
Liver Breaks down glycogen into glucose
Gall bladder Relaxes Contracts
GUT Bladder wall (Detrusor) Relaxes Contracts
Sphincter vesicae Contracts Relaxes
Kidney Decrease output due to constriction of arteries
Erectile tissue of penis & clitoris Causes erection (relaxes erectile tissue)
Ejaculation Contracts SM of vas deferens, seminal vesicles & prostate
Systemic arteries Skin Contracts
Abdominal Contracts
Muscle α receptors – Constricts
β receptors – Dilates
Dilate (Cholinergic)
Skin  Erector pili muscles Contracts
Supra renal gland Cortex Stimulates
Medulla Liberate epinephrine & nor epinephrine
The autonomic nervous system I The autonomic nervous system I Reviewed by Radiology Madeeasy on August 05, 2010 Rating: 5
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