Transcript The Autonomic Nervous System

15
The Autonomic
Nervous System
PowerPoint® Lecture Presentations prepared by
Leslie Hendon
University of Alabama, Birmingham
© 2014 Pearson Education, Inc.
I. The Autonomic Nervous System (ANS)
A.The ANS is a system of motor neurons
B. The ANS is the general visceral motor division of the PNS
C. It innervates: Smooth muscle; Cardiac muscle; Glands
D. It regulates visceral functions such as:
1. Heart rate
2. Blood pressure
3. Digestion
4. Urination
E. It also contains the general visceral sensory system of the PNS
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Central nervous system (CNS)
Peripheral nervous system (PNS)
Sensory (afferent) division
Somatic
sensory
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Visceral
sensory
Motor (efferent) division
Somatic nervous
system
Autonomic nervous
system (ANS)
Sympathetic
division
Parasympathetic
division
II. Comparison Autonomic and Somatic Motor Systems
A. Somatic motor system
1. one motor neuron extends from the CNS to skeletal muscle
2. axons are well myelinated, conduct impulses rapidly
B. Autonomic nervous system
1. Chain of two motor neurons to smooth muscle, cardiac muscle,
glands
a. preganglionic neuron ► ►► postganglionic neuron
2. Conduction is slower than somatic nervous system because
a. axons are thinly myelinated (white) or nonmyelinated (grey)
b. motor neuron synapses in a ganglion outside the CNS
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III. Divisions of the Autonomic Nervous System
A. Sympathetic and parasympathetic divisions
1. chains of two motor neurons
2. innervate same structures - cause opposite effects
3. Sympathetic division - during extreme situations
a. examples: fear, rage, exercise
4. Parasympathetic division - routine maintenance functions
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B. Sympathetic -“fight or flight”
1. activated during EXTREME situations
a. examples: exercise, excitement, emergencies
2. sympathetic responses help respond to dangerous situations
a. increase heart rate and breathing rate
b. increase blood and oxygen to skeletal muscles
c. vasoconstriction of other blood vessels
d. dilate pupils and bronchioles
e. inhibit motility of the digestive tract and urinary tracts
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C. Parasympathetic – “rest and digest” (“sit or shit”)
1. Active when the body is at rest
2. Concerned with conserving energy
3. Directs “housekeeping” activities
a. digestion
b. elimination of feces and urine
c. heart rate, b.p. , respiration at low-normal levels
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Parasympathetic
Sympathetic
 Eye
(constricts
pupil)
Eye 
(dilates
pupil)
Brain stem
 Salivary
glands
 Heart
 Lungs
(constricts
airways)
Skin* 
Cranial
Sympathetic
ganglia
Cervical
Salivary 
glands
Lungs 
(dilates
airways)
T1
Heart 
Stomach 
 Stomach
Thoracic
Pancreas
Liver 
 Pancreas
Gall- 
bladder
L1
 Gallbladder
Adrenal 
gland
Lumbar
 Bladder
Bladder 
 Genitals
(erection)
Genitals 
(ejaculation)
Sacral
 stimulatory effect
 inhibitory effect
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IV. Anatomical Comparisons
A. Emerge from different regions of the CNS
1. sympathetic - also called the thoracolumbar division
a. originate from spinal segments (T1–L2)
2. parasympathetic - also called the craniosacral division
a. originate from III, VII, IX, X and (S2,3,4)
B. Length of postganglionic fibers
1. sympathetic - long postganglionic fibers
2. parasympathetic - short postganglionic fibers
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C. Branching of fibers
1. sympathetic fibers
a. highly branched; influence many organs at once
2. parasympathetic fibers
a. few branches; only localized effect
D. Neurotransmitter released by postganglionic axons
1. sympathetic - most release norepinephrine (adrenergic)
2. parasympathetic - release acetylcholine (cholinergic)
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© 2014 Pearson Education, Inc.
V. The Parasympathetic Division
A. Cranial outflow
1. originates from the brain (III, VII, IX, X)
2. innervates - organs of the head, neck, thorax, and abdomen
B. Sacral outflow
1. originates from spinal segments (S2,3,4)
2. “(S2,3,4) keeps your penis off the floor”
3. innervates - remaining abdominal and pelvic organs
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Ciliary
ganglion
CN III
Eye
Lacrimal
gland
CN VII
Pterygopalatine
ganglion
CN IX
Nasal
mucosa
CN X
Submandibular
ganglion
Submandibular
and sublingual
glands
Otic ganglion
Parotid gland
Heart
Cardiac and
pulmonary
plexuses
Lung
Preganglionic
CN
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Postganglionic
Cranial nerve
Celiac
plexus
Liver and
gallbladder
Stomach
Pancreas
S2
S3
Large
intestine
S4
Small
intestine
Pelvic
splanchnic
nerves
Inferior
hypogastric
plexus
Rectum
Urinary
bladder
and ureters
Genitalia (penis, clitoris, and vagina)
Preganglionic
CN
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Postganglionic
Cranial nerve
VI. Cranial Outflow (Parasympathetic)
A. Preganglionic fibers run via
1. oculomotor nerve (III)
2. facial nerve (VII)
3. glossopharyngeal nerve (IX)
4. vagus nerve (X)
B. Cell bodies of preganglionic neurons located in motor cranial
nerve nuclei in gray matter of the brain stem
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C. Oculomotor Nerve (III)
1. innervate smooth muscles in the eye
2. cause pupil constriction
D. Facial Nerve (VII)
1. stimulate secretions of glands in the head
2. examples: lacrimal gland, submandibular salivary glands
E. Glossopharyngeal Nerve (IX)
1. stimulate secretion of other salivary glands
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F. Vagus Nerve (X)
1. innervate visceral organs of the thorax and most of the abdomen
2. stimulates digestion, lower heart rate, and lower blood pressure
3. sends branches through autonomic nerve plexuses
a. cardiac plexus
b. pulmonary plexus
c. esophageal plexus
d. celiac plexus
e. superior mesenteric plexus
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Superior cervical
ganglion
Middle cervical
ganglion
Left vagus nerve
Cardiac branches
of the vagus
Stellate ganglion
Cardiac plexus
Pulmonary plexus
Vagus nerve
Esophageal plexus
Stomach with vagus nerve
Celiac plexus
Superior mesenteric
plexus
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VI. Sacral Outflow (Parasympathetic)
A. Emerges from S2 to S4
B. Innervates organs of the pelvis and lower abdomen
1. contraction of urinary bladder for urination
2. erection of the penis - (S2,3,4)
3. inhibits contraction of uterine smooth muscles
4. vasodilation - clitoris and contraction of smooth m. of vagina
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VI. The Sympathetic Division
A. Issues from T1 to L2
B. Preganglionic fibers form the lateral gray horn of spinal cord
C. Supplies visceral organs in internal body cavities and structures
of superficial body regions
D. Contains more ganglia than the parasympathetic division
E. Located on both sides of the vertebral column
F. Linked by short nerves into sympathetic trunks
G. Sympathetic trunk ganglia also called:
1. chain ganglia or
2. paravertebral ganglia
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VII. Sympathetic Trunk Ganglia
A Joined to ventral rami by white and gray rami communicantes
(the next picture will show what this actually means)
B. Fusion of ganglia  there are fewer ganglia than spinal nerves
C. Sympathetic ganglia form a “chain” along the vertebral column
1. most apparent in the cervical region
a. superior cervical ganglia
b. middle cervical ganglia
c. inferior cervical ganglia
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1. preganglionic nerve cell body in lateral horn of spinal cord
2. axon goes through ventral root of spinal nerve
3. to ventral ramus of spinal nerve
4. through white communicans (myelinated)
5. synapses on postganglionic nerve cell body in sympathetic
ganglion
6. postganglionic axon through grey communicans (unmyelinated!!!)
Lateral horn
(visceral
motor zone)
7. to effector organ
Ventral ramus of
spinal nerve
Gray ramus
communicans
White ramus
communicans
Skin (arrector
pili muscles
and sweat
glands)
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Sympathetic
trunk ganglion
Sympathetic trunk
To effector
Blood vessels
Ventral root
1. Synapses with a postganglionic neuron at the same
level and exit on a spinal nerve at that same level or
Lateral horn
(visceral
motor zone)
Ventral ramus of
spinal nerve
Gray ramus
communicans
White ramus
communicans
Skin (arrector
pili muscles
and sweat
glands)
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Sympathetic
trunk ganglion
Sympathetic trunk
To effector
Blood vessels
Ventral root
2. Synapses with a postganglionic neuron at a
different level and exits on a spinal nerve at
that same level
Skin (arrector
pili muscles
and sweat
glands)
To effector
Blood vessels
5
6
4
1. Preganglionic nerve in lateral horn
2. Ventral root of spinal nerve
3. White ramus communicans
1
4. Sympathetic chain ganglion
5. Grey ramus communicans
6. Postganglionic nerve axon
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3
2
Ventral root
Sympathetic
trunk ganglion
Sympathetic
trunk
Ventral ramus
of spinal nerve
Gray ramus
communicans
White ramus
communicans
Location of the sympathetic trunk
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Dissection of posterior thoracic wall, right side
D. Pathways to Body Periphery
1. innervate sweat glands, arrector pili muscles, blood vessels
E. Pathways to the Head
1. originate from T1–T4
2. synapse in superior cervical ganglion
3. innervate glands, smooth muscles, blood vessels of head
F. Pathways to Thoracic Organs
1. originate from T1–T6
2. run directly to the effector organ
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G. Pathways to Thoracic Organs
1. originate from T1–T6
2. run directly to the effector organ
3. functions in this region are to:
a. increase heart rate
b. dilate the bronchioles
c. dilate arteries of the heart
d. inhibit muscles and glands of the digestive system
H. Pathways to Pelvic Organs
1. originate from T5–L2
2. inhibit activity of smooth m. and glands in the visceral organs
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Eye
Lacrimal gland
Nasal mucosa
Pons
Sympathetic trunk
(chain) ganglia
Blood vessels;
skin (arrector pili
muscles and
sweat glands)
Superior
cervical
ganglion
Salivary glands
Middle
cervical
ganglion
Heart
Inferior
cervical
ganglion
Lung
T1
Liver and
gallbladder
Celiac ganglion
L2
Stomach
Superior
mesenteric
ganglion
Spleen
Adrenal medulla
Kidney
Inferior
mesenteric
ganglion
Small
intestine
Large
intestine
Rectum
Preganglionic
Postganglionic
Genitalia (uterus, vagina, and
penis) and urinary bladder
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VIII. The Role of the Adrenal Medulla
A. Major organ of the sympathetic nervous system
B. Constitutes largest sympathetic ganglia
C. Secretes large amounts of norepinephrine and epinephrine
D. Stimulated to secrete by preganglionic sympathetic fibers
Remember: “Fight or Flight”
Example: bear running out of the woods to eat your child!!!!
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Sympathetic trunk
Spinal
cord:
T8–L1
Ventral
root
Thoracic
splanchnic
nerves
Kidney
Adrenal
medulla
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Adrenal gland
Epinephrine and
norepinephrine
Adrenal
medulla cells
Capillary
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© 2014 Pearson Education, Inc.
© 2014 Pearson Education, Inc.
IX. Visceral Sensory Neurons
A. General visceral sensory neurons monitor these sensations
1. stretch
2. temperature
3. chemical changes
4. irritation
B. Nerve cell bodies are located in the dorsal root ganglion
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C. Visceral pain
1. no pain results when visceral organs are cut
2. visceral pain results from chemical irritation or inflammation
3. visceral pain often perceived to be of somatic origin
► phenomenon of referred pain
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A map of referred pain
Lungs and
diaphragm
Heart
Gallbladder
Liver
Appendix
Stomach
Pancreas
Small intestine
Ovaries
Colon
Kidneys
Urinary bladder
Ureters
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X. Visceral Reflexes
A. Visceral sensory/autonomic neurons role in visceral reflex arcs:
1. defecation reflex
2. micturition reflex (urination impulse)
B. NOTE: you do not “think” these reflexes; like patellar tendon reflex
C. Some visceral reflexes are simple spinal reflexes
D. Others do not involve the CNS - strictly peripheral reflexes
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Stimulus
1 Sensory
receptor in viscera
2 Visceral sensory
neuron
3 Integration center
• May be preganglionic
neuron (as shown)
• May be a dorsal horn
interneuron
• May be within walls
of gastrointestinal
tract
Dorsal root ganglion
Spinal cord
Autonomic ganglion
4 Efferent pathway
(two-neuron chain)
• Preganglionic neuron
• Postganglionic
neuron
5 Visceral effector
Response
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A visceral reflex
Increased blood pressure
1 Baroreceptors in carotid
sinus are simulated.
2 Sensory impulses are
carried on visceral sensory
fibers in the glossopharyngeal nerves (CN IX).
3 Integration occurs in
cardiac center of medulla
oblongata.
4 Efferent pathway via the
vagus nerves (CN X)
3
2
4
1
5 Parasympathetic
stimulation of heart
decreases heart rate.
Blood pressure decreases
The baroreceptor reflex
5
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XI. CNS Control of the ANS
A. The ANS is not under direct voluntary control
B. Some parts of the CNS help coordinate the ANS
1. brain stem
2. spinal cord
3. hypothalamus
4. amygdala
5. cerebral cortex
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C. Hypothalamus—the main integration center of the ANS
A. medial and anterior parts
► direct parasympathetic functions
B. lateral and posterior parts
► direct sympathetic functions
D. People can exert some control over autonomic functions
1. feelings of calm during meditation
a. influence of cerebral cortex on parasympathetic
centers in hypothalamus
2. voluntary sympathetic response
a. recalling scary event
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Communication at
subconscious level
Cerebral cortex
(frontal lobe)
Limbic system
(emotional input)
Hypothalamus
The “boss”: Overall
integration of ANS
Brain stem
(reticular formation, etc.)
Regulates pupil size, heart,
blood pressure, airflow,
salivation, etc.
Spinal cord
Reflexes for urination,
defecation, erection,
and ejaculation
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XII. Disorders of the ANS
A. Raynauds disease - characterized by constriction of blood vessels
1. provoked by exposure to cold or by emotional stress
B. Achalasia of the cardia
1. defect in the autonomic innervation of the esophagus
C. Congenital megacolon (Hirschsprung’s disease)
1. birth defect
2. parasympathetic innervation of distal large intestine fails to
develop correctly
3. feces and gas accumulate proximal to defect
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D. Achalasia of the cardia
1. defect in the autonomic innervation of the esophagus
E. Congenital megacolon (Hirschsprung’s disease)
1. birth defect
2. parasympathetics of distal large intestine fails to develop
correctly
3. feces and gas accumulate proximal to defect
© 2014 Pearson Education, Inc.