l nervous system

Central Nervous SystemCentral Nervous System

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Anatomical subdivisions of NS

Made up of neurons and neuroglia cells


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


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


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


AstrocytesAstrocytes: : largest & most numerouslargest & most numerousFunction: BBB

structural framework & repairsregulation of ions, nutrients, gases


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 = ?


Microglia cellsMicroglia cells

SmallestSmallest

Phagocytosis of ?Phagocytosis of ?

# during infection # during infection or injuryor injury


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


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


StructuralStructural Neuron ClassificationNeuron Classification

AnaxonicAnaxonicIn CNSIn CNS

UnipolarUnipolarAlso called Also called

pseudounipolarpseudounipolarSensory neuronsSensory neurons

Axon hillock

See fig. 13-10


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


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


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


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


Chem. Chem. Synapse Synapse

StructureStructure

1.1. Axon terminal of presynaptic cellAxon terminal of presynaptic cell

2.2. Synaptic cleftSynaptic cleft

3.3. Dendrite or cell body of postsynaptic cellDendrite or cell body of postsynaptic cellwww.freelivedoctor.comwww.freelivedoctor.com

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


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


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

http://www.neuroskills.com/tbi/brainstemflash.shtml

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.


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.


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

?


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

Effects of Sympathetic Division?Effects of Sympathetic Division?www.freelivedoctor.comwww.freelivedoctor.com

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


Sympathetic Sympathetic Neuroeffector Neuroeffector

JunctionsJunctions

Differ from somatic Differ from somatic neuromuscular neuromuscular junctionsjunctions

VaricositiesVaricosities


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


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 ?


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.


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


l nervous system

Technology

effector cells

nerve cells

neurons synapse

ventricles csf

cells signal transduction

neuronsand neuroglia

cell body of postsynaptic

cell types