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Lecture 19

Lecture 19 - Autonomic Nervous System

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University of Toronto St. George
Michelle French

L19 Oct 26 2011Autonomic Nervous SystemAutonomic Nervous SystemPart of CNS controlling internal organs endocrine fn blood flow etc maintains le milieu intrieur internal body envtMost important in general healthOutput end efferents get instructns from autonomic ns2 efferent subsystems1sympathetic stressrelated fight or flightwhen out of controlhealth problems high blood pressure gastrointestinal problems depression2parasympathetic restorative calming nutritivemost of time should be dominant outputSympathetic efferentsPreganglionic efferents from intermediolateral horn of thoracic cordHorn sticks out lateral side of grey mattersynapse in chain of ganglia parallel to cord have cell bodies of neurons that project out to various tissue so postganglionic in pnspostganglionic efferents project to target tissue classic transmitternoradrenaline NAalmost always usedexception ACh is transmitter at skin sweat glands temp regulation separate from many other fns of sym nsMuscle Sympathetic EffectsMajor influence is noradrenergic vasoconstriction tonically active to maintain blood pressureBasal constriction in musclesSym revs up motor system so muscle activity would think want to increase blood flow to muscles but actually via NA vasocontricts the muscles extremely important for regulation of blood pressure part of baroreflexMetabolite accumulation during muscle contractionvasodilationAs soon as muscles starts contractingproduce metabolites CO phosphate lactic acids other 2acidsdirectly trigger vasodilation potentlyIf vasodilation allowed to take place unopposed all bodys blood would be in musclenone left for brainfaintSo sym system designed to counteract that natural vasodilation in muscles by constricting so dont take all the bloodSym efferents originate in thoracic segments of spinal cordhave protuderants in grey matter in intermedialateral horn at lateral white matterSympathetic nuclei cell bodies originating of the efferentsLeave ventral root but then terminate in sym ganglion which parallels spinal cord in pnsThen neurons wi ganglia exittravel out w various spinal nerves to target organsSym chain running along spinal cord but outside vertebrae chain on both side of spinal cordNetwork of nerves connecting all ganglia nerves crossing overconnecting to other wide complex
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