Transcript 12 Physiology of autonomic nervous system

Physiology of autonomic
nervous system
Comparison of Somatic and
Autonomic Nervous System
Somatic
 Skeletal muscle
 Conscious and
unconscious movement
 Skeletal muscle
contracts
 One synapse
 Acetylcholine
Autonomic
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Smooth and cardiac muscle
and glands
Unconscious regulation
Target tissues stimulated or
inhibited
Two synapses
Acetycholine by
preganglionic neurons and
ACh or norepinephrine by
postganglionic neurons
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Autonomic nervous system
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Chain of two motor neurons
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Preganglionic neuron
Postganglionic neuron
Conduction is slower due to thinly or
unmyelinated axons
Pre-ganglionic
Post-ganglionic
Ganglion
Comparison of ANS & PNS
Compare
the one motor neuron of the somatic
motor division with the two neuron chain of the
autonomic nervous system
Figure 15.2
Somatic and Autonomic Nervous System
Divisions of ANS
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There are two division of the ANS
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Parasympathetic
Sympathetic
Metasympathetic
Generally the two divisions have chains of two
motor neurons that innervate same visceral organs
but cause essentially opposite effects
If one division stimulates certain smooth muscle
to contract or a gland to secrete, the other division
inhibits that action
Through this process of duel innervation the two
systems counterbalance each other
Divisions of ANS
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Both the sympathetic
and parasympathetic
divisions issue from
the brain and spinal
cord
Two neuron pathways
are shown for both
divisions
Solid lines indicate
pre-ganglionic axons
while broken lines
indicate postganglionic axons
Where they come from
Parasympathetic:
craniosacral
Sympathetic:
thoracolumbar
Sympathetic
ACh
Nicotine
Tyramine,
Ephedrine
amphetamine
+
N
NE
+
αβ
Divisions of the Autonomic
Nervous System
Sympathetic – “fight, flight, or fright”
 Activated during exercise,
excitement, and emergencies
 Parasympathetic – “rest and digest”
 Concerned with conserving energy
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Functions of the Autonomic
Nervous System
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Sympathetic activities
 “E situations”
 Exercise
 Emergency
 Excitement
 Embarrassment
Functions of the Autonomic
Nervous System
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Parasympathetic activities
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Stimulated by:
 Quiet periods
 Paradoxical fear
SLUDD
Produces “rest-and-digest” response
 Supports body functions that conserve and
restore body energy
 Reduce body functions that support physical
activity
Function of the Sympathetic Nerve
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Sympathetic nervous system prototypically
“fight” or “flight”.
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Associated with increased
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energy expenditure,
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cardiopulmonary adjustments for intense
activity,
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blood flow adjustments for maximum energy
expenditure.
SNS - Fight & Flight Reaction
You’re walking alone at night and all the sudden you hear an
unfamiliar noise near by… In a matter of seconds,
 your heart rate increases dramatically,
 blood vessels in your skeletal muscles dilate,
 blood vessels in the visceral muscles constrict,
 digestion is ceased,
 your liver ramps up glucose release,
 your pupils dilate,
 salivary production decreases,
 sweat increases.
Sympathetic
Preganglionic
cell bodies in
lateral horns
of spinal cord
T1-L2
Sympathetic Trunk Ganglia
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
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Sympathetic Pathways to
Periphery
Figure 15.9
Sympathetic Pathways to the
Head
Figure 15.10
Sympathetic Pathways to Thoracic
Organs
Figure 15.11
Parasympathetic Nervous
System
If that noise turns out to be the
result of wind, then the body is
returned to “pre-noise” state.
 This is the job of the
parasympathetic nervous system.
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Autonomic Nervous System
• Parasympathicus
• Sympathicus
• Wind down, relaxation,
digestion
• Dominated by
Acetylcholine
• Fight & Flight Reaction
• Dominated by
Noradrenaline
(Adrenaline)
• Fear, exercise, rage
Different Lengths of their
Fibers
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Sympathetic is the opposite
with short preganglionic and
long postganglionic fibers
Parasympathetic division has
long preganglionic and short
postganglionic fibers
Anatomical Differences in Sympathetic
and Parasympathetic Divisions
Figure 15.4a
Divisions of ANS
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Therefore, all
sympathetic
ganglia lie near
the spinal cord
and vertebral
column, and all
parasympathetic
ganglia lie far
from the CNS, in
or near the
organs innervated
Parasympathetic
Parasympathetic Division
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The parasympathetic division is most effective in
non-stressful situations
This division is chiefly concerned with keeping
body energy use as low as possible, even as it directs
body processes such as digestion and elimination
Resting and digesting division
Parasympathetic
ACh
Nicotine
Black widow
Spider venom
+ N
ACh
+
M
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
Form splanchnic nerves
Sacral Outflow
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The sacral outflow
arises from neurons
located in the lateral
horn of the spinal
cord at S2 - S4
The axons of these
neurons run in the
ventral roots of the
spinal nerves to the
ventral rami
Sacral Outflow
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From the ventral rami
the neurons branch to
form the pelvic
splanchnic nerves
Most neurons synapse
in the intramural
ganglia located in the
walls of the distal
large intestine, urinary
bladder and
reproductive organs
Neurotransmitters and Neuroreceptors
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Acetylcholine and Norepinephrine
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All preganglionic neurons are cholinergic
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Parasympathetic post ganglionic neurons are
cholinergic
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Sympathetic post ganglionic neurons are
adrenergic except
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Sympathetics innervating sweat glands, blood
vessels in skeletal muscle, and piloerection
muscles are cholinergic
Cholinergic Receptors
The two types of receptors that
bind ACh are nicotinic and
muscarinic
 These are named after drugs that
bind to them and mimic ACh
effects
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Acetylcholine
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Nicotinic receptors
 Nm (muscular-type or N2): skeletal muscle
 Nn (neuron-type, or N1): autonomic ganglia,
CNS
Muscarinic receptors
 Postganglionic parasympathetic and a few
sympathetic sites, CNS (also autonomic gang.)
 Receptor subtypes: M1-5
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