The Autonomic Nervous System Pages 468-480 15 PART 1 The Autonomic Nervous System Pages 468-480

The ANS and Visceral Sensory Neurons The ANS—a system of motor neurons Regulates visceral functions Heart rate Blood pressure Digestion Urination The ANS is the General visceral motor division of the PNS

The Autonomic Nervous System and Visceral Sensory Neurons Figure 15.1

Comparison of Autonomic and Somatic Motor Systems 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 Preganglionic neuron Postganglionic neuron Conduction is slower than somatic nervous system due to Thinly myelinated or unmyelinated axons Motor neuron synapses in a ganglion

Figure 15.2 Comparing Somatic Motor and Autonomic Innervation

Autonomic and Somatic Motor Systems Skeletal muscle Cell bodies in central nervous system Peripheral nervous system Effect Effector organs ACh Smooth muscle (e.g., in gut), glands, cardiac muscle Ganglion Adrenal medulla Blood vessel NE Epinephrine and norepinephrine Heavily myelinated axon Lightly myelinated preganglionic axon preganglionic axons Neurotransmitter at effector Unmyelinated postganglionic axon postganglionic axon Stimulatory or inhibitory, depending on neuro- transmitter and receptors on effector Single neuron from CNS to effector organs Two-neuron chain from CNS to effector organs SOMATIC NERVOUS SYSTEM AUTONOMIC NERVOUS SYSTEM PARASYMPATHETIC SYMPATHETIC

Divisions of the Autonomic Nervous System Sympathetic and parasympathetic divisions Chains of two motor neurons Innervate mostly the same structures Cause opposite effects Sympathetic division mobilizes the body during extreme situations Parasympathetic division controls routine maintenance functions

Divisions of the Autonomic Nervous System Sympathetic—“fight, flight, or fright” Activated during EXTREME situations Sympathetic 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

Divisions of the Autonomic Nervous System Parasympathetic division Active when the body is at rest Concerned with conserving energy Directs “housekeeping” activities Heart rate and breathing are at low-normal levels Gastrointestinal tract digests food Pupils are constricted

Anatomical Differences in Sympathetic and Parasympathetic Divisions Salivary glands Eye Skin* Heart Lungs Liver and gall- bladder Genitals Pancreas Bladder Liver and gall- Stomach Cervical Sympathetic ganglia Cranial Lumbar Thoracic Adrenal gland Parasympathetic Sacral Brain stem L1 T1 Issue from different regions of the CNS Sympathetic—also called the thoracolumbar division Parasympathetic—also called the craniosacral division Figure 15.3

Anatomical Differences in Sympathetic and Parasympathetic Divisions Length of postganglionic fibers Sympathetic—long postganglionic fibers Parasympathetic—short postganglionic fibers Branching of axons Sympathetic axons—highly branched Influences many organs Parasympathetic axons—few branches Localized effect

Biochemical Differences in Sympathetic and Parasympathetic Divisions Neurotransmitter released by postganglionic axons Sympathetic Most release norepinephrine (adrenergic) Parasympathetic Release acetylcholine (cholinergic)

Parasympathetic and Sympathetic Divisions Table 15.1

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

Cranial Outflow (Parasympathetic) Preganglionic fibers run via Oculomotor nerve (III) Facial nerve (VII) Glossopharyngeal nerve (IX) Vagus nerve (X) Cell bodies of preganglionic neurons located in cranial nerve nuclei in the brain stem

The Parasympathetic Division Eye Lacrimal gland Nasal mucosa Ciliary ganglion Pterygopalatine Submandibular and sublingual glands CN III CN VII CN IX CN X Otic ganglion Parotid gland Heart Lung Liver and gallbladder Stomach Pancreas Urinary bladder and ureters Small intestine Large S2 Pelvic splanchnic nerves Genitalia (penis, clitoris, and vagina) Rectum Celiac plexus Inferior hypogastric Cardiac and pulmonary plexuses S4 Preganglionic Postganglionic Cranial nerve CN Figure 15.4

Outflow via the Oculomotor Nerve (III) Parasympathetic fibers innervate smooth muscles in the eye Cause pupil constriction Preganglionic cell bodies Located in the oculomotor nucleus in the midbrain Post ganglionic cell bodies Lie in the ciliary ganglion

Outflow via the Facial Nerve (VII) Parasympathetic fibers stimulate secretion of glands in the head Lacrimal nucleus Located in the pons Synapse in the pterygopalatine ganglion Superior salivatory nucleus Synapse in the submandibular ganglion

The Parasympathetic Division Eye Lacrimal gland Nasal mucosa Ciliary ganglion Pterygopalatine Submandibular and sublingual glands CN III CN VII CN IX CN X Otic ganglion Parotid gland Heart Lung Liver and gallbladder Stomach Pancreas Urinary bladder and ureters Small intestine Large S2 Pelvic splanchnic nerves Genitalia (penis, clitoris, and vagina) Rectum Celiac plexus Inferior hypogastric Cardiac and pulmonary plexuses S4 Preganglionic Postganglionic Cranial nerve CN Figure 15.4

Outflow via the Glossopharyngeal Nerve (IX) Parasympathetic fibers Stimulate secretion of parotid gland Inferior salivatory nucleus—located in the medulla Synapse in the otic ganglion

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 Preganglionic cell bodies Located in dorsal motor nucleus in the medulla Postganglionic neurons Confined within the walls of organs being innervated Cell bodies form intramural ganglia

The Parasympathetic Division Eye Lacrimal gland Nasal mucosa Ciliary ganglion Pterygopalatine Submandibular and sublingual glands CN III CN VII CN IX CN X Otic ganglion Parotid gland Heart Lung Liver and gallbladder Stomach Pancreas Urinary bladder and ureters Small intestine Large S2 Pelvic splanchnic nerves Genitalia (penis, clitoris, and vagina) Rectum Celiac plexus Inferior hypogastric Cardiac and pulmonary plexuses S4 Preganglionic Postganglionic Cranial nerve CN Figure 15.4

Sends branches through Path of the Vagus Nerve Sends branches through Autonomic nerve plexuses Cardiac plexus Pulmonary plexus Esophageal plexus Celiac plexus Superior mesenteric plexus

Autonomic nerves, plexuses and ganglia Left vagus nerve Cardiac branches of the vagus Trachea Thoracic spinal nerves (ventral rami) Cardiac plexus Pulmonary plexus on the bronchus Vagus nerve Esophageal plexus Diaphragm Stomach with vagus nerve Celiac ganglion and plexus Superior mesenteric ganglion and plexus Inferior mesenteric Aortic plexus Inferior hypogastric (pelvic) plexus Pelvic sympathetic trunk Superior cervical ganglion Middle cervical Sympathetic cardiac nerves Stellate ganglion Aortic arch trunk ganglia Esophagus Thoracic splanchnic nerves Adrenal (suprarenal) gland Kidney Lumbar and sacral Superior hypogastric plexus Aorta Figure 15.5

Innervates organs of the pelvis and lower abdomen Sacral Outflow Emerges from S2–S4 Innervates organs of the pelvis and lower abdomen Preganglionic cell bodies Located in visceral motor region of spinal gray matter Axons run in ventral roots to ventral rami

Gray Matter of the Spinal Cord and Spinal Roots Somatic sensory neuron Dorsal root (sensory) ganglion Visceral sensory neuron Somatic motor Spinal nerve Ventral root (motor) Ventral horn (motor neurons) Dorsal horn (interneurons) motor SS VS VM SM Interneurons receiving input from somatic sensory neurons Interneurons receiving input from visceral sensory neurons Visceral motor (autonomic) neurons Somatic motor neurons Figure 13.27

Anatomy of the Spinal Cord (b) The spinal cord and its meningeal coverings Dorsal funiculus Dorsal median sulcus Central canal Ventral median fissure Pia mater Arachnoid mater Spinal dura mater Gray commissure Dorsal horn Gray matter Lateral horn Ventral horn Ventral funiculus Lateral funiculus White Dorsal root ganglion Dorsal root (fans out into dorsal rootlets) Ventral root (derived from several ventral rootlets) Spinal nerve Figure 13.26

The Sympathetic Division Basic organization Issues from T1–L2 Preganglionic fibers form the lateral gray horn Supplies visceral organs and structures of superficial body regions Contains more ganglia than the parasympathetic division; sympathetic trunk ganglia & collateral ganglia

Sympathetic Trunk Ganglia Located on both sides of the vertebral column Linked by short nerves into sympathetic trunks Sympathetic trunk ganglia are also called Chain ganglia Joined to ventral rami by white and gray rami communicantes

Sympathetic Trunk Ganglia Spinal cord Dorsal root Ventral root Sympathetic trunk ganglion trunk Rib Ventral ramus of spinal nerve Gray ramus communicans White ramus Thoracic splanchnic nerves (a) Location of the sympathetic trunk To effector Blood vessels Skin (arrector pili muscles and sweat glands) Dorsal root ganglion Dorsal ramus of spinal nerve Dorsal root Sympathetic trunk ganglion Lateral horn (visceral motor zone) Ventral root Sympathetic trunk Gray ramus communicans White ramus Ventral ramus of Synapse at the same level 1 Splanchnic nerve Collateral ganglion (such as the celiac) Target organ in abdomen (e.g., intestine) Synapse in a distant collateral ganglion anterior to the vertebral column (b) Three pathways of sympathetic innervation 3 2 To effector Blood vessels Skin (arrector pili muscles and sweat glands) Synapse at a higher or lower level Figures 15.6 & 15.7

Preganglionic axons follow one of three pathways Sympathetic Pathways Preganglionic axons follow one of three pathways Synapes with a postganglionic neuron at the same level and exit on a spinal nerve at that level Axon ascends or descends in the sympathetic trunk to synapse in another ganglion Axon passes through the sympathetic trunk and exits on a splanchnic nerve

Sympathetic Pathways to Organs Superior cervical ganglion Middle Inferior Sympathetic trunk (chain) ganglia Pons L2 T1 White rami communicantes Liver and gallbladder Stomach Spleen Kidney Adrenal medulla Small intestine Large Genitalia (uterus, vagina, and penis) and urinary bladder Celiac ganglion mesenteric Lesser splanchnic nerve Greater splanchnic nerve Lumbar splanchnic nerves Eye Lacrimal gland Nasal mucosa Blood vessels; skin (arrector pili muscles and sweat glands) Salivary glands Heart Lung Rectum Cardiac and pulmonary plexuses Preganglionic Postganglionic Sacral Figure 15.8

The Role of the Adrenal Medulla in the Sympathetic Division Major organ of the sympathetic nervous system Constitutes largest sympathetic ganglia Secretes great quantities of norepinephrine and adrenaline Stimulated to secrete by preganglionic sympathetic fibers

The Adrenal Medulla Sympathetic trunk Spinal cord: T8–L1 Ventral root medulla cells Sympathetic trunk Ventral root Thoracic splanchnic nerves Epinephrine and norepinephrine Adrenal gland medulla Capillary Kidney Figure 15.9

Table 15.2 (1 of 3)

Table 15.2 (2 of 3)

Table 15.2 (3 of 3)