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Autonomic Nervous System ANS Overview
- 1. © 2012 Pearson Education, Inc. 17 The Nervous System: Autonomic Nervous System PowerPoint® Lecture Presentations prepared by Steven Bassett Southeast Community College Lincoln, Nebraska
- 2. Introduction • The autonomic nervous system functions outside of our conscious awareness • The autonomic nervous system makes routine adjustments in our body’s systems • The autonomic nervous system: • Regulates body temperature • Coordinates cardiovascular, respiratory, digestive, excretory, and reproductive functions © 2012 Pearson Education, Inc.
- 3. A Comparison of the Somatic and Autonomic Nervous Systems • Autonomic nervous system • Axons innervate the visceral organs • Has afferent and efferent neurons • Afferent pathways originate in the visceral receptors • Somatic nervous system • Axons innervate the skeletal muscles • Has afferent and efferent neurons • Afferent pathways originate in the skeletal muscles ANIMATION The Organization of the Somatic and © 2012 Pearson Education, Inc. Autonomic Nervous Systems
- 4. Subdivisions of the ANS • The autonomic nervous system differs from the somatic nervous system in the arrangement of the neurons connecting the central nervous system to the effector organs. • Visceral motor neurons in the CNS, known as preganglionic neurons, send their axons, called preganglionic fibers, to synapse on ganglionic neurons, whose cell bodies are located outside the CNS, in autonomic ganglia. • Axons from the ganglionic neurons are called postganglionic fibers because they carry impulses away from the ganglion. • Postganglionic fibers innervate peripheral tissues and organs, such as cardiac and smooth muscle, adipose tissue, and glands. © 2012 Pearson Education, Inc.
- 5. Figure 17.1b Components and Anatomic Subdivisions of the ANS (Part 1 of 2) © 2012 Pearson Education, Inc. AUTONOMIC NERVOUS SYSTEM THORACOLUMBAR DIVISION Thoracic nerves T1 T2 T3 T4 T5 T6 T7 T8 Anatomical subdivisions. At the thoracic and lumbar levels, the visceral efferent fibers that emerge form the sympathetic division, detailed in Figure 17.4. At the cranial and sacral levels, the visceral efferent fibers from the CNS form the parasympathetic division, detailed in Figure 17.8. (sympathetic division of ANS) CRANIOSACRAL DIVISION (parasympathetic division of ANS) Cranial nerves (N III, N VII, N IX, and N X)
- 6. Figure 17.1b Components and Anatomic Subdivisions of the ANS (Part 2 of 2) Thoracic nerves nerves (L1, L2 only) © 2012 Pearson Education, Inc. Sacral nerves (S2, S3, S4 only) Lumbar T9 T10 T11 T12 L1 L2 L3 L4 L5 S1 S2 S3 S4 S5 Anatomical subdivisions. At the thoracic and lumbar levels, the visceral efferent fibers that emerge form the sympathetic division, detailed in Figure 17.4. At the cranial and sacral levels, the visceral efferent fibers from the CNS form the parasympathetic division, detailed in Figure 17.8.
- 7. Subdivisions of the ANS • Sympathetic division • Thoracic and upper lumbar nerves synapse in ganglia near the spinal cord • Sympathetic activation results in: • Increased metabolism and alertness • Generally kicks in during times of exertion, stress, or emergency • Parasympathetic division • Synapses are located near the target organ • Parasympathetic activation results in: • Energy conservation • Generally predominant under resting conditions © 2012 Pearson Education, Inc.
- 8. Figure 17.1a Components and Anatomic Subdivisions of the ANS © 2012 Pearson Education, Inc. AUTONOMIC NERVOUS SYSTEM Consists of 2 divisions SYMPATHETIC (thoracolumbar) DIVISION PARASYMPATHETIC (craniosacral) DIVISION Preganglionic neurons in lateral gray horns of spinal segments T1–L2 Preganglionic neurons in brain stem and in lateral portion of anterior gray horns of S2–S4 Send preganglionic fibers to Which send postganglionic fibers to Ganglia near spinal cord Ganglia in or near target organs Preganglionic fibers release ACh (excitatory), stimulating ganglionic neurons Preganglionic fibers release ACh (excitatory), stimulating ganglionic neurons Target organs Target organs Most postganglionic fibers release NE at neuroeffector junctions All postganglionic fibers release ACh at neuroeffector junctions “Fight or flight” response “Rest and repose” response Functional components of the ANS
- 9. The Sympathetic Division • Sympathetic division consists of: • Preganglionic neurons between T1 and L2 • Two types of ganglionic neurons near the vertebral columns: sympathetic chain ganglia (lateral to the vertebral column) and collateral ganglia (anterior to the vertebral column) • Specialized neurons in the interior of the suprarenal gland © 2012 Pearson Education, Inc.
- 10. The Sympathetic Division • Sympathetic division • Preganglionic neurons • Cell bodies are in the lateral gray horns • Axons enter the ventral roots • Sympathetic chain ganglia (paravertebral ganglia) • Control effectors in the body wall, head, neck, limbs, and thoracic cavity © 2012 Pearson Education, Inc.
- 11. The Sympathetic Division •Sympathetic division • Collateral ganglia (prevertebral ganglia) • Neurons innervate effectors in the abdominopelvic cavity • Specialized neurons • Modified sympathetic ganglion in the suprarenal gland • Neurons release neurotransmitters that act like hormones © 2012 Pearson Education, Inc.
- 12. Figure 17.2 Organization of the Sympathetic Division of the ANS Lateral gray horns of spinal segments T1–L2 Preganglionic fibers Postganglionic fibers Hormones released into circulation KEY © 2012 Pearson Education, Inc. Sympathetic chain ganglia (paired) Collateral ganglia (unpaired) Suprarenal medullae (paired) Preganglionic Neurons Ganglionic Neurons Innervation by postganglionic fibers Through release of hormones into the circulation Target Organs Visceral effectors in thoracic cavity, head, body wall, and limbs Visceral effectors in abdominopelvic cavity Organs and systems throughout body Sympathetic Division of ANS
- 13. Figure 17.3a Sympathetic Pathways and Their General Functions Spinal nerve Preganglionic Autonomic ganglion of left sympathetic chain Sympathetic nerve (postganglionic fibers) © 2012 Pearson Education, Inc. Sympathetic Chain Ganglia KEY Preganglionic neurons Ganglionic neurons Innervates visceral organs in thoracic cavity via sympathetic nerves neuron Autonomic ganglion of right sympathetic chain Innervates visceral effectors via spinal nerves White ramus Ganglionic neuron Gray ramus Major effects produced by sympathetic postganglionic fibers in spinal nerves: • Constriction of cutaneous blood vessels, reduction in circulation to the skin and to most other organs in the body wall • Acceleration of blood flow to skeletal muscles and brain • Stimulation of energy production and use by skeletal muscle tissue • Release of stored lipids from subcutaneous adipose tissue • Stimulation of secretion by sweat glands • Stimulation of arrector pili • Dilation of the pupils and focusing for distant objects Major effects produced by postganglionic fibers entering the thoracic cavity in sympathetic nerves: • Acceleration of heart rate and increasing the strength of cardiac contractions • Dilation of respiratory passageways
- 14. Figure 17.4 Anatomical Distribution of Sympathetic Postganglionic Fibers Superior Middle Inferior © 2012 Pearson Education, Inc. PONS Cervical sympathetic ganglia Gray rami to spinal nerves Greater splanchnic nerve Superior mesenteric ganglion Sympathetic nerves Cardiac and pulmonary plexuses Celiac ganglion T1 T1 T2 T2 T3 T3 T4 T4 T5 T5 T6 T6 T7 T7 T8 T8 T9 T9 T10 T10 T11 T11 T12 T12 L1 L1 L2 L2 L3 L3 L4 L4 L5 L5 S1 S1 S2 S2 S3 S3 S4 S4 S5 S5 Postganglionic fibers to spinal nerves (innervating skin, blood vessels, sweat glands, arrector pili muscles, adipose tissue) Sympathetic chain ganglia Spinal cord Coccygeal ganglia (Co1) fused together (ganglion impar) Preganglionic neurons Ganglionic neurons KEY Lesser splanchnic nerve Lumbar splanchnic nerves Inferior Sacral splanchnic nerves Uterus Ovary mesenteric ganglion Penis Scrotum Urinary bladder Heart Lung Liver and gallbladder Stomach Spleen Pancreas Large intestine Small intestine Suprarenal medulla Kidney Eye Salivary glands
- 15. Figure 17.3b Sympathetic Pathways and Their General Functions © 2012 Pearson Education, Inc. Collateral Ganglia Lateral gray horn White ramus Collateral Postganglionic ganglion fibers Splanchnic nerve (preganglionic fibers) Innervates visceral organs in abdominopelvic cavity Major effects produced by preganglionic fibers innervating the collateral ganglia: • Constriction of small arteries and reduction in the flow of blood to visceral organs • Decrease in the activity of digestive glands and organs • Stimulation of the release of glucose from glycogen reserves in the liver • Stimulation of the release of lipids from adipose tissue • Relaxation of the smooth muscle in the wall of the urinary bladder • Reduction of the rate of urine formation at the kidneys • Control of some aspects of sexual function, such as ejaculation in males
- 16. Figure 17.3c Sympathetic Pathways and Their General Functions © 2012 Pearson Education, Inc. The Suprarenal Medullae Secretes neurotransmitters into general circulation Suprarenal medullae Preganglionic fibers Endocrine cells (specialized ganglionic neurons) Major effect produced by preganglionic fibers innervating the suprarenal medullae: • Release of epinephrine and norepinephrine into the general circulation
- 17. Figure 17.5a Suprarenal Medulla © 2012 Pearson Education, Inc. Relationship of a suprarenal gland to a kidney Cortex Medulla Suprarenal gland Right kidney
- 18. The Sympathetic Division • In summary: • The sympathetic division of the ANS includes two sympathetic chains, three collateral ganglia, and two suprarenal medullae. • Preganglionic fibers are short because the ganglia are close to the spinal cord. • The postganglionic fibers of the sympathetic system are relatively longer than those of the parasympathetic system. • The sympathetic division shows extensive divergence. • All preganglionic neurons release ACh at their synapses with ganglionic neurons. • The effector response depends on the function of the membrane receptor © 2012 Pearson Education, Inc.
- 19. Figure 17.6 Sympathetic Postganglionic Nerve Endings Preganglionic fiber © 2012 Pearson Education, Inc. (myelinated) Ganglionic neuron Ganglion Postganglionic fiber (unmyelinated) Varicosities Mitochondrion Vesicles containing norepinephrine 5 mm Schwann cell cytoplasm Smooth muscle cells Varicosities
- 20. Figure 17.4 Anatomical Distribution of Sympathetic Postganglionic Fibers Superior Middle Inferior © 2012 Pearson Education, Inc. PONS Cervical sympathetic ganglia Gray rami to spinal nerves Greater splanchnic nerve Superior mesenteric ganglion Sympathetic nerves Cardiac and pulmonary plexuses Celiac ganglion T1 T1 T2 T2 T3 T3 T4 T4 T5 T5 T6 T6 T7 T7 T8 T8 T9 T9 T10 T10 T11 T11 T12 T12 L1 L1 L2 L2 L3 L3 L4 L4 L5 L5 S1 S1 S2 S2 S3 S3 S4 S4 S5 S5 Postganglionic fibers to spinal nerves (innervating skin, blood vessels, sweat glands, arrector pili muscles, adipose tissue) Sympathetic chain ganglia Spinal cord Coccygeal ganglia (Co1) fused together (ganglion impar) Preganglionic neurons Ganglionic neurons KEY Lesser splanchnic nerve Lumbar splanchnic nerves Inferior Sacral splanchnic nerves Uterus Ovary mesenteric ganglion Penis Scrotum Urinary bladder Heart Lung Liver and gallbladder Stomach Spleen Pancreas Large intestine Small intestine Suprarenal medulla Kidney Eye Salivary glands
- 21. The Parasympathetic Division • Parasympathetic Division • Preganglionic neurons are in the brain stem and sacral segments • Preganglionic neurons do not diverge as much as the sympathetic division • Therefore, the parasympathetic division is more localized and specific as compared to the sympathetic division • Postganglionic neurons are near (terminal) the target organ or within (intramural) the target organ © 2012 Pearson Education, Inc.
- 22. Figure 17.7 Organization of the Parasympathetic Division of the ANS © 2012 Pearson Education, Inc. Parasympathetic Division of ANS Preganglionic Neurons Ganglionic Neurons Target Organs Ciliary ganglion Pterygopalatine and submandibular ganglia Otic ganglion Intramural ganglia Intrinsic eye muscles (pupil and lens shape) Nasal glands, tear glands, and salivary glands Visceral organs of neck, thoracic cavity, and most of abdominal cavity N III N VII N IX N X Nuclei in brain stem Nuclei in spinal cord segments S2–S4 Pelvic nerves Intramural ganglia Visceral organs in inferior portion of abdominopelvic cavity KEY Preganglionic fibers Postganglionic fibers Parotid salivary gland
- 23. Figure 17.8 Autonomic Distribution of the Parasympathetic Output KEY © 2012 Pearson Education, Inc. Pterygopalatine ganglion PONS N III N VII N IX N X (Vagus) Ciliary ganglion Submandibular ganglion Otic ganglion Autonomic plexuses (see Figure 17.9) Pelvic nerves Lacrimal gland Eye Salivary glands Heart Lungs Liver and gallbladder Stomach Spleen Pancreas Large intestine Small intestine Rectum Kidney Uterus Ovary Penis Scrotum Urinary bladder S2 S3 S4 Spinal cord Preganglionic neurons Ganglionic neurons
- 24. The Parasympathetic Division • General functions of the parasympathetic division: • Constriction of the pupils to restrict the amount of light entering the eyes; assists in focusing on nearby objects • Secretion by digestive glands, including salivary glands, gastric glands, duodenal and other intestinal glands, the pancreas, and the liver • Secretion of hormones that promote nutrient absorption by peripheral cells • Increased smooth muscle activity along the digestive tract • Stimulation and coordination of defecation © 2012 Pearson Education, Inc.
- 25. The Parasympathetic Division •General functions of the parasympathetic division (continued) • Contraction of the urinary bladder during urination • Constriction of the respiratory passageways • Reduction in heart rate and force of contraction • Sexual arousal and stimulation of sexual glands in both sexes © 2012 Pearson Education, Inc.
- 26. The Parasympathetic Division • In summary: • The parasympathetic division includes visceral motor nuclei in the brain stem associated with four cranial nerves (III, VII, IX, and X). • The ganglionic neurons are situated in intramural ganglia or in ganglia closely associated with their target organs. • The parasympathetic division innervates structures in the head and organs in the thoracic and abdominopelvic cavities. • All parasympathetic neurons are cholinergic. • The effects of parasympathetic stimulation are usually brief and restricted to specific organs and sites. © 2012 Pearson Education, Inc.
- 27. Relationships between the Sympathetic and Parasympathetic Divisions • Sympathetic • Widespread effect on visceral organs • Parasympathetic • Modifies the activity of structures innervated by specific cranial nerves and pelvic nerves • Most vital organs are innervated by both the sympathetic and parasympathetic nerves • The two often oppose (antagonistic) each other © 2012 Pearson Education, Inc.
- 28. Figure 17.10 A Comparison of the Sympathetic and Parasympathetic Divisions Sympathetic Parasympathetic CNS PNS © 2012 Pearson Education, Inc. KEY Sympathetic ganglion Circulatory system Preganglionic neuron Preganglionic fiber or Epinephrine Ganglionic neurons Postganglionic fiber TARGET Neurotransmitters Acetylcholine Norepinephrine Parasympathetic ganglion
- 29. Figure 17.9a The Peripheral Autonomic Plexuses Trachea Left vagus nerve Right vagus nerve Aortic arch Thoracic spinal nerves Splanchnic nerves Diaphragm Celiac trunk Superior mesenteric artery Inferior mesenteric Autonomic Plexuses and Ganglia Hypogastric plexus This is a diagrammatic view of the distribution of ANS plexuses in the thoracic cavity (cardiac, esophageal, and pulmonary plexuses) and the abdominopelvic cavity (celiac, inferior mesenteric, and hypogastric plexuses). © 2012 Pearson Education, Inc. artery Esophagus Cardiac plexus Pulmonary plexus Thoracic sympathetic chain ganglia Esophageal plexus Celiac plexus and ganglion Superior mesenteric ganglion Inferior mesenteric plexus and ganglion Pelvic sympathetic chain
- 30. Figure 17.9b The Peripheral Autonomic Plexuses © 2012 Pearson Education, Inc. Cranial nerve III Cranial nerve VII Cranial nerve IX Autonomic Plexuses Trachea Esophagus Heart Diaphragm Stomach Colon A sectional view of the autonomic plexuses and Ganglia Cardiac plexus Thoracic sympathetic chain ganglia Esophageal plexus Celiac plexus and ganglion Superior mesenteric ganglion Inferior mesenteric plexus and ganglion Hypogastric plexus Pelvic sympathetic chain Urinary bladder Vagus nerve (N X)
- 31. Visceral Reflexes • The ANS is organized into a series of interacting levels • Visceral reflexes • Short reflexes • Long reflexes • Enteric nervous system (ENS) • Higher levels of autonomic control • Hypothalamus © 2012 Pearson Education, Inc.
- 32. Figure 17.11 Visceral Reflexes Receptors in peripheral tissue Stimulus Response © 2012 Pearson Education, Inc. Afferent (sensory) fibers Short reflex Long reflex Peripheral effector Ganglionic neuron CENTRAL NERVOUS Processing center in spinal cord (or brain) Preganglionic neuron Autonomic ganglion (sympathetic or parasympathetic) SYSTEM