The autonomic nervous system regulates involuntary body functions and is divided into the sympathetic and parasympathetic systems. The sympathetic system is associated with the "fight or flight" response and increases heart rate and metabolism. The parasympathetic system is involved in "rest and digest" functions and decreases heart rate and increases digestion. Both systems contain two neurons - a preganglionic neuron originating in the CNS and a postganglionic neuron connecting to the target organ. The sympathetic system uses norepinephrine and the parasympathetic system uses acetylcholine as neurotransmitters. The autonomic nervous system is regulated by regions of the brainstem and limbic system.

1. FUNCTIONAL ASPECTS OF THE
AUTONOMIC NERVOUS SYSTEM

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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6. PARASYMPATHETIC
SYSTEM
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7. PARASYMPATHETIC
OUTFLOW
 Cranial outflow
 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 7

8. SYMPATHETIC SYSTEM
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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

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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

15. Figure 8-2

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.

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25. ADRENAL GLAND IS
EXCEPTION
On top of kidneys
Adrenal medulla
(inside part) is a
major organ of
the sympathetic
nervous system
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26. Adrenal gland is exception
 Synapse in gland
 Can cause body-wide
release of epinephrine
and norepinephrine
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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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