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1 PowerPoint Lecture Slides prepared by Leslie Hendon University of Alabama, Birmingham C H A P T E R 15 Part 1 The Autonomic Nervous System and Visceral Sensory Neurons The ANS and Visceral Sensory Neurons The ANS a system of motor neurons Innervates Smooth muscle Cardiac muscle Glands Regulates visceral functions such as rate Blood pressure Digestion Urination The ANS is the General visceral motor division of the PNS The Autonomic Nervous System and Visceral Sensory Neurons Comparison of Autonomic and Somatic Motor Systems Somatic motor system One motor neuron extends from the CNS to skeletal muscle Axons are well myelinated, conduct impulses rapidly Autonomic nervous system Chain of two motor neurons Preic neuron Ganglionic neuron Conduction is slower than somatic nervous system due to Thinly myelinated or unmyelinated axons Motor neuron synapses in a Figure 15.1 Autonomic and Somatic Motor Systems Figure 15.2 Comparing Somatic Motor and Autonomic Innervation Cell bodies in central nervous system Peripheral nervous system Neurotransmitter at effector Effector organs Effect SOMATIC NERVOUS SYSTEM Single neuron from CNS to effector organs Heavily myelinated axon ACh Skeletal muscle Stimulatory Two-neuron chain from CNS to effector organs AUTONOMIC NERVOUS SYSTEM PARASYMPATHETIC SYMPATHETIC ACh Unmyelinated Lightly myelinated postic axon Ganglion preic axons Epinephrine and ACh norepinephrine Adrenal medulla Blood vessel ACh Lightly myelinated Unmyelinated preic axon Ganglion postic axon NE ACh Stimulatory or inhibitory, depending on neurotransmitter and receptors on effector Smooth muscle organs (e.g., in gut), glands, cardiac muscle Figure

2 Divisions of the Autonomic Nervous System Divisions of the Autonomic Nervous System and parasympathetic divisions Chains of two motor neurons Innervate mostly the same structures Cause opposite effects (usually) division mobilizes the body during extreme situations Parasympathetic division controls routine maintenance functions fight, flight, or fright Activated during EXTREME situations Exercise Excitement Emergencies Divisions of the Autonomic Nervous System Divisions of the Autonomic Nervous System responses help us respond to dangerous situations Increase heart rate and breathing rate Increases blood and oxygen to skeletal muscles Dilates pupils and airways Motility of the digestive tract and urinary tracts are inhibited Parasympathetic division Active when the body is at rest Concerned with conserving energy Directs housekeeping activities: rest & digest rate and breathing are at low-normal levels Gastrointestinal tract digests food Pupils are constricted Anatomical Differences in and Parasympathetic Divisions 1. Issue from different regions of the CNS also called the thoracolumbar division Parasympathetic also called the craniosacral division Parasympathetic Eye Salivary glands Lungs Stomach Pancreas Liver and gallbladder Bladder Genitals Cervical T 1 Thoracic L 1 Lumbar Brain stem Cranial ganglia Sacral Eye Skin* Salivary glands Lungs Stomach Pancreas Liver and gallbladder Adrenal gland Bladder Genitals Figure 15.3 Anatomical Differences in and Parasympathetic Divisions 2. Length of postic fibers long postic fibers Parasympathetic short postic fibers 3. Branching of axons axons highly branched Influences many organs Parasympathetic axons few branches Localized effect 2

3 CN Preic Postic Cranial nerve Anatomical Differences in and Parasympathetic Divisions 4. Neurotransmitter released by postic axons Most release norepinephrine (adrenergic) Parasympathetic Release acetylcholine (cholinergic) Parasympathetic and Divisions Table 15.1 A. The Parasympathetic Division The Parasympathetic Division Cranial outflow Comes from the brain Innervates organs of the head, neck, thorax, and abdomen Sacral outflow Innervation supplies remaining abdominal and pelvic organs CN III CN VII CN IX CN X S 2 S 4 Ciliary Pterygopalatine Submandibular Otic Cardiac and pulmonary plexuses Celiac plexus Eye Lacrimal gland Nasal mucosa Submandibular and sublingual glands Parotid gland Lung Liver and gallbladder Stomach Pancreas Large intestine Pelvic splanchnic Small intestine Inferior hypogastric plexus Rectum Urinary bladder and ureters Genitalia (penis, clitoris, and vagina) Figure 15.4 Cranial Outflow (Parasympathetic) Outflow via the Oculomotor Nerve (III) Preic fibers travel in 4 C.N.s: Oculomotor nerve (III) Facial nerve (VII) Glossopharyngeal nerve (IX) Vagus nerve (X) Cell bodies of C.N.s located in cranial nerve nuclei in the brain stem Parasympathetic fibers innervate smooth muscles in the eye Cause pupil constriction Preic cell bodies Located in the oculomotor nucleus in the midbrain Ganglionic cell bodies Lie in the ciliary 3

4 Outflow via the Facial Nerve (VII) Outflow via the Glossopharyngeal Nerve (IX) Parasympathetic fibers stimulate secretion of glands in the head Lacrimal nucleus Located in the pons Synapse in the pterygopalatine Superior salivatory nucleus Located in the pons Synapse in the submandibular Parasympathetic fibers Stimulate secretion of glands in the head Lacrimal nucleus located in the pons Synapse in the pterygopalatine Superior salivatory nucleus located in the pons Synapse in the submandibular Outflow via the Vagus Nerve (X) Fibers innervate visceral organs of the thorax and most of the abdomen Stimulates: Digestion, reduction in heart rate, and reduction in blood pressure Preic cell bodies Located in dorsal motor nucleus in the medulla Postic neurons Confined within the walls of organs being innervated Cell bodies form intramural ganglia Path of the Vagus Nerve Sends branches through Autonomic nerve plexuses Cardiac plexus Pulmonary plexus Esophageal plexus Celiac plexus Superior mesenteric plexus Autonomic, plexuses and ganglia Superior cervical Middle cervical Stellate cardiac Aortic arch trunk ganglia Esophagus Thoracic splanchnic Adrenal (suprarenal) gland Kidney Lumbar and sacral splanchnic Left vagus nerve Cardiac branches Trachea of the vagus Thoracic spinal (ventral rami) Cardiac plexus Pulmonary plexus Aorta on the bronchus Vagus nerve Esophageal plexus Diaphragm Stomach with vagus nerve Celiac and plexus Superior mesenteric and plexus Aortic plexus Inferior mesenteric and plexus Superior hypogastric plexus Inferior hypogastric (pelvic) plexus Pelvic sympathetic trunk Figure 15.5 Sacral Outflow Emerges from S 2 S 4 Innervates organs of the pelvis and lower abdomen Preic cell bodies Located in visceral motor region of spinal gray matter Axons run in ventral roots to ventral rami Form pelvic splanchnic Run through the inferior hypogastric plexus 4

5 B. The Division Trunk Ganglia Basic organization Issues from T 1 L 2 Preic cell bodies form the lateral gray horn Supplies visceral organs and structures of superficial body regions Contains more ganglia than the parasympathetic division Located on both sides of the vertebral column Linked by short into sympathetic trunks trunk ganglia are also called Chain ganglia Paravertebral ganglia Trunk Ganglia Joined to ventral rami by white and gray rami communicantes Fusion of ganglia fewer ganglia than spinal Fusion of ganglia most apparent in the cervical region Superior, middle, and inferior cervical ganglia Trunk Ganglia Spinal cord Dorsal root Ventral root Rib trunk trunk Ventral ramus of spinal nerve Gray ramus White ramus Thoracic splanchnic (a) Location of the sympathetic trunk Dorsal root Dorsal root Dorsal ramus of spinal nerve Ventral ramus of spinal nerve Gray ramus White ramus Skin (arrector pili muscles and sweat glands) Blood vessels To effector Splanchnic nerve Collateral (such as the celiac) 1 Ventral root Lateral horn (visceral motor zone) trunk trunk Synapse at the same level Skin (arrector pili muscles and sweat glands) To effector Target organ in abdomen (e.g., intestine) Blood vessels 2 Synapse at a higher or lower level 3 Synapse in a distant collateral anterior to the vertebral column (b) Three pathways of sympathetic innervation Figure 15.6 Collateral Ganglia Pathways Differ from sympathetic trunk ganglia in three ways Unpaired, not segmentally arranged Occur only in abdomen and pelvis Lie anterior to the vertebral column Main ganglia Celiac, superior mesenteric, inferior mesenteric, and inferior hypogastric ganglia Preic neurons in the thoracolumbar spinal cord send motor axons through: Adjacent ventral root into Spinal nerve, then the White ramus And to the associated sympathetic trunk 5

6 Pathways Pathways Preic axons follow one of three pathways 1. Synapes with a postic neuron at the same level and exit on a spinal nerve at that level 2. Axon ascends or descends in the sympathetic trunk to synapse in another 3. Axon passes through the sympathetic trunk and exits on a splanchnic nerve Skin (arrector pili muscles and sweat glands) Blood vessels To effector Dorsal root Dorsal root Dorsal ramus of spinal nerve Ventral ramus of spinal nerve Gray ramus White ramus Skin (arrector pili muscles and sweat glands) Blood vessels 2 To effector Synapse at a higher or lower level 1 Ventral root Lateral horn (visceral motor zone) trunk trunk Synapse at the same level Splanchnic nerve Collateral (such as the celiac) Target organ in abdomen (e.g., intestine) (b) Three pathways of sympathetic innervation 3 Synapse in a distant collateral anterior to the vertebral column Figure 15.6b Pathways to the Body Periphery: Pathways to the Body Periphery Innervate Sweat glands Arrector pili muscles Peripheral blood vessels Preic fibers enter the sympathetic trunk ganglia and synapse there Some preic fibers travel superiorly or inferiorly on the sympathetic trunk Postic axons travel in gray rami communicantes Pathways to the Body Periphery Pathways to the Head Gray and white rami communicantes Gray rami contain only postic fibers traveling to peripheral structures Fibers are unmyelinated White rami contain preic fibers traveling to sympathetic trunk ganglia Fibers are myelinated Preic fibers originate in spinal cord at T 1 T 4 Fibers ascend in the sympathetic trunk Synapse in superior cervical 6

7 Pathways to the Head Pathways to Thoracic Organs Postic fibers associate with large arteries Carried by these structures to Glands Smooth muscle Vessels throughout the head Preic fibers originate at spinal levels T 1 T 6 Some fibers synapse in nearest sympathetic trunk Postic fibers run directly to the organ supplied Pathways to Thoracic Organs Pathways to Thoracic Organs Eye Lacrimal gland fibers to heart have a less direct route Functions Increase heart rate Dilate bronchioles Dilate blood vessels to the heart wall Inhibit muscles and glands in the esophagus and digestive system Pons trunk (chain) ganglia Superior cervical Middle cervical Inferior cervical Cardiac and T 1 pulmonary plexuses Greater splanchnic nerve Lesser splanchnic nerve Celiac L 2 White rami Superior communicantes mesenteric Sacral splanchnic Lumbar splanchnic Inferior mesenteric Preic Postic Nasal mucosa Blood vessels; skin (arrector pili muscles and sweat glands) Salivary glands Lung Liver and gallbladder Stomach Spleen Adrenal medulla Kidney Small intestine Large intestine Rectum Genitalia (uterus, vagina, and penis) and urinary bladder Figure 15.7 Pathways to Abdominal Organs Pathways to the Pelvic Organs Preic fibers originate in spinal cord (T 5 L 2 ) Pass through adjacent sympathetic trunk ganglia Then travel in thoracic splanchnic Synapse in prevertebral ganglia on the abdominal aorta Celiac and superior mesenteric ganglia Inhibit activity of muscles and glands in visceral organs Preic fibers originate in the spinal cord from T 10 L 2 Fibers descend in the sympathetic trunk to lumbar and sacral ganglia Some postic fibers run in lumbar and sacral splanchnic to plexuses Inferior mesenteric plexus, aortic plexus, or hypogastric plexus Other preic fibers pass directly to autonomic plexuses and synapse in collateral ganglia Inferior mesenteric ganglia or inferior hypogastric ganglia Postic fibers go from these plexuses to the Bladder, reproductive organs, and distal large intestine 7

8 The Role of the Adrenal Medulla in the Division The Adrenal Medulla trunk Major organ of the sympathetic nervous system Constitutes largest sympathetic ganglia Secretes great quantities of norepinephrine and adrenaline Stimulated to secrete by preic sympathetic fibers Spinal cord: T 8 L 1 Thoracic splanchnic Adrenal medulla Ventral root Kidney Adrenal gland Epinephrine and norepinephrine Adrenal medulla cells Capillary Figure 15.8 Table 15.2 (1 of 3) Table 15.2 (2 of 3) Visceral Sensory Neurons General visceral sensory neurons monitor Stretch, temperature, chemical changes, and irritation Cell bodies are located in the dorsal root Visceral pain No pain results when visceral organs are cut Visceral pain results from chemical irritation or inflammation Visceral pain often perceived to be of somatic origin Phenomenon of referred pain Table 15.2 (3 of 3) 8

9 A Map of Referred Pain Visceral Reflexes Gallbladder Appendix Lungs and diaphragm Liver Liver Stomach Pancreas Small intestine Ovaries Colon Kidneys Urinary bladder Ureters Visceral sensory and autonomic neurons Participate in visceral reflex arcs Defecation reflex Micturition reflex Some are simple spinal reflexes Others do not involve the CNS Strictly peripheral reflexes Figure 15.9 Visceral Reflex Arc Stimulus Visceral Reflex Arc Increased blood pressure 1 Sensory receptor in viscera 2 Visceral sensory neuron 3 Integration center May be preic neuron (as shown) May be a dorsal horn interneuron May be within walls of gastrointestinal tract 4 Efferent pathway (two-neuron chain) Preic neuron Postic neuron Dorsal root Spinal cord Autonomic 1 Baroreceptors in carotid sinus are stimulated. 2 Sensory impulses are carried on visceral sensory fibers in the glossopharyngeal (CN IX). 3 Integration occurs in cardiac center of medulla oblongata. 4 Efferent pathway via the vagus (CN X) 5 Parasympathetic stimulation of heart decreases heart rate Visceral effector Blood pressure decreases Response Figure Figure Central Control of the ANS ANS is not under direct voluntary control Activities regulated by CNS Brain stem Spinal cord Hypothalamus Amygdaloid body Cerebral cortex Figure Levels of ANS control. Cerebral cortex (frontal lobe) Limbic system (emotional input) Communication at subconscious level 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 9

10 Control by the Brain Stem and Spinal Cord Control by the brain stem and spinal cord Reticular formation exerts most direct influence Medulla oblongata Periaqueductal gray matter Control by the Hypothalamus and Amygdala Hypothalamus the main integration center of the ANS Medial and anterior parts Direct parasympathetic functions Lateral and posterior parts Direct sympathetic functions Amygdaloid body Main limbic region for emotions Control by the Cerebral Cortex Disorders of the Autonomic Nervous System People can exert some control over autonomic functions Feelings of calm during meditation Influence of cerebral cortex on parasympathetic centers in hypothalamus Voluntary sympathetic response Recalling scary event Raynaud s disease characterized by constriction of blood vessels Provoked by exposure to cold or by emotional stress Disorders of the Autonomic Nervous System The ANS Throughout Life Achalasia of the cardia Defect in the autonomic innervation of the esophagus Congenital megacolon (Hirschsprung s disease) Birth defect Parasympathetic innervation of distal large intestine fails to develop correctly Feces and gas accumulate proximal to defect Preic neurons of the ANS develop from the neural tube Postic neurons develop from the neural crest Development of the sympathetic division Some cells migrate ventrally Form the sympathetic trunk ganglia Other cells migrate Form the prevertebral ganglia 10

11 Figure Embryonic development of some sympathetic structures, including the adrenal medulla. Neural crest (future dorsal root ) trunk Adrenal medulla cells Urogenital ridge (kidney) Coelom Dorsal Neural tube Aorta Collateral cells Cortex of adrenal (suprarenal) gland Organ plexus The ANS Throughout Life Efficiency of the ANS declines with advancing age Constipation due to reduced mobility of gastrointestinal (GI) tract Dry eyes due to reduced tear formation Digestive tube 11