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Neurons and Nervous Systems

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Neurons and Nervous Systems

Neurons and Nervous Systems

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    Neurons and Nervous Systems Neurons and Nervous Systems Presentation Transcript

    • Neurons & NervousChapter 39
    • 2Neurons & Nervous SyNeurons & Nervous SyOutlineOutlineEVOLUTION OF THE NERVOUS SYSTEMEVOLUTION OF THE NERVOUS SYSTEM Gradual increase in the complexity of the nervous systemGradual increase in the complexity of the nervous system All vertebrates have a well-developed brainAll vertebrates have a well-developed brainNERVOUS TISSUENERVOUS TISSUE NeuronsNeurons Nerve impulseNerve impulseBRAIN AND SPINAL CORDBRAIN AND SPINAL CORD Spinal cordSpinal cord CerebrumCerebrum­ Sensory inputSensory input­ Motor controlMotor control HomeostasisHomeostasis Limbic systemLimbic systemPERIPHERAL NERVOUS SYSTEMPERIPHERAL NERVOUS SYSTEM NervesNerves Somatic systemSomatic system Autonomic systemAutonomic system
    • 3Neurons & Nervous SyNeurons & Nervous SyInvertebrate Nervous OrganizationInvertebrate Nervous OrganizationHydrasHydrasNerve net composed of neurons in contactNerve net composed of neurons in contactwith one anotherwith one anotherAlso in contact with contractileAlso in contact with contractileepitheliomuscular cellsepitheliomuscular cellsPlanariansPlanariansLadderlike nervous systemLadderlike nervous systemCephalization - a concentration of gangliaCephalization - a concentration of gangliaand sensory receptors in the headand sensory receptors in the headAnnelids, Arthropods and MolluscsAnnelids, Arthropods and MolluscsComplex animalsComplex animalsTrue nervous systemsTrue nervous systems
    • 4Evolution of the NervousSystem
    • 5Neurons & Nervous SyNeurons & Nervous SyVertebrate Nervous OrganizationVertebrate Nervous OrganizationCentral nervous systemCentral nervous systemDevelops from an embryonic dorsalDevelops from an embryonic dorsaltubular nerve cordtubular nerve cordCephalization and bilateral symmetryCephalization and bilateral symmetryresult in several paired sensory receptorsresult in several paired sensory receptorsVertebrate brain is organized into threeVertebrate brain is organized into threeareasareasHindbrainHindbrainMidbrainMidbrainForebrain
    • 6Neurons & Nervous SyNeurons & Nervous SyHuman Nervous SystemHuman Nervous SystemNervous system has three specificNervous system has three specificfunctionsfunctionsReceiving sensory inputReceiving sensory inputPerforming integrationPerforming integrationGenerating motor outputGenerating motor output
    • 7Organization of theHuman NervousSystem
    • 8Neurons & Nervous SyNeurons & Nervous SyHuman Nervous SystemHuman Nervous SystemCentral nervous system (CNS)Central nervous system (CNS)Includes the brain and spinal cordIncludes the brain and spinal cordLies in the midline of the bodyLies in the midline of the bodyThe peripheral nervous system (PNS)The peripheral nervous system (PNS)Contains cranial nerves and spinal nervesContains cranial nerves and spinal nervesthatthatGather info from sensors and conductGather info from sensors and conductdecisions to effectorsdecisions to effectorsLies outside the CNSLies outside the CNS
    • 9Neurons & Nervous SyNeurons & Nervous SyNervous TissueNervous TissueNeuronsNeuronsCell body contains nucleusCell body contains nucleusDendrites receive signals from sensoryDendrites receive signals from sensoryreceptorsreceptorsAxon conducts nerve impulsesAxon conducts nerve impulses­ Covered by myelin sheathCovered by myelin sheath­ Any long axon is also called a nerve fiberAny long axon is also called a nerve fiber
    • 10Neurons & Nervous SyNeurons & Nervous SyTypes of NeuronsTypes of NeuronsMotor NeuronsMotor NeuronsAccept nerve impulses from the CNSAccept nerve impulses from the CNSTransmit them to muscles or glandsTransmit them to muscles or glandsSensory NeuronsSensory NeuronsAccept impulses from sensory receptorsAccept impulses from sensory receptorsTransmit them to the CNSTransmit them to the CNSInterneuronsInterneuronsConvey nerve impulses between variousConvey nerve impulses between variousparts of the CNSparts of the CNS
    • 11NeuronAnatomy
    • 12Neurons & Nervous SyNeurons & Nervous SyNerve Impulses:Nerve Impulses:Resting PotentialResting PotentialResting PotentialResting PotentialThe membrane potential (voltage) whenThe membrane potential (voltage) whenthe axon is not conducting an impulsethe axon is not conducting an impulse­ The inside of a neuron is more negativeThe inside of a neuron is more negativethan the outside -65 mVthan the outside -65 mV­ Due in part to the action of the sodium-Due in part to the action of the sodium-potassium pumppotassium pump
    • 13Neurons & Nervous SyNeurons & Nervous SyAction PotentialAction PotentialAn action potential is generated only afterAn action potential is generated only aftera stimulus larger than the thresholda stimulus larger than the thresholdGated channel proteinsGated channel proteinsSuddenly allows sodium to pass throughSuddenly allows sodium to pass throughthe membranethe membraneAnother allows potassium to pass throughAnother allows potassium to pass throughother directionother direction
    • 14Resting and Action Potentialof theAxonal Membrane
    • 15Neurons & Nervous SyNeurons & Nervous SyPropagation of Action PotentialsPropagation of Action PotentialsIn myelinated fibers, an action potentialIn myelinated fibers, an action potentialat one node causes an action potentialat one node causes an action potentialat the next nodeat the next nodeSaltatory (jumping) ConductionSaltatory (jumping) ConductionConduction of a nerve impulse is an all-Conduction of a nerve impulse is an all-or-nothing eventor-nothing eventIntensity of signal is determined by howIntensity of signal is determined by howmany impulses are generated within amany impulses are generated within agiven time spangiven time span
    • 16Neurons & Nervous SyNeurons & Nervous SyTransmission Across a SynapseTransmission Across a SynapseA synapse is a region where neuronsA synapse is a region where neuronsnearly touchnearly touchSmall gap between neurons is theSmall gap between neurons is thesynaptic cleftsynaptic cleftTransmission across a synapse is carriedTransmission across a synapse is carriedout by neurotransmittersout by neurotransmittersSudden rise in calcium at end of oneSudden rise in calcium at end of oneneuronneuronStimulates synaptic vesicles to mergeStimulates synaptic vesicles to mergewith the presynaptic membranewith the presynaptic membraneNeurotransmitter molecules are releasedNeurotransmitter molecules are released
    • 17Synapse Structure andFunction
    • 18Neurons & Nervous SyNeurons & Nervous SySynaptic IntegrationSynaptic IntegrationA single neuron is on the receiving end ofA single neuron is on the receiving end ofMany excitatory signals, andMany excitatory signals, andMany inhibitory signalsMany inhibitory signalsIntegrationIntegrationThe summing of signals fromThe summing of signals fromExcitatory signals, andExcitatory signals, andInhibitory signalsInhibitory signals
    • 19SynapseIntegration
    • 20Neurons & Nervous SyNeurons & Nervous SyCNS: Brain and Spinal CordCNS: Brain and Spinal CordSpinal cord and brain are wrapped inSpinal cord and brain are wrapped inthree protective membranes, meningesthree protective membranes, meningesSpaces between meninges are filled withSpaces between meninges are filled withcerebrospinal fluidcerebrospinal fluidFluid is continuous with that of centralFluid is continuous with that of centralcanal of spinal cord and the ventricles ofcanal of spinal cord and the ventricles ofthe brainthe brain
    • 21Neurons & Nervous SyNeurons & Nervous SySpinal CordSpinal CordThe spinal cord has two main functionsThe spinal cord has two main functionsCenter for many reflex actionsCenter for many reflex actionsMeans of communication between theMeans of communication between thebrain and spinal nervesbrain and spinal nervesThe spinal cord is composed of grayThe spinal cord is composed of graymatter and white mattermatter and white matterCell bodies and short unmyelinated fibersCell bodies and short unmyelinated fibersgive the gray matter its colorgive the gray matter its colorMyelinated long fibers of interneuronsMyelinated long fibers of interneuronsrunning in tracts give white matter itsrunning in tracts give white matter itscolorcolor
    • 22Neurons & Nervous SyNeurons & Nervous SyThe BrainThe BrainCerebrum is the largest portion of theCerebrum is the largest portion of thebrain in humansbrain in humansCommunicates with, and coordinates theCommunicates with, and coordinates theactivities of, the other parts of the brainactivities of, the other parts of the brainLongitudinal fissure divides into left andLongitudinal fissure divides into left andright cerebral hemispheresright cerebral hemispheres
    • 23The HumanBrain
    • 24Neurons & Nervous SyNeurons & Nervous SyCerebral CortexCerebral CortexA thin but highly convoluted outer layer ofA thin but highly convoluted outer layer ofgray mattergray matterCovers the cerebral hemispheresCovers the cerebral hemispheresContains motor areas and sensory areasContains motor areas and sensory areasas well as association areasas well as association areasPrimary motor area is in the frontal lobePrimary motor area is in the frontal lobejust ventral to central sulcusjust ventral to central sulcusPrimary somatosensory area is just dorsalPrimary somatosensory area is just dorsalto central sulcusto central sulcus
    • 25The Lobes of a CerebralHemisphere
    • 26Neurons & Nervous SyNeurons & Nervous SyCerebrumCerebrumRest of cerebrum is composed of whiteRest of cerebrum is composed of whitemattermatterDescending tracts communicate withDescending tracts communicate withlower brain centerslower brain centersAscending tracts send sensoryAscending tracts send sensoryinformation to primary somatosensoryinformation to primary somatosensoryareaareaBasal nucleiBasal nuclei­ Integrate motor commandsIntegrate motor commands­ Ensure that the proper muscle groups areEnsure that the proper muscle groups are
    • 27Neurons & Nervous SyNeurons & Nervous SyDiencephalonDiencephalonA region encircling the third ventricleA region encircling the third ventricleConsists of hypothalamus and thalamusConsists of hypothalamus and thalamusHypothalamus forms floor of the thirdHypothalamus forms floor of the thirdventricleventricleThalamus consists of two masses of grayThalamus consists of two masses of graymatter located in the sides and roof of thematter located in the sides and roof of thethird ventriclethird ventriclePineal glandPineal glandAlso located in the diencephalonAlso located in the diencephalon
    • 28Neurons & Nervous SyNeurons & Nervous SyCerebellumCerebellumSeparated from the brain stem by theSeparated from the brain stem by thefourth ventriclefourth ventricleReceives sensory input from the eyes,Receives sensory input from the eyes,ears, joints, and musclesears, joints, and musclesSends motor impulses out the brain stemSends motor impulses out the brain stemto the skeletal musclesto the skeletal muscles
    • 29Neurons & Nervous SyNeurons & Nervous SyBrain StemBrain StemContains the midbrain, the pons, and theContains the midbrain, the pons, and themedulla oblangatamedulla oblangataMidbrainMidbrain­ Acts as a relay station for tracts passingActs as a relay station for tracts passingbetweenbetween The cerebrum, andThe cerebrum, and The spinal cord or cerebellumThe spinal cord or cerebellumPonsPons­ Helps regulate breathing and headHelps regulate breathing and headmovementsmovementsMedulla oblongataMedulla oblongata­ Contains reflex centers for vomiting,Contains reflex centers for vomiting,coughing, sneezing, hiccuping, andcoughing, sneezing, hiccuping, and
    • 30Neurons & Nervous SyNeurons & Nervous SyLimbic SystemLimbic SystemComplex network of tracts and “nuclei”Complex network of tracts and “nuclei”Incorporates medial portions ofIncorporates medial portions ofThe cerebral lobes,The cerebral lobes,The subcortical basal nuclei, andThe subcortical basal nuclei, andThe dicenephalonThe dicenephalonIntegrates higher mental functions andIntegrates higher mental functions andprimitive emotionsprimitive emotionsHippocampusHippocampusAmygdalaAmygdala
    • 31The LimbicSystem
    • 32Neurons & Nervous SyNeurons & Nervous SyPeripheral Nervous SystemPeripheral Nervous SystemSomatic systemSomatic system Contains cranial nerves and spinal nervesContains cranial nerves and spinal nerves­ Gather info from sensors and conduct decisions to effectorsGather info from sensors and conduct decisions to effectors­ Controls the skeletal musclesControls the skeletal muscles Conscious of its activityConscious of its activityAutonomic systemAutonomic system Controls the smooth muscles, cardiac muscles, and glandsControls the smooth muscles, cardiac muscles, and glands Usually unaware of its actionsUsually unaware of its actions Divided into two divisionsDivided into two divisions­ Sympathetic divisionSympathetic division­ Parasympathetic divisionParasympathetic division
    • 33Cranial and SpinalNerves
    • 34A Reflex Arc ShowingthePath of a SpinalReflex
    • 35Neurons & Nervous SyNeurons & Nervous SyAutonomic SystemAutonomic SystemRegulates activity of cardiac and smoothRegulates activity of cardiac and smoothmuscle, and glandsmuscle, and glandsDivided into sympathetic andDivided into sympathetic andparasympathetic divisionsparasympathetic divisionsFunction automatically and usually in anFunction automatically and usually in aninvoluntary mannerinvoluntary mannerInnervate all internal organsInnervate all internal organsUtilize two neurons and one ganglion forUtilize two neurons and one ganglion foreach impulseeach impulse
    • 36Autonomic SystemStructure andFunction
    • 37Neurons & Nervous SyNeurons & Nervous SySympathetic andSympathetic andParasympathetic DivisionsParasympathetic DivisionsSympathetic divisionSympathetic divisionEspecially important during fight or flightEspecially important during fight or flightresponsesresponsesAccelerates heartbeat and dilates bronchiAccelerates heartbeat and dilates bronchiParasympathetic divisionParasympathetic divisionPromotes all internal responsesPromotes all internal responsesassociated with a relaxed stateassociated with a relaxed statePromotes digestion and retards heartbeatPromotes digestion and retards heartbeat
    • 38Neurons & Nervous SyNeurons & Nervous SyReviewReviewEVOLUTION OF THE NERVOUS SYSTEMEVOLUTION OF THE NERVOUS SYSTEM Gradual increase in the complexity of the nervous systemGradual increase in the complexity of the nervous system All vertebrates have a well-developed brainAll vertebrates have a well-developed brainNERVOUS TISSUENERVOUS TISSUE NeuronsNeurons Nerve impulseNerve impulseBRAIN AND SPINAL CORDBRAIN AND SPINAL CORD Spinal cordSpinal cord CerebrumCerebrum­ Sensory inputSensory input­ Motor controlMotor control HomeostasisHomeostasis Limbic systemLimbic systemPERIPHERAL NERVOUS SYSTEMPERIPHERAL NERVOUS SYSTEM NervesNerves Somatic systemSomatic system Autonomic systemAutonomic system
    • Neurons & NervousEnding Slide Chapter 39