ANS.ppt - Chapter 14 The Autonomic Nervous System Autonomic...

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The AutonomicNervousSystemChapter 14
Autonomic NervousSystem (ANS)ANS consists of motor neurons thatInnervate smooth and cardiac muscle, and glandsMake adjustments to ensure optimal support for body activitiesOperate via subconscious controlAlso calledinvoluntary nervous systemorgeneralvisceral motor system
Figure 14.1Place of the ANS in the structural organization of the nervous system.Central nervous system (CNS)Peripheral nervous system (PNS)Sensory (afferent)divisionMotor (efferent) divisionSomatic nervoussystemAutonomic nervoussystem (ANS)SympatheticdivisionParasympatheticdivision
Somatic Versus AutonomicNervous SystemsBoth have motor fibersDiffer inEffectorsEfferent pathways and gangliaTarget organ responses to neurotransmitters
EffectorsSomatic nervous systemSkeletal musclesANSCardiac muscleSmooth muscleGlands
Efferent Pathways andGangliaSomatic nervous systemCell body in CNS; thick, myelinated, group A fiber extends in spinal orcranial nerve to skeletal muscleANS pathway uses two-neuron chain1.Preganglionic neuron(in CNS) has a thin, lightly myelinatedpreganglionic axon.2.Postganglionic (ganglionic)neuroninautonomic ganglionoutsideCNS has nonmyelinatedpostganglionic axonthat extends to effectororgan
Neurotransmitter EffectsSomatic nervous systemAll somatic motor neurons release acetylcholine (ACh)Effects always stimulatoryANSPreganglionic fibers release AChPostganglionic fibers release norepinephrine or ACh at effectorsEffect is either stimulatory or inhibitory, depending on type of receptors
Figure 14.2Comparison of motor neurons in the somatic and autonomic nervous systems.Cell bodies in centralnervous systemPeripheral nervous systemNeurotransmitterat effectorEffectororgansEffectSOMATICNERVOUSSYSTEMAUTONOMIC NERVOUS SYSTEMSYMPATHETICPARASYMPATHETICSingle neuron from CNS to effector organsHeavily myelinated axonAChSkeletalmuscleStimulatoryTwo-neuron chain from CNS to effector organsLightly myelinatedpreganglionic axonsGanglionNonmyelinatedpostganglionic axonEpinephrine andnorepinephrineAChAChAdrenal medullaBlood vesselLightly myelinatedpreganglionic axonGanglionAChNonmyelinatedpostganglionicaxonAChSmooth muscle(e.g., in gut), glands,cardiac muscleStimulatoryor inhibitory,dependingon neuro-transmitterand receptorson effectororgansAcetylcholine (ACh)Norepinephrine (NE)NE++
Overlap of Somatic andAutonomic FunctionMost spinal and many cranial nerves contain bothsomatic and autonomic fibersAdaptations usually involve both skeletal muscles andvisceral organs
Divisions of the ANSSympathetic divisionParasympathetic divisionDual innervation~ All visceral organs served by both divisions, but cause oppositeeffectsDynamic antagonism between two divisions maintainshomeostasis
Role of theParasympathetic DivisionPromotes maintenance activities and conserves bodyenergyDirects digestion, diuresis, defecation

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Term
Winter
Professor
N/A
Tags
Physiology, Anatomy, Parasympathetic division

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