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Biology 218 – Human Anatomy Lecture Outline Adapted from Martini Human Anatomy 7th ed. Session: Section: Days / Time: Instructor: FALL 52999 MW 5:00 PM – 9:20 PM RIDDELL Chapter 17 The Nervous System Authonomic Nervous System 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 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 Subdivisions of the ANS The autonomic nervous system consists of two major subdivisions Sympathetic division Also called the thoracolumbar division Known as the “fight or flight” system Parasympathetic division Also called the craniosacral division Known as the “rest and repose” system 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 Parasympathetic division Synapses are located near the target organ Parasympathetic activation results in: Energy conservation Subdivisions of the ANS Sympathetic division All preganglionic fibers release acetylcholine. The effects are stimulatory. Most postganglionic fibers release norepinephrine.The effects are stimulatory. Parasympathetic division All preganglionic fibers release acetylcholine. The effects are stimulatory. Postganglionic fibers release acetylcholine but the effects can be inhibitory. © 2012 Pearson Education, Inc. Page 1 of 6 565331767 Biology 218 – Human Anatomy Session: Section: Days / Time: Instructor: Lecture Outline Adapted from Martini Human Anatomy 7th ed. FALL 52999 MW 5:00 PM – 9:20 PM RIDDELL 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 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 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 The Sympathetic Division Sympathetic Chain Ganglia The ventral root joins a dorsal root Forms a spinal nerve Passes through an intervertebral foramen White ramus branches off the spinal nerve Goes to a nearby sympathetic chain ganglion The Sympathetic Division Functions of Sympathetic Chain Ganglia Reduction of circulation to the skin More circulation to skeletal muscles Stimulates more energy production by skeletal muscles Releases stored adipose Stimulation of arrector pili muscles Dilation of pupils Increased heart rate Dilation of respiratory tubes The Sympathetic Division Anatomy of the Sympathetic Chain Ganglia Each spinal nerve consists of: Preganglionic and postganglionic fibers There are: © 2012 Pearson Education, Inc. Page 2 of 6 565331767 Biology 218 – Human Anatomy Lecture Outline Adapted from Martini Human Anatomy 7th ed. Session: Section: Days / Time: Instructor: FALL 52999 MW 5:00 PM – 9:20 PM RIDDELL cervical sympathetic chain ganglia thoracic sympathetic chain ganglia lumbar sympathetic chain ganglia sacral sympathetic chain ganglia coccygeal sympathetic chain ganglia The Sympathetic Division Collateral Ganglia Preganglionic neurons originate in the inferior thoracic and superior lumbar areas of the spinal cord Fibers pass through the sympathetic chain ganglia without synapsing Converge to form the greater, lesser, and lumbar splanchnic nerves Splanchnic nerves converge on the collateral ganglia The Sympathetic Division Functions of the Collateral Ganglia Reduction of flow of blood to the visceral organs Decrease in activity of the digestive organs Stimulation of the release of glucose from glycogen in the liver Stimulates adipose cells to release energy reserves Relaxation of smooth muscles in the urinary bladder Cause ejaculation in males The Sympathetic Division Anatomy of the Collateral Ganglia Splanchnic nerves innervate: Celiac ganglion: fibers innervate the stomach, duodenum, liver, gallbladder, pancreas, spleen, and kidney Superior mesenteric ganglion: fibers innervate the small intestine and the first parts of the large intestine Inferior mesenteric ganglion: fibers innervate the kidney, urinary bladder, sex organs, and terminal ends of the large intestine The Sympathetic Division Suprarenal Medullae Fibers pass through sympathetic chain and the celiac ganglion without synapsing Proceed to the suprarenal medulla Fibers then synapse on modified neurons that when stimulated will release neurotransmitters that act as hormones: Epinephrine and norepinephrine The Sympathetic Division Functions of the suprarenal medullae Increase alertness by activating the reticular activating system Increase cardiovascular and respiratory activity Increase muscle tone Increase the mobilization of energy reserves Increased release of lipids from adipose cells © 2012 Pearson Education, Inc. Page 3 of 6 565331767 Biology 218 – Human Anatomy Session: Section: Days / Time: Instructor: Lecture Outline Adapted from Martini Human Anatomy 7th ed. FALL 52999 MW 5:00 PM – 9:20 PM RIDDELL Increased breakdown of glycogen in liver cells The Sympathetic Division Sympathetic activation and neurotransmitter release Sympathetic ganglion fibers release acetylcholine at the synapse with ganglionic neurons These are cholinergic synapses The stimulation of ganglionic neurons causes the release of norepinephrine at the neuroeffector junction These terminals are adrenergic Some ganglionic neurons also release acetylcholine Especially at the neuroeffector junctions of skeletal muscles The Sympathetic Division Summary of the Sympathetic Division Consists of parallel chains on either side of the spinal cord Preganglionic fibers are short and extend from the spinal cord to the sympathetic chain Postganglionic fibers are long and extend from the spinal cord to the body organs The sympathetic division shows considerable divergence All preganglionic neurons release ACh / most postganglionic neurons release norepinephrine 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 The Parasympathetic Division Organization and Anatomy of the Parasympathetic Division Preganglionic fibers leave the brain via: CN III (to the intrinsic eye muscles, pupil, and lens) CN VII (to the tear glands and salivary glands) CN IX (to the parotid salivary glands) CN X (to the visceral organs of the thoracic cavity and abdominal cavity) Preganglionic fibers leave the sacral region via: Pelvic nerves (to the visceral organs in the inferior portion of the abdominopelvic cavity The Parasympathetic Division Functions of the Parasympathetic Division Pupil constriction Secretion of digestive enzymes from digestive glands Increased smooth muscle activity of the digestive system Stimulation and coordination of defecation Contraction of the urinary bladder Constriction of respiratory passages © 2012 Pearson Education, Inc. Page 4 of 6 565331767 Biology 218 – Human Anatomy Lecture Outline Adapted from Martini Human Anatomy 7th ed. Session: Section: Days / Time: Instructor: FALL 52999 MW 5:00 PM – 9:20 PM RIDDELL Reduced heart rate Sexual arousal The Parasympathetic Division Parasympathetic Activation and Neurotransmitter Release All preganglionic and postganglionic fibers release ACh at their synapses and neuroeffector junctions Most stimulations are short lived due to the immediate breakdown of ACh by acetylcholinesterase The Parasympathetic Division Plasmalemma Receptors and Responses Two types of ACh receptors are found on the postsynaptic plasmalemmae: Nicotinic receptors: respond to nicotine Found on surfaces of parasympathetic and sympathetic ganglionic neurons Muscarinic receptors: respond to muscarine Found on surfaces of parasympathetic cholinergic neuroeffector junctions The Parasympathetic Division Summary of the Parasympathetic Division Involves CN III, CN VII, CN IX, and CN X Involves sacral segments S2 to S4 All parasympathetic neurons are cholinergic Release of ACh stimulates nicotinic receptors on ganglionic neurons Release of ACh on neuroeffector junctions stimulates muscarinic receptors 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 Relationships between the Sympathetic and Parasympathetic Divisions Anatomy of Dual Innervation Head region The parasympathetic fibers accompany the sympathetic fibers to the target organ Thoracic and abdominopelvic regions The parasympathetic and sympathetic fibers mingle together forming plexuses Cardiac plexus Pulmonary plexus Esophageal plexus Celiac plexus Inferior mesenteric plexus Hypogastric plexus Visceral Reflexes © 2012 Pearson Education, Inc. Page 5 of 6 565331767 Biology 218 – Human Anatomy Lecture Outline Adapted from Martini Human Anatomy 7th ed. Session: Section: Days / Time: Instructor: FALL 52999 MW 5:00 PM – 9:20 PM RIDDELL Provide autonomic motor responses to: Modify or facilitate higher centers All are polysynaptic Reflexes can be: Long reflexes Short reflexes Visceral Reflexes Long Reflexes Visceral sensory neurons go to the CNS via the dorsal roots There are interneurons within the CNS Information is “interpreted” in the spinal cord or brain ANS sends motor commands to the visceral organs Visceral Reflexes Short Reflexes Sensory nerve impulses go to the ganglionic neurons Motor commands are distributed by the postganglionic fibers Impulses bypass the CNS © 2012 Pearson Education, Inc. Page 6 of 6 565331767
