16_LectureOutline - An Introduction to the ANS *Somatic...

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An Introduction to the ANS *Somatic Nervous System (SNS) *Operates under conscious control *Seldom affects long-term survival *SNS controls skeletal muscles *Autonomic Nervous System (ANS) *Operates without conscious instruction *ANS controls visceral effectors *Coordinates system functions: cardiovascular, respiratory, digestive, urinary, reproductive Autonomic Nervous System Organization of the ANS * Integrative centers For autonomic activity in hypothalamus Neurons comparable to upper motor neurons in SNS * Visceral motor neurons *In brain stem and spinal cord, are known as preganglionic neurons Preganglionic fibers: –axons of preganglionic neurons *leave CNS and synapse on ganglionic neurons Autonomic ganglia Contain many ganglionic neurons Ganglionic neurons innervate visceral effectors: –such as cardiac muscle, smooth muscle, glands, and adipose tissue Postganglionic fibers: –axons of ganglionic neurons Divisions of the ANS The autonomic nervous system Operates largely outside our awareness Has two divisions * Sympathetic division –increases alertness, metabolic rate, and muscular abilities * Parasympathetic division –reduces metabolic rate and promotes digestion * “Kicks in” only during exertion, stress, or emergency *“Fight or flight” * Parasympathetic Division *Controls during resting conditions *“Rest and digest”
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Two divisions may work independently Some structures innervated by only one division * Two divisions may work together Each controlling one stage of a complex process * Sympathetic Division *Preganglionic fibers (thoracic and superior lumbar; thoracolumbar) synapse in ganglia near spinal cord *Preganglionic fibers are short *Postganglionic fibers are long *Prepares body for crisis, producing a “fight or flight” response *Stimulates tissue metabolism *Increases alertness *Seven Responses to Increased Sympathetic Activity *Heightened mental alertness *Increased metabolic rate *Reduced digestive and urinary functions *Energy reserves activated *Increased respiratory rate and respiratory passageways dilate *Increased heart rate and blood pressure *Sweat glands activated * Parasympathetic Division *Preganglionic fibers originate in brain stem and sacral segments of spinal cord; craniosacral *Synapse in ganglia close to (or within) target organs *Preganglionic fibers are long *Postganglionic fibers are short *Rest and repose *Parasympathetic division stimulates visceral activity *Conserves energy and promotes sedentary activities *Decreased metabolic rate, heart rate, and blood pressure *Increased salivary and digestive glands secretion *Increased motility and blood flow in digestive tract *Urination and defecation stimulation * Enteric Nervous System (ENS) Third division of ANS Extensive network in digestive tract walls Complex visceral reflexes coordinated locally Roughly 100 million neurons All neurotransmitters are found in the brain The Sympathetic Division
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This note was uploaded on 12/29/2011 for the course BIOLOGY 24011 taught by Professor Pan during the Fall '11 term at HCCS.

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16_LectureOutline - An Introduction to the ANS *Somatic...

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