When motor nervous severed (cut, damaged), SK. Ms enter state of paralysis & atrophy

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1 11/25/2012 1

2 Somatic NS have their cell bodies within CNS Conduct impulses along single axon from spinal cord to neuromuscular junction Send axon to SK.M Muscles consciously induced to contract or relax When motor nervous severed (cut, damaged), SK. Ms enter state of paralysis & atrophy

3 ANS Outline Introduction ANS Neurons Divisions of ANS ANS Neurotransmitters ANS Innervation of Organs Higher Control of ANS

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5 Nervous system Central NS Peripheral NS Autonomic NS Somatic NS Sympathetic NS Parasympathetic NS 11/25/2012 5

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8 Autonomic nervous system (ANS) manages our physiology By regulating organs & organ systems, & their smooth muscles & glands Majority of organs (effectors) that receive efferent fiber from ANS are hollow (heart, blood vessels, stomach, bladder, uterus, glands) & located within viscera so ANS= visceral NS Most of these organs can not be controlled consciously ANS= involuntary NS 9-4

9 Autonomic Nervous system (ANS): That controls involuntary body activities i.e.. controls visceral activities (heart, gastrointestinal tract, blood vessels ). Somatic Nervous System: That controls voluntary body activities (skeletal muscle). 11/25/2012 9

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11 Smooth muscle maintains resting tone in absence of nerve stimulation i.e. effectors are independent of their innervation Smooth becomes more sensitive when ANS input is cut (= denervation hypersensitivity) Many types of smooth are spontaneously active & contract rhythmically without ANS input ANS input simply increases or decreases intrinsic activity

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13 ANS has 2 neurons in its efferent pathway 1 st neuron (=preganglionic neuron) has cell body in brain or spinal cord Synapses with 2 nd neuron (=postganglionic neuron) in an autonomic ganglion Autonomic ganglion= is a collection of cell bodies outside CNS

14 Postganglionic axon extends from autonomic ganglion to target tissue Preganglionic fibers originate in: midbrain, hindbrain (pons, cerebellum & medulla oblengata), & upper thoracic to 4 th sacral level of spinal cord Autonomic gangli located in head, neck & abdomin

15 Depending on origin of preganglionic fibers & location of autonomic ganglia ANS can distinguish between sympathetic & parasympathetic divisions Usually have antagonistic effects These coordinate physiology with what s going on in person's life Sympathetic mediates "fight, flight, & stress" reactions Parasympathetic mediates "rest & digest" reactions 11/25/

16 Fight & flight division. It prepare the body to deal with stress. 11/25/

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18 Is also called thoracolumbar division because its preganglionics exit spinal cord from thoracic (T)1 to lumber (L)2

19 Most of these preganglionics then synapse on postganglionics in the paravertebral ganglia Which form chain of interconnected ganglia paralleling spinal cord i.e located on either side of spinal cord

20 Is characterized by divergence & convergence which cause Symp to mostly act as a unit (mass activation)

21 Divergence: preganglionics branch to synapse with number of postganglionic neurons

22 Convergence: postganglionics receive synaptic input from large number of preganglionics

23 Some postganglionics do not synapse in paravertebral ganglion but go to outlying collateral ganglion form splanchnic nerves

24 The adrenal medulla, located in adrenal gland on top of kidney, appears to be a modified collateral ganglion Its secretory cells appear to be modified postganglionics That release 85% epinephrine (Epi) or adrenaline & 15% norepinephrine (Norepi) or noradrenaline into blood in response to preganglionic stimulation Stimulated during mass activation

25 Epi is made by methylating Norepi

26 Parasympathetic NS is called the rest & sleep division of the ANS. It allows the body to recover from stress 11/25/

27 Is also called craniosacral division because long preganglionics originate in midbrain, medulla, pons, involving cranial nerves III, VII, IX & X & sacral (S)2 - S4 Synapse on postganglionic in terminal ganglia located next to or within target organ Postganglionic has short axon that innervates target

28 The long vagus nerve (X) carries most Parasymp fibers Innervates heart, lungs, esophagus, stomach, pancreas, liver, small intestine, & upper half of the large intestine Preganglionic fibers from S2-4 innervate lower half of large intestine, rectum, urinary & reproductive systems

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30 Parasympathetic NS Sympathetic division of the ANS is called the fight & flight division. It prepare the body to deal with stress. Parasympathetic NS is called the rest and sleep division of the ANS. It allows the body to recover from stress 11/25/

31 It is a collection of neurons outside the CNS. It is the site of synapse between preganglionic & postganglionic neurons It act as a distributing center. 11/25/

32 Types of autonomic ganglia 1- Lateral ganglia 3- Terminal ganglia (sympathetic chain) 2-Collateral ganglia (Prevertebral) 11/25/

33 Chemical Transmission in ANS Parasympathetic NS Sympathetic NS 11/25/

34 Sites of the Cholinergic Autonomic Fibers All preganglionic fibers Some postganglionic sympathetic fibers such as sweat glands & blood vessels of skeletal muscles 11/25/

35 Sites of the Adrenergic Fibers Adrenergic fibers All postganglionic sympathetic fibers except (sweat glands & blood vessels Of skeletal muscle) 11/25/

36 Chemical Transmission in Sympathetic NS The postganglionic effect of sympathetic NS is mediated mainly by noradrenaline, so it is called adrenergic system. The majority of adrenal medulla secretion is adrenaline 85% & 15% noradrenaline. 11/25/

37 Chemical Transmission in Parasympathetic NS The postganglionic effect of parasympathetic NS is mediated mainly by acetyl choline, so it is called the cholinergic system. 11/25/

38 Two subdivisions Sympathetic nervous system Parasympathetic nervous system

39 Autonomic Receptors They are chemical structures found mainly on the cell membrane of the effector organs. They are affected by chemicals or drugs. They are classified into 2 main groups: Cholinergic receptors Adrenergic receptors 11/25/

40 Cholinergic Receptors It is the division of the autonomic receptors which can be stimulated by acetyl choline. It is classified into 2 types according to its sensitivity to drugs. Muscarinic Rs Stimulated by muscarine Nicotinic Rs Stimulated by nictotine 11/25/

41 Site Stimulated by: Muscarinic receptors Effector organs supplied by: -All parasympathetic postganglionic fibers. -Sympathetic cholinergic fibers (sweat glands & blood vessels of skeletal muscles) -Acetyl choline. -Muscarine. Nicotinic receptors -All autonomic ganglia. -Adrenal medulla. -Motor end plate. -Acetyl choline. -Nicotine small dose. Blocked by: Atropine Curare; Nicotine large dose 11/25/

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43 Adrenergic Receptors It is the division of the autonomic receptors which can be stimulated by catecholamine (epinephrine & norepinephrine). It is classified into 2 types according to its sensitivity to drugs Subdivided Alpha (α) Rs α1 & α2 Beta (ß)- Rs ß 1 and ß 2 - α1 & ß 1 receptors have excitatory actions. - α2 & ß 2 receptors have inhibitory actions. 11/25/

44 Action Alpha (α) receptors They are mostly excitatory. i.e. on stimulation, they cause smooth muscle to contract. Beta (ß) receptors They are mostly inhibitory. i.e. on stimulation, they cause smooth muscle to relax. Site Stimulated by: Blocked by: -Blood vessels (vasoconstriction). -Splenic capsule (contraction). -GIT sphincter ( contraction). Mainly by noradrenaline. Phentolamine -Blood vessels (vasodilation). -Bronchi (bronchodilation). -GIT wall (relaxation). Exception: cardiac muscle (increase its contraction force) ß 1 Mainly by adrenaline. Propranolol. 11/25/

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46 Many useful drugs have been developed to affect ANS receptors Drugs that promote actions of a NT are agonists Drugs that inhibit actions of a NT are antagonists

47 Agonists Bind to same receptor as neurotransmitter Elicit an effect that mimics that of neurotransmitter Antagonists Bind with receptor Block neurotransmitter s response

48 People with hypertension 1 located in heart propranolol (block receptor) decrease cardiac rate & blood pressure 2 located in bronchioles of lungs reduce bronchodilation Produce asthma in susceptible people More selective 1 antagonist (atenolol) is now used to decrease cardiac rate & lower blood pressure

49 People with asthmatics inhaled epinephrine (stimulate receptor) stimulate 1 receptor located in heart stimulate 2 receptor located in air way Drugs such as terbutaline selectively function as 2 agonist are commonly used

50 What is the difference between adrenaline and noradrenaline? 11/25/

51 Adrenaline Site of release -Adrenal medulla (80% of its secretion ). Noradrenaline -Adrenal medulla (20% of its secretion ). -Sympathetic postganglionic nerve endings. Action on adrenergic-rs Effect on heart Effect on blood vessels Relaxing effect on GIT Metabolic actions Glycolytic lipolytic & increasing metabolic rate Acts on both α & β receptors. More strong Vasoconstriction, but it causes vasodilation in blood vessels of skeletal muscle & liver More strong More strong Acts mainly on α receptors. Less strong Vasoconstrictor only. Less strong Less strong 51

52 Functions of the sympathetic NS Sympathetic NS is characterized by: It discharges during emergency & stress (fear, fight & flight reaction). It acts as one unit (generalized action). It has catabolic action. Delays evacuation of visceral content. 11/25/

53 Sympathetic NS is divided into 4 divisions: Cervical division head & neck. Cardiopulmonary division heart & lung. Splanchnic division abdomen & pelvis. Somatic division skeletal muscle. 11/25/

54 11/25/2012 Prof Maha Hegazi 54

55 Cervical division ( 3X3 ) Head & neck Eye Salivary glands Skin 1- Pupil dilation (contraction of radial muscle; mydriasis = prolonged dilation of pupil of eye ). 2- Widening of the palpebral fissure (فتحة الجفن ( 3- Exophthalmos. )جحوظ ) 11/25/

56 Cervical division ( 3X3 ) Head & neck Eye Salivary glands Skin 1- Pupil dilation (contraction of radial muscle; mydriasis). 2- Widening of the palpeberal fissure. 3- Exophthalmos. 1- Stimulate viscid salivary )لزج ) secretion. (thick saliva rich in mucus) 2- Squeezing of the salivary ducts. 3- Vasoconstriction 11/25/

57 Cervical division ( 3X3 ) Head & neck Eye Salivary glands Skin 1- Pupil dilation (contraction of radial muscle; mydriasis) 1- Stimulate viscid salivary secretion. (thick saliva rich in mucus) 1- Increase sweat secretion. 2- Widening of the palpeberal fissure. 2- Squeezing of the salivary ducts. 2- Hair erection. 3- Exophthalmos. 3- Vasoconstriction 3- Vasoconstriction 11/25/

58 Thorax Heart Ooooooooooooooooooooo Lung 1- Increase in cardiac activities: Increases heart rate & force of contraction. 2- Vasodilatation of coronary blood vessels indirectly by increasing cardiac work & accumulation of metabolites. 1- Bronchodilatation. 2- Decreased bronchial secretion. 3- Vasoconstriction of bronchial blood vessels. 11/25/

59 3- sympathetic function to abdomen & pelvis (حشوى Abdomen (supplied by greater splanchnic (= visceral nerve): Liver: Glycogenolysis. Gall bladder: Relaxation of the wall & contraction of the sphincter. GIT: Relaxation of wall & contraction of sphincter i.e. inhibition of motility & delay of evacuation. Spleen : Contraction of its capsule. Pancreas : net decrease insulin secretion. 11/25/

60 Adrenal medulla It is supplied by preganglionic cholinergic fibers. So it is considered as modified sympathetic ganglia). Its stimulation causes release of catecholamine to blood (80% of its secretion is adrenaline & 20% noradrenaline). It augments & potentiates the effects of sympathetic stimulation. 11/25/

61 Pelvis (supplied by lesser splanchnic nerve) : Urinary bladder : Relaxation of wall & contraction of internal sphincter i.e. urine retention. Rectum : Relaxation of wall & contraction of internal sphincter. Male sex organ : ejaculation. 11/25/

62 4- Sympathetic action on blood vessels of skeletal muscles It increases blood flow to skeletal muscles through vasodilation of its blood vessels (sympathetic cholinergic fibers). So when sympathetic NS is activated skeletal muscles will have: Better contraction force. Delayed fatigue. Rapid recovery from fatigue. 11/25/

63 Functions of the parasympathetic NS Parasympathetic NS is characterized by: It discharges during rest & sleep. Its action is localized. It has anabolic action (conserve body stores). It increases gastrointestinal secretion & motility i.e. secretomotor. 11/25/

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65 Cranial division 3 rd cranial nerve (Occulomotor nerve): Eye: 1-constriction of the pupil (contraction of circular muscle) 2-Accommodation of eye to near vision due to contraction of ciliary muscle. 7 th cranial nerve (Facial nerve) Submandebular & sublingual salivary glands: Increases its secretion of watery saliva (large volume). : 9 th cranial nerve (Glossopharyngeal nerve): Parotid salivary glands: Increases its secretion of watery saliva (large volume) 11/25/

66 Cranial division 10 th Cranial nerve (X) (= vagus nerve) (supply viscera in thorax & abdomen) Heart Thorax Ooooooooooooooooooooo Lung Decrease heart rate. Decrease force of contraction of atria. Vasoconstriction of coronary blood vessels indirectly due to decreased cardiac work & O2 demand Bronchoconstriction Increase mucous secretion from bronchial glands. 11/25/

67 Abdominal Viscera Gall bladder : Contraction of wall & relaxation of sphincter. GIT : Contraction of wall & relaxation of sphincter (increase its secretion & motility). Pancreas : Increase insulin secretion. 11/25/

68 Sacral division (supply pelvic organs): Urinary bladder : Contraction of wall & relaxation of internal sphincter. Rectum : Contraction of wall & Relaxation of internal sphincter. External genitalia : Vasodilatation of blood vessels induce erection. 11/25/

69 Dual innervation Almost all visceral organs are supplied by both sympathetic & parasympathetic divisions of autonomic NS. Which division predominate at any given time is determined by the body demands at that time. The parasympathetic discharge to heart is more powerful at rest (vagal tone) While sympathetic discharge to blood vessels is more potent at rest (sympathetic tone) 11/25/

70 Dual innervation Most visceral organs receive dual innervation (supplied by both Symp & Parasymp) While 2 branches are usually antagonistic, such as their effects on heart rate Can be complementary (cause similar effects) such as with salivation Or cooperative (produce different effects that work together to cause desired effect) such as with sexual function Parasym stimulate erection (dilation of blood vessels) while Sym stimulate ejaculation & orgasmic both division work to ensure complete sexual function 11/25/

71 Structures supplied only by sympathetic nervous system Skin sweat glands sympathetic cholinergic) Pilo erector muscle. Blood vessels all over the body except the penis. Dilator pupillae muscle (= radial muscle of iris). Blood vessels of the skeletal muscles sympathetic cholinergic. Adrenal medulla. Capsule of the spleen. 11/25/

72 Structures supplied only by Parasympathetic nervous system Constrictor pupillae muscle (= iris sphincter muscle; circular muscle of iris). 11/25/

73 Regulation achieved by increasing or decreasing firing rate Adrenal medulla, arrector pili muscle, sweat glands, & most blood vessels receive only sympathetic innervation

74 Some postganglionics do not use Norepi or ACh Called nonadrenergic, noncholinergic fibers Appear to use ATP, VIP (vasoactive intestinal peptide), or NO as NTs NO produces smooth muscle relaxation in many tissues

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76 Medulla most directly controls activity of ANS It has centers for control of cardiovascular, pulmonary, urinary, reproductive, & digestive systems Hypothalamus has centers for control of body temperature, hunger, & thirst; & can regulate medulla Limbic system is responsible for visceral responses that reflect emotional states Cerebral cortex & cerebellum also influence ANS