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BIOL455 COMPARITIVE NEUROBIOLOGY LECTURE#22: VISCERAL MOTOR" DR. OLLIE HULME" FALL 2010 " UBC Housekeeping" [email protected]" [email protected]" office hours (Fri 1.30-4.30) Answer key + sample questions (inserted into slides) are now up on website www.hyooom.com" Neuroanatomy from lecture 9 is recommended for helping to understand all sensory, motor and cognitive topics, but will not be explicitly tested Visceral motor system" Viscus = internal organ Visceral= plural of viscus Visceral motor system = Autonomic nervous system History" Gaskell stimulated different parts of visceral motor system demonstrating effects on downstream organs Every tissue is innervated by two sets of nerve fibres of opposite characters Pioneered pharmacology of visceral system – Ach + NA History" Walter Cannon elucidated relationship between visceral motor system, homeostasis and emotion Visceral motor function" Controls involuntary bodily functions mediated by smooth muscle, cardiac muscle and glands 3 major divisions 1. Sympathetic 2. Parasympathetic 3. Enteric Sympathetic" Specialised for challenging situations fight or flight Expends resources Parasympathetic" Specialised for quiescent conditions ‘rest and digest’ Replenishes resources Restores homeostasis Central control for…" somatic motor system = Upper motor system (Motor cortices + brain stem nuclei) visceral motor system = hypothalamus Differences between somatic & visceral" 1. Less distinct somatopy 2. Lower motor system of visceral motor located outside of CNS 3. Contacts between motor neurons and viscera are less differentiated – e.g no endplates 4. Visceral neurons release diversity of neuroTs including cotransmission of neuropeptides 5. Greater diversity in receptors mediating greater range of postsynaptic effects in smooth + cardiac muscle and glands Sympathetic" Sympathetic neurons contribute to virtually all peripheral nerves innervating a huge range of organs Sympathetic responses" Fight or flight Pupil dilation / Eyelid retraction Skin + gut vessels constrict Piloerection Bronchi dilate Cardiac rate + force increase Adrenaline + Noradrenaline into blood Sympathetic" Sympathetic neurons driving these effects Sympathetic responses" Not only active during fight or flight, just maximally active Maintains tonic activity in all circumstances Also it doesn’t activate all together since different components of the system can be independently controlled according to functions required Exercise, sex, urination, sleep etc. Parasympathetic sources" Parasympathetic stems from… Brain stem nuclei Or Sacral section of spinal cord Parasympathetic brain stem" Pupillary response Saliva + tear glands Cardiac inhibition Sacral region " Colon Rectum Bladder Genitals Parasympathetic in spinal cord" Parasympathetic effects" ‘Rest and digest’ Constriction of pupils Slowing of heart Peristalsis of gut Dilation of vessels in skin + gut Piloerector relaxation Decreased Adrenaline and noradrenaline released Enteric system" Modulated by parasympathetic + sympathetic Works largely independently through its own reflexes Sensory components of visceral system" 1. Provides local feedback (stretch, pressure, chemical, nociceptive) for ongoing motor activity 2. Informs higher integrative centers Sensory input is sparse therefore explains why hard to localise visceral pain Convey only limited information to consciousness e.g unaware of blood pressure, heart rate etc Nucleus of solitary tract" Central control over visceral motor" Cortical regions of visceral motor" = Primary visceral motor = Primary visceral sensory Regions involved in integrating visceral information with input from other senses / cognitive processes Hypothalamic region of visceral motor" Hypothalamus" Critical role in coordination + expression of visceral motor activity Hypothalamic function" Computes error signal and uses this to correct homeostasis through visceral motor system Cardiac reflexes, Bladder control, sexual reflexes, Temperature, Breathing, Eating, Hypothalamic function" Can group its homeostatic functions as regulation of Blood flow Energy metabolism Reproduction Threat responses Neurotransmission" Transmission in final synapse onto muscle and glands mediated by Noradrenaline + Acetylcholine Sympathetic = Noradrenaline Parasympathetic = Ach These chemicals have opposing effects on smooth muscle e.g contraction vs. relaxation of smooth muscle Noradrenergic receptors" Receptor subtypes allow for coordinated control of different groups of sympathetic responses Cholinergic receptors" Same is true for Ach for parasympathetic Regulation of cardiac function" To regulate provision of O2 to ∆ tissues under many∆ conditions Mechanical Barosensory information about pressure Chemosensory information about O2 levels Determines balance of parasymp + symp Cardiac Receptors" Chemoreceptors in specialised Carotid bodies Baroreceptors in Heart + major vessels Cardiac reflex" Reflex coordinated by Nucleus of solitary tract Rise in Blood Pressure - Inhibit sympathetic + Excite parasymp + + - Control of bladder" Higher integrative centres for decision making afferent Control of bladder" Governed by integration of visceral sensory info, emotional, social, contextual cues Bladder emptying achieved by coordinated activation of sacral parasympathetic + inactivation of somatic motor Sample questions" Essays: How does the visceral motor system control the body for challenging and quiescent states? Describe the three main divisions of the visceral motor system and how they interact. Multiple choice: Enteric nervous system is part of the… visceral motor system Sympathetic nervous system uses… noradrenaline Baroreceptors in the heart are sensitive to… arterial pressure Next lecture" Association cortices – chapter 26