Download Autonomic nervous system

The Autonomic
Nervous System and
Visceral Sensory Neurons
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
The ANS and Visceral Sensory Neurons


The ANS – a system of motor neurons
Innervates
 Smooth muscle
 Cardiac muscle
 Glands
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
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
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
The Autonomic Nervous System
and Visceral Sensory Neurons
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.1
Comparison of Autonomic and Somatic Motor Systems

Somatic motor system
 One motor neuron extends from the CNS to skeletal
muscle
 Axons are well myelinated, conduct impulses
rapidly
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Comparison of Autonomic and Somatic Motor Systems

Autonomic nervous system
 Chain of two motor neurons
 Preganglionic neuron
 Ganglionic neuron
 Conduction is slower than somatic nervous system
due to
 Thinly myelinated or unmyelinated axons
 Motor neuron synapses in a ganglion
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Autonomic and Somatic Motor Systems
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.2
Divisions of the Autonomic Nervous System

Sympathetic and parasympathetic divisions
 Chains of two motor neurons
 Innervate mostly the same structures
 Cause opposite effects
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Divisions of the Autonomic Nervous System

Sympathetic – “fight, flight, or fright”
 Activated during EXTREME situations
 Exercise
 Excitement
 Emergencies

Parasympathetic – “rest and digest”
 Concerned with conserving energy
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Anatomical Differences in Sympathetic
and Parasympathetic Divisions

Issue from different
regions of the CNS
 Sympathetic – also called
the thoracolumbar
division
 Parasympathetic – also
called the craniosacral
division
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Figure 15.3
Sympathetic part
 Lower center: located

in lateral gray horn of
spinal cord segments
T1~L3
Sympathetic ganglia


Paravertebral ganglia
Prevertebral ganglia
Paravertebral ganglia
 Arranged on either side of

vertebral column
Consist of 19~22 of ovalshaped ganglia





Three cervical
10~12 thoracic
4 lumbar
2~3 sacral
Ganglion impar: unpaired
on the anterior face of
coccyx
Sympathetic trunk



Formed by paravertebral
ganglia and interganglionic
branches
Lie on either side of vertebral
column from base of skull to
coccyx
The trunks of two side unite in
front of the coccyx at a small
swelling, the ganglion impar
Prevertebral ganglia





Lie anterior to vertebral
column and near the arteries
for which they are named
Celiac ganglion
Aorticorenal ganglion
Superior mesenteric ganglion
Inferior mesenteric ganglion
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
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Anatomical Differences in Sympathetic
and Parasympathetic Divisions

Neurotransmitter released by postganglionic axons
 Sympathetic –
 most release norepinephrine (adrenergic)
 Parasympathetic –
 release acetylcholine (cholinergic)
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Anatomical Differences in Sympathetic
and Parasympathetic Divisions
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.4a
Anatomical Differences in Sympathetic
and Parasympathetic Divisions
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.4b
Parasympathetic and Sympathetic Divisions
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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
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Cranial portion
Ⅲ
ciliary ganglion
sphincter pupillae
and ciliary
muscles
lacrimal gland
Ⅶ pterygopalatine ganglion
Ⅸ
Ⅹ
sublingual gland
submandibular gland
submandibular ganglion
parotid gland
otic ganglion
heart, lungs, liver, spleen
kidneys,alimentary tract
terminal ganglia
as far as left colic flexure
PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
15
HUMAN
ANATOMY
fifth edition
MARIEB | MALLATT | WILHELM
Copyright © 2008 Pearson Education, Inc.,
publishing as Benjamin Cummings
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

Ganglionic neurons
 Confined within the walls of organs being
innervated
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Path of the Vagus Nerve

Sends branches through
 Autonomic nerve plexuses
 Cardiac plexus
 Pulmonary plexus
 Esophageal plexus
 Celiac plexus
 Superior mesenteric plexus
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Path of the Vagus Nerve
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.6
Sacral portion



Preganglionic fibers from sacral
parasympathetic nucleus leave
spinal cord with anterior roots of
the spinal nerves S2~S4,
Then leave sacral nerves and form
pelvic splanchnic nerve and travel
by way of pelvic plexus to
terminal ganglia in pelvic cavity
Postganglionic fibers terminate in
descending and sigmoid colon,
rectum and pelvic viscera
Main differences between sympathetic and
parasympathetic
Visceral plexuses

Cardiac plexuses


Superficial , below aortic
arch
Deep, anterior to
bifurcation on trachea
 Pulmonary plexus
 Celiac plexus
 Abdominal aortic plexus
 Hypogastric plexus


Superior hypogastric
plexus
Inferior hypogastric plexus
(pelvic plexus)
Autonomic plexuses in the abdomen and pelvis
Illustrator: Markus Voll
Gilroy et al., THIEME Atlas of Anatomy. All rights reserved. © THIEME 2008, www.thieme.com
Sympathetic Trunk Ganglia


Joined to ventral rami by white and gray rami
communicantes
Fusion of ganglia  fewer ganglia than spinal
nerves
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Sympathetic Trunk Ganglia
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.8
Autonomic nervous system circuitry.
Illustrator: Karl Wesker
Gilroy et al., THIEME Atlas of Anatomy. All rights reserved. © THIEME 2008, www.thieme.com
Three fates of preganglionic fibers
15 pairs white communicating branch
Preganglionic fibers (only spinal levels T1~L3 have
white communicating branch)
Sympathetic trunk
Three fates of preganglionic fibers
 Relay in corresponding


ganglion
Ascend or descend in
sympathetic trunk and relay
in higher or lower ganglia
Pass without synapse to a
prevertebral ganglion for
relay
Three fates of postganglionic fibers



Back to a spinal nerve along
gray communicating
branches ( 31 pairs ) to
terminate in blood vessels,
arrectores pilorum and sweat
glands of head, neck, trunk and
limbs
The fibers from their networks
around blood vessels passing
to visceral end organs
Terminate directly in certain
organs
Sympathetic Pathways to the Body Periphery

Innervate
 Sweat glands
 Arrector pili muscles
 Peripheral blood vessels
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Sympathetic Pathways to the Head


Preganglionic fibers originate in spinal cord at
T1–T4
Fibers ascend in the sympathetic trunk
 Synapse in superior cervical ganglion
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Sympathetic Pathways to the Head
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.10
Sympathetic Pathways to Thoracic Organs



Preganglionic fibers originate at spinal levels T1–
T6
Some fibers synapse in nearest sympathetic trunk
ganglion
Postganglionic fibers run directly to the organ
supplied
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Sympathetic Pathways to Thoracic Organs


Sympathetic fibers to heart have a less direct
route
Functions
 Increase heart rate
 Dilate bronchioles
 Dilate blood vessels to the heart wall
 Inhibit muscles and glands in the esophagus and
digestive system
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Sympathetic Pathways to Thoracic Organs
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.11
Sympathetic Pathways to Abdominal Organs


Preganglionic fibers originate in spinal cord (T5–
L2)
Pass through adjacent sympathetic trunk ganglia
 Then travel in thoracic splanchnic nerves
 Synapse in prevertebral ganglia on the abdominal
aorta
 Celiac and superior mesenteric ganglia
 Inhibit activity of muscles and glands in visceral
organs
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Sympathetic Pathways to the Abdominal Organs
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.12

Greater splanchnic nerve formed by
preganglionic fibers from T5~T9 ganglia,
and relay in celiac ganglion.

Lesser splanchnic nerve formed by
preganglionic fibers from T10~T12 ganglia,
and relay in aorticorenal ganglion.

The postganglionic fibers supply the liver,
spleen, kidney and alimentary tract as far as
the left colic flexure.
Sympathetic Pathways to the Pelvic Organs




Preganglionic fibers originate in spinal cord
(T10 –L2)
Some fibers synapse in sympathetic trunk
Other preganglionic fibers synapse in
prevertebral ganglia
Postganglionic fibers proceed from plexuses to
pelvic organs
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Sympathetic Pathways to the Pelvic Organs
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.13
The Adrenal Medulla
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.14
Visceral Sensory Neurons

General visceral sensory neurons monitor
 Stretch, temperature, chemical changes, and
irritation


Cell bodies are located in the dorsal root ganglion
Visceral pain – perceived to be somatic in origin
 referred pain
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A Map of Referred Pain
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Figure 15.15
Visceral Reflexes

Visceral sensory and autonomic neurons
 Participate in visceral reflex arcs
 Defecation reflex
 Micturition reflex


Some are simple spinal reflexes
Others do not involve the CNS
 Strictly peripheral reflexes
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Visceral Reflex Arc
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.16
Central Control of the ANS

Control by the brain stem and spinal cord
 Reticular formation exerts most direct influence
 Medulla oblongata
 Periaqueductal gray matter
 Control by the hypothalamus and amygdala
 Hypothalamus – the main integration center of the
ANS
 Amygdala – main limbic region for emotions
 Control by the cerebral cortex
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Central Control of the ANS
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.17
Disorders of the Autonomic Nervous System

Raynaud’s disease – characterized by
constriction of blood vessels
 Provoked by exposure to cold or by emotional
stress

Hypertension – high blood pressure
 Can result from overactive sympathetic
vasoconstriction
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Sympathectomy: raynaud disease
PAMEL
P for Ptosis, Anhydrosis, Miosis, Enophthalmos and Loss of
ciliospinal reflex
Disorders of the Autonomic Nervous System

Achalasia of the cardia
 Defect in the autonomic innervation of the
esophagus
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 1 Esophagrams of a patient with early achalasia pre- and posttreatment.
GI Motility online (May 2006) | doi:10.1038/gimo53
The ANS Throughout Life
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.18
The ANS Throughout Life

Efficiency of the ANS declines with advancing
age
 Constipation due to reduced mobility of
gastrointestinal (GI) tract
 Dry eyes due to reduced tear formation
Copyright © 2008 Pearson Education, Inc., publishing as Benjamin Cummings
EPSP :Excitatory post synaptic potential
Regulatory effects of the autonomic neurotransmitters



Two Symp. Receptor α &
β
α is excitatory
β is often inhibitory
Illustrator: Karl Wesker
Gilroy et al., THIEME Atlas of Anatomy. All rights reserved. © THIEME 2008, www.thieme.com
Stimulating & Blocking agents


Stimulating agents such
as nicotine,
lobeline,methylphenol
piperazium
Blocking agents such as
nicotin in high
concentration and
hexamethonium,
tetraethylammonium
Blocking of cholinergic & adernergic receptors




Cholinergic atropine(antagonist)
Adrenergic
Alpha receptor phenoxybenzamine
Beta receptor proprranolol