Nervous System (ANS) PDF

Control (regulatory) system 1. Endocrine system 2. nervous system Nervous System muscle tension Light & sound...

Control (regulatory) system 1. Endocrine system 2. nervous system Nervous System muscle tension Light & sound ↑ f 1. Receive information from internal & external environment. 2. Integration (processing) of information Level of integration (3 levels) Spinal cord e Reflex response Lower brain (subcortical level) Higher brain (cortical level) respiration Feat , rate thinking & reasoning 3. Rapid & precise response quich reaction to stimuli Anatomical division of the nervous system Central nervous system (CNS) Peripheral nervous system Brain & Spinal cord Peripheral nerves & ganglia - main processing center-transmits signals between CNS & body Histology Neuron (nerve cell): is the basic structural unit of the nervous system, Formed of Cell body (contain nucleus & organelles) Dendrites: receive impulse to cell body Axon (nerve fiber): carry impulse from cell body, may be ✓ Myelinated (cover by myelin sheath) or > - faster conduction ✓ Non-myelinated A nerve is formed of many nerve fibers (neuron) Synapse sites where axon of one neuron terminate on dendrites, soma or axon of another neuron Synaptic cleft space where chemical transmitter is released at synaptic site (no direct communication) Function of synapse: transmission of impulse (signals or electrical activity) from one nerve cell to another 1 Physiological division of the nervous system/ Peripheral nerves are of 2 kinds: Sensory nervous system Motor nervous system Transmit information from peripheral receptors to CNS Transmit information from CNS to periphery (muscles, glands, others) through sensory (afferent) A fibers→ through motor (efferent) e fiber→ Enter the spinal cord via posterior root Leave the spinal cord via anterior root Receptors: receive external information (light, sound, temperature, pressure) or internal information (muscle tension, visceral distention) Somatic sensory division Visceral sensory division Somatic nervous system Autonomic nervous system Receive information from Receive information from viscera For reflex or Voluntary For Involuntary control of Surface of the body Control of Skeletal muscles Plain (smooth) (visceral) muscle, (skin, muscles, joints), Cardiac muscle Special sense glands One type 2 types (sympathetic & parasympathetic) 2  Reflex arc: The functional unit of the nervous system ✓ Components: Stimulus higger Receptor (sensory organ): where impulse is initiated detect stimmler Afferent neuron transmits signal to CNS Center: One or more synapse in CNS Type of reflexes: (knee-jerk reflex m o Monosynaptic reflex (simplest reflex) (one synapse) o Polysynaptic reflex: one or more interneurons between afferent & efferent Efferent neuron caries response from CUS to effector Effector organ muscle /gland that performe response Response pathways that trans mit signals from priphery to CNS sensory & Afferent fibers Somatic reflexes Autonomic /visceral reflexes Relay at dorsal horn cell or cranial nuclei Relay at lateral horn cell or cranial nuclei Efferent fibers Origin Anterior horn cells (AHCs) of spinal cord/ Lateral horn cell (LHC) / Cranial nuclei Cranial nuclei Efferent fibers One neuron system 2 neuron system from CNS to ganglion ganglion & to target organ & (motor pathway) From cord to skeletal muscle (preganglionic, postganglionic) Myelination Myelinated (A) Preganglionic: myelinated (B) -faster Postganglionic: unmyelinated (C) > - shower Chemical Acetyl-choline Acetyl choline and Norepinephrine transmitter 3  Autonomic ganglia Definition: Collection of neurons outside CNS. Description: A- Preganglionic fiber - myelinated (B) (cell bodies are located in LHCs of spinal cord or motor cranial nuclei), synapse with B- 8-9 postganglionic fibers -unmyelinated (C ) (1: 8-9), (cell bodies -mother neurons- are in autonomic ganglion outside CNS) Function: Act as distributing centers ……………….. (description) Types 1- Paravertebral 2- Collateral ganglia 3- Terminal ganglia sympathetic chain Site On both sides of vertebral Column Midway between spinal cord & Near or in viscera, G heart, lange digestive tract , Pair of ganglia for each segment of viscera, (internal organs Has very short that part were of ↑ carrier signde from spinal cord At origin of vessels arise from postganglionic ganglion- > organ except cervical (3 only) abdominal aorta, (1mm to several cm) to because close ganglic are so Superior Named according to the vessel. to the target organ Middle Inferior cervical ganglia. regulates digestive processes dering stress I For relay Sympathetic only Sympathetic e.g. Celiac, Parasympathetic only. T slowing of heart ratel of superior, inferior mesenteric stimulating digestion fight or flight (heat rote dilate pupile , ganglia, aorticorenal) Parasympathetic (Ciliary, & "rest and digest" ↳ relaxen organsdin n sphenopalatine, submaxillary, otic ganglia) 4- 4. Adrenal medulla Modified sympathetic ganglion supplied by preganglionic (cholinergic) sympathetic fiber Postganglionic neuron lost their axons Secrete catecholamine directly into blood (80% adrenaline & 20% noradrenaline) to all organs These hormones have the same effects as sympathetic except that their effects lasts 5 – 10 times longer as they are removed slowly from the blood 4  Functions of Sympathetic Nervous System (Thoraco-lumbar) ✓ Arise from LHCs of all thoracic and upper 2 lumbar segments 51 - La ✓ Course Preganglionic sympathetic fibers leave spinal cord via the ventral roots with the spinal nerves Pass into ganglia of paravertebral sympathetic chain. Course: one of 3 ways: a. Fibers synapse with postganglionic neurons in the same ganglion that it enters, b. Fibers pass up or down in the chain and synapse in one of the other ganglia. Post ganglionic fibers from paravertebral sympathetic chain reenter spinal nerves 8% of fibers in spinal nerves are sympathetic fibers. c. Fibers pass through the chain without relay and pass to synapse in collateral ganglion. 5 I- Head & Neck Functions Origin preganglionic 1) Eye: neuron arise from LHCs Contraction of smooth muscle of upper eyelid (elevation) of T1 & T2 → widening of palpebral fissure Relay Cervical ganglia →↑visual field Course: post ganglionic Contraction of muller’s muscle in some animals fibers run in the outer → forward eye protrusion (exophthalmos) coat of the blood →↑visual field vessels Vasoconstriction (VC) of conjunctival vessels to various structures Contraction of dilator pupillae muscle →Pupil dilatation (mydriasis) 2) Skin: VC of cutaneous blood vessels Contraction of piloerector muscles → Hair erection ↑sweat gland secretion (secretory) 3) Salivary glands (mainly submaxillary): VC. Trophic secretion→ small amount, concentrated, viscid 4) Cerebral circulation: ↑Cerebral blood flow due to ↑of arterial blood pressure Cerebral vessels: mild VC 5) brain: ↑ mental alertness Horner's Syndrome: lesion on one side of the cervical sympathetic chain Manifestations: on the same side of the lesion: - 1. Miosis (pupil constriction) 2. Ptosis: drop of superior eye lid 3. Anhydrosis: no Sweating on affected side of the head & neck →dry skin 4. warm & red skin: due to VD of blood vessels of the head & neck 6 II- Thorax Functions Origin LHCs of T1→4 1) Heart ↑all cardiac properties Relay ↑ conduction Cervical & upper 4 ↑excitability thoracic ganglia in the ↑ heart rate O2 supply paravertebral better ↑force of contraction sympathetic chain Vasodilatation (VD) of coronary vessels (indirect effect) Course postganglionic 2) Lung fibers run with blood Bronchodilatation (relaxation of bronchial muscles). vessels to different Mild VC of pulmonary vessels organs III- Abdomen Functions Origin LHCs T5→T12 1) Gastrointestinal tract: Zit Pass via paravertebral Relaxation of plain muscle of wall of chain without relay, ✓ Stomach leave the chain as ✓ Small intestine seinio splanchnic nerve to ✓ Proximal part of large intestine relay in collateral Contraction of sphincters e.g. pyloric sphincter. ganglia * part of shorach that connect duodenum to Greater splanchnic 2) Liver: stimulate glycogenolysis nerve (T5-T9) relay on. → hyperglycemia (↑blood glucose) celiac & superior 3) Spleen: contraction of capsule mesenteric ganglia → release stored blood rich in RBC’s into circulation Lesser splanchnic nerve 4) Adrenal medulla: secretion of 80% adrenaline & 20% noradrenaline in blood (T10-T11) relay on. 5) Blood vessels: mainly VC of ………………….. , aorticorenal & superior VD of some arterioles. mesenteric ganglia Least splanchnic nerve (T12) relay on. aorticorenal ganglic Course: post ganglionic fibers run with blood vessels to abdominal viscera 7 IV- Pelvic viscera Functions Origin 1) GIT: retention of feces LHCs of T12, L1,2 Relaxation of plain muscles of wall of distal part of large intestine & rectum Relay: Contraction of internal anal sphincter Preganglionic fibers to GIT Pass via paravertebral chain without relay, leave it 2) Urinary bladder: retention of urine as Relaxation of plain muscles of wall of bladder lumbar splanchnic nerve Contraction of internal urethral sphincter to relay in inferior mesenteric ganglia Preganglionic fibers to 3) Male genitalia: the urinary bladder & Contraction of vas deferens, seminal vesicles & prostate → semen ejaculation external genitalia exit VC of blood vessel → shrinkage of penis (external genital organ) paravertebral chain through sacral ganglia as sacral splanchnic nerve 4) Female genitalia: variable effect on uterine muscle according to menstrual cycle Course: post ganglionic fibers run with blood vessels to pelvic viscera V-On limbs 1- Contraction of piloerector muscles (hair erection) 2- Skeletal muscles: ↑glycogenolysis, ↑strength of contraction and delay fatigue VI-On metabolism and 1- Basal metabolism: ↑100% blood 2- Blood: Enhance clotting 3- ↑blood glucose and stimulates lipolysis of Fat cells (Brown fat), Distribution of sympathetic nerve is only approximate and overlap greatly Alarm "Stress" response of sympathetic nervous system ✓ Sympathetic system discharge as one unit in emergency to prepares body for (stress, flight, fight, fear). 1. ↑ field of vision, pupil dilatation→ letting more light 2. Lowers threshold in reticular formation → alert (aroused). 3. Cardiovascular system: ↑HR, blood pressure → better perfusion to vital organs. 4. VC of skin blood vessels → limits bleeding from wound. 5. Glycogenolysis → hyperglycemia, Lipolysis: ↑ Free fatty acids →more energy 8  Functions of parasympathetic (craniosacral outflow) On Head Oculomotor:3rd cranial nerve Facial (7th cranial nerve) Glossopharyngeal (9th ) Preganglionic Edinger-Westphal nucleus Superior salivary nucleus Inferior salivary nucleus arise from in midbrain in lower pons between pons & medulla Relay & Ciliary ganglion Some fibers relay in Otic ganglia course sphenopalatine ganglion Post ganglionic Postganglionic: Post ganglionic: supply parotid gland short ciliary nerves supply nasal & lacrimal glands Other fiber in Chorda tympani branch relay in submandibular ganglion Post ganglionic: supply submandibular & sublingual gland Function Contraction of constrictor Vasodilator Vasodilator pupillae muscle Secretomotor Secretomotor →pupil constriction (miosis) Contraction of ciliary muscle → ↑ lens power → for near vision 9 On thorax & abdomen Functions Vagus (10th cranial nerve): a) Thorax: Preganglionic: 1) Heart: Vagal nucleus in medulla Inhibit all atrial properties (NO vagal supply to ventricles) Course: ↓ coronary flow preganglionic fibers supply ↓ 02 consumption thoracic and abdominal viscera 2) Lungs: (contain75 % of all Bronchial constriction parasympathetic fibers) VD of pulmonary blood vessels Stimulate bronchial gland → ↑secretion. Relay: terminal ganglia b)- Abdomen: GIT: Contraction of wall of ✓ esophagus ✓ Stomach ✓ Small intestine ✓ Proximal part of large intestine Relaxation of sphincters Secretory to glands of GIT, liver, pancreas Gall bladder: (evacuation of gall bladder) Contraction of wall Relaxation of sphincters of oddi On pelvis GIT: Defecation Preganglionic: from S-2-3-4 Contraction of wall of rectum Course: Relaxation of internal anal sphincter Pelvic splanchnic nerve/ Urinary bladder: Micturition (nervi erigentes) Contraction of wall of urinary bladder Relay: terminal ganglia. Relaxation of internal urethral sphincter Male genitalia: Erection (VD of blood vessels of penis) Female genitalia: VD N.B. No parasympathetic to sweat glands, skin, spleen, suprarenal medulla, ventricles Sympathetic is catabolic (energy consuming) Parasympathetic is anabolic (energy preserving), (rest, digest, reading) 10  Centers of the Autonomic Reflexes (level) A- Simple reflexes: are integrated in the spinal cord B- More complex reflexes: are integrated at higher levels in the C.N.S. Examples: Reflexes Integrated in Simple reflexes as contraction of the full bladder Sacral segments of spinal cord More complex reflexes which regulate Medulla Respiration and blood pressure Pupillary reflexes Mid brain 11  Chemical transmission in autonomic nervous system Acetyl Choline Noradrenaline = Norepinephrine Formation Formation In the axo-plasma of cholinergic nerve terminal In adrenergic nerve terminal via via choline acetyl transferase enzyme hydroxylation decarboxylation Tyrosine → DOPA → Acetyl choline is stored in small clear vesicles dopamine (in dark granulated vesicle) is converted into → Noradrenalin (Stored with ATP + chromogranin(protein) Release of acetylcholine Release of noradrenalin Action potential open Ca+2 channel in terminal nerve→↑ Ca+2 influx → rupture of vesicles→ release of …………. by exocytosis Removal of acetyl choline Removal of norepinephrine After release, within fraction of seconds, split within few secs by 3ways: Acetyl choline acetyl choline esterase Acetate + choline 1- Active Reuptake into nerve ending (50- 80%) Choline → reuptake for resynthesis 2- Diffusion away to surrounding fluid or blood. Acetyl choline esterase is 2 types: 3- Destruction by: 1-True (specific)(great affinity): in MAO (monoamine oxidase): on outer surface Synaptic area bound to collagen of mitochondria →in adrenergic nerve Membranes of cholinergic nerve endings endings, brain, liver, kidney, (deamination) 2-Pseudo (non specific): in plasma, COMT (catechol-O-methyl transferase): in all Acts on acetylcholine diffuse into surrounding fluid or tissues except nerve ending (methylation) plasma Sites of cholinergic fibers Sites of adrenergic fibers All preganglionic All postganglionic sympathetic fibers except Sympathetic & parasympathetic Secretory fiber to sweat gland To adrenal medulla VD fibers to blood vessels of skeletal muscle All postganglionic parasympathetic fibers. Noradrenalin is also secreted from adrenal Some postganglionic sympathetic → medulla with adrenalin Secretory fiber to sweat gland VD fibers to blood vessels of skeletal muscle 12  Receptors 1) Cholinergic receptor Nicotinic (activated by nicotine) Muscarinic (activated by muscarine) Site at autonomic ganglia In effector cells stimulated by (membrane of all postganglionic fibers & all postganglionic parasympathetic & adrenal medulla) Postganglionic cholinergic sympathetic 2) Adrenergic receptors α adrenergic receptors β adrenergic receptors Types α1, α2 β1, β2, β3 Mechanism of action α1 →↑intracellular Ca++ Both β1 & β2 → stimulate adenyl cyclase → α2 →inhibit adenyl cyclase → ↓cAMP ↑ cAMP Action α1 =excitatory (contraction) (Motor) Β2 =inhibitory (relaxation) (Postsynaptic receptor on 1- VC (skin, viscera, male genitalia) 1- VD of coronaries, skeletal Blood vessels surface of effector organ) 2- Contraction of 2- Relaxation of plain muscle of wall of a) Dilator papillae (mydriasis) a) Bronchi (dilatation) b) Spleen capsule b) GIT c) GIT & internal urethral sphincters c) Urinary bladder d) Seminal vesicles & vas deferens d) Uterus α2= inhibitory β1 (excitatory) Relaxation of plain muscle of intestine Cardiac acceleration, ↑force β3 lipolysis Action Regulate release of noradrenalin (presynaptic receptors on Stimulation of α presynaptic receptor→ Stimulation of β presynaptic receptor→ postganglionic nerve ↓noradrenalin release ↑noradrenalin release ending) = auto-receptor Adrenalin & noradrenalin have different effects on adrenergic receptors Adrenaline excites α & β equally Noradrenaline excites α mainly & β to slight extent Relative effect of the 2 hormones on different organs is determined by the type of adrenergic receptor in the organ Adrenalin: has greater effect on β receptor > noradrenalin → greater effect on cardiac activity and metabolism > noradrenalin Noradrenalin: has greater effects on α receptor > adrenalin →(VC) →↑ arterial blood pressure (↑total peripheral resistance) > adrenalin 13  Autonomic drugs Drugs affecting Parasympathetic Drugs affecting Sympathetic Drugs augment parasympathetic activity Drugs augment sympathetic activity 1) Ganglion stimulants: stimulate postganglionic 1) Ganglion stimulants: as parasympathetic a) Nicotine in small dose b) Anticholinesterase enzyme: Prostigmine Di-isopropyl fluorophosphate (DFp) (war poison) 2) Sympathomimetic drugs: 2) Parasympathomimetic drugs: stimulate Drugs stimulate α- receptors: Phenylephrine. muscarinic receptors= effector organs Drugs stimulate β- receptors: Isoprenaline Muscarine Pilocarpine Anticholinesterase Drugs depress parasympathetic activity Drugs depress sympathetic activity 1) Ganglion blockers 1) Ganglion blockers: as parasympathetic a) Nicotine large dose. b) Tetraethyl ammonium.(TEA) 2) Parasympatholytic drugs: block muscarinic 2) Sympatholytic drugs: receptors: Block α receptors : Phentolamine Atropine. Block β- receptors: Propranolol 14