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Central Nervous SystemCentral Nervous System
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Anatomical subdivisions of NS
Made up of neurons and neuroglia cells
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Functional Overview of NSFunctional Overview of NSCNSCNS Integration, Integration,
processing and processing and coordination of coordination of sensory data and sensory data and motor commandsmotor commands
Higher functionsHigher functions
PNSPNS
1.1. Sensory or afferent divisionSensory or afferent division with sensory neurons. with sensory neurons. Brings sensory info to CNS. Brings sensory info to CNS.
Begins as receptors, ends Begins as receptors, ends in? in?
2.2. Motor or efferent divisionMotor or efferent division with motor neurons.with motor neurons.Brings motor commands to Brings motor commands to peripheral tissue.peripheral tissue.Ends at effector cells.Ends at effector cells.www.freelivedoctor.comwww.freelivedoctor.com
Peripheral Nervous SystemPeripheral Nervous System
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Cellular Organization of Neural Tissue Cellular Organization of Neural Tissue
Two cell types:Two cell types:
1.1. NeuronsNeurons
2.2. NeurogliaNeuroglia Schwann cellsSchwann cells Satellite cellsSatellite cells AstrocytesAstrocytes OligodendrocytesOligodendrocytes Microglial cellsMicroglial cells Ependymal cellsEpendymal cells
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General Neuron StructureGeneral Neuron Structure
Cell body or Soma with PerikaryonCell body or Soma with Perikaryon DendritesDendrites Axon with axon hillockAxon with axon hillock Synaptic terminalsSynaptic terminals
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AstrocytesAstrocytes: : largest & most numerouslargest & most numerousFunction: BBB
structural framework & repairsregulation of ions, nutrients, gases
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OligodendrocyteOligodendrocyteSmaller than astrocyteSmaller than astrocyte
Produce myelin in CNS Produce myelin in CNS (white matter vs. gray matter!)(white matter vs. gray matter!)
Myelin = ?Myelin = ?
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Microglia cellsMicroglia cells
SmallestSmallest
Phagocytosis of ?Phagocytosis of ?
# during infection # during infection or injuryor injury
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Ependymal Ependymal cellscells
Lining of ventricles & central canalLining of ventricles & central canal
Some regions ciliatedSome regions ciliated
Some specialized to produce CSFSome specialized to produce CSF
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Schwann Cells Schwann Cells and Peripheral Axonsand Peripheral Axons
myelinated
Responsible for Responsible for myelination, but myelination, but surround all peripheral surround all peripheral axons!axons!
Involved in repair Involved in repair mechanism after injury mechanism after injury Wallerian DegenerationWallerian Degeneration
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StructuralStructural Neuron ClassificationNeuron Classification
AnaxonicAnaxonicIn CNSIn CNS
UnipolarUnipolarAlso called Also called
pseudounipolarpseudounipolarSensory neuronsSensory neurons
Axon hillock
See fig. 13-10
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Structural Neuron Classification cont. . .Structural Neuron Classification cont. . .
BipolarBipolarUnmyelinatedUnmyelinatedRare, but important Rare, but important
in special sensesin special senses
MultipolarMultipolarMost commonMost commonAll motor neuronsAll motor neurons
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Functional Neuron ClassificationFunctional Neuron Classification1) somatic vs. 1) somatic vs.
visceral visceral sensory sensory or afferentor afferent
monitoring of ?monitoring of ?
2) somatic vs. 2) somatic vs. visceral motor or visceral motor or efferentefferentcarry instructions to ?carry instructions to ?
3) 3) Inter- or Inter- or association neuronsassociation neurons
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SynapseSynapse
Site of communication between two nerve Site of communication between two nerve cells or nerve cell and effector cell cells or nerve cell and effector cell
neuro-effector junctionsneuro-effector junctions (example?) (example?)
Electrical vs. Electrical vs. chemical synapses chemical synapses
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Chemical SynapseChemical Synapse vs.vs. Electrical SynapseElectrical Synapse
Space between two cells
Signal transduction via NT
Most common
Direct physical contact between cells = gap junctions
Direct signal transduction
Rare, but occurs in CNS and heart
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Chem. Chem. Synapse Synapse
StructureStructure
1.1. Axon terminal of presynaptic cellAxon terminal of presynaptic cell
2.2. Synaptic cleftSynaptic cleft
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Neuron OrganizationNeuron Organization Divergence - One neuron synapses with several,
effectively "spreading the word".
Convergence - Several neurons synapse with a single neuron, concentrating the input.
Serial processing - step-wise, sequential
Parallel processing - simultaneous processing of different information
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Anatomical Organizatin of NSAnatomical Organizatin of NS
Collections of cell bodies - ganglion in PNS, center or nucleus in CNS
Bundles of axons - tracts in CNS, nerves in PNS
“White” = myelinated axons, both nerves and tracts
“Gray” = non-myelinated material, dendrites, synapses and cell bodies as well as nonmyelinated axons. In CNS – nucleus; in PNS - ganglia
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Brain and Cranial NervesBrain and Cranial Nerves Discuss the organization of the brain, including the Discuss the organization of the brain, including the
major structures and their functionsmajor structures and their functions
Describe the meninges of the spinal cord and Describe the meninges of the spinal cord and brain, and integrate the formation and flow of brain, and integrate the formation and flow of CSF with this information.CSF with this information.
Describe the structures that constitute the BBB Describe the structures that constitute the BBB and their functionsand their functions
Review the cranial nerves, again giving a brief Review the cranial nerves, again giving a brief
function of each.function of each.
Major Brain Subdivisions Major Brain Subdivisions
Telencephalon (= Cerebrum)Telencephalon (= Cerebrum)
Diencephalon (Thalamus Diencephalon (Thalamus and hypothalamus)and hypothalamus)
MesencephalonMesencephalon
Metencephalon (Pons Metencephalon (Pons and cerebellum)and cerebellum)
Myelencephalon (= Medulla Myelencephalon (= Medulla oblongata)oblongata)
Brainstem
Gray & White Matter OrganizationGray & White Matter Organization
In In brain stem brain stem similar to similar to spinal cord (spinal cord (nuclei around nuclei around ventricles, tracts on outside)ventricles, tracts on outside)
In In cerebrumcerebrum and and cerebellumcerebellum: white : white matter covered with matter covered with layer of neural cortex layer of neural cortex (grey)(grey)
Cranial MeningesCranial Meninges1. 1. Dura materDura mater - strong, "tough mother" - strong, "tough mother"
a. falx cerebri a. falx cerebri b. falx cerebelli b. falx cerebelli c. tentorum cerebelli c. tentorum cerebelli
2. 2. ArachnoidArachnoid - spidery, holds - spidery, holds blood vesselsblood vessels
3. 3. Pia materPia mater - "delicate mother" - "delicate mother"
Arachnoid granulations: This is where the CSF produced in the choroid plexuses of the ventricles and which has circulated into the subarachnoid space is reabsorbed.
Longitudinal fissure
Four VentriclesFour VentriclesCSF filled chambersCSF filled chambers
Communicating with central canal of spinal cordCommunicating with central canal of spinal cord
Lined by ependymal cells
CSF: Cerebro-Spinal Fluid Formation in ventricles by specialized ependymal cells of Formation in ventricles by specialized ependymal cells of choroid choroid
plexusesplexuses (~500 mL/day; total volume ~ 150 mL)(~500 mL/day; total volume ~ 150 mL)
FunctionsFunctions transport medium, in transport medium, in shock absorption shock absorption buoyancybuoyancy (floats the brain)(floats the brain)
CSF circulation: Ventricles → central canal → subarachnoid spaceCSF circulation: Ventricles → central canal → subarachnoid space
Reabsorption into circulation via Reabsorption into circulation via arachnoid granulationsarachnoid granulations into into superior sagittal sinus. superior sagittal sinus.
Fig 15.6
Blood Brain Barrier (BBB)Blood Brain Barrier (BBB)
what is it?what is it?
3 areas in brain don’t have BBB3 areas in brain don’t have BBB
1.1. portion of hypothalamus portion of hypothalamus
2.2. pineal gland (in diencephalon) pineal gland (in diencephalon)
3.3. choroid plexuschoroid plexus
Two hemispheres Two hemispheres separated by separated by longitudinal longitudinal fissurefissure
Gyrus (gyri) separated by sulcus (sulci)Gyrus (gyri) separated by sulcus (sulci)
Major lobes named Major lobes named after overlaying bonesafter overlaying bones
CerebrumCerebrum
Cerebral Hemispheres . . .Cerebral Hemispheres . . .
. . have functional regions (motor, sensory and association areas)
. . . have some functional differences (in spite of anatomical resemblance) → Lateralization of cortical functioning
. . . receive information and generate commands for opposite side of body
Cerebral Cortex and Central White MatterCerebral Cortex and Central White Matter
Gray surface (cortex) with white tracts internallyGray surface (cortex) with white tracts internally
CommissuresCommissures – connect corresponding gyri of the two – connect corresponding gyri of the two hemispheres hemispheres 1) corpus callosum1) corpus callosum2) anterior commissure2) anterior commissure
Projection tracts (fibers)Projection tracts (fibers) – connect more or less vertically – connect more or less vertically
Association tracts (fibers)Association tracts (fibers) – connect one gyrus to another in – connect one gyrus to another in the same hemispherethe same hemisphere
Basal (or cerebral) NucleiBasal (or cerebral) Nuclei
Misnomer: basal ganglia
Gray matter internal to the cerebral cortex, below floor of lateral ventricles.
Function: modulate motor output from the cerebral cortex. Subconscious control of skeletal muscle tone and coordination of learned movement patterns.
Parkinson's disease is caused by the loss of at least 80% of the dopaminergic neurons in basal nuclei and substantia nigra (resting tremor)
Fig 15.11
DiencephalonDiencephalon
Epithalamus Pineal gland - produces melatonin, sets diurnal cycles
Thalamus (~12 nuclei)
Hypothalamus Just superior to optic chiasma Infundibulum - connects to pituitary gland
Some functions:Control of autonomic nervous system Coordination of nervous and endocrine systems Secretion of hormones - ADH and oxytocin
Mesencephalon)Mesencephalon)= Midbrain = Midbrain
Corpora quadrigemina Corpora quadrigemina = 2 pairs of sensory nuclei= 2 pairs of sensory nuclei1.1. Superior colliculi Superior colliculi (relay station for visual information)2.2. Inferior colliculi Inferior colliculi (relay station for auditory informationinformation
Substantia nigra - regulates motor outputSubstantia nigra - regulates motor output
Cerebral peduncles - ascending and descending tracts to Cerebral peduncles - ascending and descending tracts to thalamusthalamus
Nuclei of ori for CN III and IVNuclei of ori for CN III and IV
Metencephalon: Metencephalon: CerebellumCerebellum
Hemispheres and lobes
Cortex -gray surface with folia - fine ridges and sulci - grooves between the ridges
Purkinje cells , axons of which become arbor vitae (white matter) in center
Regulation of posture and balance
Metencephalon: PonsMetencephalon: PonsMyelencephalon: Medulla oblongataMyelencephalon: Medulla oblongata
Mostly ascending and descending tractsMostly ascending and descending tracts
Nuclei of ori for many cranial nervesNuclei of ori for many cranial nerves
Location of autonomic nuclei involved in respiratory and cardiovascular control
Relay stations for sensory and Relay stations for sensory and motor neurons motor neurons
Cranial NervesCranial Nerves Twelve pairs:Twelve pairs:
2 attach to forebrain 2 attach to forebrain (Telen- & (Telen- & Diencephalon)Diencephalon)
10 attach to 10 attach to brainstembrainstem
(Mes-, Met- and Myelencephalon)(Mes-, Met- and Myelencephalon)
Names relate toNames relate to appearance or function appearance or function
Classification ?Classification ?
Olfactory Nerve (= CN or N I)Olfactory Nerve (= CN or N I)
1º function?1º function?
Origin?Origin?
Destination? _____________(By way of Destination? _____________(By way of cribiform plate of ethmoidcribiform plate of ethmoid))
Only CN directly attached to CerebrumOnly CN directly attached to Cerebrum
Optic Nerve (N II)Optic Nerve (N II)
1º fu?1º fu?
ori?ori?
dest? - dest? - by way of by way of optic foramen of optic foramen of sphenoid to sphenoid to Diencephalon Diencephalon (optic chiasma) (optic chiasma) and to occipital and to occipital lobelobe
Oculomotor (N III)Oculomotor (N III)
C: Motor C: Motor
O: MesencephalonO: Mesencephalon
D: Somatic motor to superior, inferior, medial recti and D: Somatic motor to superior, inferior, medial recti and inferior oblique; visceral motor to intrinsic eye inferior oblique; visceral motor to intrinsic eye musclesmuscles
by way of superior orbital fissure by way of superior orbital fissure
Trochlear (N IV)Trochlear (N IV)
C: Motor C: Motor
O: MesencephalonO: Mesencephalon
D: superior obliqueD: superior oblique
by way of superior orbital fissureby way of superior orbital fissure
Trigeminal (N V)Trigeminal (N V)
C: Mixed C: Mixed three major branchesthree major branches
1. ophthalmic (sensory)1. ophthalmic (sensory)2. Maxillary (sensory)2. Maxillary (sensory)3. Mandibular (mixed)3. Mandibular (mixed)
O: face / nuclei of ponsO: face / nuclei of pons
D: sensory nuclei in pons / muscles of masticationD: sensory nuclei in pons / muscles of mastication
AbducensAbducens(CN VI)(CN VI)
C: Motor O: PonsD: Runs lateral rectus eye muscle
Facial (N VII)Facial (N VII)
C: Mixed C: Mixed
O: sensory from taste receptors of anterior 2/3 of O: sensory from taste receptors of anterior 2/3 of tongue / motor from pons tongue / motor from pons
D: Sensory to sensory nuclei of pons / motor D: Sensory to sensory nuclei of pons / motor muscles of facial expression, visceral motor to muscles of facial expression, visceral motor to tear gland.tear gland.
Vestibulocochlear (N VIII)Vestibulocochlear (N VIII)
Glossopharyngeal (CN IX)Glossopharyngeal (CN IX)
C: mixed
O: sensory from posterior 1/3 of tongue / motor from medulla oblongata
D: medulla / muscles for swallowing, parotid gland
Vagus (N X)Vagus (N X)
C: Mixed C: Mixed
O: O: Sensation from pharyngeal area and outer Sensation from pharyngeal area and outer earear / motor from medulla / motor from medulla
D: D: Sensory to medullaSensory to medulla / / visceral motor to visceral motor to thoracic and abdominal cavities and thoracic and abdominal cavities and their organs. their organs. Major motor pathway Major motor pathway for ANSfor ANS
Accessory (N XI) and Accessory (N XI) and C: Motor C: Motor O: Motor nuclei of medulla O: Motor nuclei of medulla and spinal cordand spinal cordD: Swallowing, trapezius & scm musclesD: Swallowing, trapezius & scm muscles
Hypoglossal (N XII)Hypoglossal (N XII)C: Motor C: Motor O: Motor nuclei of medulla O: Motor nuclei of medulla D: Tongue musculatureD: Tongue musculature
Spinal Cord and Spinal Cord and Spinal NervesSpinal Nerves
Explain spinal cord anatomy, including gray and white matter and meninges (give the general functions of this organ).
Discuss the structure and functions of the spinal nerves and plexuses.
Describe the structural components of reflexes.
Resides inside Resides inside vertebral canalvertebral canal
Extends to L1/ L2Extends to L1/ L2
31 segments, each 31 segments, each associated with a pair associated with a pair of dorsal root gangliaof dorsal root ganglia
Two enlargementsTwo enlargements
Adult spinal cord:Adult spinal cord:
1. Cervical Enlargement1. Cervical Enlargement
Gray matter expanded to incorporate more sensory input from limbs and more cell bodies for motor control of limbs
3) Pia mater
2) Arachnoid
1) Dura mater
Spinal MeningesSpinal Meninges
Three membranes surround all of CNS
1) Dura materDura mater - "tough mother", strong
2) Arachnoid meninxArachnoid meninx - spidery looking, carries blood vessels, etc.
Subarachnoid space
3) Pia materPia mater - "delicate mother", adheres tightly to surface of spinal cord
Inferior End of Inferior End of Spinal CordSpinal Cord
Conus medullarisConus medullaris - inferior end inferior end
of spinal cord properof spinal cord proper
Cauda equinaCauda equina - - individual spinal individual spinal nerves within spinal canal nerves within spinal canal
Filum terminaleFilum terminale - - filamentous filamentous end of meninges, "tie-down" end of meninges, "tie-down"
Lumbar Puncture Lumbar Puncture (= Spinal Tap)(= Spinal Tap)
For clinical examination of CSF or administration of radiopaque dyes, drugs and sometimes anesthetics
However: mostly “epidurals” for anesthetics
L3
L4
Organization of Cord Cross Section Organization of Cord Cross Section
Gray matter - interior hornsposterior - somatic and visceral sensory nucleianterior (and lateral) gray horns – somatic and visceral motor controlgray commissures - axons carrying information from side to side
White matter - tracts or columnsposterior white column - anterior white columnlateral white columnanterior white commissure
functions ascending tracts - sensory toward brain descending tracts - motor from brain
Peripheral NervesPeripheral Nerves
Definition: bundles of axons. AKA tracts in CNS
Organization – coverings:
Epineurium wraps entire nerve
Perineurium wraps fascicles of tracts
Endoneurium wraps individual axons
Anatomy of a Peripheral nerve Anatomy of a Peripheral nerve
Function:sensory - afferentmotor - efferentmixed - contains axons of both
Organization of Spinal Nerves:Organization of Spinal Nerves:
1. Root – inside vertebral canala. dorsal sensory root with a ganglionb. ventral motor
2. Mixed spinal nerve
3. Ramia. dorsal - mixed to skin and muscles of backb. ventral - mixed “spinal nerve” to ventrolateral body surfaces and limbsc. white ramus communicans motor ANSd. gray ramus communicans motor ANS
1.
Fig 14-7
DermatomesDermatomes
Sensory Sensory innervations by innervations by specific spinal specific spinal nerves nerves Each pair Each pair of spinal nerves of spinal nerves monitors specific monitors specific region of body surface.region of body surface.
Clinical significance ?Clinical significance ?
4 Principal4 Principal PlexusesPlexusesBraids of ventral rami of cervical, thoracic, lumbar or sacral spinal nerves
Cervical Plexus
Phrenic nerve - innervates diaphragm
Musculocutaneous nerve - innervates biceps and brachialis muscles
Median nerve - innervates lateral flexors
Ulnar nerve - innervates medial flexors
Radial nerve - innervates forearm extensors
Brachial PlexusBrachial Plexus
ReflexesReflexesFast, stereotypical, inborn, Fast, stereotypical, inborn,
protective actionsprotective actions
Occur at spinal cord or Occur at spinal cord or brainstem levelsbrainstem levels
May be either monosynaptic or May be either monosynaptic or polysynaptic polysynaptic
All require All require a. stimulus at receptora. stimulus at receptorb. sensory information relayb. sensory information relayc. processing at CNS levelc. processing at CNS leveld. activation of motor responsed. activation of motor responsee. response of peripheral e. response of peripheral effectoreffector
Autonomic Division of NSAutonomic Division of NS
Compare and contrast the structures of the sympathetic Compare and contrast the structures of the sympathetic and the parasympathetic divisions, including functions and the parasympathetic divisions, including functions and neurotransmitters.and neurotransmitters.
Show the levels of integration in the ANS, and compare Show the levels of integration in the ANS, and compare these with the SNS.these with the SNS.
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Overview of ANSOverview of ANS
Pathway for Visceral Motor Output Pathway for Visceral Motor Output
ANS has two antagonistic divisions:ANS has two antagonistic divisions:
1.1. SympatheticSympathetic
2.2. ParasympatheticParasympathetic
ANS output always involves two neurons between spinal cord ANS output always involves two neurons between spinal cord (CNS) and effector.(CNS) and effector.
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Synapsing takes place in gangliaSynapsing takes place in ganglia
Naming of neurons:Naming of neurons:
neuron #1neuron #1
preganglionic preganglionic
presynaptic presynaptic
neuron #2neuron #2
GanglionicGanglionic
postsynapticpostsynaptic effectoreffector
Preganglionic fiber (=axon):Always myelinated
Postganglionic fiber:Always unmyelinated
?
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Sympathetic DivisionSympathetic Division
Thoracolumbar division Thoracolumbar division
Preganglionic neurons (cell bodies) located between T1 & Preganglionic neurons (cell bodies) located between T1 & L2 of spinal cordL2 of spinal cord
Ganglionic neurons (cell bodies) in ganglia near vertebral Ganglionic neurons (cell bodies) in ganglia near vertebral columncolumnParavertebral gangliaParavertebral ganglia = sympathetic chain ganglia = sympathetic chain gangliaPrevertebral gangliaPrevertebral ganglia = collateral ganglia = collateral ganglia
Special case: adrenal medullaSpecial case: adrenal medulla
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Special Case: Adrenal medullaAdrenal medulla
Modified sympathetic ganglionModified sympathetic ganglion
Terminus for neuron #1, stimulates specialized 2nd order Terminus for neuron #1, stimulates specialized 2nd order neurons with very short axons in adrenal medulla to neurons with very short axons in adrenal medulla to release NT into blood stream (= hormones)release NT into blood stream (= hormones)
Epinephrine (adrenalin) ~ 80% and norepinephrine Epinephrine (adrenalin) ~ 80% and norepinephrine (noradrenalin)(noradrenalin)
Endocrine effects are longer lasting than nervous system Endocrine effects are longer lasting than nervous system effects effects
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Sympathetic Sympathetic Neuroeffector Neuroeffector
JunctionsJunctions
Differ from somatic Differ from somatic neuromuscular neuromuscular junctionsjunctions
VaricositiesVaricosities
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Summary of Sympathetic DivisionSummary of Sympathetic Division
A. Neuron #1 is short, neuron #2 is longA. Neuron #1 is short, neuron #2 is long
B. Synapsing occurs in prevertebral chain ganglia or B. Synapsing occurs in prevertebral chain ganglia or paravertebral collateral gangliaparavertebral collateral ganglia
C. Neuron #1 releases Ach, usually neuron #2 releases NEC. Neuron #1 releases Ach, usually neuron #2 releases NE
D. Prepares for emergency action, excitatory to many organs, D. Prepares for emergency action, excitatory to many organs, inhibitory to others ( digestive for example)inhibitory to others ( digestive for example)
E. Effects very widespread and somewhat persistentE. Effects very widespread and somewhat persistent
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Para – SympatheticPara – SympatheticDivisionDivision
CraniosacralCraniosacral division division
Preganglionic neurons (cell bodies) located in brain Preganglionic neurons (cell bodies) located in brain stem & sacral segments of spinal cordstem & sacral segments of spinal cord
Ganglionic neurons (cell bodies) in ganglia near Ganglionic neurons (cell bodies) in ganglia near target organs: target organs: Intramural gangliaIntramural ganglia
Effects of parasympathetic division ?Effects of parasympathetic division ?
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Summary of Parasympathetic DivisionSummary of Parasympathetic Division
A. Neurons #1 are long, come from the brain A. Neurons #1 are long, come from the brain stem or sacral spinal cord, run with the spinal stem or sacral spinal cord, run with the spinal or pelvic nerves and produce ACh. or pelvic nerves and produce ACh.
B. Neurons #2 are short, produce ACh, and may B. Neurons #2 are short, produce ACh, and may be either excitory or inhibitory.be either excitory or inhibitory.
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Anatomy of Dual InnervationAnatomy of Dual Innervation
Each organ receives innervation Each organ receives innervation from sympathetic and from sympathetic and parasympathetic fibersparasympathetic fibers
Fibers of both divisions meet & Fibers of both divisions meet & commingle at plexuses (fig commingle at plexuses (fig 17-9) to innervate organs 17-9) to innervate organs close to those centersclose to those centers
Names of plexuses derived Names of plexuses derived from locations or organs from locations or organs involvedinvolved
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