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Physiology of Autonomic Nervous System Dr. Ahmed Al-Sehli

Physiology of Autonomic Nervous System Dr. Ahmed Al-Sehli. AUTONOMIC NRVOUS SYSTEM. Definition : It is the system for involuntary subconscious functions , it controls the internal environment to maintain homeostasis . DIVISION OF NERVOUS SYSTEM : 1- Central nervous system :

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Physiology of Autonomic Nervous System Dr. Ahmed Al-Sehli

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  1. PhysiologyofAutonomic Nervous System Dr. Ahmed Al-Sehli

  2. AUTONOMIC NRVOUS SYSTEM Definition:It is the system for involuntary subconscious functions , it controls the internal environment to maintain homeostasis . DIVISION OF NERVOUS SYSTEM : 1- Central nervous system : a) Brain b) Spinal cord 2- Peripheral nervous system : a) Cranial nerves Autonomic (involuntary) Somatic (voluntary) b) Spinal nerves Autonomic Somatic

  3. A.N.S differs from Somatic N.S in :-In A.N.S there is : 1-Autonomic ganglia 2-Connector neurone is outside CNS 3-It regulates smooth muscles Q: Discuss and differentiate the two divisions of A.N.S ?

  4. A.N.SSympatheticParasympathetic 1- ORIGIN: Thoraco-Lumber Cranio - sacral(Tl - T12 , LI,2,3) 3,7,9,10 S2 , 3 , 4 1- ORIGIN: Thoraco-Lumber Cranio - sacral(Tl - T12 , LI,2,3) 3,7,9,10, s2,3,4, 2-FUNCTION: Stress muscular exercise - Digestion and sleep, fear Empting fightmicturationflightdefication - Catabolic - Anabolic (energy lost from the body)(energy preserved) 4- DISTRIBUTION: widspreadLocalised 5- DISCHARGE : as one unit (most actions) To each system at the same time) separetly

  5. RELATIONSHIP BETWEEN SYMP ATHETC AND PARASYMPATHETIC 1- RECIPROCAL : once sympathetic is stimulated, parasympaethetic is inhibited and vise - versa 2- COMPLEMENTAL : e.g micturation and defication reflex. sympathetic for FILLING and parasympathetic for EVACUATION N.Bboth sympathetic and parasympathetic together help acurate control over an organ's activity.

  6. AUTONOMIC GANGLIA DEFINITION :It is the site of physiological contact between pre and post ganglionic fibers . TYPES: a) lateral (sympathetic) b) collateral (mixed) or pure sympathetic c) terminal ( parasympathetic ) Lateral( paravertebral) 23 ganglia: 3 = cervical sympathetic chain 12 = thoracic 4 = lumber 4 = sacral

  7. Collateral:Around large .B.V as: - Caeliac ganglion - Superior mesentric ganglion - Inferior mesentric ganglion Terminal(in the wall of organ, no post-ganglionic as vagus or may be present very short post-ganglionic fiber

  8. Pathway of pre-ganglionic sympathetic fibers: 1- May synapse in first sympathetic chain ganglion, it enters. 2- Synapsing in other sympathetic chain ganglia up or down. 3- Synapse in collateral ganglia. 4- Synapse in substance of adrenal medulla itself.

  9. Function :1) Distributing center: Sympathetic Parasympathetic 1 : 32 1:9 or 1:2 ?? 2) Relay station between pre and post ganglionic fiber Localization :To diagnose site of relay, by Nicotine test: (Langlay's test) painting the ganglia with large doses of nicotine to block the site of relay, after that if it gives no post - ganglionic response = relay Cervical Division of sympathetic

  10. DESTRIBUTION OF SYMPATHETIC NERVOUS SYSTEM 1) CERVICAL DIVISION: Origin: It arises from lateral horn cell of Ti and T2 and end in superior cervical ganglion I) EYE : a) dilatorpupilllary muscels = pupillary dilatation = Mydriasis b) Tarsal m.=elevation of eye lid = widening of eye superior inferior c) Muller's m. = Exophthalamos = Protrusion of eye ball in animals d) Blood vessels of eye = V.C e) relaxation of the ciliary muscle for vision

  11. II) SALIVARY GLANDS : a) Secretion of small amount of saliva, rich in organic matters (enzymes) i.e viscus saliva . b) Squeezing around acinin of salivary glands push saliva outside III) SKIN : a) Erector pilae m = erection of hairs b) Vaso-conistriction of blood vessels = pallor c) Sweat :Secretion = mental sweat. IV) Cerebral blood vessels = vaso-conistriction

  12. HORNER'S SYNDROME It IsCerviaclSympathectomy: characterized by : 1-PTOSIS : drop of upper eyelid. 2- MIOSIS :pupillaryconstriction . 3- ANHYDROSIS :dryness of skin 4-Emrophthalamos 5- Flushing of the face ALL THESE EFFECTS ARE AT SAME SIDE OF LESHON

  13. 2) CARDIQ-PULMONARY DIVISION : Segments and end in 3rd cervical and upper 4 thoracic ganglia I)HEART : increase all cardiac prosperities as: - positive inotropic effects = ↑ contractility - positive chronotropic effect = ↑ Heart rate. - = ↑ Conductivity - = ↑ Excitability II) CORONARY BLOOD VESSELS vasodilatation III) LUNG : a) bronco-dilatation . b) inhibits bronchial glands secretion of mucous IV) PULMONARY BLOOD VESSELS: vasoconstriction.

  14. 3- SPLANCHIC DIVISION:To Abdomen and pelvis

  15. A) Greater Splanchic Nerve : it supplies the abdomen e.g : (From T5–T9, relay in caeliac ganglion) a) wall of G.I.T → relaxation of its walls = retention ↓ motility. b) sphincters → its contraction e.g pyloric sphincter of stomach c) liver → glycogenolysis = glycogen converted to glucose . d) adrenal medulla → release of epinephrin and nor epinephrine . e) spleen → contraction & release of RBCs in case of heamorrhage f) adipose tissues → lipolysis . g) inhibite the intestinal juice secretion h) relaxation of gall bladder and contraction of its sphincter. N.B Stimulation of greater splanchic nerve causes two peaks rise in blood pressure : a) First rise due to V.C of visceral blood vessel b) Second peak due to release of catecholamin into blood.

  16. ADRENAL MEDULLA: Supplied by pre-ganglionic sympathetic fibers (greater splanchnic nerve). The circulating catecholamin have same effects of direct sympathetic stimulation, but more prolonged , So body organs can be stimulated by 2 ways, Nervous (direct) & Hormonal (indirect), Also catecholamines can stimulate sites not supplied by direct sympathetic nerves .

  17. N.B adrenal meddulla is modified by sympethetic ganglion because : 1- No post-ganglionic fibers 2- Causes release of 80% epinephrin. 20% nor epinephrin. N.BSelective secretion of adrenal medulla: a) More epinephrine in unexpected stresses as haemorrhaege b) More nor-epinephrine in familiar stresses as hypoxia

  18. B) Lesser splanchnic nerve: From LI - L3, relays in inferior mesentric ganglion It supplies the pelvis e.g :- a) Rectum → retention of stool (+) of internal anal sphincter b) Urinary bladder → retention of urine by relaxation of its wall and contraction of internal uretheral sphincter. c) Sex organs → ejaculation . External genitalia: In males : Inhibition of erection (v.c of erectile tissue)-Ejaculation of semen (contraction of vas deferens, prostate and ejaculatory duct( In females: Contraction or relaxation of female genital organ according to the stage of menstrual cycle and level of hormones in blood. N.B Small splanchnic nerve (from T10 – T12, relayes in caeliac and superior mesentric ganglion(

  19. 4- SOMATIC DIVISION : (Orbelli phenomenon( It is sympethetic supply of limbs, upper limbs (T4- Ts) lower limbs (T10T12), both relay in sympathetic chain = Sympethetic stimulation delays fatigue of muscle due to vasodilatation of skeletal blood vessels

  20. ORGANS SUPPLIED BY SYMPATHETIC ONLY : 1- Ventricles (vagal escape). 2- Skin structures 3- Skeletal B.V. 4- Dilator pupillary muscles . 5- Adrenal medulla

  21. ORGANS SUPPLIED BY PARASYMPATHETIC 1- Constrictor pupillary muscle . 2- Oesophagus . 3- Gastric glands . 4- Erectile tissue . N.B Sympethetic → causes V.C of all blood vessels, except 1. Coronaries. 2. Skeletal blood vessels.

  22. DISTRIBUTION OF PARASYMPATHETIC I- CRANIAL DIVISION : A) Oculomotor nerve ( III N ): It arises from occulomotor nucleus , relays in ciliary ganglion FUNCTION : responsible for near visions

  23. During fixation of eyes to near object, III nerve causes : 1) Contraction of ciliary muscle → Increases convexity of the eye lens . 2) Contraction of medical rectus muscle → medial convergence of both eyes together. 3) Contraction of constrictor pupillae muscle → papillary constriction

  24. B) Fascial Nerve (VII N): It arises from superior salivary nucleus, relays in sphenopalatine ganglion. FUNCTION : secretion of tears and saliva which is watery, poor in enzymes and big in amount . C) Glossopharyngeal Nerve (IX N): It arises from inferior salivary nucleus 9 relays in optic ganglion . FUNCTION : secretion of saliva

  25. D) Vagus Nerve (XN): 75% of parasympathetic fibers of the body are the vagus nerve. It arises from dorsal nucleus, relays in terminal ganglia. FUNCTION : 1- Inhibition (supression) of heart rate and contractility. 2- Broncho-constriction and inhibition of inspirartory center and secretion of mucous from bronchial glands. 3- Stimulation (excitation) of G.I.T motility and secretions .

  26. EFFECT OF VAGUS NERVE 1-) ON HEART * Inhibits all cardiac roperties, but it does not supply the ventricles (vagus escape). * Tonic (continuous) effect on the heart , which is more marked in athelets. * Coronary vaso-constriction (V.C ) . 2) ON LUNGS: Mentioned before . 3) ON G.I.T: * Evacuation of food (stimulation of G.I.T . motility ). * Evacuation of gall bladder. * Stimulates secretion of: gastric juice , bile , pancreatic juice and mucus (Brunner's glands) * Increased hepatic blood flow. N.B Vagus nerve has no post-ganglionic fibers

  27. WHY IT'S CALLED VAGUS ? Because it has :- 1- Afferent & efferent 2- Stimulatory & inhibitory 3- Widely distributed

  28. II- SACRAL DIVISION OF PARAS YMPATHETIC ( nerve erigentis) It is 82 ,3,4 and called pelvic nerve and relays in hypogastric ganglia. FUNCTION : 1- It supplies urinary bladder → causes micturation 2- distal 2/3 of large intestine and rectum → causes defecation 3- Male and female sex organs → erection by vasodilatation of blood vessels of penis (♂) or clitoris (♀)

  29. MICTURATION: Pelvic nerve causes contraction of wall of urinary bladder and relaxation of internal uretheral sphincter → passage of urine

  30. DEFECATION : pelvic nerve causes contraction of wall of rectum and relaxation of internal anal sphincter → passage of stool N.B External uretheral or anal sphincters are not under autonomic control but under somatic control via pudendal nerve . N.B Internal sphincter is more important than external sphincter because it is smooth muscle i.e fatigue resistant, while external sphincter is skeletal muscle i.e fatigable .

  31. CHEMICAL TRANSMITTERS DEFINITION : it is the substance which transmits the nerve impulse from pre - synaptic to post - synaptic membrane . MECHANISM : Arrival of nerve impulse to Pre-synaptic membrane → causes Ca+ uptake by acetyl choline vesicles → causes swelling and rupture of vesicles → causes release of acetyle choline which can cross the synaptic cleft → formation of acetylcholin - receptor complex → Increase Na permeability → Depolarisation Action potential This Causes Propagation of Nerve Impulse

  32. TYPES OF NERVE ENDINGSADRENERGICCHOLINERGIC(nor adrenaline)(ac . Choline( I ) Cholinergic neurotransmission :- ( six steps ) 1- Synthesis of acetyl choline :-( In cytoplasm) choline + acetyl CoA CAT Ach + CoA. ( choline - acetyl - transferase) 2- Storage of acetyl choline in vesicles In the synaptic vesicles . 3- Release of Acetyl choline :- Ca++ channels in the presynaptic membrane opens → Ac.ch. Release by exocytosis 4- Binding to receptors . 5- Degradation of Ac.ch. choline Ac.ch. choline + acetate esterase 6- Recycling of choline Into the neurone for resynthesis of Ac .ch.

  33. SITES OF RELEASE OF ACETYL CHOLINE 1- Autonomic ganglia (i.e all preganglionic fibers) 2- All parasympathetic post - ganglionic fibers . 3- Some sympathetic post - gangljpnic as sweet glands and blood vessels of skeletal muscles. 4- M.E.P = motor end plate (i.e neuro - muscular junction) 5- Adrenal medulla (pre ganglionic ) 6- C.N.S .

  34. TYPES OF CHQLINERGIC RECEPTORS

  35. A) Muscarinic receptors Sites : In cardiac muscles, smooth muscle and exocrine glands . Subtypes : Ml , M2 , M3 and M4 . -Some sympathetic post-ganglionic as sweet glands and blood vessels of skeletal muscles. - M.E.P = motor end plate (i.e neuro - muscular junction) - Adrenal medulla (pre ganglionic ) - C.N.S . Ml : in autonomic ganglia, CNS and gastric mucosa M2 : in cardiac cells and smooth muscles . M3 : in smooth muscles and secretory glands . M4 and M5 : unknown sites .

  36. Functions of muscarinic receptors It has prolonged reseponse, lasts for seconds, either exitation or inhibition : 1- Cardiac inhibition ( slow heart rate.) 2- Broncho-constriction . 3- Salivary secretion 4- Increases G.I.T secretion and motility. 5- Pupillary constriction . 6- Contraction of ciliary muscle. 7- Contraction of urinary bladder and rectum .

  37. B) Function of Nicotinic Receptors It has short timed receponse only exitatory : 1- Help ganglion transmission . 2- Secretion of epinephrine and nor-epinephrine from Ad. Medulla. 3- Stimulates N.M.J (MEP) to produce skeletal muscle contraction

  38. FATE (REMOVAL) OF AC CHOLINE .By choline-estrase enzyme 2 types. True pseudo (false) - present in nerve –endings - present in plasma. specific only for Ac - non specific, can act on any ester - highly potent (strong) - less potent.

  39. PARASYMPATHOMIM ETIC DRUGS Acts By Two Ways : A) Direct : on tissues as muscarine, nicotine in small dose and carbachol. B) Indirect : anticholinesterases as DFP and Eserine (war gas)

  40. Anti cholinesterases : Two types : a) Reversible : short acting e.g Eserine : generalized i.e. ↑ both muscarinic and nicotinic actions. Prostigmine: Nicotinic i.e ↑ skeletal muscles MEP activity = used in treatment of myasthenia gravis . b) Irreversible : long acting drugs i.e toxic, called nerve gases, or insecticides as DFP which causes paralysis of motor functions → difficulty in breathing → death

  41. PARASYMATHOLYTIC DRUGS Mechanism of action : 1) Persistent depolarization 2) Competitive inhibition as curare. Types : A) ganglion blockers -Nicotine in large doses - Hexamethonium They cause paralysis of autonomic ganglia by persistant depolarization . B) post - ganglionic blockers -Atropine C) MEP blockers - Curare - Botulinum - Flexidil - Succinyl cholin . ( persistent depolarization)

  42. Curare :- acts by competitive inhibition to Ac.ch . It can be used together with succinyl choline as muscle relaxants ATROPINE (anti-muscarinic drug ): ACTION : a) ON THE EYES :- Mydriasis and cycloplegia(loss of ability for near vision) b) ON SALIVARY GLANDS :- Dryness of mouth c) ON G.I.T :- Decrease motility = antispasmodic d) ON RESPIRATION : - Block secretions in respiratory tract e) ON C.V.S :- Tachycardia = ↑ heart rate . f) ON URINARY TRACT :- ↓ motility of urinary bladder .

  43. Effect of injection of Ac.ch. after Atropine on A.B.P Nicotinic receptors in adrenal medulla unblocked rise in A.B.P CLINICAL USES OF ATROPINE 1- Fundus examination → Mydriasis 2- Bronchial asthma → Bronchodilatation . 3- Treatment of colic →↓ motility of G.I.T . 4- pre anaethetic drugs to prevent cardiac arrest. 5- Befor surgery → to block respiratory secretions

  44. ADRENERGIC TRANSMISSION 5 STEPS : Hydroxylase enz. 1- Tyrosine DOPA (In cytoplasm). Dopa dopamine . 2- Storage of nor epinephrine in vesicles :- OH Dopamine Nor. epinephrine ( In synaptic vesicles .) N.B In adrenal medulla only: CH3 Nor - epinephrine epinephrine . 3- Release of nor-epinephrine :- Into the synapse. 4- Binding by receptors : either post-synaptic ( on the effector organ) or pre- synaptic receptors ( on nerve endings.) 5- Removal of nor- epinephrine ( Fate ) .

  45. SITES OF RELEASE OF CATECHOLAMINES 1- Adrenergic endings :- only nor - adrenaline . 2- Adrenal medulla :- causes release of : 80% epinephrine 20% nor-epinephrine FATE OF CATECHOLAMINES 1- Active reuptake = 80-90% back into ad. vesicles. (Na-k Atpase sys.) 2- Destruction = 7 % by MAO (oxidation) COMT (methylation) 3- Excretion as such = 3 %

  46. ADRENERGIC RECEPTORS (ALQUISTE) α1 : STIMULATORY a) V.C b) stimulation of sphincters . α2 :- INHIBITORY 0 a) relaxation of walls of G.I.T b) pre - synaptic inhibition of release of nor epinephrine (-ve feedback) βl :- STIMULATORY (+) a) heart +ve increase H.R & contraction b) adipose tissue = lipolysis c) renin - angiotensin . system = ↑ ABP. β2 :-INHIBITORYO (–)relaxation of smooth muscles in : 1- bronchi = bronchodilatation . 2- blood vessels = V.D in skeletal blood vessels & coronaries.

  47. N.B β1 receptors are stimulated equally by epinephrine and nor-epinephrine B2 receptors stimulated more by epinephrine than N.E β2 adrcnoreceptors : tow groups α 1 & α2: αl receptors have high affinity for phenyl-ephrine present on post.synaptic membrane of effector organ . α2 receptors have high affinity for clonidine. present on Pre-synaptic nerve endings to control release of nor-epinephrine (causes its inhibition). N.B β2 pre-synaptic receptors stimulate NE release, both a 2 and β2 receptors are called pre - synoptic receptors.

  48. RECEPTOR STIMULANTS α Receptors stimulated by : nor - adrenaline ]- adrenaline} isoproterenol β Receptors stimulated by : isoproterenol J. adrenalin]- nor - adrenaline N.B nor - adrenaline, has a more pressor effect because it acts mainly on α due to receptor sensitivity. RECEPTOR BLOCKERS : α Blockers : ergot alkaloids . β Blockers : inderal .(Propranolol.) N.B In G.I.T inhibition of the wall is by α2 and may be β2 receptors. While stimulation of sphincters only by al receptors (not β1 ). N.B α is stimulatory except on G.I.T, it is inhibitory While β is inhibitory except on heart, it is stimulatory.

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