Chapter 14 Autonomic Nervous System

Chapter 14 Autonomic Nervous System - Chapter14...

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Chapter 14 The Autonomic Nervous System Angela Peterson-Ford, PhD
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Autonomic Nervous System (ANS) The ANS consists of motor neurons that: Innervate smooth and cardiac muscle and glands Make adjustments to ensure optimal support for body activities Operate via subconscious control Have viscera as most of their effectors
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ANS Versus Somatic Nervous System (SNS) The ANS differs from the SNS in the following three areas Effectors Efferent pathways Target organ responses
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Effectors The effectors of the SNS are skeletal muscles The effectors of the ANS are cardiac muscle, smooth muscle, and glands
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Efferent Pathways Heavily myelinated axons of the somatic motor neurons extend from the CNS to the effector Axons of the ANS are a two-neuron chain The preganglionic (first) neuron has a lightly myelinated axon The ganglionic (second) neuron extends to an effector organ
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Neurotransmitter Effects All somatic motor neurons release Acetylcholine (ACh), which has an excitatory effect In the ANS: Preganglionic fibers release ACh Postganglionic fibers release norepinephrine or ACh and the effect is either stimulatory or inhibitory ANS effect on the target organ is dependent upon the neurotransmitter released and the receptor type of the effector.
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Comparison of Somatic and Autonomic Systems Figure 14.2
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Divisions of the ANS The two divisions of the ANS are the sympathetic and parasympathetic The sympathetic mobilizes the body during extreme situations The parasympathetic performs maintenance activities and conserves body energy The two divisions counterbalance each other’s activity
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Role of the Parasympathetic Division Concerned with keeping body energy use low Involves the D activities – digestion, defecation, and diuresis Its activity is illustrated in a person who relaxes after a meal Blood pressure, heart rate, and respiratory rates are low Gastrointestinal tract activity is high The skin is warm and the pupils are constricted
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Role of the Sympathetic Division The sympathetic division is the “fight-or-flight” system Involves E activities – exercise, excitement, emergency, and embarrassment Promotes adjustments during exercise – blood flow to organs is reduced, flow to muscles is increased Its activity is illustrated by a person who is threatened Heart rate increases, and breathing is rapid and deep
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Anatomy of ANS Division Origin of Fibers Length of Fibers Location of Ganglia Sympathetic Thoracolumbar region of the spinal cord Short preganglionic and long postganglionic Close to the spinal cord Parasympathetic Brain and sacral spinal cord Long preganglionic and short postganglionic In the visceral effector organs
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Anatomy of ANS Figure 14.3
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Parasympathetic Division Outflow Cranial Outflow Cranial Nerve Ganglion Effector Organ(s) Occulomotor (III) Ciliary Eye Facial (VII) Pterygopalatin Submandibular
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This note was uploaded on 01/06/2012 for the course BIOL 2401 taught by Professor Elainefanin during the Spring '11 term at Collins.

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Chapter 14 Autonomic Nervous System - Chapter14...

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