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15 The Autonomic Nervous System PowerPoint® Lecture Presentations prepared by Leslie Hendon University of Alabama, Birmingham © 2014 Pearson Education, Inc. I. The Autonomic Nervous System (ANS) A.The ANS is a system of motor neurons B. The ANS is the general visceral motor division of the PNS C. It innervates: Smooth muscle; Cardiac muscle; Glands D. It regulates visceral functions such as: 1. Heart rate 2. Blood pressure 3. Digestion 4. Urination E. It also contains the general visceral sensory system of the PNS © 2014 Pearson Education, Inc. Central nervous system (CNS) Peripheral nervous system (PNS) Sensory (afferent) division Somatic sensory © 2014 Pearson Education, Inc. Visceral sensory Motor (efferent) division Somatic nervous system Autonomic nervous system (ANS) Sympathetic division Parasympathetic division II. Comparison Autonomic and Somatic Motor Systems A. Somatic motor system 1. one motor neuron extends from the CNS to skeletal muscle 2. axons are well myelinated, conduct impulses rapidly B. Autonomic nervous system 1. Chain of two motor neurons to smooth muscle, cardiac muscle, glands a. preganglionic neuron ► ►► postganglionic neuron 2. Conduction is slower than somatic nervous system because a. axons are thinly myelinated (white) or nonmyelinated (grey) b. motor neuron synapses in a ganglion outside the CNS © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. III. Divisions of the Autonomic Nervous System A. Sympathetic and parasympathetic divisions 1. chains of two motor neurons 2. innervate same structures - cause opposite effects 3. Sympathetic division - during extreme situations a. examples: fear, rage, exercise 4. Parasympathetic division - routine maintenance functions © 2014 Pearson Education, Inc. B. Sympathetic -“fight or flight” 1. activated during EXTREME situations a. examples: exercise, excitement, emergencies 2. sympathetic responses help respond to dangerous situations a. increase heart rate and breathing rate b. increase blood and oxygen to skeletal muscles c. vasoconstriction of other blood vessels d. dilate pupils and bronchioles e. inhibit motility of the digestive tract and urinary tracts © 2014 Pearson Education, Inc. C. Parasympathetic – “rest and digest” (“sit or shit”) 1. Active when the body is at rest 2. Concerned with conserving energy 3. Directs “housekeeping” activities a. digestion b. elimination of feces and urine c. heart rate, b.p. , respiration at low-normal levels © 2014 Pearson Education, Inc. Parasympathetic Sympathetic Eye (constricts pupil) Eye (dilates pupil) Brain stem Salivary glands Heart Lungs (constricts airways) Skin* Cranial Sympathetic ganglia Cervical Salivary glands Lungs (dilates airways) T1 Heart Stomach Stomach Thoracic Pancreas Liver Pancreas Gall- bladder L1 Gallbladder Adrenal gland Lumbar Bladder Bladder Genitals (erection) Genitals (ejaculation) Sacral stimulatory effect inhibitory effect © 2014 Pearson Education, Inc. IV. Anatomical Comparisons A. Emerge from different regions of the CNS 1. sympathetic - also called the thoracolumbar division a. originate from spinal segments (T1–L2) 2. parasympathetic - also called the craniosacral division a. originate from III, VII, IX, X and (S2,3,4) B. Length of postganglionic fibers 1. sympathetic - long postganglionic fibers 2. parasympathetic - short postganglionic fibers © 2014 Pearson Education, Inc. C. Branching of fibers 1. sympathetic fibers a. highly branched; influence many organs at once 2. parasympathetic fibers a. few branches; only localized effect D. Neurotransmitter released by postganglionic axons 1. sympathetic - most release norepinephrine (adrenergic) 2. parasympathetic - release acetylcholine (cholinergic) © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. V. The Parasympathetic Division A. Cranial outflow 1. originates from the brain (III, VII, IX, X) 2. innervates - organs of the head, neck, thorax, and abdomen B. Sacral outflow 1. originates from spinal segments (S2,3,4) 2. “(S2,3,4) keeps your penis off the floor” 3. innervates - remaining abdominal and pelvic organs © 2014 Pearson Education, Inc. Ciliary ganglion CN III Eye Lacrimal gland CN VII Pterygopalatine ganglion CN IX Nasal mucosa CN X Submandibular ganglion Submandibular and sublingual glands Otic ganglion Parotid gland Heart Cardiac and pulmonary plexuses Lung Preganglionic CN © 2014 Pearson Education, Inc. Postganglionic Cranial nerve Celiac plexus Liver and gallbladder Stomach Pancreas S2 S3 Large intestine S4 Small intestine Pelvic splanchnic nerves Inferior hypogastric plexus Rectum Urinary bladder and ureters Genitalia (penis, clitoris, and vagina) Preganglionic CN © 2014 Pearson Education, Inc. Postganglionic Cranial nerve VI. Cranial Outflow (Parasympathetic) A. Preganglionic fibers run via 1. oculomotor nerve (III) 2. facial nerve (VII) 3. glossopharyngeal nerve (IX) 4. vagus nerve (X) B. Cell bodies of preganglionic neurons located in motor cranial nerve nuclei in gray matter of the brain stem © 2014 Pearson Education, Inc. C. Oculomotor Nerve (III) 1. innervate smooth muscles in the eye 2. cause pupil constriction D. Facial Nerve (VII) 1. stimulate secretions of glands in the head 2. examples: lacrimal gland, submandibular salivary glands E. Glossopharyngeal Nerve (IX) 1. stimulate secretion of other salivary glands © 2014 Pearson Education, Inc. F. Vagus Nerve (X) 1. innervate visceral organs of the thorax and most of the abdomen 2. stimulates digestion, lower heart rate, and lower blood pressure 3. sends branches through autonomic nerve plexuses a. cardiac plexus b. pulmonary plexus c. esophageal plexus d. celiac plexus e. superior mesenteric plexus © 2014 Pearson Education, Inc. Superior cervical ganglion Middle cervical ganglion Left vagus nerve Cardiac branches of the vagus Stellate ganglion Cardiac plexus Pulmonary plexus Vagus nerve Esophageal plexus Stomach with vagus nerve Celiac plexus Superior mesenteric plexus © 2014 Pearson Education, Inc. VI. Sacral Outflow (Parasympathetic) A. Emerges from S2 to S4 B. Innervates organs of the pelvis and lower abdomen 1. contraction of urinary bladder for urination 2. erection of the penis - (S2,3,4) 3. inhibits contraction of uterine smooth muscles 4. vasodilation - clitoris and contraction of smooth m. of vagina © 2014 Pearson Education, Inc. VI. The Sympathetic Division A. Issues from T1 to L2 B. Preganglionic fibers form the lateral gray horn of spinal cord C. Supplies visceral organs in internal body cavities and structures of superficial body regions D. Contains more ganglia than the parasympathetic division E. Located on both sides of the vertebral column F. Linked by short nerves into sympathetic trunks G. Sympathetic trunk ganglia also called: 1. chain ganglia or 2. paravertebral ganglia © 2014 Pearson Education, Inc. VII. Sympathetic Trunk Ganglia A Joined to ventral rami by white and gray rami communicantes (the next picture will show what this actually means) B. Fusion of ganglia there are fewer ganglia than spinal nerves C. Sympathetic ganglia form a “chain” along the vertebral column 1. most apparent in the cervical region a. superior cervical ganglia b. middle cervical ganglia c. inferior cervical ganglia © 2014 Pearson Education, Inc. 1. preganglionic nerve cell body in lateral horn of spinal cord 2. axon goes through ventral root of spinal nerve 3. to ventral ramus of spinal nerve 4. through white communicans (myelinated) 5. synapses on postganglionic nerve cell body in sympathetic ganglion 6. postganglionic axon through grey communicans (unmyelinated!!!) Lateral horn (visceral motor zone) 7. to effector organ Ventral ramus of spinal nerve Gray ramus communicans White ramus communicans Skin (arrector pili muscles and sweat glands) © 2014 Pearson Education, Inc. Sympathetic trunk ganglion Sympathetic trunk To effector Blood vessels Ventral root 1. Synapses with a postganglionic neuron at the same level and exit on a spinal nerve at that same level or Lateral horn (visceral motor zone) Ventral ramus of spinal nerve Gray ramus communicans White ramus communicans Skin (arrector pili muscles and sweat glands) © 2014 Pearson Education, Inc. Sympathetic trunk ganglion Sympathetic trunk To effector Blood vessels Ventral root 2. Synapses with a postganglionic neuron at a different level and exits on a spinal nerve at that same level Skin (arrector pili muscles and sweat glands) To effector Blood vessels 5 6 4 1. Preganglionic nerve in lateral horn 2. Ventral root of spinal nerve 3. White ramus communicans 1 4. Sympathetic chain ganglion 5. Grey ramus communicans 6. Postganglionic nerve axon © 2014 Pearson Education, Inc. 3 2 Ventral root Sympathetic trunk ganglion Sympathetic trunk Ventral ramus of spinal nerve Gray ramus communicans White ramus communicans Location of the sympathetic trunk © 2014 Pearson Education, Inc. Dissection of posterior thoracic wall, right side D. Pathways to Body Periphery 1. innervate sweat glands, arrector pili muscles, blood vessels E. Pathways to the Head 1. originate from T1–T4 2. synapse in superior cervical ganglion 3. innervate glands, smooth muscles, blood vessels of head F. Pathways to Thoracic Organs 1. originate from T1–T6 2. run directly to the effector organ © 2014 Pearson Education, Inc. G. Pathways to Thoracic Organs 1. originate from T1–T6 2. run directly to the effector organ 3. functions in this region are to: a. increase heart rate b. dilate the bronchioles c. dilate arteries of the heart d. inhibit muscles and glands of the digestive system H. Pathways to Pelvic Organs 1. originate from T5–L2 2. inhibit activity of smooth m. and glands in the visceral organs © 2014 Pearson Education, Inc. Eye Lacrimal gland Nasal mucosa Pons Sympathetic trunk (chain) ganglia Blood vessels; skin (arrector pili muscles and sweat glands) Superior cervical ganglion Salivary glands Middle cervical ganglion Heart Inferior cervical ganglion Lung T1 Liver and gallbladder Celiac ganglion L2 Stomach Superior mesenteric ganglion Spleen Adrenal medulla Kidney Inferior mesenteric ganglion Small intestine Large intestine Rectum Preganglionic Postganglionic Genitalia (uterus, vagina, and penis) and urinary bladder © 2014 Pearson Education, Inc. VIII. The Role of the Adrenal Medulla A. Major organ of the sympathetic nervous system B. Constitutes largest sympathetic ganglia C. Secretes large amounts of norepinephrine and epinephrine D. Stimulated to secrete by preganglionic sympathetic fibers Remember: “Fight or Flight” Example: bear running out of the woods to eat your child!!!! © 2014 Pearson Education, Inc. Sympathetic trunk Spinal cord: T8–L1 Ventral root Thoracic splanchnic nerves Kidney Adrenal medulla © 2014 Pearson Education, Inc. Adrenal gland Epinephrine and norepinephrine Adrenal medulla cells Capillary © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc. IX. Visceral Sensory Neurons A. General visceral sensory neurons monitor these sensations 1. stretch 2. temperature 3. chemical changes 4. irritation B. Nerve cell bodies are located in the dorsal root ganglion © 2014 Pearson Education, Inc. C. Visceral pain 1. no pain results when visceral organs are cut 2. visceral pain results from chemical irritation or inflammation 3. visceral pain often perceived to be of somatic origin ► phenomenon of referred pain © 2014 Pearson Education, Inc. A map of referred pain Lungs and diaphragm Heart Gallbladder Liver Appendix Stomach Pancreas Small intestine Ovaries Colon Kidneys Urinary bladder Ureters © 2014 Pearson Education, Inc. X. Visceral Reflexes A. Visceral sensory/autonomic neurons role in visceral reflex arcs: 1. defecation reflex 2. micturition reflex (urination impulse) B. NOTE: you do not “think” these reflexes; like patellar tendon reflex C. Some visceral reflexes are simple spinal reflexes D. Others do not involve the CNS - strictly peripheral reflexes © 2014 Pearson Education, Inc. Stimulus 1 Sensory receptor in viscera 2 Visceral sensory neuron 3 Integration center • May be preganglionic neuron (as shown) • May be a dorsal horn interneuron • May be within walls of gastrointestinal tract Dorsal root ganglion Spinal cord Autonomic ganglion 4 Efferent pathway (two-neuron chain) • Preganglionic neuron • Postganglionic neuron 5 Visceral effector Response © 2014 Pearson Education, Inc. A visceral reflex Increased blood pressure 1 Baroreceptors in carotid sinus are simulated. 2 Sensory impulses are carried on visceral sensory fibers in the glossopharyngeal nerves (CN IX). 3 Integration occurs in cardiac center of medulla oblongata. 4 Efferent pathway via the vagus nerves (CN X) 3 2 4 1 5 Parasympathetic stimulation of heart decreases heart rate. Blood pressure decreases The baroreceptor reflex 5 © 2014 Pearson Education, Inc. XI. CNS Control of the ANS A. The ANS is not under direct voluntary control B. Some parts of the CNS help coordinate the ANS 1. brain stem 2. spinal cord 3. hypothalamus 4. amygdala 5. cerebral cortex © 2014 Pearson Education, Inc. C. Hypothalamus—the main integration center of the ANS A. medial and anterior parts ► direct parasympathetic functions B. lateral and posterior parts ► direct sympathetic functions D. People can exert some control over autonomic functions 1. feelings of calm during meditation a. influence of cerebral cortex on parasympathetic centers in hypothalamus 2. voluntary sympathetic response a. recalling scary event © 2014 Pearson Education, Inc. Communication at subconscious level Cerebral cortex (frontal lobe) Limbic system (emotional input) Hypothalamus The “boss”: Overall integration of ANS Brain stem (reticular formation, etc.) Regulates pupil size, heart, blood pressure, airflow, salivation, etc. Spinal cord Reflexes for urination, defecation, erection, and ejaculation © 2014 Pearson Education, Inc. XII. Disorders of the ANS A. Raynauds disease - characterized by constriction of blood vessels 1. provoked by exposure to cold or by emotional stress B. Achalasia of the cardia 1. defect in the autonomic innervation of the esophagus C. Congenital megacolon (Hirschsprung’s disease) 1. birth defect 2. parasympathetic innervation of distal large intestine fails to develop correctly 3. feces and gas accumulate proximal to defect © 2014 Pearson Education, Inc. D. Achalasia of the cardia 1. defect in the autonomic innervation of the esophagus E. Congenital megacolon (Hirschsprung’s disease) 1. birth defect 2. parasympathetics of distal large intestine fails to develop correctly 3. feces and gas accumulate proximal to defect © 2014 Pearson Education, Inc.