Presentation on theme: "Chapter 11 Autonomic Nervous System (ANS)"— Presentation transcript:
1 Chapter 11 Autonomic Nervous System (ANS) Copyright 2010, John Wiley & Sons, Inc.
2 Introduction to the ANS Somatic nervous system (SNS) + ANS peripheral nervous system (PNS)ANSNot under conscious controlIs regulated by hypothalamus, brainstemThe ANS supplies nerves to visceraSmooth muscle (stomach, blood vessels)Cardiac muscle (heart)Glands (sweat and digestive glands)Copyright 2010, John Wiley & Sons, Inc.
3 Comparison: SNS vs ANS SNS ANS Controls skeletal muscle Conscious, voluntary controlMotor pathway: one neuron from CNS to effectorDoes include sensory neurons (from skin, skeletal muscles, and special sense organs)All release the neurotransmitter AChANSControls viscera: smooth and cardiac muscle, and glandsUnconscious, involuntaryMotor pathway: series of two neurons from CNS to effectorDoes include sensory neurons (monitors viscera)Two divisions: sympathetic, parasympatheticRelease either ACh or NECopyright 2010, John Wiley & Sons, Inc.
4 Somatic Nervous System Copyright 2010, John Wiley & Sons, Inc.
5 ANS Motor Pathways Autonomic motor pathway includes two motor neurons Preganglionic neuron from CNS to neuron in autonomic ganglionPostganglionic neuron from cell body in ganglion to effectorCopyright 2010, John Wiley & Sons, Inc.
6 ANS Motor PathwaysCopyright 2010, John Wiley & Sons, Inc.
7 Divisions of the ANSSympathetic (S) division + parasympathetic (P) divisionMost viscera supplied with nerves of both S and P divisions: dual innervationS and P have opposite (antagonistic) effectsHeart rate: S stimulates, P inhibitsDigestive organs: S inhibit, P stimulateS: “flight or flight,” P: “rest and digest”Some viscera receive only S (not P) nerves:Sweat glands, many blood vessels, hair musclesCopyright 2010, John Wiley & Sons, Inc.
8 Sympathetic (S) Division Sympathetic preganglionic neuronsHave cell bodies located in lateral gray of spinal cord segments T1-T12 + L1-L2So S division is called “thoracolumbar”Axons pass through ventral roots of spinal nervesMay branch many timesMay ascend or descend to many levels of S trunk ganglia (from cervical to sacral)Can synapse with 20 or more postganglionic neuron cell bodiesResults: widespread S effects (viscera respond “in sympathy with one another”)Copyright 2010, John Wiley & Sons, Inc.
9 Sympathetic (S) Division Sympathetic postganglionic neuronsS postganglionic neurons cell bodies locatedIn S “trunk ganglia” (2 long chains lateral to vertebrae)From cervical to sacral regions widespread S effectsMany axons from these cell bodies pass back into spinal nerves to reach viscera in skin (sweat glands, hair muscles, blood vessels)In S “prevertebral ganglia” anterior to 3 large abdominal arteriesNamed celiac, superior and inferior mesenteric gangliaSupply abdominal viscera: stomach, intestine, kidneys, liver, spleenAxons pass from ganglia to viscera in S nervesCopyright 2010, John Wiley & Sons, Inc.
10 Sympathetic (S) Division Copyright 2010, John Wiley & Sons, Inc.
11 Parasympathetic (P) Division P preganglionic neuronsCell bodies located in brainstem + in spinal cord segments S2-S4Therefore P division is called “craniosacral”Axons in cranial nerves III, VII, IX and X and in pelvic nerves from S2-S4Vagus nerves (cranial nerves X) carry 80% of all P nerve impulses.Vagus nerves carry both motor and sensory neurons to/from viscera within the thorax and most of the abdominal cavity.P preganglionic axons do not branch or pass though S trunk ganglia but pass directly almost to visceraCopyright 2010, John Wiley & Sons, Inc.
12 Parasympathetic (P) Division P postganglionic neuronsCell bodies lie in terminal gangliaLocated within or near the innervated organSo P nerves cause precise, localized (not widespread) effectsBecause of anatomical arrangement, S nerves supply all viscera but P nerves do not reach some viscera. These include sweat glands, arrector pili muscles of hairs in skin, kidneys, spleen, adrenal medullae, and the walls of most blood vessels.Axons pass from ganglia to viscera in P nervesCopyright 2010, John Wiley & Sons, Inc.
13 Parasympathetic (P) Division Copyright 2010, John Wiley & Sons, Inc.
14 ANS Neurotransmitters: Comparison Acetylcholine (ACh)ACh more common; released by:All S and P preganglionic axonsAll P postganglionic axonsSome S postganglionic axons (to sweat glands)ACh destroyed by enzyme ACh-ase so short-lived responseNorepinephrine (NE)NE less common; released by:Almost all S postganglionic axonsNE has longer lasting effects enhanced by epinephrine + NE from adrenal medullaeCopyright 2010, John Wiley & Sons, Inc.
15 Sympathetic Effects Fight-or-flight activities Increase heart rate and contraction, and blood pressure (BP)Dilate pupilsDilate airwaysDilate vessels to skeletal muscles, heart, liver and adipose tissueConstrict blood vessels to nonessential organs: skin, GI tract, kidneysMobilize nutrients for energy: glucose and fatsCopyright 2010, John Wiley & Sons, Inc.
16 Parasympathetic Effects Rest-and-digest activitiesSLUDDSalivationLacrimationUrinationDigestionDefecationDecrease heart rate, airway diameter, pupil diameterCopyright 2010, John Wiley & Sons, Inc.
17 End of Chapter 11Copyright 2010 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permission Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publishers assumes no responsibility for errors, omissions, or damages caused by the use of theses programs or from the use of the information herein.Copyright 2010, John Wiley & Sons, Inc.
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