Download Autonomic nervous system

Objectives
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What is Autonomic Nervous System.
Describe Sympathetic and Parasympathetic
Nervous System.
Give their Functions.
The Autonomic Nervous System and Visceral
Sensory Neurons
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The Autonomic Nervous System
• 1- Innervates smooth muscle, cardiac muscle, and
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glands
2- Regulates visceral functions:
• A) Heart rate, blood pressure, digestion, urination
B) The general visceral motor division of the
PNS
The Autonomic Nervous System and Visceral
Sensory Neurons
Comparison of Autonomic and Somatic Motor Systems
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Somatic motor system
• One motor neuron extends from the CNS to
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skeletal muscle
Axons are well myelinated, conduct impulses
rapidly
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Comparison of Autonomic and Somatic Motor Systems
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Autonomic nervous system
• Chain of two motor neurons
• Preganglionic neuron
• Postganglionic neuron
• Conduction is slower due to thinly or unmyelinated
axons
Pre-ganglionic
Post-ganglionic
Ganglion
Autonomic and Somatic Motor Systems
Divisions of the Autonomic Nervous System
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Sympathetic and parasympathetic divisions
• Innervate mostly the same structures
• Cause opposite effects
Divisions of the Autonomic Nervous System
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Sympathetic – “fight, flight, or fright”
• Activated during exercise, excitement, and
emergencies
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Parasympathetic – “rest and digest”
• Concerned with conserving energy
Anatomical Differences in Sympathetic
and Parasympathetic Divisions
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Issue from different
regions of the CNS
• Sympathetic – also
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called the
thoracolumbar
division
Parasympathetic –
also called the
craniosacral division
Figure 15.3
Anatomical Differences in Sympathetic
and Parasympathetic Divisions
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Length of postganglionic fibers
• Sympathetic – long postganglionic fibers
• Parasympathetic – short postganglionic fibers
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Branching of axons
• Sympathetic axons – highly branched
• Influences many organs
• Parasympathetic axons – few branches
• Localized effect
Neurotransmitters of Autonomic Nervous System
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Neurotransmitter released by preganglionic axons
• Acetylcholine for both branches (cholinergic)
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Neurotransmitter released by postganglionic
axons
• Sympathetic – most release norepinephrine
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(adrenergic)
Parasympathetic – release acetylcholine
Anatomical Differences in Sympathetic
and Parasympathetic Divisions
Anatomical Differences in Sympathetic
and Parasympathetic Divisions
The Parasympathetic Division
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Cranial outflow
• Comes from the brain
• Innervates organs of the head, neck, thorax, and
abdomen
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Sacral outflow
• Supplies remaining abdominal and pelvic organs
The Parasympathetic Division
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.5
Cranial Outflow
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Preganglionic fibers run via:
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Oculomotor nerve (III)
Facial nerve (VII)
Glossopharyngeal nerve (IX)
Vagus nerve (X)
Cell bodies located in cranial nerve nuclei in the
brain stem
 Cranial outflow
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III - pupils constrict
VII - tears, nasal mucus, saliva
IX – parotid salivary gland
X (Vagus n) – visceral organs of thorax &
abdomen:
 Stimulates digestive glands
 Increases motility of smooth muscle of
digestive tract
 Decreases heart rate
 Causes bronchial constriction
 Sacral outflow (S2-4): form pelvic splanchnic
nerves
 Supply 2nd half of large intestine
 Supply all the pelvic (genitourinary) organs
Outflow via the Vagus Nerve (X)
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Fibers innervate (visceral
organs of the thorax) and
most of the abdomen
Stimulates - digestion,
reduction in heart rate and
blood pressure
Preganglionic cell bodies
• Located in dorsal motor
nucleus in the medulla
Post Ganglionic neurons
• Confined within the walls of
organs being innervated
Parasympathetic Nervous System: Sacral Outflow
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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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Form splanchnic nerves
Functions of Parasympathetic Nervous System
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Decreased Heart Rate
Decreased Blood Pressure
Pupil Constriction
Increased Urination
Decreased Sweating
Bronchial Constriction
Increased Salivation
The Sympathetic Division
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Basic organization
• Issues from T1-L2
• Preganglionic fibers form the lateral gray horn
• Supplies visceral organs and structures of
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superficial body regions
Contains more ganglia than the parasympathetic
division
Functions of Sympathetic Nervous System
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Increased Heart Rate
Increased Blood Pressure
Pupil Dilation
Decreased Urination
Increased Sweating
Bronchial Dilation
Decreased Salivation
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Horner`s Syndrome??????
Sympathetic Trunk Ganglia
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Located on both sides of the vertebral column
Linked by short nerves into sympathetic trunks
Joined to ventral rami by white and gray rami
communicantes
Fusion of ganglia  fewer ganglia than spinal
nerves
Stellate Ganglion ?????
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Regardless of target, all begin same
Preganglionic axons exit spinal cord through
ventral root and enter spinal nerve
Exit spinal nerve via communicating ramus
Enter sympathetic trunk/chain where
postganglionic neurons :Has three options…
Options of preganglionic axons in sympathetic trunk
1.
Synapse on postganglionic neuron in chain
ganglion then return to spinal nerve and follow
its branch to the skin
Ascend or descend within sympathetic trunk,
synapse with a postganglionic neuron within a
chain ganglion, and return to spinal nerve at that
level and follow branches to skin
Enter sympathetic chain, pass through without
synapsing, form a splanchnic nerve that passes
toward thoracic or abdominal organs
2.
3.
• These synapse in prevertebral ganglion in front
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of aorta
Postganglionic axons follow arteries to organs
Sympathetic Pathways to Periphery:Synapse in chain ganglia
at same level or different level
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 15.9
Pass through ganglia and synapse in prevertebral ganglion
Sympathetic Trunk Ganglia
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Prevertebral Ganglia
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Unpaired, not segmentally arranged
Occur only in abdomen and pelvis
Lie anterior to the vertebral column
Main ganglia
• Celiac, superior mesenteric, inferior mesenteric,
inferior hypogastric ganglia
Sympathetic Division of the ANS
Sympathetic Pathways to the Head
Sympathetic Pathways to Thoracic Organs
Sympathetic Pathways to the Abdominal Organs
Sympathetic Pathways to the Pelvic Organs
The Role of the Adrenal Medulla in the Sympathetic Division
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Major organ of the sympathetic nervous system
Secretes great quantities epinephrine (a little
norepinephrine)
Stimulated to secrete by preganglionic
sympathetic fibers
The Adrenal Medulla
Visceral Sensory Neurons
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General visceral sensory neurons monitor:
• Stretch, temperature, chemical changes, and
irritation
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Cell bodies are located in the dorsal root ganglia
Visceral pain – perceived to be somatic in origin
• Referred pain
Disorders of the Autonomic Nervous System: Hypertension
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Hypertension – high blood pressure
• Can result from overactive sympathetic
vasoconstriction
Disorders of the Autonomic Nervous System: Mass Reflex
Reaction
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Mass reflex reaction
• Uncontrolled activation of autonomic and somatic
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motor neurons
Affects quadriplegics and paraplegics
Disorders of the Autonomic Nervous System: Achalasia of the
Cardia
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Achalasia of the cardia
• Defect in the autonomic
innervation of the
esophagus