ch 17_lecture_presentation

© 2012 Pearson Education, Inc.

17The Nervous System: Autonomic Nervous System

PowerPoint® Lecture Presentations prepared bySteven BassettSoutheast Community College Lincoln, Nebraska


Introduction

• The autonomic nervous system functionsoutside of our conscious awareness

• The autonomic nervous system makesroutine 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

ANIMATION The Organization of the Somatic and Autonomic Nervous Systems


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.


Figure 17.1b Components and Anatomic Subdivisions of the ANS (Part 1 of 2)

Anatomical subdivisions. At the thoracic and lumbarlevels, the visceral efferent fibers that emerge form thesympathetic division, detailed in Figure 17.4. At thecranial and sacral levels, the visceral efferent fibersfrom the CNS form the parasympathetic division,detailed in Figure 17.8.

Thoracicnerves

T1

T2

T3

T4

T5

T6

T7

T8

AUTONOMIC NERVOUS SYSTEM

THORACOLUMBAR DIVISION(sympathetic

division of ANS)

CRANIOSACRAL DIVISION(parasympatheticdivision of ANS)

Cranial nerves(N III, N VII, N IX,

and N X)


Figure 17.1b Components and Anatomic Subdivisions of the ANS (Part 2 of 2)

Anatomical subdivisions. At the thoracic and lumbarlevels, the visceral efferent fibers that emerge form thesympathetic division, detailed in Figure 17.4. At thecranial and sacral levels, the visceral efferent fibersfrom the CNS form the parasympathetic division,detailed in Figure 17.8.

Sacralnerves

(S2, S3, S4 only)

Lumbarnerves (L1, L2 only)

Thoracicnerves

T10

T11

T12

L1

L2

L3

L4

L5

S1

S2

S3

S4

S5

T9


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


Figure 17.1a Components and Anatomic Subdivisions of the ANS

AUTONOMIC NERVOUS SYSTEM

Consists of 2 divisions

SYMPATHETIC(thoracolumbar)

DIVISION

PARASYMPATHETIC(craniosacral)

DIVISION

Preganglionicneurons in

lateral gray horns ofspinal segments T1–L2

Preganglionicneurons in brain

stem and in lateralportion of anteriorgray horns of S2–S4

Send preganglionicfibers to

Which send postganglionicfibers to

Ganglia nearspinal cord

Ganglia in ornear target organs

Preganglionic fibersrelease ACh (excitatory),

stimulatingganglionic neurons

Preganglionic fibersrelease ACh (excitatory),

stimulatingganglionic neurons

Target organs Target organs

Most postganglionicfibers release NE at

neuroeffector junctions

All postganglionic fibersrelease ACh at

neuroeffector junctions

“Fight or flight”response

“Rest and repose”response

Functional components of the ANS


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



• 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


Figure 17.2 Organization of the Sympathetic Division of the ANS

Preganglionic fibers

Postganglionic fibers

Hormones releasedinto circulation

KEY

Lateral grayhorns of spinal

segmentsT1–L2

Sympatheticchain ganglia

(paired)Collateralganglia

(unpaired)

Suprarenalmedullae(paired)

PreganglionicNeurons

Ganglionic Neurons

Innervation bypostganglionic

fibers

Through release ofhormones intothe circulation

Target Organs

Visceral effectorsin thoracic cavity,head, body wall,

and limbs

Visceral effectorsin abdominopelvic

cavity

Organs and systemsthroughout body

Sympathetic Division of ANS


Figure 17.3a Sympathetic Pathways and Their General Functions

Sympathetic Chain Ganglia

KEYPreganglionic neuronsGanglionic neurons

Innervates visceralorgans in thoracic

cavity viasympathetic nerves

Sympathetic nerve(postganglionic

fibers)

Autonomic ganglionof left sympathetic chain

Spinal nerve Preganglionicneuron

Autonomic ganglion ofright sympathetic chain

Innervatesvisceral

effectors viaspinal nerves

White ramus

Ganglionicneuron

Gray ramus

Major effects produced by sympathetic postganglionicfibers in spinal nerves:

Major effects produced by postganglionic fibersentering the thoracic cavity in sympathetic 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

• Acceleration of heart rate and increasing the strength of cardiac contractions• Dilation of respiratory passageways


Figure 17.4 Anatomical Distribution of Sympathetic Postganglionic Fibers

Superior

Middle

Inferior

PONS

Cervicalsympathetic

ganglia

Gray rami tospinal nerves

Greatersplanchnic

nerve

Superiormesenteric

ganglion

Cardiac andpulmonaryplexuses

Celiac ganglion

Sympathetic nerves

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

L3L3

L4 L4

L5 L5

S1 S1

S2 S2

S3 S3S4

S4S5

S5

Postganglionic fibersto spinal nerves

(innervating skin, bloodvessels, sweat glands,arrector pili muscles,

adipose tissue)


Spinal cord

Coccygealganglia (Co1)

fused together(ganglion impar)

Preganglionic neuronsGanglionic neurons

KEY

Uterus Ovary

Sacralsplanchnic

nerves

Lessersplanchnic

nerve

Lumbarsplanchnic nerves Inferior

mesentericganglion

Penis Scrotum Urinary bladder

Kidney

Suprarenalmedulla

Small intestine

Large intestine

Pancreas

Spleen

Stomach

Liver andgallbladder

Lung

Heart

Eye

Salivaryglands


Figure 17.3b Sympathetic Pathways and Their General Functions

Collateral Ganglia

Lateral gray horn

White ramus

CollateralganglionPostganglionic

fibers

Splanchnic nerve(preganglionic

fibers)

Innervatesvisceral organs inabdominopelvic

cavity

Major effects produced by preganglionic fibersinnervating 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


Figure 17.3c Sympathetic Pathways and Their General Functions

The Suprarenal Medullae

Secretesneurotransmitters

into generalcirculation

Suprarenalmedullae


Endocrine cells(specialized ganglionic

neurons)

• Release of epinephrine and norepinephrine into the general circulation

Major effect produced by preganglionic fibersinnervating the suprarenal medullae:


Figure 17.5a Suprarenal Medulla

Relationship of a suprarenal gland to a kidney

Cortex

Medulla

Suprarenalgland

Rightkidney



• 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


Figure 17.6 Sympathetic Postganglionic Nerve EndingsPreganglionic fiber

(myelinated)Ganglionic

neuron

Ganglion

Postganglionic fiber(unmyelinated)

Varicosities

Mitochondrion

5 m

Vesicles containingnorepinephrine

Schwann cellcytoplasm

Smooth muscle cells Varicosities


Figure 17.4 Anatomical Distribution of Sympathetic Postganglionic Fibers

Superior

Middle

Inferior

PONS

Cervicalsympathetic

ganglia

Gray rami tospinal nerves

Greatersplanchnic

nerve

Superiormesenteric

ganglion

Cardiac andpulmonaryplexuses

Celiac ganglion

Sympathetic nerves

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

L3L3

L4 L4

L5 L5

S1 S1

S2 S2

S3 S3S4

S4S5

S5

Postganglionic fibersto spinal nerves

(innervating skin, bloodvessels, sweat glands,arrector pili muscles,

adipose tissue)


Spinal cord

Coccygealganglia (Co1)

fused together(ganglion impar)


KEY

Uterus Ovary

Sacralsplanchnic

nerves

Lessersplanchnic

nerve

Lumbarsplanchnic nerves Inferior

mesentericganglion

Penis Scrotum Urinary bladder

Kidney

Suprarenalmedulla

Small intestine

Large intestine

Pancreas

Spleen

Stomach


Lung

Heart

Eye

Salivaryglands


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


Figure 17.7 Organization of the Parasympathetic Division of the ANS

Parasympathetic Division of ANS

Preganglionic Neurons Ganglionic Neurons Target Organs

Ciliary ganglion

Pterygopalatineand submandibular

ganglia

Otic ganglion

Intramuralganglia

Intrinsic eye muscles(pupil and lens shape)

Nasal glands, tearglands, and salivary

glands

Visceral organsof neck,

thoracic cavity,and most of

abdominal cavity

N III

N VII

N IX

N X

Nuclei inbrain stem

Nuclei inspinal cordsegments

S2–S4

Pelvicnerves Intramural

ganglia

Visceral organs ininferior portion of

abdominopelvic cavityKEY


Postganglionic fibers

Parotid salivary gland


Figure 17.8 Autonomic Distribution of the Parasympathetic OutputPterygopalatine ganglion

PONS

N III

N VII

N IX

N X (Vagus)

Ciliary ganglion

Submandibularganglion

Otic ganglion

Autonomic plexuses(see Figure 17.9)

Pelvicnerves

Lacrimal gland

Eye

Salivary glands

Heart

Lungs


Stomach

Spleen

Pancreas

Large intestine

Small intestine

Rectum

Kidney

Urinary bladderScrotumPenisOvaryUterus

S2

S3

S4

Spinalcord


KEY



• 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



• 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



• 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.


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 thesympathetic and parasympathetic nerves

• The two often oppose (antagonistic) each other


Figure 17.10 A Comparison of the Sympathetic and Parasympathetic Divisions

Sympathetic Parasympathetic

CNS

PNS

KEYSympatheticganglion

Circulatorysystem

Preganglionicneuron

Preganglionicfiber

Ganglionicneurons

Postganglionicfiber

TARGET

Parasympatheticganglion

Neurotransmitters

Acetylcholine

Norepinephrine

Epinephrineor


Figure 17.9a The Peripheral Autonomic Plexuses

This is a diagrammatic view of the distribution of ANS plexuses in thethoracic cavity (cardiac, esophageal, and pulmonary plexuses) and theabdominopelvic cavity (celiac, inferior mesenteric, and hypogastric plexuses).

Splanchnicnerves

Inferior mesentericartery

Superior mesentericartery

Celiac trunk

Diaphragm

Esophagus

Thoracicspinal

nerves

Left vagus nerve

Right vagus nerve

Aortic arch

Trachea

Cardiac plexus

Autonomic Plexusesand Ganglia

Pulmonary plexus

Thoracic sympatheticchain ganglia

Esophageal plexus

Celiac plexus andganglion

Superior mesentericganglion

Inferior mesentericplexus and ganglion

Pelvic sympatheticchain

Hypogastric plexus


Figure 17.9b The Peripheral Autonomic Plexuses

A sectional view of the autonomic plexuses

Cardiac plexus

Autonomic Plexusesand Ganglia

Thoracic sympatheticchain ganglia

Esophageal plexus

Celiac plexus andganglion

Superior mesentericganglion

Inferior mesentericplexus and ganglion

Pelvic sympatheticchain

Hypogastric plexus

Urinarybladder

Colon

Stomach

Diaphragm

Heart

Esophagus

Trachea

Vagus nerve(N X)

Cranial nerve III

Cranial nerve VII

Cranial nerve IX


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


Figure 17.11 Visceral Reflexes

Stimulus

Response

Receptors inperipheral tissue

Afferent (sensory)fibers

Shortreflex

Longreflex

Peripheraleffector

Ganglionicneuron

Preganglionicneuron

Processing centerin spinal cord

(or brain)

Autonomic ganglion(sympathetic or parasympathetic)

CENTRAL NERVOUSSYSTEM

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autonomic nervous systems

autonomic ganglia

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sympathetic ganglion

form thesympathetic

types of ganglionic

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