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© 2012 Pearson Education, Inc.
17The Nervous System: Autonomic Nervous System
PowerPoint® Lecture Presentations prepared bySteven BassettSoutheast Community College Lincoln, Nebraska
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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.
© 2012 Pearson Education, Inc.
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)
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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)
Sympatheticchain ganglia
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
Figure 17.3c Sympathetic Pathways and Their General Functions
The Suprarenal Medullae
Secretesneurotransmitters
into generalcirculation
Suprarenalmedullae
Preganglionic fibers
Endocrine cells(specialized ganglionic
neurons)
• Release of epinephrine and norepinephrine into the general circulation
Major effect produced by preganglionic fibersinnervating the suprarenal medullae:
© 2012 Pearson Education, Inc.
Figure 17.5a Suprarenal Medulla
Relationship of a suprarenal gland to a kidney
Cortex
Medulla
Suprarenalgland
Rightkidney
© 2012 Pearson Education, Inc.
The Sympathetic Division
• 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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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)
Sympatheticchain ganglia
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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
Preganglionic fibers
Postganglionic fibers
Parotid salivary gland
© 2012 Pearson Education, Inc.
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
Liver andgallbladder
Stomach
Spleen
Pancreas
Large intestine
Small intestine
Rectum
Kidney
Urinary bladderScrotumPenisOvaryUterus
S2
S3
S4
Spinalcord
Preganglionic neuronsGanglionic neurons
KEY
© 2012 Pearson Education, Inc.
The Parasympathetic Division
• 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
© 2012 Pearson Education, Inc.
The Parasympathetic Division
• 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
© 2012 Pearson Education, Inc.
The Parasympathetic Division
• 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.
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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
© 2012 Pearson Education, Inc.
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