A.F. 2021 1 Physiology for 1st year medical students A.N.S. “Written Questions” A.F.2023
A.F. 2021 1 ➢ Q. Autonomic is different from somatic (voluntary) motor nerves in: Somatic Autonomic controls Voluntary skeletal muscles involuntary = visceral: internal organs Afferent relay dorsal horn cells lateral horn cells. Efferent : Origin Anterior horn cells of S.C. lateral horn cells Eff. One neuron. Two neurons. Myelination Mostly myelinated -Pregang. : myelinated B - Postgang. : unmyelinated C ➢ Q. Autonomic Ganglia: - • Ganglion: collection of neurons )postganglionic( outside CNS. • Function: distribution centers : Each preganglionic fiber synapse with 8-9 postganglionic neurons. Types : (4) adrenal medulla : (3) Terminal ganglia : (2) Collateral ganglia : (1) Paravertebral sympathetic chain : - modified sympathetic Stimulation causes adrenaline (80%) and noradrenaline (20%) release into blood. very near to organ midway between origin and organ, at origin of big vessels on both sides of vertebral column site parasympathetic Sympathetic mainly sympathetic only For postganglionic are very short - ciliary, sphenopalatine, and otic are collateral parasympathetic ganglia. ganglion for each segment of spinal cord except cervical which are three: superior, middle and inferior N.B.
A.F. 2021 2 Functions of Sympathetic Nervous System (thoraco-lumbar) Q. Head and Neck Q. Thoracic Viscera Q. Abdominal Viscera Q. Pelvic Viscera Origin T1,2 T 1-4 T 7-12 T12 & L 1-3 Course greater splanchnic n. lesser splanchnic n. Ganglia in paravertebral chain Collateral cervical ganglia cervical and upper 4 thoracic coeliac & superior mesenteric. - inferior mesenteric Functions 1- EYE : 1) Mydriasis (dilatation of pupil): 2) decrease power of lens to see far: relaxation of ciliary muscle 3) widening of palpebral fissure (increase field of vision) 4) exophthalmus (increase field) 5) VC 2- Skin : 1) Secretory to sweat glands. 2) Vasoconstriction 3) erection of hairs. 3- Salivary Glands : trophic secretion: conc. and viscid. 4- Cerebral circulation : flow increased: 1) rise of systemic ABP 2) cerebral vessels mildly constricted . 5- Brain : increase mental alertness 1. Heart - 1) Increase all properties: Rate, force 2) VD of coronaries (indirect). 2. Lungs : - Dilatation of bronchi. - VC 1. ( GIT ): - relaxation of wall - contraction of sphincters. 2. Liver : glycogenolysis ↑ blood glucose 3. Spleen : Contraction: pouring blood 4. Adrenal Medulla : - adrenaline and noradrenaline in blood 5. Blood vessels : VC 1. GIT : • relaxation of wall • Contraction of internal anal sphincter 2. Urinary Bladder: - relaxation of wall. - Contraction of internal urethral sphincter. 3. Male genital: - VC (shrinkage of penis). - ejaculation 4. Female genital: Variable effects
A.F. 2021 3 Functions of Parasympathetic Nervous System (cranio-sacral) Q. Head and Neck Q. Thoracic & Abdominal Viscera Q. Pelvic Viscera Origin Oculomotor (III): Facial (VII): Glossopharyngeal (IX): vagus nerve (X ) S2,3,4 Course 1) Some in sphenopalatine ganglion: supply lacrimal and nasal glands. 2) Other fibers run to submandibular ganglion: supply submanadibular and sublingual salivary glands • secretion and vasodilator . pelvic nerve Ganglia ciliary otic terminal terminal Functions 1) Miosis (pupil constriction): Contraction increase power of lens: Contraction of ciliary muscle for near vision supply parotid gland: secretion and vasodilator 1. Heart : - Inhibition of all properties of atria only - does not supply the ventricles - ↓ coronary flow. (indirect). 2- Lungs - Broncho-Constriction - Dilatation of blood vessels. 3. GIT: - contract wall - relax sphincters - Secretory to GIT glands. 4. On Gall Bladder : evacuation: contract to wall and relax sphincter of Oddi 1- Defecation : contraction of wall of rectum and relaxation of internal anal sphincter. 2. Micturition : contraction of wall of bladder and relaxation of internal urethral sphincter. 3. Erection : VD of penis. 4. Female genital : VD.
A.F. 2021 4 Chemical Transmission at Autonomic junctions I. Q. Acetylcholine II. Q. Noradrenaline (Norepinephrine) Sites of release 1) All preganglionic fibers: sympathetic & parasympathetic 2) All postganglionic parasympathetic fibers. 3) Some postganglionic sympathetic fibers: • to sweat glands. • to blood vessels of skeletal muscles. Postganglionic sympathetic fibers, except: 1. to sweat glands 2. to the blood vessels of skeletal muscles Release: “exocytosis” - action potential spreads over terminal fibers - calcium diffuse into nerve terminals → exocytosis. Removal acetylcholine esterase : true pseudo specificity specific non-specific affinity great less site nerve endings plasma 1 ) Re-uptake : - by active transport (50-80%). 2) Diffusion : to surrounding fluids then blood. 3) Destruction by enzymes such as: 1. M.A.O . (deamination): 2. C.OM.T. (methylation):
A.F. 2021 5 ➢ RECEPTORS A. Q. Cholinergic: I. nicotinic (nicotine activated): in autonomic ganglia II. muscarinic (muscarine activated): in organs B. Q. Adrenergic : On effector organs Q. Drugs affecting A.N.S Alpha Beta 1 2 1 2 Mechanism of Action ↑ intracellular Ca ++ . decreasing c-AMP increasing c-AMP Actions • Vasoconstriction. • Contraction of : - Sphincters of G.I.T. - Spleen. - Internal urethral sphincter. • Inhibition of muscles of intestine. • Vasodilatation • Inhibition of muscle of: -Bronchioles -Urinary bladder. • ↑ HR & force of contraction of heart (B1) • Metabolic: Lipolysis . Glycogenolysis receptor Increase activity: Decrease activity: nicotinic 1. Nicotine small dose 1) Nicotine large dose muscarinic Muscarine Atropine adrenergic 1. Stimulate alfa: Phenylephrine 2. Stimulate beta: Isoprenaline 1) block alfa: phentolamine 2) block beta: propranolol