structure and function of the neurologic system chapter 14 mosby items and derived items © 2010,...

Structure and Function of the Structure and Function of the Neurologic SystemNeurologic System

Chapter 14Chapter 14

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.

2Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.

Overview of the Nervous SystemOverview of the Nervous System Central nervous system (CNS)Central nervous system (CNS)

Brain and spinal cordBrain and spinal cord Peripheral nervous system (PNS)Peripheral nervous system (PNS)

Cranial nervesCranial nerves Spinal nervesSpinal nerves PathwaysPathways

• Afferent (ascending; sensory to spinal column)Afferent (ascending; sensory to spinal column)

• Efferent (descending; innervate effector organs)Efferent (descending; innervate effector organs)


Overview of the Nervous SystemOverview of the Nervous System PNSPNS

Somatic nervous systemSomatic nervous system• Motor and sensory pathways regulating voluntary motor Motor and sensory pathways regulating voluntary motor

control of skeletal musclecontrol of skeletal muscle Autonomic nervous system (ANS)Autonomic nervous system (ANS)

• Motor and sensory pathways regulating the body’s Motor and sensory pathways regulating the body’s internal environment through involuntary control of organ internal environment through involuntary control of organ systemssystems

SympatheticSympathetic ParasympatheticParasympathetic


Cells of the Nervous SystemCells of the Nervous System NeuronNeuron

Variable size and structure throughout the nervous Variable size and structure throughout the nervous systemsystem

Cellular constituentsCellular constituents• Microtubules, neurofibrils, Nissl substancesMicrotubules, neurofibrils, Nissl substances

• Some neurons, such as olfactory neurons, continue to Some neurons, such as olfactory neurons, continue to dividedivide


NeuronNeuron Three componentsThree components

Cell body (soma)Cell body (soma)• Located mainly in the CNSLocated mainly in the CNS

• Densely packed cell bodies in the CNS are nucleiDensely packed cell bodies in the CNS are nuclei

• Densely packed cell bodies in the PNS are gangliaDensely packed cell bodies in the PNS are ganglia

DendritesDendrites• Receptive portion of the neuron (sends impulses to cell Receptive portion of the neuron (sends impulses to cell

body)body)


NeuronNeuron AxonsAxons

Carry nerve impulses away from cell bodyCarry nerve impulses away from cell body Axon hillockAxon hillock

• Cone-shaped, Nissl-free area where the axon leaves the Cone-shaped, Nissl-free area where the axon leaves the cell bodycell body

Initial segment of the axonInitial segment of the axon• Area of axon with lowest threshold for stimulation, so Area of axon with lowest threshold for stimulation, so

action potentials begin hereaction potentials begin here



MyelinMyelin• Segmented layer of lipid materialSegmented layer of lipid material• Insulating substanceInsulating substance• Formed and maintained by the Schwann cellFormed and maintained by the Schwann cell

EndoneuriumEndoneurium• Delicate layer of connective tissue around each axonDelicate layer of connective tissue around each axon

NeurilemmaNeurilemma• Thin membrane between the myelin sheath and the Thin membrane between the myelin sheath and the

endoneuriumendoneurium



Nodes of RanvierNodes of Ranvier• Regular interruptions of the myelin sheathRegular interruptions of the myelin sheath

Saltatory conductionSaltatory conduction• Flow of ions between segments of myelin rather than Flow of ions between segments of myelin rather than

along the entire length of the axonalong the entire length of the axon DivergenceDivergence

• Ability of branching axons to influence many neuronsAbility of branching axons to influence many neurons ConvergenceConvergence

• Branches of numerous neurons converging on one or a Branches of numerous neurons converging on one or a few neuronsfew neurons


Structural Classification of Structural Classification of NeuronsNeurons

Based on the number of processes extending Based on the number of processes extending from the cell bodyfrom the cell body UnipolarUnipolar PseudounipolarPseudounipolar BipolarBipolar MultipolarMultipolar


Functional Classification of Functional Classification of NeuronsNeurons

SensorySensory Transmit impulses from sensory receptors to the Transmit impulses from sensory receptors to the

CNSCNS AssociationalAssociational

Transmit impulses from neuron to neuronTransmit impulses from neuron to neuron MotorMotor

Transmit impulses from the CNS to an effector Transmit impulses from the CNS to an effector organorgan


NeurogliaNeuroglia ““Nerve glue”Nerve glue” Support the neurons of the CNSSupport the neurons of the CNS

AstrocytesAstrocytes Oligodendroglia (oligodendrocytes)Oligodendroglia (oligodendrocytes) MicrogliaMicroglia Ependymal cellsEpendymal cells


NeurogliaNeuroglia


Nerve Injury and RegenerationNerve Injury and Regeneration Wallerian degenerationWallerian degeneration

Occurs distal to the cutOccurs distal to the cut• Swelling appearsSwelling appears

• Neurofilaments hypertrophyNeurofilaments hypertrophy

• Myelin sheath shrinks and disintegratesMyelin sheath shrinks and disintegrates

• Axon portion degenerates and disappearsAxon portion degenerates and disappears


Nerve Injury and RegenerationNerve Injury and Regeneration Proximal to the cutProximal to the cut

Swelling and dispersal of the Nissl substanceSwelling and dispersal of the Nissl substance Cell increases in metabolic activity, protein Cell increases in metabolic activity, protein

synthesis, and mitochondrial activitysynthesis, and mitochondrial activity New terminal sprouts project from proximal New terminal sprouts project from proximal

segmentsegment Process limited to myelinated axonsProcess limited to myelinated axons

• Generally only in the PNSGenerally only in the PNS

Depends on location, type of injury, inflammatory Depends on location, type of injury, inflammatory response, and scar tissue formationresponse, and scar tissue formation


NeurogliaNeuroglia


Nerve ImpulseNerve Impulse Neurons generate and conduct electrical and Neurons generate and conduct electrical and

chemical impulses by selectively changing chemical impulses by selectively changing the electrical portion of their plasma the electrical portion of their plasma membranes and influencing other nearby membranes and influencing other nearby neurons by the release of neurotransmittersneurons by the release of neurotransmitters


SynapsesSynapses Region between adjacent neuronsRegion between adjacent neurons Impulses are transmitted across the synapse by Impulses are transmitted across the synapse by

chemical and electrical conductionchemical and electrical conduction Presynaptic neurons and postsynaptic neuronsPresynaptic neurons and postsynaptic neurons

Connections between pre- and postsynaptic neuronsConnections between pre- and postsynaptic neurons• AxoaxonicAxoaxonic

• AxosomaticAxosomatic

• AxodendriticAxodendritic

• DendrodentriticDendrodentritic


SynapsesSynapses NeurotransmittersNeurotransmitters

More than 30 substances (e.g., dopamine, GABA, More than 30 substances (e.g., dopamine, GABA, endorphins)endorphins)

Excitatory (excitatory postsynaptic potential)Excitatory (excitatory postsynaptic potential) Inhibitory (inhibitory postsynaptic potential)Inhibitory (inhibitory postsynaptic potential)

Synaptic boutonsSynaptic boutons Synaptic cleft Synaptic cleft SummationSummation

Temporal summationTemporal summation Spatial summationSpatial summation FacilitationFacilitation


Central Nervous SystemCentral Nervous System ForebrainForebrain

Cerebral hemispheresCerebral hemispheres Midbrain Midbrain

Corpora quadrigemina, tegmentum, and cerebral Corpora quadrigemina, tegmentum, and cerebral pedunclespeduncles

Hindbrain (brain stem)Hindbrain (brain stem) Cerebellum, pons, and medullaCerebellum, pons, and medulla


Central Nervous SystemCentral Nervous System Reticular formationReticular formation

Network of connected nuclei that regulate viral Network of connected nuclei that regulate viral reflexes, such as cardiovascular and respiratory reflexes, such as cardiovascular and respiratory functionfunction

Together with the cerebral cortex is referred to as Together with the cerebral cortex is referred to as the reticular activating systemthe reticular activating system


Central Nervous SystemCentral Nervous System


Central Nervous SystemCentral Nervous System ForebrainForebrain

TelencephalonTelencephalon• Cerebrum Cerebrum

Gyri, sulci, and fissuresGyri, sulci, and fissures Gray matter and white matterGray matter and white matter

• Cerebral nuclei (basal ganglia)Cerebral nuclei (basal ganglia)


ForebrainForebrain


Central Nervous SystemCentral Nervous System Hemispheres (right, left)Hemispheres (right, left) Frontal lobeFrontal lobe

Prefrontal Prefrontal • Goal-directed behaviorGoal-directed behavior

PremotorPremotor• Basal gangliaBasal ganglia

Primary motor areaPrimary motor area Broca speech areaBroca speech area


Central Nervous SystemCentral Nervous System Parietal lobeParietal lobe

Sensory inputSensory input Occipital lobeOccipital lobe

Visual cortexVisual cortex Temporal lobeTemporal lobe

Wernicke area (speech)Wernicke area (speech)


Central Nervous SystemCentral Nervous System DiencephalonDiencephalon

EpithalamusEpithalamus ThalamusThalamus HypothalamusHypothalamus SubthalamusSubthalamus


Central Nervous SystemCentral Nervous System MidbrainMidbrain

Corpora quadrigemina (tectum)Corpora quadrigemina (tectum)• Superior and inferior colliculiSuperior and inferior colliculi

TegmentumTegmentum• Red nucleus and substantia nigraRed nucleus and substantia nigra

Basis pedunculiBasis pedunculi


Central Nervous SystemCentral Nervous System Hindbrain (metencephalon)Hindbrain (metencephalon)

CerebellumCerebellum PonsPons

MyelencephalonMyelencephalon Medulla oblongataMedulla oblongata


Central Nervous SystemCentral Nervous System


Spinal CordSpinal Cord Lies within the vertebral canal and is Lies within the vertebral canal and is

protected by the vertebral columnprotected by the vertebral column Connects the brain and the bodyConnects the brain and the body Conducts somatic and autonomic reflexesConducts somatic and autonomic reflexes Provides motor pattern control centersProvides motor pattern control centers Modulates sensory and motor functionModulates sensory and motor function


Spinal CordSpinal Cord SectionsSections

Cervical, thoracic, lumbar, and sacralCervical, thoracic, lumbar, and sacral HornsHorns

PosteriorPosterior LateralLateral AnteriorAnterior


Spinal CordSpinal Cord


Reflex ArcReflex Arc ReceptorReceptor Afferent (sensory) neuronAfferent (sensory) neuron Efferent neuronEfferent neuron EffectorEffector


Reflex ArcReflex Arc


Upper and Lower Motor NeuronsUpper and Lower Motor Neurons Upper motor neuronsUpper motor neurons

Efferent pathways primarily relaying information Efferent pathways primarily relaying information from the cerebrum to the brainstem or spinal cordfrom the cerebrum to the brainstem or spinal cord

Synapse with interneuronsSynapse with interneurons Destruction = partial recoveryDestruction = partial recovery

Lower motor neuronsLower motor neurons Neurons having direct influence on musclesNeurons having direct influence on muscles Cell bodies originate in gray matter of spinal cord, Cell bodies originate in gray matter of spinal cord,

but their axons extend into the PNSbut their axons extend into the PNS Destruction = permanent paralysisDestruction = permanent paralysis


Neuromuscular JunctionNeuromuscular Junction


Motor PathwaysMotor Pathways Lateral corticospinalLateral corticospinal CorticobulbarCorticobulbar Basal gangliaBasal ganglia Vestibulospinal Vestibulospinal


Sensory PathwaysSensory Pathways Anterior spinothalamicAnterior spinothalamic Lateral spinothalamic Lateral spinothalamic Posterior (dorsal)Posterior (dorsal)

Three neuron chainThree neuron chain Ipsilateral transmissionIpsilateral transmission Contralateral transmissionContralateral transmission


Protective StructuresProtective Structures CraniumCranium

Eight bonesEight bones• FrontalFrontal

• OccipitalOccipital

• Temporal (2)Temporal (2)

• Parietal (2)Parietal (2)

• SphenoidSphenoid

• EthmoidEthmoid

Galea aponeuroticaGalea aponeurotica


Protective StructuresProtective Structures MeningesMeninges

Protective membranes surrounding the brain and Protective membranes surrounding the brain and spinal cordspinal cord• Dura materDura mater

• ArachnoidArachnoid

• Pia materPia mater


MeningesMeninges


Protective StructuresProtective Structures Cerebrospinal fluid (CSF) and the ventricular Cerebrospinal fluid (CSF) and the ventricular

systemsystem CSF is a clear, colorless fluid similar to blood CSF is a clear, colorless fluid similar to blood

plasma and interstitial fluidplasma and interstitial fluid 125 to 150 ml125 to 150 ml Produced by the choroid plexuses in the lateral, Produced by the choroid plexuses in the lateral,

third, and fourth ventriclesthird, and fourth ventricles Reabsorbed through the arachnoid villiReabsorbed through the arachnoid villi


Protective StructuresProtective Structures Vertebral columnVertebral column

33 vertebrae33 vertebrae• 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, and 4 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, and 4

fused coccygealfused coccygeal

Intervertebral disksIntervertebral disks• Nucleus pulposusNucleus pulposus


Vertebral ColumnVertebral Column


Blood Supply to the BrainBlood Supply to the Brain 800 to 1000 ml per minute800 to 1000 ml per minute COCO22 is the primary regulator for CNS blood is the primary regulator for CNS blood

flowflow Internal carotid and vertebral arteriesInternal carotid and vertebral arteries Arterial circle (circle of Willis)Arterial circle (circle of Willis) Blood-brain barrierBlood-brain barrier


Blood Supply to the BrainBlood Supply to the Brain


Blood Supply to the Spinal CordBlood Supply to the Spinal Cord Vertebral arteriesVertebral arteries

Anterior spinal arteriesAnterior spinal arteries Posterior spinal arteriesPosterior spinal arteries

AortaAorta


Blood Supply to the Spinal CordBlood Supply to the Spinal Cord

INSERT Figure 14-22


Peripheral Nervous SystemPeripheral Nervous System 31 pairs of spinal nerves31 pairs of spinal nerves

Names correlate with the vertebral level from Names correlate with the vertebral level from which they exitwhich they exit

Mixed nervesMixed nerves Arise from the anterior and posterior horn cells of Arise from the anterior and posterior horn cells of

the spinal cordthe spinal cord 12 pairs of cranial nerves12 pairs of cranial nerves

Sensory, motor, and mixedSensory, motor, and mixed


Peripheral Nervous SystemPeripheral Nervous System FasciclesFascicles

Bundles of myelinated axons in the PNSBundles of myelinated axons in the PNS Rami Rami PlexusesPlexuses

Brachial plexusBrachial plexus Lumbar plexusLumbar plexus Sacral plexusSacral plexus

DermatomesDermatomes


Peripheral Nervous SystemPeripheral Nervous System


Autonomic Nervous SystemAutonomic Nervous System Located in both the CNS and PNSLocated in both the CNS and PNS Coordinates and maintains a steady state Coordinates and maintains a steady state

among the visceral (internal) organsamong the visceral (internal) organs NeuronsNeurons

Preganglionic (myelinated)Preganglionic (myelinated) Postganglionic (unmyelinated)Postganglionic (unmyelinated)

Two divisionsTwo divisions SympatheticSympathetic Parasympathetic Parasympathetic


Sympathetic Nervous SystemSympathetic Nervous System Mobilizes energy stores in times of needMobilizes energy stores in times of need

““Fight or flight response”Fight or flight response” Receives innervation from cell bodies located Receives innervation from cell bodies located

from the first thoracic through the second from the first thoracic through the second lumbarlumbar Thoracolumbar divisionThoracolumbar division

Sympathetic (paravertebral) gangliaSympathetic (paravertebral) ganglia


Sympathetic Nervous SystemSympathetic Nervous System


Parasympathetic Nervous Parasympathetic Nervous SystemSystem

Functions to conserve and restore energyFunctions to conserve and restore energy ““Rest or repose response”Rest or repose response”

Receives innervation from cell bodies located Receives innervation from cell bodies located in the cranial nerve nuclei and sacral region in the cranial nerve nuclei and sacral region of the spinal cordof the spinal cord Craniosacral divisionCraniosacral division

Preganglionic neurons travel to ganglia close Preganglionic neurons travel to ganglia close to the organs they innervateto the organs they innervate


Parasympathetic Nervous Parasympathetic Nervous SystemSystem


Neurotransmitters and Neurotransmitters and Neuroreceptors of the ANSNeuroreceptors of the ANS

Sympathetic preganglionic fibersSympathetic preganglionic fibers Acetylcholine and cholinergic receptorsAcetylcholine and cholinergic receptors

Sympathetic postganglionic fibersSympathetic postganglionic fibers Norepinephrine and adrenergic receptorsNorepinephrine and adrenergic receptors

Parasympathetic pre- and postganglionic fibersParasympathetic pre- and postganglionic fibers Acetylcholine and cholinergic receptorsAcetylcholine and cholinergic receptors


Neurotransmitters and Neurotransmitters and Neuroreceptors of the ANSNeuroreceptors of the ANS


Aging and the Nervous SystemAging and the Nervous System

Structural changesStructural changes Decrease in the number of neuronsDecrease in the number of neurons Decreased brain weight and sizeDecreased brain weight and size Increased adherence of the dura mater to the skullIncreased adherence of the dura mater to the skull Fibrosis and thickening of the meningesFibrosis and thickening of the meninges Narrowed gyri and widened sulci with a Narrowed gyri and widened sulci with a

corresponding increase in the size of the corresponding increase in the size of the subarachnoid spacesubarachnoid space

Basal ganglia and ventricular system Basal ganglia and ventricular system • Aberrations in vascular structuresAberrations in vascular structures


Aging and the Nervous SystemAging and the Nervous System Cellular changesCellular changes

Deposition of lipofuscin Deposition of lipofuscin Presence of senile plaquesPresence of senile plaques Multiple neurofibrillary tanglesMultiple neurofibrillary tangles Lewy bodies Lewy bodies


Aging and the Nervous SystemAging and the Nervous System Functional changesFunctional changes

Slowed response to neural signalsSlowed response to neural signals


Tests of Nervous System Tests of Nervous System FunctionFunction

Skull and spine roentgenogramsSkull and spine roentgenograms Computed tomographyComputed tomography Magnetic resonance imagingMagnetic resonance imaging

Magnetic resonance angiographyMagnetic resonance angiography Positron emission tomography scanPositron emission tomography scan Brain scanBrain scan Cerebral angiographyCerebral angiography


Tests of Nervous System Tests of Nervous System FunctionFunction

MyelographyMyelography Echoencephalography (ultrasound)Echoencephalography (ultrasound) ElectroencephalographyElectroencephalography Evoked potentialsEvoked potentials Cerebrospinal fluid analysisCerebrospinal fluid analysis

structure and function of the neurologic system chapter 14 mosby items and derived items © 2010,...

Documents