1. PowerPoint ® Lecture Slides prepared by Janice Meeking, Mount Royal College C H A P T E R Copyright © 2010 Pearson Education, Inc. 14 The Autonomic Nervous System

2. Copyright © 2010 Pearson Education, Inc. 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

3. Copyright © 2010 Pearson Education, Inc. Autonomic Nervous System (ANS) Other names Involuntary nervous system General visceral motor system

4. Copyright © 2010 Pearson Education, Inc. Central nervous system (CNS)Peripheral nervous system (PNS) Motor (efferent) division Sensory (afferent) division Somatic nervous system Autonomic nervous system (ANS) Sympathetic division Parasympathetic division Figure 14.1

5. Copyright © 2010 Pearson Education, Inc. Somatic and Autonomic Nervous Systems The two systems differ in Effectors Efferent pathways (and their neurotransmitters) Target organ responses to neurotransmitters

6. Copyright © 2010 Pearson Education, Inc. Effectors Somatic nervous system Skeletal muscles ANS Cardiac muscle Smooth muscle Glands

7. Copyright © 2010 Pearson Education, Inc. Skeletal muscle Cell bodies in central nervous system Peripheral nervous systemEffect + + Effector organs ACh Smooth muscle (e.g., in gut), glands, cardiac muscle Ganglion Adrenal medullaBlood vessel ACh NE Epinephrine and norepinephrine Acetylcholine (ACh)Norepinephrine (NE) Ganglion Heavily myelinated axon Lightly myelinated preganglionic axon Lightly myelinated preganglionic axons Neuro- transmitter at effector Unmyelinated postganglionic axon Unmyelinated postganglionic axon Stimulatory or inhibitory, depending on neuro- transmitter and receptors on effector organs Single neuron from CNS to effector organs Two-neuron chain from CNS to effector organs SOMATIC NERVOUS SYSTEM AUTONOMIC NERVOUS SYSTEM PARASYMPATHETIC SYMPATHETIC Figure 14.2

8. Copyright © 2010 Pearson Education, Inc. Divisions of the ANS 1.Sympathetic division 2.Parasympathetic division Dual innervation Almost all visceral organs are served by both divisions, but they cause opposite effects

9. Copyright © 2010 Pearson Education, Inc. Role of the Parasympathetic Division Promotes maintenance activities and conserves body energy Its activity is illustrated in a person who relaxes, reading, after a meal Blood pressure, heart rate, and respiratory rates are low Gastrointestinal tract activity is high Pupils are constricted and lenses are accommodated for close vision

10. Copyright © 2010 Pearson Education, Inc. Role of the Sympathetic Division Mobilizes the body during activity; is the “fight- or-flight” system Promotes adjustments during exercise, or when threatened Blood flow is shunted to skeletal muscles and heart Bronchioles dilate Liver releases glucose

11. Copyright © 2010 Pearson Education, Inc. Salivary glands Eye Skin* Heart Lungs Liver and gall- bladder Genitals Pancreas Eye Lungs Bladder Liver and gall- bladder Pancreas Stomach Cervical Sympathetic ganglia Cranial Lumbar Thoracic Genitals Heart Salivary glands Stomach Bladder Adrenal gland ParasympatheticSympathetic Sacral Brain stem L1L1 T1T1 Figure 14.3

12. Copyright © 2010 Pearson Education, Inc. Figure 14.5a Spinal cord Dorsal root Ventral root Sympathetic trunk ganglion Sympathetic trunk Rib Ventral ramus of spinal nerve Gray ramus communicans White ramus communicans Thoracic splanchnic nerves (a) Location of the sympathetic trunk

13. Copyright © 2010 Pearson Education, Inc. Visceral Reflexes Visceral reflex arcs have the same components as somatic reflexes Main difference: visceral reflex arc has two neurons in the motor pathway Visceral pain afferents travel along the same pathways as somatic pain fibers, contributing to the phenomenon of referred pain

14. Copyright © 2010 Pearson Education, Inc. Figure 14.7 Spinal cord Dorsal root ganglion Autonomic ganglion Stimulus Response Visceral sensory neuron Integration center May be preganglionic neuron (as shown) May be a dorsal horn interneuron May be within walls of gastrointestinal tract Sensory receptor in viscera 2 3 1 5 Visceral effector Efferent pathway (two-neuron chain) Preganglionic neuron Ganglionic neuron 4

15. Copyright © 2010 Pearson Education, Inc. Referred Pain Visceral pain afferents travel along the same pathway as somatic pain fibers Pain stimuli arising in the viscera are perceived as somatic in origin

16. Copyright © 2010 Pearson Education, Inc. Figure 14.8 Heart Lungs and diaphragm Liver Stomach Kidneys Ovaries Small intestine Ureters Urinary bladder Colon Pancreas Liver Heart Appendix Gallbladder

17. Copyright © 2010 Pearson Education, Inc. Figure 14.2 + ACh Smooth muscle (e.g., in gut), glands, cardiac muscle Ganglion Adrenal medullaBlood vessel ACh NE Epinephrine and norepinephrine Acetylcholine (ACh)Norepinephrine (NE) Ganglion Lightly myelinated preganglionic axon Lightly myelinated preganglionic axons Unmyelinated postganglionic axon Unmyelinated postganglionic axon Stimulatory or inhibitory, depending on neuro- transmitter and receptors on effector organs Two-neuron chain from CNS to effector organs AUTONOMIC NERVOUS SYSTEM PARASYMPATHETIC SYMPATHETIC

18. Copyright © 2010 Pearson Education, Inc. Sympathetic Tone Sympathetic division controls blood pressure, even at rest Sympathetic tone (vasomotor tone) Keeps the blood vessels in a continual state of partial constriction

19. Copyright © 2010 Pearson Education, Inc. Parasympathetic Tone Parasympathetic division normally dominates the heart and smooth muscle of digestive and urinary tract organs Slows the heart Dictates normal activity levels of the digestive and urinary tracts The sympathetic division can override these effects during times of stress Drugs that block parasympathetic responses increase heart rate and block fecal and urinary retention

20. Copyright © 2010 Pearson Education, Inc. Cooperative Effects Best seen in control of the external genitalia Parasympathetic fibers cause vasodilation; are responsible for erection of the penis or clitoris Sympathetic fibers cause ejaculation of semen in males and reflex contraction of a female’s vagina

21. Copyright © 2010 Pearson Education, Inc. Unique Roles of the Sympathetic Division The adrenal medulla, sweat glands, arrector pili muscles, kidneys, and most blood vessels receive only sympathetic fibers The sympathetic division controls Thermoregulatory responses to heat Release of renin from the kidneys Metabolic effects Increases metabolic rates of cells Raises blood glucose levels Mobilizes fats for use as fuels

22. Copyright © 2010 Pearson Education, Inc. Localized Versus Diffuse Effects Parasympathetic division: short-lived, highly localized control over effectors Sympathetic division: long-lasting, bodywide effects

23. Copyright © 2010 Pearson Education, Inc. Control of ANS Functioning Hypothalamus—main integrative center of ANS activity Subconscious cerebral input via limbic lobe connections influences hypothalamic function

24. Copyright © 2010 Pearson Education, Inc. Figure 14.9 Cerebral cortex (frontal lobe) Limbic system (emotional input) Communication at subconscious level Hypothalamus Overall integration of ANS, the boss Spinal cord Urination, defecation, erection, and ejaculation reflexes Brain stem (reticular formation, etc.) Regulation of pupil size, respiration, heart, blood pressure, swallowing, etc.

25. Copyright © 2010 Pearson Education, Inc. Hypothalamic Control Control may be direct or indirect (through the reticular system) 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

26. Copyright © 2010 Pearson Education, Inc. Developmental Aspects of the ANS Effects of age on ANS Constipation Dry eyes Frequent eye infections Orthostatic hypotension Low blood pressure occurs because aging pressure receptors respond less to changes in blood pressure with changes in body position and because of slowed responses by sympathetic vasoconstrictor centers