Peripheral Nervous System

Peripheral Nervous System - Peripheral Nervous System...

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Peripheral Nervous System
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Outline Autonomic NS Sympathetic Parasympathetic Neurotransmitters Somatic NS Cranial Nerves Spinal Nerves Motor Control
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Peripheral Nervous System (PNS) Includes: sensory receptors, peripheral nerves, associated ganglia, and motor endings Can be divided into: Autonomic Nervous System Somatic Nervous System Provides links to and from the external environment
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Autonomic Nervous System Efferent innervation of all tissues other than skeletal muscle Parallel chains of two neurons connect the CNS and effector cells – Preganglionic Neuron – Preganglionic Fibers – Autonomic ganglia – Postganglionic Neuron – Postganglionic Fibers
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Autonomic Nervous System Two Divisions – Dual Innervation (sympathetic and parasympathetic) – Two divisions usually activated reciprocally – Autonomic responses usually occur without conscious control – Distinguished by • Their unique origin sites • Relative fiber lengths • Location of their ganglia • Degree of fiber branching • Functional role • Neurotransmitters
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Anatomy of ANS
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Figure 6.44
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Anatomy of ANS
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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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Sympathetic Nervous System Extensive branching of the preganglionic fibers Innervates visceral organs in the internal body cavities and in the superficial part of the body Anatomy ties the entire system together so that it can act as a single unit
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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
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Unique Roles of the Sympathetic Division • Regulates many functions not subject to parasympathetic influence • These include the activity of the adrenal medulla, sweat glands, arrector pili muscles, kidneys, and most blood vessels • The sympathetic division controls: – Thermoregulatory responses to heat – Release of renin from the kidneys – Metabolic effects
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Thermoregulatory Responses to Heat • Reflex dilation (local reaction) • Widespread dilation (systemic reaction) • Brings blood vessels to surface • Activates sweat glands (evaporative cooling)
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Metabolic Effects • The sympathetic division promotes metabolic effects that are not reversed by the parasympathetic division – Increases the metabolic rate of body cells – Raises blood glucose levels – Mobilizes fat as a food source – Stimulates the reticular activating system (RAS) of the brain, increasing mental alertness
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This note was uploaded on 02/09/2012 for the course BIO 102 taught by Professor William during the Spring '11 term at Harvard.

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Peripheral Nervous System - Peripheral Nervous System...

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