Autonomic Nervous System

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17 The Nervous System: Autonomic Nervous System

PowerPoint® Lecture Presentations prepared by Steven Bassett Southeast Community College Lincoln, Nebraska

• 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

• 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 Autonomic Nervous Systems

• 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

THORACOLUMBAR DIVISION CRANIOSACRAL DIVISION (sympathetic (parasympathetic division of ANS) division of ANS)

Cranial nerves (N III, N VII, N IX, and N X)

T1 T2

T5 T Thoracic 6 nerves 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. © 2012 Pearson Education, Inc. Figure 17.1b Components and Anatomic Subdivisions of the ANS (Part 2 of 2)

T9 T Thoracic 10

nerves T11

T12

L1 Lumbar

nerves (L1, L2 only) L2

S2 Sacral nerves S3 (S2, S3, S4 only) S4

• 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

• 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.

Consists of 2 divisions

SYMPATHETIC PARASYMPATHETIC (thoracolumbar) (craniosacral) DIVISION DIVISION

Preganglionic Preganglionic neurons in brain neurons in stem and in lateral lateral gray horns of portion of anterior spinal segments T1–L2 gray horns of S2–S4

Send preganglionic fibers to

Ganglia near Ganglia in or spinal cord near target organs Preganglionic fibers Preganglionic fibers release ACh (excitatory), release ACh (excitatory), stimulating stimulating ganglionic neurons ganglionic neurons

Which send postganglionic fibers to

Target organs Target organs Most postganglionic All postganglionic fibers fibers release NE at release ACh at neuroeffector junctions neuroeffector junctions

“Fight or flight” “Rest and repose” response response

• 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

• 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

•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

Sympathetic Division of ANS

Innervation by postganglionic

fibers Ganglionic Neurons Target Organs

Preganglionic Visceral effectors Neurons Sympathetic in thoracic cavity, chain ganglia head, body wall, (paired) and limbs Lateral gray horns of spinal Collateral Visceral effectors segments ganglia in abdominopelvic (unpaired) T1–L2 cavity Suprarenal medullae Organs and systems

(paired) throughout body KEY Preganglionic fibers Through release of hormones into Postganglionic fibers the circulation Hormones released into circulation

• 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

• 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

Sympathetic Chain Ganglia Major effects produced by sympathetic postganglionic Spinal nerve Preganglionic Autonomic ganglion of fibers in spinal nerves: neuron right sympathetic chain • Constriction of cutaneous blood vessels, reduction in circulation to the skin and to most other organs in Autonomic ganglion the body wall Innervates of left sympathetic chain • Acceleration of blood flow to skeletal muscles visceral and brain effectors via • Stimulation of energy production and use by skeletal spinal nerves muscle tissue • Release of stored lipids from subcutaneous White adipose tissue ramus • Stimulation of secretion by sweat glands Sympathetic nerve • Stimulation of arrector pili Ganglionic • Dilation of the pupils and focusing for distant objects (postganglionic neuron fibers) Gray ramus Major effects produced by postganglionic fibers Innervates visceral entering the thoracic cavity in sympathetic nerves: organs in thoracic • Acceleration of heart rate and increasing the cavity via KEY strength of cardiac contractions sympathetic nerves • Dilation of respiratory passageways Preganglionic neurons Ganglionic neurons

• Anatomy of the Sympathetic Chain Ganglia • Each spinal nerve consists of: • Preganglionic and postganglionic fibers • There are: • cervical sympathetic chain ganglia • thoracic sympathetic chain ganglia • lumbar sympathetic chain ganglia • sacral sympathetic chain ganglia • coccygeal sympathetic chain ganglia

Eye

PONS

Salivary glands

Sympathetic nerves Superior Middle Cervical Heart sympathetic ganglia Inferior Cardiac and T1 T1 pulmonary Greater plexuses Gray rami to T2 T2 splanchnic spinal nerves T3 T3 nerve Lung Celiac ganglion T4 T4

T5 T5 Superior T6 T6 mesenteric Liver and ganglion gallbladder T7 T7

T8 T8 Stomach

T9 T9 Lesser splanchnic Spleen T10 T10 nerve Pancreas T11 T11

T12 T12 Large intestine Postganglionic fibers L1 L1 to spinal nerves Lumbar L2 L2 (innervating skin, blood splanchnic nerves Inferior Small intestine vessels, sweat glands, L mesenteric L3 3 ganglion arrector pili muscles, L L adipose tissue) 4 4 L L 5 5 Suprarenal S S 1 1 Sacral medulla S2 S2 S S splanchnic Sympathetic 3 3 Kidney S4 S4 nerves chain ganglia S5 S5

Spinal cord Coccygeal KEY ganglia (Co1) Preganglionic neurons fused together Ganglionic neurons (ganglion impar) Uterus Ovary Penis Scrotum Urinary bladder © 2012 Pearson Education, Inc. 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

• 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

Collateral Ganglia 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 Lateral gray horn organs • Stimulation of the release of glucose from glycogen reserves in the liver Splanchnic nerve White • Stimulation of the release of lipids from adipose (preganglionic ramus tissue fibers) • Relaxation of the smooth muscle in the wall of the urinary bladder • Reduction of the rate of urine formation at the kidneys Collateral Innervates • Control of some aspects of sexual function, such as Postganglionic ganglion visceral organs in ejaculation in males fibers abdominopelvic cavity

• 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

• 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

• 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 • Increased breakdown of glycogen in liver cells

The Suprarenal Medullae Major effect produced by preganglionic fibers innervating the suprarenal medullae: • Release of epinephrine and norepinephrine into the general circulation

Preganglionic fibers Suprarenal Secretes medullae neurotransmitters Endocrine cells into general (specialized ganglionic circulation neurons)

Cortex

Medulla Suprarenal gland

Right kidney

Modified neurons Capillaries (sympathetic ganglion cells) Cortex of suprarenal medulla

Medulla

Nucleolus in nucleus

Suprarenal medulla LM  426

Histology of the suprarenal medulla, Relationship of a suprarenal gland to a kidney a modified sympathetic ganglion

• 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

Postganglionic fiber (unmyelinated) Ganglion

Varicosities

Vesicles containing Mitochondrion norepinephrine

Schwann cell cytoplasm

5 m

• 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

Eye

PONS

Salivary glands

T5 T5 Superior T6 T6 mesenteric Liver and ganglion gallbladder T7 T7

T8 T8 Stomach

T9 T9 Lesser splanchnic Spleen T10 T10 nerve Pancreas T11 T11

ANIMATION The Distribution of Sympathetic Innervation

• 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

• 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

Preganglionic Neurons Ganglionic Neurons Target Organs N III Nuclei in Intrinsic eye muscles brain stem Ciliary ganglion (pupil and lens shape) N VII

N IX Pterygopalatine Nasal glands, tear and submandibular glands, and salivary ganglia glands

Otic ganglion Parotid salivary gland N X

Intramural Visceral organs ganglia of neck, thoracic cavity, and most of abdominal cavity

Pelvic Nuclei in Visceral organs in spinal cord nerves Intramural KEY inferior portion of segments ganglia Preganglionic fibers abdominopelvic cavity S2–S4

Postganglionic fibers

N III Lacrimal gland

Eye Ciliary ganglion PONS N VII Salivary glands Submandibular ganglion N IX

Otic ganglion

N X (Vagus) Heart

Lungs

Autonomic plexuses (see Figure 17.9) Liver and gallbladder Stomach

Spleen

Pancreas

Large intestine

Pelvic Small intestine nerves Rectum

Spinal S Kidney cord 2 S3

• 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 • Reduced heart rate • Sexual arousal

• 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

• 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

• 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

ANIMATION The Distribution of Parasympathetic Innervation

• 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

CNS Preganglionic neuron

PNS Preganglionic KEY Sympathetic fiber Neurotransmitters ganglion Acetylcholine Norepinephrine or Epinephrine

Ganglionic neurons

Circulatory system Postganglionic Parasympathetic fiber ganglion

TARGET

• 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

Trachea

Left vagus nerve

Right vagus nerve Autonomic Plexuses Aortic arch and Ganglia

Thoracic Cardiac plexus spinal nerves

Pulmonary plexus

Thoracic sympathetic Esophagus chain ganglia

Splanchnic Esophageal plexus nerves Celiac plexus and ganglion Diaphragm Superior mesenteric ganglion Celiac trunk

Superior mesenteric Inferior mesenteric artery plexus and ganglion Inferior mesenteric artery

Hypogastric plexus

Pelvic sympathetic chain

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. Figure 17.9b The Peripheral Autonomic Plexuses

Cranial nerve III

Cranial nerve VII

Cranial nerve IX

Vagus nerve (N X)

Trachea Autonomic Plexuses and Ganglia

Cardiac plexus

Esophagus

Thoracic sympathetic Heart chain ganglia Esophageal plexus Diaphragm

Stomach Celiac plexus and ganglion Superior mesenteric ganglion

Inferior mesenteric plexus and ganglion

Hypogastric plexus Colon

Urinary Pelvic sympathetic bladder chain

• Provide autonomic motor responses to: • Modify or facilitate higher centers • All are polysynaptic • Reflexes can be: • Long reflexes • Short 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

• Short Reflexes • Sensory nerve impulses go to the ganglionic neurons • Motor commands are distributed by the postganglionic fibers • Impulses bypass the CNS

Receptors in Afferent (sensory) peripheral tissue fibers CENTRAL NERVOUS SYSTEM Stimulus

Long reflex Short reflex

Processing center in spinal cord (or brain) Peripheral Response effector Autonomic ganglion Ganglionic (sympathetic or Preganglionic neuron parasympathetic) neuron