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PowerPoint® Lecture Slides prepared by Vince Austin, University of Kentucky The Autonomic Nervous System Human Anatomy & Physiology, Sixth Edition Elaine N. Marieb Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 14 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 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings ANS Versus Somatic Nervous System (SNS) The ANS differs from the Somatic Nervous System (SNS) in the following three areas: Effectors Efferent pathways Target organ responses Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Effectors The effectors of the SNS are skeletal muscles The effectors of the ANS are cardiac muscle, smooth muscle, and glands Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Efferent Pathways Axons of the SMS are of a single motor neuron from CNS to the skeletal muscle 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 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 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 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Comparison of Somatic and Autonomic Systems Figure 14.2 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Divisions of the ANS The two divisions of the ANS are the sympathetic and parasympathetic The sympathetic mobilizes the body during extreme situations (“fight or flight”) The parasympathetic performs maintenance activities and conserves body energy (“sit and shit”; “rest and digest”) The two divisions counterbalance each other’s activity Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Parasympathetic Division - Concerned with keeping body energy use low - Involves the D activities – digestion and defecation 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 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 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 The skin is cold and sweaty, and the pupils dilate Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of ANS Division Length of Fibers Location of Ganglia Sympathetic Short preganglionic and long postganglionic Close to the spinal cord Parasympathetic Long preganglionic and short postganglionic In the visceral effector organs Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of ANS A. preganglionic neurons - spinal cord -> ganglion 1. sympathetic (thoracolumbar) a. lateral grey horn of T1-L3 2. parasympathetic a. nuclei of cranial nerves III, VII, IX, X b. lateral grey horn of S2-S4 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of ANS B. autonomic ganglia - house cell bodies of effector n. 1. sympathetic a. vertebral ganglia - along the spine b. prevertebral ganglia - near arteries 2. parasympathetic a. terminal ganglion - near effected organ C. postganglionic neurons - motor to effected organ Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Sympathetic Ganglia 1. superior cervical ganglion a. sweat glands, eye, face vessels and glands 2. middle cervical ganglion a. heart 3. inferior cervical ganglion a. heart 4. thoracic ganglia a. heart, lungs, bronchi, thoracic viscera 5. lumbar and sacral ganglia a. viscera of abdominopelvic cavity Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Parasympathetic Ganglia 1. ciliary ganglion a. smooth muscle of the eye 2. pterygopalantine ganglion a. nasal mucosa, palate, pharynx, lacrimal gland 3. submandibular and otic ganglia a. salivary glands 4. cardiac and pulmonary plexuses a. to the heart and lungs Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of ANS Figure 14.3 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Visceral Reflexes Visceral reflexes have the same elements as somatic reflexes They are always polysynaptic pathways Afferent fibers are found in spinal and autonomic nerves Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Visceral Reflexes Figure 14.7 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Levels of ANS Control The hypothalamus is the main integration center of ANS activity Subconscious cerebral input via limbic lobe connections influences hypothalamic function Other controls come from the cerebral cortex, the reticular formation, and the spinal cord Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Levels of ANS Control Figure 14.9 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Hypothalamic Control Centers of the hypothalamus control: Heart activity and blood pressure Body temperature, water balance, and endocrine activity Emotional stages (rage, pleasure) and biological drives (hunger, thirst, sex) Reactions to fear and the “fight-or-flight” system Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings