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

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Chapter 14 The Autonomic Nervous System
Central nervous system (CNS)Peripheral nervous system (PNS)Motor (efferent) divisionSensory (afferent)divisionSomatic nervoussystemAutonomic nervoussystem (ANS)SympatheticdivisionParasympatheticdivisionAutonomic Nervous System (ANS)
Somatic and Autonomic Nervous Systems The two systems differ inEffectors: to smooth muscle, cardial muscle, viscera, and glands.Efferent pathways (and their neurotransmitters)Target organ responses to neurotransmittersMajor anatomical differences between ANS and somatic motor system:ANS utilizes a 2-neuron pathway from CNS to effector = preganglionic fiber and a
Visceral motor (efferent) system – every organ and gland has 2 fibers, one of each typeSympathetic – neurons arise in the thoracic and lumbar segments of spinal cord (thoraco-lumbar division); generally excitatoryParasympathetic – neurons arise in the brain (via cranial nerves) and sacral region of the spinal cord (cranio-sacral division);
Skeletal muscleCell bodies in centralnervous systemPeripheral nervous systemEffect++EffectororgansAChAChSmooth muscle(e.g., in gut),glands, cardiacmuscleGanglionAdrenal medullaBlood vesselAChAChAChNEEpinephrine andnorepinephrineAcetylcholine (ACh)Norepinephrine (NE)GanglionHeavily myelinated axonLightly myelinatedpreganglionic axonLightly myelinatedpreganglionic axonsNeuro-transmitterat effectorUnmyelinatedpostganglionicaxonUnmyelinatedpostganglionic axonStimulatoryStimulatoryor inhibitory,dependingon neuro-transmitterandreceptorson effectororgansSingle neuron from CNS to effector organsTwo-neuron chain from CNS to effector organsSOMATICNERVOUSSYSTEMAUTONOMIC NERVOUS SYSTEMPARASYMPATHETICSYMPATHETIC
Efferent PathwaysSomatic nervous systemA, thick, heavily myelinated somatic motor fiber makes up each pathway from the CNS to the muscleANS pathway is a two-neuron chain1.Preganglionic neuron (in CNS) has a thin, lightly myelinated preganglionic axon2.Ganglionic neuron in autonomic ganglion has an unmyelinated postganglionic axon that extends to the effector organ
Neurotransmitter EffectsSomatic nervous systemAll somatic motor neurons release acetylcholine (ACh)Effects are always stimulatoryANSPreganglionic fibers release AChPostganglionic fibers release norepinephrine or ACh at effectorsEffect is either stimulatory or inhibitory, depending on type of receptors
Divisions of the ANS1.Sympathetic division2.Parasympathetic division•.Dual innervationAlmost all visceral organs are served by both divisions, but they cause opposite effects
Role of the Parasympathetic DivisionPromotes maintenance activities and conserves body energyDoes not work by general reaction but rather by slow one organ responses sending messages to every effector individuallyIts activity is illustrated in a person who relaxes, reading, after a meal
Parasympathetic Division

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Term
Spring
Professor
Jones
Tags
Parasympathetic division, sympathetic division, sympathetic trunk, sympathetic chain ganglia, sympathetic trunks

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