AUTONOMIC NERVOUS SYSTEM SYMPATHETIC & PARASYMPATHETIC

AUTONOMIC NERVOUS SYTEM

1. AUTONOMIC NERVOURS SYSTEM MOGERA MWAMBA mongera mwamba

2. AUTONOMIC NERVOUS SYSTEM primarily concerned with regulation of visceral or vegetative functions also called vegetative or involuntary nervous system Divisions of the ANS Sympathetic division Parasympathetic division mongera mwamba

3. Sympathetic nervous system SNS/ thoracolumbar outflow because , the preganglionic neurons are situated in lateral gray horns of 12 thoracic and first two lumbar segments of spinal cord Preganglionic fibers leave the spinal cord through anterior nerve root and white rami communicantes and terminate in the postganglionic neurons, which are situated in the sympathetic ganglia. mongera mwamba

4. Sympathetic nervous system Sympathetic division supplies smooth muscle fibers of all the visceral organs such as blood vessels, heart, lungs, glands, gastrointestinal organs, etc. Classification of sympathetic ganglia: Paravertebral or sympathetic chain ganglia Prevertebral or collateral ganglia Terminal or peripheral ganglia mongera mwamba

5. Sympathetic ganglia mongera mwamba

6. Paravertebral or sympathetic chain ganglia arranged in a segmental fashion along the anterolateral surface of vertebral column Ganglia on either side of the spinal cord are connected with each other by longitudinal fibers, to form the sympathetic chains Both the chains extend from skull to coccyx mongera mwamba

7. Paravertebral chain ganglia Ganglia of the sympathetic chain (trunk) on each side are divided into four groups: Cervical ganglia : 8 in number Thoracic ganglia : 12 in number Lumbar ganglia : 5 in number Sacral ganglia : 5 in number. mongera mwamba

8. Paravertebral chain ganglia Cervical Ganglion Superior cervical ganglion formed by the fusion of upper four cervical ganglia Largest ganglion of ANS Receives preganglionic fibers from first thoracic spinal segment (T1) via white rami Postganglionic fibers from this ganglion, supply the blood vessels, glands etc. Superior cervical ganglion also sends some fibers to heart through superior cervical sympathetic nerve and cardiac plexus mongera mwamba

9. Paravertebral chain ganglia II .middle cervical ganglion It is formed by fifth and sixth cervical ganglia Preganglionic fibers arise from T1 segment Postganglionic fibers from here supply the sweat glands, thyroid gland and parathyroid glands It also sends fibers to heart via middle cervical sympathetic nerve and cardiac plexus mongera mwamba

10. Paravertebral chain ganglia III. Inferior cervical ganglion : formed by the fusion of seventh and eighth cervical ganglia First thoracic ganglion fuses with inferior cervical ganglion, forming stellate ganglion It receives preganglionic fibers from T1 segment It sends postganglionic fibers to heart through inferior cervical sympathetic nerve and cardiac plexus Postganglionic fibers also form the plexus around subclavian artery and its branches. mongera mwamba

11. Thoracic Ganglia 12 evenly spaced thoracic ganglia on each side Thoracic ganglia receive preganglionic fibers from the thoracic segments Postganglionic fibers from thoracic ganglia are distributed to visceral organs in the thorax and abdomen mongera mwamba

12. Lumbar ganglia 5 lumbar ganglia Preganglionic fibers rise from L1 and L2 and reach the lumbar ganglia From here, the fibers extend down to sacral ganglia Postganglionic fibers from these ganglia supply the abdominal and pelvic organs mongera mwamba

13. Sacral Ganglia 5 sacral ganglia, which receive the preganglionic fibers from L1 and L2 segments Postganglionic fibers from sacral ganglia innervate the blood vessels and sweat glands in the lower limb Bilateral sympathetic chains converge and fuse upon the anterior surface of the coccyx to form the coccygeal ganglion Unpaired coccygeal ganglion is called ganglion impar Coccygeal ganglion/ ganglion impar receives preganglionic fibres from L2 and L2 ,and sends postganglionic fibers to abdominal viscera and pelvic region mongera mwamba

14. Prevertebral or collateral ganglia Prevertebral ganglia are situated in thorax, abdomen and pelvis, in relation to aorta and its branches : Celiac ganglion Superior mesenteric ganglion Inferior mesenteric ganglion . Prevertebral ganglia receive preganglionic fibers from T5 - L2 segments Postganglionic fibers from these ganglia supply the visceral organs of thorax, abdomen and pelvis. mongera mwamba

15. Terminal peripheral ganglia Terminal ganglia are situated within or close to structures innervated by them Heart, bronchi, pancreas and urinary bladder are innervated by the terminal ganglia mongera mwamba

16. PARASYMPATHETIC DIVISION OF ANS Has a craniosacral outflow Fibers of this division arise from brain and sacral segments of spinal cord Cranial outflow or cranial portion of parasympathetic division arises from brainstem It innervates the blood vessels of head and neck and many thoracoabdominal visceral organs. mongera mwamba

17. CRANIAL OUTFLOW OF PSNS Cranial outflow includes the following nerves: Oculomotor (III) nerve Facial (VII) nerve Glossopharyngeal (IX) nerve Vagus (X) nerve Preganglionic fibers of these cranial nerves arise from neurons situated at two different levels: Tectal or midbrain outflow (CN III ) Bulbar level or bulbar outflow (VII, IX and X cranial nerves). mongera mwamba

18. CRANIAL OUTFLOW OF PSNS Preganglionic fibers are longer and reach the postganglionic neurons situated within the organs or close to the organs innervated by these nerves Preganglionic fibers are myelinated, postganglionic fibers are non-myelinated mongera mwamba

19. CRANIAL OUTFLOW OF PSNS Tectal or Midbrain Outflow Group of cells forming Edinger-Westphal nucleus of CN III gives rise to tectal fibers. Fibers from this nucleus end in ciliary ganglion . Postganglionic fibers from here supply the sphincter pupillae and ciliary muscle mongera mwamba

20. CRANIAL OUTFLOW OF PSNS Bulbar Level or Bulbar Outflow Preganglionic fibers arise from CN VII, IX and X whose nuclei are present in the medulla oblongata. CN VII :- Preganglionic fibers of this nerve end in sphenopalatine ganglion and submaxillary ganglion . Postganglionic fibers from sphenopalatine ganglion supply lacrimal and nasal glands. Postganglionic fibers from submaxillary ganglion supply sublingual and submaxillary glands. mongera mwamba

21. CRANIAL OUTFLOW OF PSNS Bulbar Level or Bulbar Outflow CN IX Preganglionic fibers synapse with neurons of otic ganglion Postganglionic fibers from otic ganglion supply the parotid gland mongera mwamba

22. CRANIAL OUTFLOW OF PSNS Bulbar Level or Bulbar Outflow CN X Vagus nerve supplies almost all the organs in the thorax and abdomen, but not the pelvic organs. Preganglionic fibers terminate in the ganglia situated on or near the organs Postganglionic fibers from the ganglia supply the organs mongera mwamba

23. SACRAL OUTFLOW/SACRAL PORTION OF PSNS arises from the sacral segments of spinal cord. Preganglionic fibers arise from S2 -S 4 and form the pelvic nerve ( nervi erigens ). Fibers end on postganglionic neurons, which are situated on or near the visceral organs. Fibers from postganglionic neurons supply descending colon, rectum, urinary bladder, internal sphincter, urethra and accessory sex organs. Sacral parasympathetic fibers supply visceral organs not supplied by vagus. mongera mwamba

24. COMPARISON BETWEEN SNS AND PSNS mongera mwamba

25. COMPARISON BETWEEN SNS AND PSNS mongera mwamba

26. COMPARISON BETWEEN SNS AND PSNS feature Sympathetic division Parasympathetic division Location of preganglionic neuron Thoracolumbar segments of spinal cord Nuclei of CN III, VII, IX and X , and S1-S2 segments Location of postganglionic neuron Away from target organ Near or in the target organ Length of preganglionic fibres Relatively short Relatively long Length of postganglionic fibres Relatively long Relatively short Preganglionic neurotransmitters acetylcholine acetylcholine Postganglionic neurotransmitter noradrenaline acetylcholine mongera mwamba

27. COMPARISON BETWEEN SNS AND PSNS Effector organ Receptor SNS PSNS Eye Pupil Dilatation Constriction ciliary muscles relaxation Contraction Lacrimal glands Decrease secretion Increase secretion Gastrointestinal tract Motility Inhibition Acceleration Secretions Decrease Increase Sphincter Constriction Relaxation Smooth muscles Relaxation Contraction Urinary bladder Detrusor muscle Relaxation Contraction Internal sphincter Constriction Relaxation Gallbladder Relaxation Contraction mongera mwamba

28. COMPARISON BETWEEN SNS AND PSNS Effector organ SNS PSNS Sweat glands Increase secretion ------- Heart rate and force Increase Decrease Blood vessels Constriction of all B.V except those in the heart and skeletal muscles Dilatation Bronchioles Dilatation Constriction mongera mwamba

29. Chemical transmission at ANS junctions mongera mwamba

30. Chemical transmission at ANS junctions Cholinergic neurons (i.e. release acetylcholine) all preganglionic neurons all parasympathetic postganglionic neurons sympathetic postganglionic neurons that innervate sweat glands sympathetic postganglionic neurons that end on blood vessels in some skeletal muscles and produce vasodilatation when stimulated ( sympathetic vasodilator nerves) The remaining sympathetic postganglionic neurons are noradrenergic (i.e., release norepinephrine). mongera mwamba

31. SYMPATHOADRENERGIC SYSTEM Sympathoadrenergic system is a functional and phylogenetic unit that includes sympathetic division and adrenal medulla. Adrenal medulla is a modified sympathetic ganglion in which the postganglionic cells have lost their axons and secrete norepinephrine and epinephrine directly into the bloodstream The cholinergic preganglionic neurons to these cells have consequently become the secretomotor nerve supply of this gland. Since adrenal medulla and SNS originate from same neural crest , any increase in sympathetic activity increases the secretion of catecholamines from adrenal medulla mongera mwamba

32. EFFECTS OF ANS Organ Sympathetic activity Parasympathetic activity Action Receptor Action Receptor Eye Iris radial muscles contracts α 1 ………. …………… Iris circular muscle ………. …………. contracts M3 Ciliary muscle Relax β contracts M3 Heart SAN Accelerates β 1, β 2 Decelerates M2 Ectopic pacemakers accelerates β 1, β 2 …………… ………………… mongera mwamba

33. EFFECTS OF ANS Organ Sympathetic activity Parasympathetic activity Action Receptor Action Receptor Contractility Increases β 1, β 2 Decreases (atria) M2 Blood vessels Skin and splanchnic vessels Contracts α ………………… ………………… Skeletal muscle vessels Relaxes β 2 …………………. ………………… Contracts α ………………… ................... Relaxes M3 ………………….. ………………….. mongera mwamba

34. EFECTS OF ANS Organ Sympathetic activity Parasympathetic activity Action Receptor Action Receptor Endothelium Releases EDRF4 M3 , M5 Bronchial smooth muscles Relaxes β 2 Contracts M3 GIT Smooth muscles , Walls Relaxes β 2 , α 2 contracts M3 Sphincters Contracts α 1 Relaxes M3 Secretions …………………… …………………… Increases M3 mongera mwamba

35. EFECTS OF ANS Organ Sympathetic activity Parasympathetic activity Action Receptor Action Receptor GUT smooth muscle Bladder wall Relaxes β 2 Contracts M3 Sphincter Contracts α 1 Relaxes M3 Uterus ,pregnant Relaxes β 2 …………………. …………………… Contracts α 1 Contracts M3 Penis,seminal vesicles Ejaculation α Erection M mongera mwamba

36. EFECTS OF ANS Organ Sympathetic activity Parasympathetic activity Action Receptor Action Receptor Skin Pilomotor smooth muscle Contracts α …………………. ………………… Sweat glands …………….. …………………… …………………. ………………… thermoregulatory Increases M ……………….. ……………….. Apocrine (stress) Increases α ………………… ……………………… mongera mwamba

37. EFECTS OF ANS Organ Sympathetic activity Parasympathetic activity Action Receptor Action Receptor Metabolic functions Liver gluconeogenesis α , β 2 …………………. ……………………… liver glycogenolysis β 2, α ……………………. ………………………. Fat cells Lipolysis β 3 …………………….. ……………………….. Kidney Renin release β 1 ………………….. ……………………. mongera mwamba

38. MAJOR AUTONOMIC RECEPTOR TYPE Cholinoceptors – respond to acetylcholine Muscarinic receptors : M1,M2 ,M3 Nicotinic receptors : Nn and Nm Adrenoceptors – respond to catecholamines α –Adrenoceptors ; α 1 and α 2 β – Adrenoceptors ; β 1, β 2 and β 3 Dopamine receptors ; D1,D2,D3 and D4 mongera mwamba

39. MAJOR AUTONOMIC RECEPTOR TYPE Receptor Name Typical locations Result of ligand binding Cholinoceptors Muscarinic M1 CNS neurones,sympathetic postganglionic neurons, some presynaptic sites Formation of IP3 and DAG,increased intracellular calcium Muscarinic M2 Myocardium, smooth muscle, some presynaptic sites ; CNS neurons Opening of K+ channels ,inhibition of adenylyl cyclase Muscarinic M3 Exocrine glands, vessels (smooth muscles and endothelium) ; CNS neurons Like M1 – receptor –ligand binding Muscarinic M4 CNS neurons ; possibly vagal nerve endings Like M2 receptor –ligand binding mongera mwamba

40. MAJOR AUTONOMIC RECEPTOR TYPE Receptor Name Typical locations Result of ligand binding Muscarinic M5 Vascular endothelium, especially cerebral vessels Like M1 receptor ligand binding Nicotinic Nn Postganglionic neurons,some presynaptic cholinergic terminals Opening of K+ ,Na+ chanels ,depolarization Nicotinic Nm Skeletal muscle neuromuscular endplates Opening of Na+ , K+ channels, depolarization Adrenoceptors Alpha 1 Postsynaptic effector cells ,especially smooth muscles Formation of IP3 and DAG,inreased intracellular Ca2+ mongera mwamba

41. MAJOR AUTONOMIC RECEPTOR TYPE Receptor Name Typical location Result of ligand binding Alpha 2 Presynaptic adrenergic nerve terminals Inhibition of adenylyl cyclase, decreased cAMP Beta 1 Postsynaptic effector cells especially heart, lipocytes,brain, ; presynaptic adrenergic and cholinergic nerve terminals, juxtaglomerular apparatus, ciliary body epithelium Stimulation of adenylyl cyclase,inreased cAMP Beta 2 Postsynaptic effector cells especially smooth muscles and cardiac muscles Stimulation of adenylyl cyclase and increased cAMP, activates cardiac Gi under some conditions mongera mwamba

42. MAJOR AUTONOMIC RECEPTOR TYPE Receptor Name Typical location Result of ligand binding Beta 3 Postsynaptic effector cells especially lipocytes ; heart Stimulation of adenylyl cyclase and increased cAMP Dopamine receptors D1 (DA1) ,D5 Brain, effector tissues ,especially smooth muscles of the renal vascular bed Stimulation of adenylyl cyclase and increased cAMP D2 (DA2) Brain; effector tissues especially smooth muscles; presynaptic nerve terminals Inhibition of adenylyl cyclase; increased K+ conductance D3 Brain Inhibition of adenylyl cyclase D4 Brain ; cardiovascular system Inhibition of adenylyl cyclase mongera mwamba