Download Chapter 15 - Las Positas College

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prepared by Leslie Hendon,
University of Alabama,
Birmingham
15
HUMAN
ANATOMY
fifth edition
MARIEB | MALLATT | WILHELM
PART 1
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
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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
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The Autonomic Nervous System
and Visceral Sensory Neurons
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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
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Autonomic and Somatic Motor Systems
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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
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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
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
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Anatomical Differences in Sympathetic
and Parasympathetic Divisions

Neurotransmitter released by postganglionic axons
 Sympathetic –
 most release norepinephrine (adrenergic)
 Parasympathetic –
 release acetylcholine (cholinergic)
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Anatomical Differences in Sympathetic
and Parasympathetic Divisions
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Figure 15.4a
Anatomical Differences in Sympathetic
and Parasympathetic Divisions
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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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The Parasympathetic Division
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Figure 15.5
Cranial Outflow (Parasympathetic)

Preganglionic fibers run via
 Oculomotor nerve (III)
 Facial nerve (VII)
 Glossopharyngeal nerve (IX)
 Vagus nerve (X)

Cell bodies of CNs located in cranial nerve nuclei
in the brain stem
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Outflow via the Oculomotor Nerve (III)

Parasympathetic fibers innervate smooth muscles
in the eye
 Cause pupil constriction

Preganglionic cell bodies
 Located in the oculomotor nucleus in the midbrain

Ganglionic cell bodies
 Lie in the ciliary ganglion
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Outflow via the Facial Nerve (VII)


Parasympathetic fibers stimulate secretion of
glands in the head
Lacrimal nucleus
 Located in the pons
 Synapse in the pterygopalatine ganglion

Superior salivatory nucleus
 Located in the pons
 Synapse in the submandibular ganglion
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Outflow via the Glossopharyngeal Nerve (IX)

Parasympathetic fibers
 Stimulate secretion of glands in the head
 Lacrimal nucleus – located in the pons

Synapse in the pterygopalatine ganglion
 Superior salivatory nucleus – located in the pons

Synapse in the submandibular ganglion
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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
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Path of the Vagus Nerve
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Figure 15.6
PowerPoint® Lecture Slides
prepared by Leslie Hendon,
University of Alabama,
Birmingham
15
HUMAN
ANATOMY
fifth edition
MARIEB | MALLATT | WILHELM
PART 2
The
Autonomic
Nervous
System and
Visceral
Sensory
Neurons
Copyright © 2008 Pearson Education, Inc.,
publishing as Benjamin Cummings
Sacral Outflow



Emerges from S2–S4
Innervates organs of the pelvis and lower
abdomen
Preganglionic cell bodies
 Located in visceral motor region of spinal gray
matter
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Sacral Outflow

Axons run in ventral roots to ventral rami
 Form splanchnic nerves
 Run through the inferior hypogastric plexus
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The Sympathetic Division

Basic organization
 Issues from T1–L2
 Preganglionic fibers form the lateral gray horn
 Supplies visceral organs and structures of
superficial body regions
 Contains more ganglia than the parasympathetic
division
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Sympathetic Trunk Ganglia


Located on both sides of the vertebral column
Linked by short nerves into sympathetic trunks
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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
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Figure 15.8
Prevertebral Ganglia




Unpaired, not segmentally arranged
Occur only in abdomen and pelvis
Lie anterior to the vertebral column
Main ganglia
 Celiac, superior mesenteric, inferior mesenteric,
and inferior hypogastric ganglia
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Sympathetic Division of the ANS
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Figure 15.7
Sympathetic Pathways to the Body Periphery

Innervate
 Sweat glands
 Arrector pili muscles
 Peripheral blood vessels
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Sympathetic Pathways to the Body Periphery
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Figure 15.9
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
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Sympathetic Pathways to the Head

Postganglionic fibers associate with large arteries
 Carried by these structures to
 Glands
 Smooth muscle
 Vessels throughout the head
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Sympathetic Pathways to the Head
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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
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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
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Sympathetic Pathways to Thoracic Organs
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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
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Sympathetic Pathways to the Abdominal Organs
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Figure 15.12
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
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Sympathetic Pathways to the Pelvic Organs
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Figure 15.13
The Role of the Adrenal Medulla in the Sympathetic Division




Major organ of the sympathetic nervous system
Constitutes largest sympathetic ganglia
Secretes great quantities of norepinephrine and
adrenaline
Stimulated to secrete by preganglionic
sympathetic fibers
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The Adrenal Medulla
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Figure 15.14
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Table 15.2 (1 of 3)
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Table 15.2 (2 of 3)
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Table 15.2 (3 of 3)
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
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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
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Central Control of the ANS
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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
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Disorders of the Autonomic Nervous System

Mass reflex reaction
 Uncontrolled activation of autonomic and somatic
motor neurons
 Affects quadriplegics and paraplegics

Achalasia of the cardia
 Defect in the autonomic innervation of the
esophagus
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The ANS Throughout Life



Preganglionic neurons of the ANS develop from
the neural tube
Ganglionic neurons develop from the neural crest
Development of the sympathetic division
 Some cells migrate ventrally
 Form the sympathetic trunk ganglia
 Other cells migrate
 Form the prevertebral ganglia
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The ANS Throughout Life
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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
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