3. AUTONOMIC NERVOUS
SYSTEM
The autonomic nervous system is the
subdivision of the peripheral nervous
system that regulates body activities that
are generally not under conscious control
Autonomic nervous system innervate
smooth muscle (eg, blood vessels, gut
wall, urinary bladder)
cardiac muscle
glands (eg, sweat glands, salivary glands)
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4. DIVISION OF ANS
Parasysmpathetic: routine maintenance
“rest &digest”
Sympathetic: mobilization & increased
metabolism
“fight, flight or fright”
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5. WHERE THEY COME FROM
Parasympathetic: Sympathetic:
craniosacral thoracolumbar
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9. SYMPATHETIC OUTFLOW
“fight, flight or fright”
Also called thoracolumbar system: all its neurons
are in lateral horn of gray matter from T1-L2
Lead to every part of the body (unlike parasymp.)
Easy to remember that when nervous, you sweat; when
afraid, hair stands on end; when excited blood pressure
rises (vasoconstriction): these sympathetic only
Also causes: dry mouth, pupils to dilate, increased heart
& respiratory rates to increase O2 to skeletal muscles,
and liver to release glucose
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10. PRE AND POST
GANGLION NEURON
Somatic division:
Cell bodies of motor neurons reside in CNS (brain or
spinal cord)
Their axons (sheathed in spinal nerves) extend all the
way to their skeletal muscles
Autonomic system: chains of two motor neurons
1st = preganglionic neuron (in brain or cord)
2nd = gangionic neuron (cell body in ganglion outside
CNS)
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11. PRE AND POSTGANGLION
FIBER
Axon of 1st (preganglionic) neuron leaves
CNS to synapse with the 2nd (ganglionic)
neuron
Axon of 2nd (postganglionic) neuron
extends to the organ it serves
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Note: the autonomic ganglion is motor
14. SYMPATHETIC AND PARA
SYMPATHETIC GANGLIA
Sympathetic ganglia
Many lie close to spinal
cord(paravertebral)
Others lie approximately midway
between spinal cord and effector
organ(prevrtebral or collateral)
Parasympathetic ganglia
Lie close to or within the walls of
Figure 8-2
effector organ
16. IMPORTANT
NEUROTRANSMITTERS
Acetylcholine =Cholinergic
Fibers that release acetylcholine are
known as cholinergic fibers
All preganglionic neurons of the autonomic
division and all postganglionic neurons of
the parasympathetic division are
cholinergic
17. Norepinephrine = Adrenergic
Neurotransmitter between the sympathetic
postganglionic fiber and the effector cell
Fibers that release norepinephrine are
adrenergic fibers
Most postganglionic neurons of the
sympathetic division are adrenergic
Few are cholinergic(sweat gland,some blood
vessels in skeletal muscle)
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18. CHOLINERGIC RECEPTOR
Nicotinic receptor
Nicotinic receptors are found on the
postganglionic cell bodies in all autonomic
ganglia.
Response to acetylcholine released from
both sympathetic and parasympathetic
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19. Muscuranic receptor
found on cell membranes of effectors
organ (smooth muscle, cardiac muscle,
and glands)
they bind with acetylcholine released from
parasympathetic postganglionic nerve
fiber
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20. ADRENERGIC RECEPTOR
Alpha receptors are located at
sympathetic neuroeffector junctions of
many organs.
In general, alpha receptors mediate
excitation or increased activity of the
effector cells.
alpha receptor have greater affinity for
norepinephrine
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21. TYPES OF α-ADRENERGIC
RECEPTOR
α-adrenergic receptors are adrenergic receptors
that respond to norepinephrine
They are subdivided into two types:
α1, found in smooth muscle, heart, and liver, with
effects including vasoconstriction, intestinal
relaxation, uterine contraction and pupillary dilation,
α2, found in platelets, vascular smooth muscle,
nerve termini, and pancreatic islets, with effects
including platelet aggregation, vasoconstriction, and
inhibition of norepinephrine release and of insulin
secretion.
22. Beta receptors are also located
postsynaptically at sympathetic
neuroeffector junctions of many organs.
beta receptors mediate relaxation or
decreased activity of the effector cells.
Heart muscle is an important exception to
this rule. Activation of beta adrenoceptors
in heart increases the automaticity and
contractility of all parts of the heart.
23. β-RECEPTOR TYPES
β-adrenergic receptors respond particularly
to epinephrine and nor epinephrine
There are three known types of beta receptor,
designated β1, β2 and β3.
β1-Adrenergic receptors are located mainly in
the heart. Sensitive to both EN and NOR EN
β2-Adrenergic receptors are located mainly in
the lungs, gastrointestinal tract, liver, uterus,
vascular smooth muscle, and skeletal muscle
sensitive to EN only.
β3-receptors are located in fat cells.
33. SYMPATHETIC PARASYMPATHETIC
TONE
DUAL INNERVATION
MASS DISCHARGE(ALARM OR STRESS
RESPONSE)
LOCAL RESPONSE
SOME EXCEPTIONS: BLOOD VESSELS
SWEAT GLAND, SALIVARY GLAND
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34. VISCERAL REFLEXES
These are the simplest functions of the ANS.
Each visceral reflex arc consists of a receptor, a sensory
neuron, an interneuron, and two visceral motor neurons.
All visceral reflexes are polysynaptic.
PS reflexes include : gastric and intestinal reflexes,
defecation, urination, direct light reflexes, swallowing
reflex, coughing reflex, baroreceptor reflex and sexual
arousal.
S reflexes: cardioaccelaratory reflex, vasomotor
reflex, pupillary reflex and ejaculation (in males).
35. VISCERAL REFLEX ARCS
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*e.g. “enteric” nervous system: 3 neuron reflex arcs entirely within the wall of the gut
36. Central control of the Amygdala: main limbic
region for emotions
Autonomic NS
Hypothalamus: main
integration center
Reticular formation:
most direct influence
over autonomic
function
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