PERIPHERAL & AUTONOMIC NERVOUS SYSTEMS Human Anatomy Sonya Schuh-Huerta, Ph.D.
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Transcript of PERIPHERAL & AUTONOMIC NERVOUS SYSTEMS Human Anatomy Sonya Schuh-Huerta, Ph.D.
PERIPHERAL & AUTONOMICPERIPHERAL & AUTONOMICNERVOUS SYSTEMSNERVOUS SYSTEMS
Human AnatomyHuman Anatomy
Sonya Schuh-Huerta, Ph.D.Sonya Schuh-Huerta, Ph.D.
Leonardo Da Vinci, The Battle of Anghiari
The Peripheral Nervous System
• The PNS– Is the nervous system outside the brain & spinal cord– Provides vital links to the body & outside world– Nerves allow the CNS to receive info & initiate action
• Sensory inputs & motor outputs– Categorized as
• Somatic or visceral• General or special
Functional Organization of the PNS
Central nervous system (CNS) Peripheral nervous system (PNS)
Motor (efferent) divisionSensory (afferent) division
Sympatheticdivision
Parasympatheticdivision
Somatic sensoryGeneral: Touch, pain, pressure, vibration, temperature, and proprioception in skin, body wall, and limbs
Special: Hearing, equilibrium, vision
Visceral sensoryGeneral: Stretch, pain, temperature, chemical changes, and irritation in viscera; nausea and hunger
Special: Taste, smell
Somatic nervoussystem
Motor innervation of all skeletal muscles
Autonomicnervous system
(ANS)
Motor innervationof smooth muscle, cardiac muscle, and glands
Basic Structural Components of PNS
• Sensory receptors pick up stimuli from
inside or outside body (we’ll cover later)• Nerves & ganglia
– Nerves bundles of peripheral axons– Ganglia clusters of peripheral neuronal cell
bodies• Motor endings axon terminals of motor neurons
– Innervate effectors (muscle fibers & glands)
The Cranial Nerves – Yes you have to know them…
• Attach to brain & pass through foramina of the skull
• Numbered I–XII (1-12)
• Cranial nerves I & II attach to the forebrain– All others attach to brain stem
• Primarily serve head & neck structures– The vagus nerve (X) is the only cranial nerve
that extends into abdomen
The Cranial Nerves
Frontal lobe
Temporal lobe
Infundibulum
Facial (VII)
Vestibulocochlear (VIII)
Glossopharyngeal (IX)
Vagus (X)
Accessory (XI)
Hypoglossal (XII)
Filaments ofolfactory nerve (I)
Olfactory bulb
Olfactory tract
Optic chiasma
Optic nerve (II)
Optic tract
Oculomotor (III)
Trochlear (IV)
Trigeminal (V)
Abducens (VI)
Cerebellum
Medulla oblongata
The Cranial Nerves
Cranial nerves
I
II
III
IV
V
VI
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Vision
General
Smell
Somaticsensory
(SS)
Visceralsensory
(VS)
Somaticmotor(SM)
Visceral motor:parasympathetic
(VM)
SM
SM
SM
SM
VM
Sensory function Motor function
OdessaOfeliaO’ConnerTakesTestsAmazingly!
The Cranial Nerves
Cranial nerves Sensory function Motor function
VII
VIII
IX
X
XI
XII
Facial
Vestibulocochlear
Glossopharyngeal
Vagus
Accessory
Hypoglossal
General;taste
General;taste
General
General
General;taste
General
Hearing;equilibrium
SM
Some
SM
SM
SM
SM
VM
VM
VM
Somaticsensory
(SS)
Visceralsensory
(VS)
Somaticmotor(SM)
Visceral motor:parasympathetic
(VM) FiestyVictorGetsVeryAgitatedHere…
I ) Olfactory Nerves
• Sensory nerves of smell
II) The Optic Nerves
• Sensory nerve of vision
III) The Oculomotor Nerves
• Innervates 4 extrinsic eye muscles
Table 14.2 (3 of 12)
IV) The Trochlear Nerves
• Innervates the superior oblique muscle (an extrinsic eye muscle)
The Trigeminal Nerves
• Largest of the cranial nerves– Has 3 divisions
• Ophthalmic• Maxillary• Mandibular
• Cell bodies of sensory neurons located in the trigeminal ganglion
• Mandibular division contains motor fibers that innervate the chewing muscles
V) The Trigeminal Nerves
VI) The Abducens Nerves
• Abducts the eyeball innervates lateral rectus muscle
VII) The Facial Nerves• Innervates muscles of facial expression
VIII) The Vestibulocochlear Nerves
• Sensory nerve of hearing & balance
IX) The Glossopharyngeal Nerves
• Innervates structures of the tongue & pharynx
X) The Vagus Nerves
• A mixed sensory & motor nerve – “Wanders” into
thorax & abdomen– Parasympathetic
innervation of organs
XI) The Accessory Nerves
• Unique among cranial nerves• Accessory nerves come from ventral rootlets of spinal cord• Do not arise from the brainstem
XII) The Hypoglossal Nerves
• Runs inferior to the tongue– Innervates the tongue muscles
The Spinal Nerves
• 31 pairs contain thousands of nerve fibers Formula C8, T12, L5, S5, Cx1 = 31
• Connect to spinal cord• Named for region of vertebral column
– 8 pairs cervical nerves (C1–C8)
– 12 pairs thoracic nerves (T1–T12)
– 5 pairs lumbar nerves (L1–L5)
– 5 pairs sacral nerves (S1–S5)
– 1 pair coccygeal nerves (Cx1)
Spinal Nerves – Posterior View
CervicalnervesC1 – C8
ThoracicnervesT1 – T12
LumbarnervesL1 – L5
SacralnervesS1 – S5 Coccygeal
nerveCo1
Cervical plexus
Intercostalnerves
Cervicalenlargement
Lumbarenlargement
Cauda equina
Brachial plexus
Lumbar plexus
Sacral plexus
Spinal Nerves
• Branch into dorsal ramus & ventral ramus– Dorsal & ventral rami contain sensory and
motor fibers
• Rami communicantes connect to the base of the ventral ramus– Lead to the sympathetic chain ganglia
Spinal Nerves
Spinalnerve
Axon ofmotorneuron
Ventralramus
Ventralroot
Neuromuscularjunction
Sensory receptors inskin (e.g., free nerveendings of sensoryneuron)
Dorsal rootDorsal rootganglion
Dorsalramus
Sensory axonand cell body
Nerves
Spinal Nerves
Dorsal rootganglion
Gray matterWhite matter
Ventral root
Dorsal root
Dorsal & ventralrootlets of spinal nerve
Dorsal ramusof spinal nerve
Ventral ramusof spinal nerve
Sympathetic trunkganglion
Spinal nerve
Rami communicantes
Innervation of the Back
• Dorsal rami – Innervate back muscles– Follow a neat, segmented pattern
• Innervate a horizontal strip of muscle & skin– In line with emergence point from the vertebral column
Innervation of the Anterior Thoracic & Abdominal Wall
• Thoracic region– Ventral rami arranged in simple, segmented
pattern– Intercostal nerves supply intercostal
muscles, skin, & abdominal wall
Introduction to Nerve Plexuses& Peripheral Nerves
• Nerve plexus a network of nerves!
• Branch from ventral rami (except T2–T12)
– Branch & join with one another – Form nerve plexuses
• In cervical, brachial, lumbar, & sacral regions
– Primarily serve the limbs– Fibers from ventral rami criss-cross
The Cervical Plexus
• Buried deep in the neck– Under the sternocleidomastoid m.
• Most are cutaneous nerves
• Some innervate muscles of the anterior neck
• Phrenic nerve the most important nerve of the cervical plexus
-Innervates diaphragm, mediastinal pleura &
pericardium Control of breathing!
The Cervical Plexus
Hypoglossalnerve (XII)
C1
C2
C3
C4
C5
Segmentalbranches
Lesser occipitalnerve
Greater auricularnerve
Ansa cervicalis
Phrenic nerve
Supraclavicularnerves
Accessory nerve (XI)
Transversecervical nerve
Ventralrami:
Ventral rami
The Brachial Plexus & Innervation of the Upper Limb
• Brachial plexus lies in the neck & axilla
• Formed by ventral rami of C5–C8
• Cords give rise to main nerves of upper limb
(c) Flowchart summarizing relationships within the brachial plexus
Major terminalbranches(peripheral nerves)
Cords Divisions TrunksRoots(ventralrami)
Musculocutaneous
Median
Ulnar
Radial
Axillary
C5
C6
C7
C8
T1
Anterior
Posterior
Anterior
Posterior
Posterior
Anterior
Upper
Middle
Lower
Lateral
Medial
Posterior
Innervation of the Upper Limb
• Musculocutaneous – Innervates the biceps brachii & brachialis m.
• Median – Innervates anterior forearm muscles & palm
• Ulnar – Innervates intrinsic hand muscles & skin of
hand
Innervation of the Upper Limb
• Radial – Largest branch of the brachial plexus– Innervates muscles of the posterior upper
limb
• Axillary– Innervates the deltoid & teres minor m.
Major Nerves of the Upper Limb
Median nerve
Musculocutaneous nerve
Radial nerve
Humerus
Ulna
Ulnar nerve
Median nerve
Radius
Radial nerve (superficial branch)
Superficial branch of ulnar nerve
Dorsal branch of ulnar nerve
Digital branch of ulnar nerve
Muscular branch
Digital branch
Axillary nerve
Anteriordivisions
Posteriordivisions
Radial nerve
Branches of axillary nerve
Axillary nerve
Ulnar nerve (cut)Median nerve (cut)
Deep radial nerve
Posterior cutaneous nerve
Superficial branch of radial nerve
Anteriordivisions
Posteriordivisions
Major Nerves of the Upper Limb
The Lumbar Plexus & Innervation of the Lower Limb
• Lumbar plexus – Arises from L1– L4
– Main branches innervate the anterior thigh• Femoral nerve innervates anterior thigh
muscles• Obturator nerve innervates adductor muscles
The Lumbar Plexus & Nerves
Lateral femoralcutaneous
Anterior femoralcutaneous
Saphenous
Obturator
Iliohypogastric
Ilioinguinal
Femoral
(c) Distribution of the major nerves from the lumbar plexus to the lower limb
The Sacral Plexus
• Arises from spinal nerves L4–S4
• Caudal to the lumbar plexus
• Often considered with the lumbar plexus– Lumbosacral plexus
The Sacral Plexus & Innervation of the Lower Limb
• Sciatic nerve the largest nerve of the sacral plexus– Actually 2 nerves in one sheath
• Tibial nerve innervates most of the posterior lower limb
• Common fibular (peroneal) nerve innervates muscles of the anterolateral leg
The Sacral Plexus & Nerves
Superior gluteal
Inferior gluteal
Common fibular
Deep fibular
Superficial fibular
Plantar branches
Tibial
Sural (cut)
Posterior femoralcutaneous
Pudendal
Sciatic
(c) Distribution of the major nerves from the sacral plexus to the lower limb
A Case Study…
• Black lab hit in car accident– Initial inability to walk or move limbs– Hospitalized for 1 week– Regained motor control of lower limbs
& front right limb– However, front left limb completely
paralyzed - no sensation or motor control
• What spinal nerves, plexus(es) or peripheral
nerves were likely damaged?
• Damage to:– Left spinal nerves C5-C8– Left Brachial plexus– Peripheral nerves: axillary,
musculocutaneous, radial,
median, & ulnar
Innervation of the Skin: Dermatomes
• Dermatome an area of skin innervated by cutaneous branches of a single spinal nerve!– Important diagnostic implications
• Upper limb– Skin is supplied by nerves of the brachial
plexus
• Lower limb – Lumbar nerves anterior surface– Sacral nerves posterior surface
C2C3
C4
C5T1
T2
T2T3T4T5
C6
C8C7 C7
C6
T6T7T8T9
T10
T11
T12L1
S2S3
L1
L2
L3
L4
L5
L2
L3
L4
L5
S1
C6
C5
C8
T2
C6
C5
S1
C2
C3
C4C5C6C7C8
C8 C8
C7 C7
T1T2T3T4T5T6T7T8T9T10
T11T12
L1L2 L3
S1
(b) Posterior view
L5S2
S1
S1
S3
S2 S1S2
S4S5
L5L5
L4L5L5
L4
C6 C6
L4
L3
L2
L1
L4
Map of Dermatomes
(a) Anterior view
Disorders of the PNS
• Shingles (Herpes zoster) – Viral infection
– Inside of neuron cell bodies of peripheral nerves – breaks out &
affects skin of that region - dermatome
– Stems from childhood chicken pox
– Often brought on by stress
– Mostly experienced by those over age 50
Varicella zoster virus (chicken pox) can become dormant in the nerve cell bodies and less frequently in non-neuronal satellite cells of dorsal root, cranial nerve or autonomic ganglion, without causing any symptoms. Years or decades after a chickenpox infection, the virus may break out of nerve cell bodies and travel down nerve axons to cause viral infection of the skin in the region of the nerve. The virus may spread from one or more ganglia along nerves of an affected segment and infect the corresponding dermatome causing a painful itching rash. Although the rash usually heals within 2-4 weeks, some sufferers experience residual nerve pain for months or years, a condition called postherpetic neuralgia. Exactly how the virus remains latent in the body, and subsequently re-activates is not understood.
Disorders of the PNS
• Migraine headache– Relates to sensory innervation of cerebral
arteries• Arteries dilate & compress & irritate sensory nerve
endings
• Myasthenia gravis – Progressive weakening of skeletal muscles– Autoimmune disorder– Antibodies destroy acetylcholine receptors
Disorders of the PNS
• Carpal Tunnel syndrome– Swelling/inflammation & compression of the median
nerve of the wrist due to repetitive, non-ergonomic movements
– Pain, discomfort, tingling, loss of feeling
The PNS Throughout Life
• Spinal nerves form late in week 4
• Each of the 31 pairs of spinal nerves:– Sends motor fibers to an individual myotome– Sends sensory fibers to overlying band of skin
• During week 5, nerves reach the organs they innervate
The Autonomic Nervous System(Ch 15)
The Autonomic Nervous System
• Autonomic nervous system (ANS) – General visceral motor part of the PNS– ANS has 2 divisions:
• Parasympathetic• Sympathetic
• Innervates: • Smooth muscle• Cardiac muscle • Glands
The ANS• The ANS a system of motor neurons
– Regulates visceral functions including:• Heart rate• Blood pressure• Digestion• Urination
Comparison of Autonomic & Somatic Motor Systems
• Autonomic nervous system– Chain of 2 motor neurons
• Preganglionic neuron• Post-ganglionic neuron
– Conduction is slower than somatic nervous system:
• Thinly myelinated or unmyelinated axons• Motor neuron synapses in a ganglion
Divisions of the ANS
• Sympathetic & Parasympathetic – Chains of 2 motor neurons
• Innervate mostly the same structures• Cause opposite effects!
–Sympathetic division mobilizes the body during
extreme situations Fight or Flight!
–Parasympathetic division controls
routine maintenance functions
Rest & Digest
Divisions of the ANS
• Sympathetic “fight, flight, or fright”– Activated during EXTREME situations
• Exercise• Excitement• Emergencies
Divisions of the ANS
• Sympathetic responses help us respond to dangerous situations– Increase heart rate & breathing rate– Increase blood & oxygen to skeletal muscles– Dilates pupils & airways– Sweating– Motility of the digestive tract & urinary tracts
is inhibited – don’t need to digest or urinate now!
Divisions of the ANS
• Parasympathetic division– Active when the body is at rest– Concerned with conserving energy– Directs “housekeeping” activities
• Heart rate & breathing are at low-normal levels• Gastrointestinal tract digests food• Urination/defecation, etc.• Pupils are constricted
• Issue from different regions of the CNS:
– Sympathetic also called thoracolumbar division
– Parasympathetic also called the craniosacral division
Anatomical Differences in Sympathetic & Parasympathetic Divisions
Salivaryglands
Eye
Skin*
Heart
Lungs
Liverand gall-bladder
Genitals
Pancreas
Eye
Lungs
Bladder
Liver and gall-bladder
Pancreas
Stomach
Cervical
Sympatheticganglia
Cranial
Lumbar
Thoracic
Genitals
Heart
Salivaryglands
Stomach
Bladder
Adrenalgland
Parasympathetic Sympathetic
Sacral
Brain stem
L1
T1
• Length of postganglionic fibers:– Sympathetic long postganglionic fibers– Parasympathetic short postganglionic fibers; long
preganglionic fibers
• Branching of axons:– Sympathetic axons highly branched
• Influences many organs– Parasympathetic axons less branching
• Localized effect (more precise output)
• Location of ganglia differ between both
Anatomical Differences in Sympathetic& Parasympathetic Divisions
• Neurotransmitter released by postganglionic axons:– Sympathetic
• Release Norepinephrine (NE) (adrenergic)
– Parasympathetic• Release Acetylcholine (ACh) (cholinergic)
Anatomical Differences in Sympathetic& Parasympathetic Divisions
Differences Between Sympathetic & Parasympathetic Divisions
Skeletal muscle
Cell bodies in centralnervous system Peripheral nervous system Effect
Effectororgans
ACh
AChSmooth muscle(e.g., in gut), glands,cardiac muscle
Ganglion
Adrenal medulla Blood vessel
ACh
ACh
ACh
NE
Epinephrine andnorepinephrine
Ganglion
Heavily myelinated axon
Lightly myelinated preganglionic axon
Lightly myelinated preganglionic axons
Neurotransmitterat effector
Unmyelinatedpostganglionic axon
Unmyelinatedpostganglionic axon
Stimulatory
Stimulatoryor inhibitory,dependingon neuro-transmitterand receptorson effectororgans
Single neuron from CNS to effector organs
Two-neuron chain from CNS to effector organs
SO
MA
TIC
NER
VO
US
SYS
TEM
AU
TO
NO
MIC
NER
VO
US
SYS
TEM
PA
RA
SYM
PA
TH
ETIC
SYM
PA
TH
ETIC
The Parasympathetic Division
• Cranial outflow – Comes from the brain– Innervates
• Organs of the head, neck, thorax, & abdomen
• Sacral outflow – Comes from the sacral region– Innervates
• Remaining abdominal & pelvic organs
Parasympathetic Division – Cranial Outflow
Eye
Lacrimalgland
Nasalmucosa
Ciliary ganglion
Pterygopalatineganglion
Submandibularganglion
Submandibularand sublingualglands
CN III
CN VII
CN IXCN X
Otic ganglion
Parotid gland
Heart
Lung
Cardiac and pulmonary plexuses
Preganglionic
Postganglionic
Cranial nerveCN
Liver andgallbladder
Stomach
Pancreas
Urinary bladder and ureters
Smallintestine
Large intestine
S2
Pelvicsplanchnicnerves
Genitalia (penis, clitoris, and vagina)
Rectum
Celiacplexus
Inferiorhypogastric plexus
S4
Preganglionic
Postganglionic
Cranial nerveCN
Parasympathetic Division – Sacral Outflow
The Sympathetic Division
• Basic organization– Issues from T1–L2
– Preganglionic fibers form the lateral gray horn of the spinal cord
– Supplies visceral organs & structures of superficial body regions
– Contains more ganglia than parasympathetic
Sympathetic Pathways to the Body Periphery
• Innervate – Sweat glands– Arrector pili muscles– Peripheral blood vessels
Sympathetic Pathways
Superiorcervicalganglion
Middlecervicalganglion
Inferiorcervicalganglion
Sympathetic trunk(chain) ganglia
Pons
L2
T1
White ramicommunicantes
Liver and gallbladder
Stomach
Spleen
Kidney
Adrenal medulla
Smallintestine
Largeintestine
Genitalia (uterus, vagina, andpenis) and urinary bladder
Celiac ganglion
Inferiormesenteric ganglion
Lesser splanchnic nerveGreater splanchnic nerve
Superiormesentericganglion
Lumbarsplanchnicnerves
EyeLacrimal gland
Nasal mucosa
Blood vessels;skin (arrector pilimuscles andsweat glands)
Salivary glands
Heart
Lung
Rectum
Cardiac and pulmonaryplexuses
PreganglionicPostganglionic
Sacralsplanchnicnerves
Sympathetic Trunk Ganglia
• Located on both sides of the vertebral column
• Linked by short nerves into sympathetic trunks
• Sympathetic trunk ganglia also called– “Chain ganglia”
Sympathetic Trunk Ganglia
• Joined to ventral rami by white & gray rami communicantes
• Fusion of ganglia fewer ganglia than spinal nerves
• Fusion of ganglia most apparent in cervical region– Superior, middle, & inferior cervical ganglia
Spinal cord
Dorsal root
Ventral root
Sympathetictrunk ganglion
Sympathetictrunk
Rib
Ventral ramusof spinal nerve
Gray ramuscommunicans
White ramuscommunicans
Thoracicsplanchnic nerves
(a) Location of the sympathetic trunk
To effector
Blood vessels
Skin (arrectorpili musclesand sweatglands)
Dorsal root ganglion
Dorsal ramus ofspinal nerve
Dorsal root
Sympathetictrunk ganglion
Lateral horn(visceralmotor zone)
Ventral root
Sympathetic trunk
Gray ramuscommunicansWhite ramuscommunicans
Ventral ramus ofspinal nerve
Synapse at the same level1
Splanchnic nerve
Collateral ganglion(such as the celiac)
Target organin abdomen(e.g., intestine)
Synapse in a distant collateral ganglion anterior to the vertebral column
(b) Three pathways of sympathetic innervation
3
Sympathetic Trunk Ganglia
2
To effector
Blood vessels
Skin (arrectorpili musclesand sweatglands)
Synapse at a higher or lower level
Autonomic Nerves, Plexuses & GangliaLeft vagus nerve
Cardiac branches of the vagus
TracheaThoracic spinalnerves (ventral rami)
Cardiac plexusPulmonary plexuson the bronchus
Vagus nerveEsophageal plexus
DiaphragmStomach withvagus nerveCeliac ganglion and plexus
Superior mesentericganglion and plexus
Inferior mesentericganglion and plexus
Aortic plexus
Inferior hypogastric(pelvic) plexus
Pelvic sympathetictrunk
Superior cervicalganglion
Middle cervical ganglion
Sympathetic cardiac nerves
Stellate ganglion
Aortic arch
Sympathetictrunk ganglia
Esophagus
Thoracicsplanchnicnerves
Adrenal(suprarenal)gland
Kidney
Lumbarand sacral splanchnicnerves
Superior hypogastricplexus
Aorta
Role of Adrenal Medulla in the Sympathetic NS
• Major organ of the sympathetic nervous system
• Is the largest sympathetic ganglia • Secretes great quantities of norepinephrine &
epinephrine • Stimulated to secrete by preganglionic
sympathetic fibers
The Adrenal Medulla
Spinal cord:T8–L1
Adrenalmedulla cells
Sympathetic trunk
Ventralroot
Thoracicsplanchnicnerves
Epinephrine andnorepinephrine
Adrenal glandAdrenalmedulla
Capillary
Kidney
A Map of Referred Pain
Heart
Lungs anddiaphragm
Liver
Stomach
Kidneys
Ovaries
Small intestine
Ureters
Urinarybladder
Colon
Pancreas
Liver
Heart
Appendix
Gallbladder
-Visceral pain – detected by visceral
sensory neurons
-No pain results when visceral
organs are cut
-Visceral pain results from chem.
irritation or inflammation
-Visceral pain often perceived to
be of somatic origin
Phenomenon of referred pain
Central Control of the ANS
Cerebral cortex(frontal lobe)
Limbic system(emotional input)
Communication atsubconscious level
HypothalamusOverall integrationof ANS, the boss
Spinal cordUrination, defecation,
erection, and ejaculationreflexes
Brain stem(reticular formation, etc.)
Regulation of pupil size,respiration, heart, blood
pressure, swallowing, etc.
The ANS Throughout Life
• Efficiency of the ANS declines with age– Constipation due to reduced mobility of GI tract– Dry eyes due to reduced tear formation– Fight or flight reaction still intact, but may be
slower to respond
Questions…?
What’s Next?Lab: PNS & ANS; & ReviewNext week: Spring Break!Mon 4/8 Lecture: no class study! Mon 4/8 Lab at 8:00 pm: Lab Exam 3(You will have sub – Andrew Allen)
Baroreceptor Reflex
Increased blood pressure
Blood pressure decreases
Sensory impulses are carried on visceral sensory fibers in the glossopharyngeal nerves (CN IX).
Integration occurs in cardiac center of medulla oblongata.
Baroreceptors in carotid sinus are stimulated.
Parasympathetic stimulation of heart decreases heart rate.
Efferent pathway via the vagus nerves (CN X)
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4
5
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Extra…..