Peripheral Nervous system

1. 1
Autonomic Nervous System

2.  Nervous System [NS]
 Peripheral Nerves [31SN & 12CN]
 Perpheral Nervous System [PNS]
 SoNS & ANS
 Autonomic ganglia
 Pre- & post-ganglionic neurons
 Autonomic Nervous System [ANS]
 Subdivisions of the ANS
a. Sympathetic division: (Thoracolumbar)
b. Parasympathetic division: (Craniosacral)
 Relationship b/n SNS & PSNS
 The enteric nervous system [ENS]
 Adrenergic & Cholinergic nerve
fibers
 Neurotransmitters of the ANS
 ANS receptors [receptors in the ANS]
 Pharmacology of the ANS
2
Learning objective
Somatic nervous system 🡆SoNS
Autonomic nervous system 🡆ANS
Sympathetic nervous system 🡆SNS
Parasympathetic nervous system 🡆PSNS
Enteric nervous system 🡆 ENS

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1.Organization of the Nervous System [NS]
Superficial stimuli
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1.Organization of the Nervous System [NS]…

5. 5
1.Organization of the Nervous System [NS]…
Somatic nervous system 🡆SoNS
Autonomic nervous system 🡆ANS
Sympathetic nervous system 🡆SNS
Parasympathetic nervous system 🡆PSNS
Enteric nervous system 🡆 ENS

6. Organization of the Nervous System [NS]
1. Central Nervous System🡆CNS
The brain + the spinal cord
The center of integration & control
2. Peripheral Nervous System 🡆PNS
The NS outside of the brain & spinal cord
Consists of:
31 pairs of Spinal nerves
12 pairs of Cranial nerves
Carry info to & from the spinal cord
1.Organization of the Nervous System [NS]…
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7. Types of Peripheral Nerves
1. Based on Origin
Cranial & Spinal nerves
2. Based on signal transmission
Afferent, efferent, mixed nerves
3. Based on control
Autonomic & somatic
4. Based on functions
General & special nerves
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2.Peripheral Nerves

8. Cranial nerves
12 pairs of cranial nerves [CN]🡆designated by Roman number [I-XII]
 Carry signal to & from the brain
 Emerge mainly from parts of CNS above SC🡆 called Brain stem
 Supply structures in the🡆
 Head, neck, & viscera (thorax & abdomen)
 Can be,
 Sensory (I, II, VIII): olfactory, optic & vestibulocochlear nerves
 Motor (III, IV, VI, XI, XII): oculomotor, trochlear, abducens, accessory & hypoglossal nerves
 Mixed (V, VII, IX, X): trigeminal, facial, glossopharyngeal & vagus
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9. 2.Peripheral Nerves…
12 pairs of cranial nerves [CN]
A. Afferent [sensory]
1. Olfactory🡆sense of smell
2. Optic 🡆 sense of vision
3. Auditory [Vestibulocochlear=acoustic] 🡆 sense of equilibrium (balance) & hearing
B. Mixed nerves
1. Trigeminal 🡆
2. Facial 🡆
3. Glossopharyngeal 🡆
4. Vagus 🡆
C. Efferent [motor]
1. Trochlear 🡆
2. Abducens 🡆
3. Occulomotor 🡆 motor to intrinsic & extrinsic muscles of the eyes
4. Spinal accessory 🡆 motor to soft palate, pharynx & larynx &
neck 9

10. mov’t]
10
12 pairs of cranial nerves
I
2.Peripheral Nerves…
No 12 cranial nerves Nerve type Function [control of]
I
[chewing]
[Facial sensation]
Muscles of facial expression, taste
r
taste
,Swallowing
nerve Throat, neck & upper back
muscles
[Spinal accessory]
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
12 pairs of CN🡆 designated by the Roman numbers (I-

11. Cranial nerves [CN]
Cranial Nerves Mediate 5 Special Senses:
Smell, Vision, Hearing, Taste, Equilibrium
1. Smell: CN-I (Olfactory)
2. Vision: CN- II (Optic)
3. Hearing: CN-VIII (Cochlear division)
4. Equilibrium: CN-VIII (vestibular division)
5. Taste: CNs -VII, IX (Facial, Glossopharyngeal)
3 Nerves Are Concerned With Eyeball Movements
6. Oculomotor (III): superior rectus, medial rectus, inferior rectus, inferior
oblique
7. Trochlear (IV): superior oblique
8. Abducens (VI): lateral rectus
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12. 4 of the CNs Carry Parasympathetic Fibers
1. Oculomotor (III): innervates iris constrictor (causes pupil constriction);
also controls ciliary muscle (focuses the lens)
2. Facial (VII) & Glossopharyngeal (IX): stimulate salivary glands to secrete
3. Vagus (X): the major nerve of the parasympathetic system: goes to
most visceral organs (heart, lungs, kidneys, liver, stomach, intestines)
Several of the Nerves Innervate Skeletal Muscles
1. The Facial nerve (VII): controls muscles of facial expression
2. The Spinal accessory (XI): stimulates the trapezius & sternocleidomastoid
muscles
3. Chewing muscles (masseter, temporalis): are innervated by the Trigeminal (V)
4. The Hypoglossal (XII): moves the tongue
Cranial nerves [CN]
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13. Damage to Cranial Nerves Causes Many Medical Problems
1.Anosmia (loss of smell): Olfactory nerve damage
2.Bell's Palsy: paralysis of the muscles of facial expression on one side.
-Caused by inflammation of the Facial nerve.
3.Tic douloureux: severe facial pain caused by inflammation of the
trigeminal
nerve.
4.Blindness: caused by damage to optic nerve.
Cranial nerves [CN]
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14. 31 pairs of spinal nerves
 All contain afferent & efferent
a. 8 cervical nerves [Ns]
b. 12 thoracic Ns
c. 5 lumbar Ns
d. 5 sacral Ns
e. 1 coccygeal Ns
A. Afferent
 Relay message to CNS by long axon
 Afferent neurons are 1st order neurons
B. Efferent
 Carry signals from CNS to muscles & glands
 More complicated than the afferent division [2nd order]
2.Peripheral Nerves…
31 pairs of spinal nerves
Spinal nerves🡆Supply structures in the limbs, trunk & neck
-All branches contain both motor & sensory fibers.

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3.Perpheral Nervous System [PNS]
 PNS further divided into:
 Somatic nervous system 🡆SoNS
 Voluntary
 Somatic nerve fibers conduct impulses from the CNS to skeletal
muscles
 Autonomic nervous system 🡆ANS
 Involuntary
 Autonomic nerve fibers conducts impulses from the CNS to smooth muscle,
cardiac muscle, & glands.

16. 4.Comparison of SoNS &
ANS
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 Structurally the SoNS includes:
 Somatic sensory neurons
 Integrating centers in the CNS (Cortex)
 Somatic motor neuron [1] to skeletal muscles only
 Structurally the ANS includes:
 Autonomic sensory neurons
 Integrating centers in the CNS
 Autonomic motor neurons [2] to smooth muscle, cardiac muscle &
glands
Autonomic Vs somatic motor nerve fiber

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SoNS [Voluntary]
 Controls or innervates
 Voluntary activities such as
 Contraction of the skeletal muscle.
 Nerve fibres are originated from
 The anterior horn of the Grey matter of the spinal cord [SC]
 The motor nerve contains
 Single [1], long, thick & well-myelinated
axon.
 The NT is always Ach &
 The receptor is always Nicotinic Receptor
 Receptor: cholinergic (nicotinic)
 Has 1 neuron b/n CNS & effector organ
ANS [Involuntary]
 Controls involuntary activities such as
 CVS, GIT, glands [smooth, cardiac muscle ]
 Nerve fibres are originated from
 The lateral horn of the Grey matter of SC
 The NT is either Ach or NE &
 The receptors are adrenergic Or cholinergic
 Autonomic fibres contain 2 neurons
 Pre-& post-ganglionic neurons &
 They connected by synapse b/n CNS & effector organs
4.Comparison of SoNS Vs
ANS…
 Preganglionic neurons are a set of nerve fibers of the ANS that connect the CNS to the ganglia
 Postganglionic neurons are a set of nerve fibers that present in the ANS which connects the ganglion to the effector
organ

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4.Autonomic & somatic reflex

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4.Comparison of SoNS &
ANS…
Smooth muscle [in GIT,blood vessels] & glands & cardiac muscle

20. Summary of PSNS, SNS & SoNS innervations
4.Comparison of SoNS &
ANS…
No Postganglionic
NN [N2]
NM [N1]

21. 5.Autonomic ganglia
 Ganglion [pl 🡆 ganglia]
 A collection of cell bodies outside the
CNS.
 Nucleus [pl🡆nuclei]
 A collection of cell bodies within the CNS.
 Function of ganglia:
 Relay [Transmit] stations
 Expansion Or as,
 Distribution centers.
3 Types of the autonomic ganglia

22.  Preganglionic (neuron#1) 🡆cell body is in the CNS &
axon extends to the ganglion outside the CNS.
 Always myelinated
 NT is always Ach
 Postganglionic (neuron#2) 🡆cell body is in the ganglion &
axon extends to the visceral effector
 Always non-myelinated
 NT is Ach or NE
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4.ANS
6.Properties of pre- & post-ganglionic neurons

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6.Properties of pre- & post-ganglionic neurons…
 All preganglionic neurons are cholinergic neurons.
 They secrete Ach & are excitatory
 Sympathetic post-ganglionic neurons are adrenergic with few
exceptions
 They secrete NE & are either excitatory or inhibitory
 But sweat glands are cholinergic
 Parasympathetic post-ganglionic neurons are cholinergic.
 They secrete Ach & are either excitatory or inhibitory.
 The ANS is subdivided in to 2 separate divisions 🡆the SNS & PSNS.
 These 2 divisions differ in their origin, fiber length, axon terminal branches, function [actions on the effectors] , the NTs they discharge & their

24. 7.Autonomic Nervous System [ANS]
 ANS🡆regulates involuntary physiologic processes.
 The effectors that respond to autonomic regulation include
 Cardiac muscle (the heart), smooth muscles, & glands.
 These effectors are part of the visceral organs (organs within the body cavities) & of blood vessels.
 The ANS pathway from the CNS to the effector always involves
 2 neurons synapse in an autonomic ganglion
 Autonomic ganglia are located in the head, neck, & abdomen
ANS divided into:
Sympathetic Nervous System [“Fight or Flight”]
Parasympathetic Nervous System [“Rest & Digest”]
 However, there are often Dual innervations
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25. Dual innervation
 Meaning🡆innervation by both PSNS & SNS
Most body structures receive dual innervations
 Purpose: For better control
 “fight/flight” response of SNS is very helpful
 E.g. When encountering snarling dog Or need to escape from a burning
building.
 When emergency is over, PSNS needs time to help body relax & recover.
 Eruction of penis or clitoris Vs Ejaculation [gentalia]
 The following structures do not receive dual innervation:
 The sweat glands
 Adrenal medulla, some blood vessels & Skin pilo erectors
7.Autonomic Nervous System [ANS]…
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26. The ANS has 3 principal functions:
1. Regulation of the heart
2. Regulation of the secretory glands
 Salivary, gastric,lacrimal, sweat, bronchial glands
3. Regulation of smooth muscles,
 Muscles of bronchi, blood vessels, urogenital, GIT
7. Principal functions of the ANS
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27. 8.Subdivisions of the
ANS
Sympathetic Division [Thoracolumbar out flow]
 Thoracolumbar division
 Fight-or-flight [ “E” division (Exercise, excitement, emergency & embarrassment]
 Parasympathetic Division [Craniosacral]
 Craniosacral division
 Rest-&-digest [“D” division (Digestion, defecation, & diuresis or micturition]
 These divisions are anatomically & functionally distinct
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Sympathetic division Parasympathetic
Originated from Thoraco-lumbar region (T1-L2) Cranio-sacral region (Brain stem + S2-S4)
Length of fibers:
-Preganglionic
-Postganglionic
Shorter Longer
Longer Shorter
Axon branches Highly branched (influence many organs) Few branches (influence few organs)

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8.Subdivisions of the ANS…
Cholinergic neurons → discharge acetylcholine (ACh)==Cholinergic neurons include-
1. All preganglionic fibers of sympathetic & parasympathetic neurons.
2. All postganglionic neuronal fibers of parasympathetic NS.
3. Postganglionic neuronal fibers of sympathetic NS that innervate sweat glands
Adrenergic neurons → discharge noradrenaline (NA=NE)
-Most sympathetic postganglionic neurons adrenergic neurons (except sweat glands)

29. 8.Subdivisions of the ANS…

30. 1. Origin of preganglionic neuron
2. Type of NT
3. Type of Receptors
4. Location of autonomic ganglia
5. Length of neurons
Effecter
Effecter
Divisions of the
ANS
Sympathetic
Parasympathetic
CNS CS CNS TL
Ganglion
Ach NA
Preganglionic
Neuron
Ganglion
Ach
Ach
Postganglionic
Neuron
8.Subdivisions of the
ANS…
Thoracolumbar🡆TL======Craniosacral🡆CS
SNS & PSNS are differ in anatomy & function.
Sympathetic nervous system 🡆SNS
Parasympathetic nervous system 🡆PSNS
Enteric nervous system 🡆 ENS

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8.1.Sympathetic Division: (Thoracolumbar out
flow)
 Originates in lateral horns of T1-T12 & L1-L2 [T1-L2] region of spinal cord
 Components of the Sympathetic neurons,
 Cell bodies of preganglionic motor neurons are located in spinal cord
 Preganglionic axons synapse in ganglia🡆ganglia are located near the spinal cord
& far away from the organs being innervated
 Contains short preganglionic neurons which are cholinergic🡆 synapse with
 Long postganglionic neurons which are adrenergic (most) & cholinergic
(some).
Sweat gland

32. Preganglionic fibers produce Ach
Postganglionic fibers produce NE or Ach
Short, lightly myelinated preganglionic
neurons.
Long, unmyelinated postganglionic neurons.
Ganglia close to spinal cord.
Spinal
Cord
8.1.Sympathetic Division: (Thoracolumbar out flow)…

33. 8.1.Major Functions of the SNS
 SNS 🡆for fight or flight response [Initiation]
 🠙metabolic rate [🡑rate of cellular metabolism throughout the body]
 🠙cardiac output ,SV & 🡑ABP &🡑heart rate & dilates pupil [ For far vision]
 Is excitatory to almost all body parts except for the GIT [Inhibits GIT activities]
 It 🠗GIT motility or secretion & at sphincters it causes constriction [closes sphincters]
 Sweat glands: produce secretions [🡑sweating]
 🡑blood flow to active muscles concurrent with 🠗blood flow to organs such as the GIT &
the kidneys.
 Diverts blood from skin & GIT to skeletal muscles & towards vital organs [cardiac muscle, liver & adipose
tissue]
 Dilates bronchioles🡆β2🡆 [Relaxation of smooth muscles of bronchioles]
 Salivary glands: produce viscous fluid
 🠙alertness [prepares the body to deal with emergencies]
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34.  🡑blood glucose concentration [glycogen to glucose]
 🡑glycolysis in the liver & muscle🡆 🡑ATP
 🡑muscle strength & 🡑mental activity
 Coronary vessels: Vasodilation (β2)🡆🡆🡆BUT PSNS
Vasoconstriction.
 Kidney vessels: Vasoconstriction 🡆↓RBF = ↓Urine output
 🡑Ejaculation
 The sum of these effects permits a person to perform far more
strenuous physical activity [emergency]
8.1.SNS Often Responds by Mass Discharge
Characteristic features of SNS:
 Shunting of blood away from the skin & visceral into skeletal muscles.
 Dilation of the bronchi to improve oxygenation
 Dilation of the pupil [mydriasis]
 Mobilization of stored energy (energy expenditure).
8.1.Major Functions of the SNS…
RBF=renal blood flow
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35. 8.2.Parasympathetic Division: (Craniosacral)
 PSNS 🡆Originates from cranial & sacral regions.
a. Cranial components are part of CN-3 (Oculomotor), 7 (Facial), 9
(Glossopharyngeal), & 10 (Vagus)
b. Sacral components from S2 - S4 segments of the spinal nerves.
 Neurons #1 are long & synapse with neurons #2 (short) in ganglia
 Ganglia are close to or on target organs or near the effector
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36. 8.2.Parasympathetic neurons…
 Cell bodies of preganglionic motor neurons located in the spinal cord
 Preganglionic neurons 🡆long 🡆are cholinergic
 Post ganglionic neurons 🡆short 🡆are cholinergic
 Both preganglionic & postganglionic fibers produce Ach 🡆Cholinergic
fibers
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37. 8.2.Parasympathetic neurons…

38. 8.2.Functions of PSNS
 PSNS 🡆for conservation of energy, is anabolic [rest & digest]
 Has inhibitory effect on almost all body tissues except in the GIT.
 Has excitatory effects on the GIT.
 ⭡GIT motility [🠙emptying of the bowel]↑GI tract smooth muscles contraction
 Slowing heart & constricts bronchioles
 Salivary glands: produces watery fluid
 Constriction of the pupil [focusing of the eye for near vision]🡆myosis
 ⭡gastric, lacrimal,nasal, pancreatic secretion & 🠙Emptying of the bladder
 Relaxes sphincters of GI tract
 Causes vasodilation & responsible for erection of penis & clitoris
 Sweat glands: normal
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🡑salivation, urination [micturition], digestion & defecation 🡆🠗[HR, diameter of airways & diameter of
pupil].
Most body structures receive dual innervations for better
control

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9.Effects of Autonomic innervation [PNS &
SNS]
Sympathetic ganglia

40. ANS physiol
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9.Effects of Autonomic innervation [PNS & SNS]

41. 9.Effects of Autonomic innervation [PNS & SNS]
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42. 10.The enteric nervous system [ENS]
 ANS has an extrinsic & an intrinsic component on the GIT.
1. Extrinsic
 SNS & PSNS innervation of GI tract
2. Intrinsic
 Called Enteric Nervous System [ENS] 🡆directly controls the GIT.
 Contained within wall of GI tract
 Communicates with Extrinsic component
 Called the little brain because it can operate with great deal of independence
 ENS is described as also a 2nd brain.
 It embedded in the lining of the GIT & can operate independently of the brain & the
spinal cord.
 Found in lining of esophagus, stomach, intestine, pancreas, & gall bladder
 It monitors or controls local GI blood flow, GI mucosal secretion & mucosal transport ,
stretch of GIT walls, hormone level in the blood, GIT motility.
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43. 11.Cholinergic nerve
fibers
 The SNS & the PSNS nerve fibers secrete synaptic transmitter subs,
 Acetylcholine [Ach] or norepinephrine [NE]
 Those fibers that secrete Ach are said to be cholinergic nerve fibers.
 All preganglionic neurons are cholinergic in both the SNS & the PSNS.
 Almost all of the postganglionic neurons of the PSNS are also
cholinergic.
PSNS
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44.  Those fiber that secrete NE are said to be adrenergic nerve fibers.
 Most of the postganglionic sympathetic neurons are adrenergic.
 The postganglionic SNS nerve fibers to the sweat glands, to the piloerector
muscles of the hairs & to a very few blood vessels are cholinergic
11.Adrenergic nerve fibers
SNS
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45. 12.Neurotransmitters of the ANS
 NTs are released:
 At synapses b/n neurons
 B/n preganglionic & postganglionic.
 To autonomic effectors
 Smooth muscle, cardiac muscle, &
glands.
Both pre- & postganglionic neurons in the PSNS release Ach & are called Cholinergic.
All preganglionic axon & a few postganglionic neurons in the SNS are also Cholinergic.
Most of the postganglionic neurons of the SNS release NE & are called Adrenergic.
2 NTs are used in the ANS.
• ACh & NE [E]
• Neurons secreting Ach are cholinergic & NE are adrenergic
PSNS
SNS

46. 46
12.Neurotransmitters of the ANS…
No Postganglionic

47. 1. Cholinergic receptors 🡆 Give responses to
Ach
a. Nicotinic receptors [N] 🡆🡆🡆 NN &
NM
b. Muscarinic receptors [M]🡆🡆🡆M1-
M5
Thus Ach activates these 2 receptors called muscarinic & nicotinic
receptors.
2. Adrenergic receptors🡆Give responses to NE & E.
a. Alpha receptors
 Alpha1 🡆[Vasoconstriction]
 Alpha2 🡆As NFM ,relaxes smooth musclevasodilate

b. Beta receptors
 Beta1 [🠙HR & contractility]
 Beta2 Bronchodilation
 Beta3for Lipolysis
NE excites mainly alpha receptors but excites the beta receptors to a lesser extent as well.
E excites both types of receptors approximately equally.
13.ANS Receptors [Receptors in the
ANS]
2 basic categories of receptors
1.Cholinergic receptors
2.Adrenergic receptors
2 principal receptors of Ach
NN [N2] =
NM [N1]=at NMJ

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13.Locations of cholinergic & adrenergic receptor subtypes
Muscarinic receptors are found on all effector cells stimulated by postganglionic cholinergic neurons of both SNS & PSNS
Nicotinic receptors are found b/n pre-& post ganglionic neurons (ganglia) of both SNA & PSNS. Also found at many non- autonomic nerves e.g.,
NN =N2
NM =N1=at NMJ

49.  Par
49
Summary
 Nervous System [NS]
 Peripheral Nerves [31SN & 12 CN]
 Perpheral Nervous System [PNS]
 SoNS & ANS
 Autonomic ganglia
 Pre- & post-ganglionic neurons
 Autonomic Nervous System [ANS]
 Subdivisions of the ANS
Sympathetic division: (Thoracolumbar)
Parasympathetic division: (Craniosacral)
 Relationship b/n SNS & PSNS
 The enteric nervous system [ENS
 Adrenergic & Cholinergic nerve fibers
 NTs of the ANS
 ANS receptors [receptors in the ANS]

50. End
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