Guyton & Hall Figure 45.2 Fundamentals Of Nervous System
Guyton & Hall – Figure 45.2Fundamentals of Nervous SystemGeneral Design of Nervous System:Analogy ComputerProcessing Integrative System 99% of sensory informationdiscardedInput Sensory SystemReceptors:Tactile Synapses determine pathwayof signalsVisual Information stored for future useAuditorOlfactoryOutput Motor SystemEffectors:Skeletal muscleSmooth muscleGlandular secretionMemory:Highly facilitated synaptic pathways(sensory input not required to excite pathway)Fundamentals of Nervous SystemFundamentals of Nervous SystemHistology of Nervous System:Organization of Nervous System:A. Neuroglia (supporting cells – “nerve glue”)Nervous systemCentral Nervous System (CNS)ciliated(most common)IntegrationCentral nervous systemPeripheral nervous system(CNS)(PNS)MotoroutputBrainSpinal cordSensoryinputMotor divisionSensory division(efferent)(afferent)Autonomic nervous systemSomatic nervous system(involuntary; smooth & cardiac muscle)(voluntary; skeletal muscle)Astrocytes: anchor neurons to capillaries repair damaged neural tissue maintain “blood / brain barrier”Microglia:Ependymal cells: macrophages; engulf invaders line canals / ventricles of brain produce cerebrospinal fluid (CSF)Peripheral Nervous System (PNS)Schwann cells: Insulate neurons (myelin sheath)Sympathetic divisionParasympathetic divisionOligodendrocytes:Satellite cells: Insulate neurons (myelin sheath)Fundamentals of Nervous SystemHistology of Nervous System:B. NeuronsFundamentals of Nervous System Long-lived ( 100 years) High metabolic rateHistology of Nervous System:B. Neurons Specialized “excitable” cells Allow for communication throughout body (via electrical impulses) Long-lived ( 100 years) High metabolic rate Specialized “excitable” cells Allow for communication throughout body (via electrical impulses)Functional Classification of Neurons:Neuron Anatomy:1) Dendrites: Receive information (environment / other neurons)2) Cell body (soma): Integrates information / initiate response1) Sensory (Afferent) neurons:3) Axon: Conducts action potential (AP – electrical impulse)4) Synaptic terminals: Transmit signal (other neurons / effector organs)2) Motor Carry information from sensory receptors to CNSAxon hillock (AP generation)Dendrites Function similar to astrocytesAxon(Efferent)neurons: Carry information from CNS to effector organs3) Association neurons (Interneurons): Interconnects neurons in brain / spinal cordSynapticterminalsSchwann Cells (PNS)Centrioles(Can not divide)Cell body1
Fundamentals of Nervous SystemCentral Nervous System Long-lived ( 100 years)Histology of Nervous System: High metabolic rateB. Neurons Specialized “excitable” cells Allow for communication throughout body (via electrical impulses)Structural Classification of Neurons (# of processes) :MultipolarBipolarUnipolar( 3 processes)(2 processes)(1 process)AxonAxonAxonDendritesTrigger zoneDendritesTrigger zoneTrigger zoneDendrites Motor neurons Interneurons Sensory neurons Sensory neurons(e.g., special sense organs)(PNS)Central Nervous SystemCentral Nervous SystemOrganization of Nervous System:Brain:No correlation exists between brainsize and intelligence 3.5 lbs (35 billion neurons) brain 10% larger than brainNervous systemIntegrationCentral nervous systemPeripheral nervous system(CNS)(PNS)MotoroutputBrainSpinal cordGross Anatomy:Cerebrum(forebrain)SensoryinputMotor divisionSensory Autonomic nervous systemSomatic nervous system(involuntary; smooth & cardiac muscle)(voluntary; skeletal muscle)BrainstemCerebellum(hindbrain)Sympathetic divisionParasympathetic divisionMarieb & Hoehn – Figure 12.1Central Nervous SystemEmbryonic Development of Brain:Central Nervous SystemHow we will considerbrain anatomyEmbryonic Development of Brain:3 week old embryoMarieb & Hoehn – Figure 12.25 week old embryoNeuraltubeNeural crestNeural platePrimary brain vesiclesStep 3:Neural fold cells migrate; form neural crestStep 1: Neural crest gives rise to PNSAnteriorNeural plate forms from surface ectoderm4 week old in)Neural foldRhombencephalon(hindbrain)Secondary brain vesiclesAdult brain Brain stem (midbrain)Metencephalon(afterbrain)Brain stem (pons)Myelencephalon(spinalbrain)Brain stem (medulla)CerebellumPosteriorStep 2:Neural grooveStep 4:Neural tubeNeural plate invaginates; forms neural grooveNeural groove becomes neural tube; sinks deep Neural folds flank neural groove Neural tube gives rise to CNSSpinal cord2
Central Nervous SystemCentral Nervous SystemSpace restriction greatly affectsbrain developmentEmbryonic Development of Brain:Nuclei:Groups of cell bodies located inthe central nervous systemBasic Layout of Neurons:(analogous to ganglia in PNS)Brain stem (pons)White matter: Regions of myelinated axons in CNSBrain stem y matter: Regions of unmyelinated axons / cell bodies in CNSBrain stem (medulla)CortexWhitematterCerebrumCervicalflexure5 week old embryoGraymatterWhitematterGraymatter13 week old embryo Flexures develop to fit rapidly growingbrain into membranous skull Cerebrum forced togrow posterior andlateral (‘horseshoe’)Nucleus Convolutions develop toincrease surface areaof brainNewbornSpinal cordCerebrum Basic pattern observed in CNS Cortex formed by migration of neurons Cerebellum similar to cerebrum in its external cortex26 week old embryoMarieb & Hoehn – Figure 12.3Marieb & Hoehn – Figure 12.4Marieb & Hoehn – Figure 12.5Central Nervous SystemBrain Anatomy:Central Nervous SystemCSF Circulation:A. Ventricles: Hollow chambers enclosed within brain (continuouswith each other )Presence of CSF in subarachnoid spacegives buoyancy to brain (97% weight reduction)Arachnoid villusCerebrospinal fluid (CSF)Lateral ventricle1) CSF produced by choroid plexus inventricles Provide constant, controlled environmentfor brain cells2) CSF flows through ventricles and intosubarachnoid space via lateral andmedian apertures Protect brain from toxinsThird ventricle Prevent escape of local neurotransmitters3) CSF exits subarachnoid space viaarachnoid villiChoroid plexus:Cerebral aqueductVascular network; produces CSFFourth ventricle Similar ion compositionto blood plasmaCentral canalLateral aperture protein contentMedian apertureVentricles lined with ependymal cells(circulate CSF) Lumbar puncture Gasses cross freely(spinal tap)Hydrocephalus 0.5 L / day producedCostanzo – Figure 3.36(‘water on the brain”)Marieb & Hoehn – Figure 12.26Central Nervous SystemCentral Nervous System 85% of brain massBrain Anatomy:B. Cerebrum (cerebral Fissure(deep groove)LateralsulcusMarieb & Hoehn – Figure 12.63
Central Nervous SystemCentral Nervous SystemBrain Anatomy:Brain Anatomy:B. Cerebrum (cerebral hemispheres):B. Cerebrum (cerebral hemispheres):The cerebralcortex is theseat of consciousbehavior1) Cerebral cortex:Basic regions:Cerebral cortex(superficial to deep)Cerebralwhite matter1) Cerebral cortex (gray matter) Contains 3 types of functional areas:Only 2 - 4 mm thickbut comprises 40%of the brain’s mass1) Motor areas (send output)2) Sensory areas (receive input)3) Association areas (interpret data)2) Cerebral white matter2.5 ft2 of surface area3) Basal nucleiCorpus callosum:White tract connectingcerebral hemispheresFunctional MRI scan(measure blood flow)Neural cartographyBasal nuclei(electrostimulation)Marieb & Hoehn – Figure 12.8Central Nervous SystemBrain Anatomy:B. Cerebrum (cerebral hemispheres):1) Cerebral cortex: Motor areas:Primary motorcortexNote:One-to-one correspondence betweencortical neurons and muscles misleading;map really “fuzzy”Conscious control of skeletalmuscle movementsSomatotopic mapping:The entire body is spatiallyrepresented in the cerebral cortexPyramidal cells extend long axonsto the spinal cord, forming pyramidaltracts, or corticospinal tractsCentral Nervous System1) Cerebral cortex: Motor areas:Conscious control of skeletalmuscle movementsPrimary somatorsensorycortexB. Cerebrum (cerebral hemispheres):communicatesdirectly withprimary motor cortexPremotor cortexControls learned motorskills of repetitiousor patterned natureMarieb & Hoehn – Figure 12.8Central Nervous SystemBrain Anatomy:Primary motorcortexFrontal eye fieldControls voluntarymovement of eyesMarieb & Hoehn – Figure 12.9Marieb & Hoehn – Figure 12.8Brain Anatomy:B. Cerebrum (cerebral hemispheres):Central Nervous SystemHomunculus (“little man”):Receives information fromsensory receptors in skin &proprioreceptors in joints1) Cerebral cortex:Spatialdiscrimination Sensory areas:SomatosensoryassociationcortexGustatory cortexReceives / interpretssensations of tasteIntegrates / interpretssomatosensory inputs(e.g., temp. / pressure)(e.g., typing)Primary visualcortexPrimary auditorycortexBroca’s areaControls muscles involvedin speech production(often more pronounced inone hemisphere of brain)Receives visualinformationReceives auditoryinformation(tonotopic mapping)AuditoryAssociation areaIntegrates / interpretsauditory inputs(e.g., music / thunder)MedialOlfactory cortexReceives olfactoryinformation Part of rhinencephalon (‘nose brain’)(retinotopic mapping)VisualassociationareaIntegrates / interpretsvisual inputs(e.g., color / form)4
Marieb & Hoehn – Figure 12.8Central Nervous SystemBrain Anatomy:Central Nervous SystemPhrenology:The brain is the organ of the mind;contains localized, specific modulesPhineus Gage (1823 – 1860)Locations where sensations, thoughts,and emotions become consciousB. Cerebrum (cerebral hemispheres):Franz Gall(makes us who we are )1) Cerebral cortex:(1758 – 1828) Association areas (multimodal):The American Crowbar Case(matures slowly)Anterior associationareaIntroduction(Prefrontal cortex) IntelligenceComplex learningRecallPersonalityMarieb & Hoehn – Figure 12.8Central Nervous SystemBrain Anatomy:Central Nervous SystemBrain Anatomy:Locations where sensations, thoughts,and emotions become consciousB. Cerebrum (cerebral hemispheres):(makes us who we are )1) Cerebral cortex:The cerebralcortex is theseat of consciousbehaviorB. Cerebrum (cerebral hemispheres):1) Cerebral cortex: Contains 3 types of functional areas Association areas (multimodal):Decussation:Only 2 - 4 mm thickbut comprises 40%of the brain’s massLocation where neural pathways cross2.5 ft2 of surface area Contralateral control (e.g., left hemisphere controls right body)Anterior associationareaPosterior associationarea Pattern recognitionSpatial recognitionSensory groupingLanguage centers Occur at different locations in CNS Lateralization(i.e., hemisphere specialization)(Wernicke’s area)Limbic associationareaProcesses emotions relatedto personal / social interactionsCentral Nervous SystemCentral Nervous SystemBrain Anatomy:B. Cerebrum (cerebral hemispheres):Basic regions:Cerebral cortex(superficial to deep)Cerebralwhite matter1) Cerebral cortex (gray matter)2) Cerebral white matter3) Basal nucleiCategoricalRepresentationalBasal nuclei5
Central Nervous SystemCentral Nervous SystemBrain Anatomy:Brain Anatomy:B. Cerebrum (cerebral hemispheres):Associationfibers2) Cerebral white matter:B. Cerebrum (cerebral hemispheres):CommissuralfibersBasic regions:Fiber tracts responsible for communicationbetween cerebral areas and lower CNSCerebral cortex(superficial to deep)Cerebralwhite matter1) Cerebral cortex (gray matter)2) Cerebral white matterA) Commissural Fibers (form commissures) : Interconnect cerebral hemispheres3) Basal nucleiB) Association Fibers: Interconnect areas of neural cortexwithin a single hemisphereC) Projection Fibers: Interconnect cerebral hemisphereswith other regions of the brainProjectionfibersCorona radiata:Point where projection fibers radiate fan-likethrough cerebral white matterInternal capsule:Compact band of projectionfibers near diencephalonBasal nucleiMarieb & Hoehn – Figure 12.10Central Nervous SystemCentral Nervous SystemBrain Anatomy:B. Cerebrum (cerebral hemispheres):3) Basal nuclei:Cerebrum Composed of gray matter (neuron cell bodies) Function:(forebrain)1) Subconscious control of skeletal muscle tone2) Control stereotypical motor movements (e.g., arm swing) Regulate intensity / inhibit unnecessary nstemCerebellum(hindbrain)Striped appearancedue to passage ofinternal capsule fibersCentral Nervous SystemCentral Nervous System“Emotional brain”Brain Anatomy:Brain Anatomy:Limbic system (functional brain system):ThalamusC. Diencephalon:Diencephalon structures: Thalamus (anterior thalamic nuclei) Hypothalamus“Gateway to thecerebral cortex”Thalamus:Cerebral cortex structures: Composes 80% of diencephalon Cingulate gyrus Parahippocampal gyrus Hippocampus Amygdala Relay station for all informationentering / exiting the cerebral cortexFornix:Fiber tract linkingregions togetherHypothalamus: Autonomic control center Center for emotional response Body temperature regulation Regulation of food / water intake Regulation of sleep-wake cycles Control of endocrine systemHypothalamus Alzheimer’s Disease: Control emotional states (e.g., fear) / behavioral drives (e.g., sex drive)Epithalamus:Epithalamus Houses pineal gland (melatonin)and choroid plexus (forms CSF)“Control centerof body”Marieb & Hoehn – Figure 12.12 / 12.13 Link conscious (cerebral cortex) with unconscious function (brain stem) Psychosomatic illnesses emotion-induced illness Long-term memory storage / retrievalProgressive degenerativedisease of the brain Memory loss Disorientation Moodiness / confusion6
Central Nervous SystemCentral Nervous SystemBrain Anatomy:D. Brain stem: Deep gray matter; superficial white matterCerebrum Produce rigidly programmed, autonomicbehaviors necessary for survival(forebrain)Thalamus Conduction pathways between higherand lower brain centersMidbrain:DiencephalonMidbrain Visual / auditory reflex centers(midbrain)Pons: Regulate respiration rate / depthPonsMedulla oblongata:BrainstemCerebellum(hindbrain) Location where fiber tracts fromspinal cord cross over (decussation)Medullaoblongata Autonomic reflex center Heart rate / blood pressure Respiratory rhythm Vomiting / hiccupping / etc.Marieb & Hoehn – Figure 12.19Central Nervous SystemMarieb & Hoehn – Figure 12.15Central Nervous SystemBrain Anatomy:Reticular Activating System (RAS - functional brain system):Aggregation of looselyclustered Raphenucleus Raphe nuclei (midline) Medial (large cell) group Lateral (small cell) groupvisualstimuliDiencephalon(midbrain)Twisting of brain stem canlead to irreversible n)generalstimuli Maintains cerebral cortical alertness (e.g., on / off switch) Filters out repetitive stimuli ( 99% of stimuli filtered )Central Nervous SystemCentral Nervous SystemBrain Anatomy:Meningitis:Protection of the Brain:1) Bone (Skull – cranium portion)E. Cerebellum: Gray matter superficial; white matter deep“Small brain”2) Meninges (specialized connective tissue membranes)(11% TBM) Precise timing of muscle coordinationA) Dura mater (“tough mother”)(balance, posture, repeated movements) All activity subconsciousInflammation of the meningesFoliaArbor vitae Fibrous outer coating(2 layers) Protects CNSC) Pia mater (“gentle mother”) Thin inner membrane Contains blood vesselsB) Arachnoid mater (“spider mother”)Cerebellar Processing: Delicate middle layerTwo layers enclosedural venous sinuses Nourishes CNSCerebral cortexsends signal to moveBoneDura mater(periosteal layer)MaintainbodycoordinationSensory informationfrom bodyDura mater(meningeal layer)Arachnoid materSubarachnoidspace(filled with CSF)Pia materCommands to motorneurons of spinal cordMarieb & Hoehn – Figure 12.17Marieb & Hoehn – Figure 12.247
Central Nervous SystemCentral Nervous SystemConstant internal environment necessaryfor proper neuronal functioning in brainProtection of the Brain:1) Bone (Skull – cranium portion)Leading cause of accidentaldeath in North AmericaHomeostatic Imbalances of the Brain:1) Traumatic brain injury2) Meninges (specialized connective tissue membranes)3) Blood-brain barrier: Astrocyte-maintained barrier lining blood capillariesThree layers of protection:A. Capillary endotheliumB. Thick basal laminaC. Bulbous ‘feet’ of astrocytes Signal tight junction formationTightly regulate substancesbathing brain:In: glucose, amino acids,selected electrolytesConcussionSubdural hemorrhageCerebral edemaAlteration in brain functionfollowing blow to headBleeding into subarachnoidspace via ruptured vesselsSwelling of the brain2) Cerebrovascular accidentOut: metabolic waste (urea),proteins, toxins, drugsThird leading cause ofdeath in North America3) Degenerative brain disordersIschemic stroke Alzheimer’s disease Displays differentially permeable (e.g., vomit center brain stem) Parkinson’s diseaseBlockage of blood supplyto brain due to blood clot Huntington’s disease May be transientMarieb & Hoehn – Figure 11.3Central Nervous SystemCentral Nervous SystemOrganization of Nervous System: Provides conduction pathway to / from brainNervous system Contains major reflex centersIntegrationCentral nervous systemPeripheral nervous system(CNS)Cervicalregion(8)(8) Independently initiates patterns of motoractivity (e.g., otected byvertebral column / meningesSpinal Cord:Spinal cordSensoryinputMotor divisionSensory division(efferent)(afferent)Autonomic nervous systemSomatic nervous system(involuntary; smooth & cardiac muscle)(voluntary; skeletal muscle)Gross Anatomy: 18 inches long (via vertebral foramen) Two enlargements (cervical / lumbar) Innervation of medullaris Cord proper ends at L1 Cauda equina (“horse’s tail”) Spinal nerves (31 Sympathetic division(5)Parasympathetic division(1)(1)Marieb & Hoehn – Figure 12.29Central Nervous SystemSpinal Cord:Cross-sectional Anatomy:Posterior median sulcusPosteriorfuniculusAscending tracts:Carry information to brainDescending tracts:Carry information from brainCentral Nervous SystemSpinal Cord:Cross-sectional Anatomy:Transverse tracts:Carry information across cordWhitematterCentral canalLateralfuniculusGraymatterCharacteristics:1) Decussation presentAnteriorfuniculusAnterior median fissure2) Multi-neuron pathways3) Somatotopy exhibited4) Symmetrical arrangementMarieb & Hoehn – Figure 12.338
Central Nervous SystemCentral Nervous SystemSpinal Cord:Spinal Cord:Cross-sectional Anatomy:Cross-sectional Anatomy:Posterior median rsal RootDorsal rootganglion(interneurons)SensoryneuronCentral ron(visceral motor orfuniculusVentral RootAnteriorhornAnterior median fissure(somatic motor neurons)Central Nervous SystemCentral Nervous SystemSpinal Cord:Homeostatic Imbalances of the Spinal Cord:Organization of Gray Matter:1) Spinal cord traumaParalysis / ParesthesiasParaplegiaQuadriplegiaDamage to spinal cord leadingleading to functional / sensory lossTransection of spinal cordbetween T1 and L1Transection of spinal cordbetween C4 and C72) Poliomyelitis3) Amyotrophic lateral sclerosis (ALS)Lou Gehrig’sdiseaseDestruction of ventral hornmotor neurons by poliovirusProgressive destruction of ventralhorn motor neurons (autoimmune?)9
Guyton & Hall –Figure 45.2 Fundamentals of Nervous System Nervous system Central nervous system (CNS) Peripheral nervous system (PNS) Brain Spinal cord Sensory division (afferent) Motor division (efferent) Somatic nervous system (voluntary; skeletal muscle) Autonomic (involuntary; smo
with integrative physiology development was the circulatory dynamics model published by Prof. Arthur C. Guyton and his collaborators (Guyton et al. 1972). Subsequently, its more detailed description was published in the monograph one year later (Guyton et al. 1973). This model represents the first large-scale mathematical
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