Autonomic NS MBBS 1st year undergraduate UG.pptx

Nervous system

1. Subdivisions of NS Def: Structure: SNS PNS Functions: Applied physiology: Autonomic nervous system

2. Definition: The autonomic nervous system is the part of the peripheral nervous system that is responsible for regulating involuntary body functions, such as heartbeat, blood flow, breathing and digestion. Easy definition– Part of nervous system which controls involuntary functions and innervate organs, glands and smooth muscles Autonomic nervous system

3. Autonomic nervous system Innervations ( provides nerve supply) of all tissue other than skeletal muscle Main aim is to maintain optimal internal environment Also called vegetative , efferent visceral and involuntary nervous system Anatomically and physiologically divided into SNS and PNS

4. Divisions of the ANS

5. Characteristics of ANS Nerve fibers: Both divisions have pre- & postganglionic fibers. - Preganglionic neuron is myelinated . - Postganglionic neuron is unmyelinated . (In contrast to the large diameter and rapidly conducting α -motor neurons, preganglionic axons are small-diameter, myelinated , relatively slowly conducting B fibers.) (The axons of the postganglionic neurons are mostly unmyelinated C fibers and terminate on the visceral effectors.) Neurotransmitters: Autonomic nerves release NT that may be excitatory or inhibitory.

6. Receptors in ANS Adrenergic receptors: Alpha 1: most of vascular smooth muscles and glands Pupillary dilator muscle Prostate Alpha 2: Blood vessels Beta 1 : heart, kidney, liver Beta 2 : blood vessels and airways Beta 3 : adipose tissue

7. Cholinergic receptors: Nicotinic receptor: All autonomic synapses between pre and post ganglionic neurons NMJ Chromaffin cells of adrenal medulla Muscarinic receptors: All parasympathetic postganglionic neuroeffector Salivary gland,heart , smooth muscle, exocrine glands

8. Somatic & Autonomic nervous system

9. Divisions of ANS SYMPATHETIC NERVOUS SYSTEM/ Thoracolumbar Division Fight, flight or Fright. Activated during exercise, excitement and emergencies. PARASYMPATHETIC NERVOUS SYSTEM/ Craniosacral Division Rest and Digest. Concerned with conserving energy.

10. Divisions of the ANS

11. The sympathetic system Fight or Flight Response Thoracolumbar Division Shows mass activation

12. The Sympathetic System Outflow

13. Sympathetic Chain Ganglion Paravertebral Ganglia Most of the sympathetic ganglia lie close to the spinal cord and form the two chains of ganglia, linked by short nerves —one on each side of the cord—known as the S ympathetic Trunks. Because the ganglia lie close to the spinal cord, thus, the preganglionic neurons are short while the postganglionic neurons reaching the target organs are very long. Joined to ventral rami by white and gray rami communicans. In contrast, the parasympathetic ganglia lie within or very close to the organs innervated and ,thus, have very short postganglionic and long preanglionic neurons. See Next slide for figure Prevertebral Ganglia Also called the Collateral ganglia. Unpaired , not segmentally arranged. Occur only in abdomen and pelvis, closer to the innervated organ. Lie anterior to the vertebral column. Main ganglia: Celiac, superior mesenteric, inferior mesenteric, inferior hypogastric ganglia. See Next slide for figure

14. The Sympathetic System Outflow Myelinated preganglionic fibers exit spinal cord in ventral roots from T1 to L2 levels. They exit from the Lateral horn of the spinal cord. Most sympathetic nerve fibers separate from somatic motor fibers and synapse with postganglionic neurons within paravertebral ganglia. Ganglia within each row are interconnected, forming a chain of ganglia that parallels spinal cord to synapse with postganglionic neurons.

15. Sympathetic System Outflow Termination of Sympathetic Preganglionic Fibers Postganglionic fibers in the paravertebral ganglion of the same segment. Postganglionic fibers of the paravertebral ganglion of an upper or lower segment. Pass thru the paravertebral ganglion chain & end on postganglionic neurons in prevertebral ganglion close to the viscera (celiac, superior and inferior mesenteric ganglion). Adrenal Medulla. Termination of Sympathetic Postganglionic fibers Axons leave the chain ganglia and re-enter the spinal nerves via gray rami communicans to reach the: Visceral targets Smooth muscles Sweat glands

16. Sympathetic System Outflow To the Periphery To the Head

17. Sympathetic System Outflow To the Thoracic regions To the Abdominal Organs

18. The Adrenal Gland The Adrenal gland is the major organ of the sympathetic nervous system. When stimulated, the adrenal medulla secretes large quantities of epinephrine and a little norepinephrine directly into the blood stream. Sympathoadrenal system: Stimulated by mass activation of the sympathetic nervous system. Innervated by preganglionic sympathetic fibers.

19. The parasympathetic system Rest or Digest Craniosacral Division Shows stimulation of separate parasympathetic nerves

20. Summary of last lecture The  sympathetic trunks  ( sympathetic chain ,  gangliated cord ) are a paired bundle of nerve fibers that run from the base of the skull to the coccyx. Sympathetic division: thoracolumbar division comes out of spinal cord between T1 to L2 Has short preganglionic and long post ganglionic neurons Neurotransmitter is ach at preganglionic fibers Except adrenal glands Neurotransmitter at post ganglionic fibers is Adr and norAdr EXCEPT Sweat gland skin and skeletal muscle blood vessel –here neurotransmittter is Ach

21. Parasymapthetic nervous sytem Craniosacral division: comes out from cns from III, VII, IX and X cranial nerve Sacral outflow: S2 to S4 spinal nerves NT at pre and postganglionic neuron is Ach

22. Organs innervated by only one division of ANS only sympathetic supply: Uterus, adrenal medulla, pilomotor muscle , skin sweat gland & most arterioles get only sympathetic supply Only parasympathetic : lacrimal glands, glands of stomach and pancreas Dual supply organ: Heart, hollow viscera

23. Effects of SNS stimulation (catabolic nervous system…utilizing body resources) Eye : iris and ciliary muscle: dilate via alpha 1 receptor lens flattens for far vision Salivary secretion becomes thick Arteriole: constrict alpha1 and 2 Heart: increased rate and force beta 1 Lungs : airway dilates…beta 2 Bronchial gland secretion decreases Stomach: reduced peristalsis Liver; glycogenolysis , gluconeogenesis

24. Spleen: contraction Adrenal medulla …secretion of epinephrine and norpinephrine Intestine : decreased motility Kidney : dec reased urine formation Urinary bladder relaxes, sphincter contracts Sex organs: genetelia : ejaculation Uterus: relaxes Skin : piloerection , sweating Sk muscle : blood vessel dilate

25. Effects of PNS stimulation Eye : constriction of pupil Lacrimal gland : increased secretion Salivary glands : stimulates watery secretion Heart : heart rate and contractility decreases, conductivity Lung : constrict bronchial muscles, increased glands secretion Stomach: increased motility, increased secretion, relaxes sphincter Intestine : increased motility, increased secretion, relaxes sphincter Pancreas: increased secretion- enzyme rich secretion, increased insulin and glucagon secretion Gallbladder: contraction Kidney: urine excretion increased Urinary bladder: detrusor contract sphincter relax. Sex ogans : erection

26. SOMATIC NERVOUS SYSTEM AUTONOMIC NERVOUS SYSTEM SENSORY INPUT Somatic senses & special senses Mostly interoceptors ; some somatic senses & special senses CONTROL OF MOTOR OUTPUT Voluntary control ; cerebral cortex, basal ganglia, cerebellum, spinal cord. Involuntary control ; hypothalamus, limbic system, brainstem . Limited control from cerebral cortex. MOTOR NEURON PATHWAY One-neuron pathway, Two-neuron pathway. NEUROTRANSMITTERS & HORMONES All Somatic neurons secrete Ach. All preganglionic fibers release Ach. Postganglionic fibers release different NT in case of Sym. & Paras . EFFECTORS Skeletal muscles. Smooth muscles, cardiac muscles, and glands. RESPONSES Contraction of skeletal muscle. Contraction or relaxation of smooth muscle; Increased or decreased strength of contraction of cardiac muscle; increased or decreased secretion of the glands. Type of nerve fibers α -motor neuron is large diameter, & rapidly conducting Preganglionic fibers: B fibers Postganglionic fibers: C fibers

27. Balance between sns and pns is maintained called autonomic tone by hypothalamus

28. Applied physiology Autonomic neuropathy Ganglion blocks

29. Stellate Ganglion A stellate ganglion block is done to: Diagnose the cause of pain in the face and head, arms and chest Manage pain in the head , neck, chest or arm caused by nerve injuries, the effects of an attack of shingles (herpes zoster) or angina that doesn't go away Reduce sweating in the face , head, arms and hands

30. hyperhydrosis