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  1. 1. LECTURE PRESENTATIONSFor CAMPBELL BIOLOGY, NINTH EDITIONJane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson© 2011 Pearson Education, Inc.Lectures byErin BarleyKathleen FitzpatrickNeurons, Synapses, and SignalingChapter 48授課老師: 曾昭能第一教學大樓 N914分機2692cntseng@kmu.edu.tw
  2. 2. Overview: Lines of Communication• The cone snail kills prey with venom that disablesneurons• Neurons are nerve cells that transfer informationwithin the body• Neurons use two types of .:1. electrical signals (long-distance)2. chemical signals (short-distance)© 2011 Pearson Education, Inc.
  3. 3. Topics• Flow of information in nervous systemand neuron• Membrane potential• Synapse• Neurotransmitter
  4. 4. Concept 48.1: Neuron organization andstructure reflect function in informationtransfer• Information Processing• Nervous systems process information inthree stages:– sensory input– integration– motor output© 2011 Pearson Education, Inc.
  5. 5. Fig. 48-3SensorSensory inputIntegrationEffectorMotor outputPeripheral nervoussystem (PNS)Central nervoussystem (CNS)Sensory neuronMotor neuronInterneuron
  6. 6. Neuron Structure and Function• Most of a neuron’s organelles are in the cellbody• Most neurons have dendrites, highly branchedextensions that receive signals from otherneurons• The axon is typically a much longer extensionthat transmits signals to other cells at synapses• The cone-shaped base of an axon is called theaxon hillock 軸突坵© 2011 Pearson Education, Inc.
  7. 7. Fig. 48-4Dendrites接收訊息StimulusNucleusCell body代謝訊息整合Axon hillock軸突丘動作電位發起處PresynapticcellAxon傳出訊息Synaptic terminalsSynapsePostsynaptic cellNeurotransmitter
  8. 8. Concept 48.2: Ion pumps and ion channelsmaintain the resting potential of a neuron• Every cell has a voltage (difference in electricalcharge) across its plasma membrane called amembrane potential (potential=電壓,電位)• Messages are transmitted as changes inmembrane potential• The resting potential is the membranepotential of a neuron not sending signals–The inside of a cell is negative relative tothe outside
  9. 9. OUTSIDECELL[K+]5 mM[Na+]150 mM[Cl–]120 mMINSIDECELL[K+]140 mM[Na+]15 mM[Cl–]10 mM[A–]100 mM(a) (b)OUTSIDECELLNa+KeyK+Sodium-potassiumpumpPotassiumchannelSodiumchannelINSIDECELLMembrane potential is established by1. uneven distribution of ions across membrane2. opening of ion-specific channel
  10. 10. Ion transport across membrane• ATPase pump• Na+/K+ pump• Ion channels• Leak K+ channel• Voltage-gated ion channel• Voltage-gated Na+ channel• Voltage-gated K+ channel
  11. 11. Resting membrane potential靜止膜電位• Caused by1. Na+/K+ pump• Na+ → out• K+ → in• 膜內外電價仍相等2. Leak K+ channel• 使部分K+漏出• 細胞內損失正電價而帶負電Na+Na+Na+Na+Na+Na+K+K+K+K+K+K+K+Na+
  12. 12. 靜止膜電位是一種平衡電位Equilibrium potential• 在造成靜止膜電位時 K+的移動會達到平衡 因為下列兩者的作用力方向相反且互相抗衡– 擴散• Chemical gradient• 驅使K+往細胞外流– 電價堆積• Electrical gradient• 逐漸變強 使K+不易外流• 因此靜止膜電位最後會維持一穩定值– 可以Nernst equation 計算
  13. 13. NERNST EQUATION (參考用)► Chemical gradient Free energy change per mole of solute moved across the plasma membrane (movingout)△Gconc = - RTln(Co/Ci)► Electrical gradient Free energy change per mole of ion with charge z moved across the plasmamembrane with inside relative voltage V△Gvolt = zFV► There is no free energy change at equilibrium; △Gconc + △Gvolt = 0(zFV) + (-RTln(Co/Ci)) = 0(zFV) = RTln(Co/Ci)V = 2.3(RT/zF).log(Co/Ci)► For a univalent ion at 37 C, 2.3(RT/zF) = 61.5 (mV)V = log(Co/Ci) × 61.5 (mV)► Typical cell Vm=-89mV, [K+]o=5mM [K+]i=140mM
  14. 14. • 只要知道膜內外某離子的濃度比值,便可預測此離子通道打開後產生之膜電位值• 藉由打開/關閉各種離子通道‚可改變膜電位
  15. 15. Figure 48.8Innerchamber90 mV 62 mVOuterchamberInnerchamberOuterchamber140 mMKCl150 mMNaCl5 mMKCl15 mMNaClPotassiumchannelSodiumchannelArtificialmembraneK NaClCl(a) Membrane selectively permeableto K(b) Membrane selectively permeableto NaEK 62 mV 90 mV ENa 62 mV 62 mV
  16. 16. 觀念回顧• 膜電位的產生– 因為 1.膜內外離子分佈不均 2.打開特定離子通道– 離子移動會達成平衡,產生穩定的電壓• 單一離子通道造成的膜電位可以 Nernst equation 計算出• 由Co/Ci比值決定 (10/1 與100/10產生相同膜電位)– 交替打開不同的離子通道就可使膜電位在不同值之間跳動• 打開K+ channel: -90 mV• 打開Na+ channel: +60 mV
  17. 17. 觀念補充• 細胞的靜止膜電位(-70mV)的實際值比K+的平衡電位理埨值(-90mV)稍高– 雖然主要由K+離子通道造成但平常仍有相對少數的Na+通道是開著• 計算單一離子通道產生之平衡電位– 與通道數目無關• 實際會受相對通道數目影響
  18. 18. Concept 48.3: Action potentials are thesignals conducted by axons• Changes in membrane potential occur becauseneurons contain gated ion channels that openor close in response to stimuli© 2011 Pearson Education, Inc.MicroelectrodeVoltagerecorderReferenceelectrodeTECHNIQUE
  19. 19. • 過極化– When gated K+ channels open, K+ diffusesout, making the inside of the cell more negative– This is hyperpolarization過極化, an increase inmagnitude of the membrane potential© 2011 Pearson Education, Inc.Hyperpolarization and Depolarization
  20. 20. • Opening other types of ion channels triggers adepolarization去極化, a reduction in themagnitude of the membrane potential• For example, depolarization occurs if gated Na+channels open and Na+ diffuses into the cell© 2011 Pearson Education, Inc.
  21. 21. StimulusThresholdRestingpotentialHyperpolarizationsTime (msec)5005010010 2 3 4 55005010050050100Time (msec)10 2 3 4 5Time (msec)10 2 3 4 5 6ThresholdRestingpotentialThresholdRestingpotentialStimulus Strong depolarizing stimulusActionpotentialDepolarizationsMembranepotential(mV)Membranepotential(mV)Membranepotential(mV)(a) Graded hyperpolarizationsproduced by two stimuli thatincrease membrane permeabilityto K(b) Graded hyperpolarizationsproduced by two stimuli thatincrease membrane permeabilityto Na(c) Action potential triggered by adepolarization that reaches thethresholdFigure 48.10
  22. 22. • 神經細胞受足夠刺激,使其興奮,且膜電位超過閾值後,才會產生動作電位• Graded potential 階梯電位– 動作電位產生前的膜電位變化– 發生於樹突及細胞本體– 刺激造成特定離子通道打開– 大小與刺激程度成比例‚可加成– 被動擴散‚會耗損
  23. 23. • Neurons contain gated ion channels thatopen or close in response to stimuli• Gated(看管,控制) ion channels open or close in responseto– membrane stretch• Mechanoreceptors– the binding of a specific ligand 配體• Ligand-gated ion channels– a change in the membrane potential• Voltage-gated ion channels
  24. 24. ACTION POTENTIAL• Two kinds of voltage-gated channels open during action potential– voltage-gated Na+ channel: 開得快 關得快– voltage-gated K+ channel: 開得慢 關得慢• Voltage-gated Na+ channel– 因受刺激→去極化→打開– Na+進入→造成更大去極化→形成連鎖反應1. 最後所有Na+通道都打開• 每次AP時所有Na+ 通道都打開• 所以AP 大小都一樣2. 在鄰近區域引發去極化並產生AP
  25. 25. 動作電位中離子通道之開關鈉離子電位閘門通道: 開--------塞住(inactivation)鉀離子電位閘門通道: 開------------------關鈉離子流入膜電位偏正 更多鉀離子流出 膜電位比平常更負
  26. 26. OUTSIDE OF CELLINSIDE OF CELLInactivation loopSodiumchannelPotassiumchannelActionpotentialThresholdResting potentialTimeMembranepotential(mV)50100500NaKKey2134512345 1Resting state UndershootDepolarizationRising phase of the action potentialFalling phase of the action potentialFigure 48.11-5
  27. 27. Refractory Period不反應期• Absolute refractory period:– Axon membrane is incapable ofproducing another AP.– VG Na + channel inactivated• Relative refractory period:– More K+ channels are open (VG+ leak K+ channels).– Hyperpolarization– Axon membrane can produceanother action potential, butrequires stronger stimulus.
  28. 28. Conduction of Action Potentials• An action potential travel by regeneratingitself along the axon– action potential is generated at the axon hillock,• Refractory period prevents the actionpotential from traveling backwards• Conduction speed is increased by– Larger diameter– Myelination
  29. 29. Fig. 48-12AxonSchwanncellMyelin sheathNodes ofRanvierNode of RanvierSchwanncellNucleus ofSchwann cellLayers of myelinAxon0.1 µmMyelin sheaths are made by glia—oligodendrocytes in the CNS and Schwanncells in the PNS
  30. 30. Saltatory Conduction• Action potentials in myelinated axons– Jump between the nodes of Ranvier in a processcalled saltatory(跳躍)conductionCell bodySchwann cellMyelinsheathAxonDepolarized region(node of Ranvier)++ +++ +++ +++––––––––––––Figure 48.15
  31. 31. Concept 48.4: Neurons communicate withother cells at synapses• At electrical synapses,– the electrical current flows from one neuron toanother• At chemical synapses,– a chemical neurotransmitter carries informationacross the gap junction• Most synapses in human brain are chemicalsynapses© 2011 Pearson Education, Inc.
  32. 32. Chemical synapse• Synaptic vesicle突觸小泡• Neurotransmitter• Voltage-gated calcium channel 因去極化而打開• Synaptic cleft 突觸溝• Ligand-gated ion channel 與神經傳導物質結合而打開
  33. 33. PresynapticcellPostsynaptic cellAxonPresynapticmembraneSynaptic vesiclecontainingneurotransmitterPostsynapticmembraneSynapticcleftVoltage-gatedCa2 channelLigand-gatedion channelsCa2NaK2134Figure 48.15
  34. 34. Generation of Postsynaptic Potentials• Postsynaptic potential– 神經傳導物質釋放後,在突觸後細胞造成的局部膜電位變化• Direct synaptic transmission– 打開 ligand-gated ion channels, ionotropicreceptor• Indirect synaptic transmission– Metabotropic receptor– 經由活化G蛋白與second messenger間接影響後突觸端的離子通道/膜電位– slower onset but last longer
  35. 35. • Postsynaptic potentials fall into twocategories:– Excitatory postsynaptic potentials (EPSPs) 興奮性更容易產生動作電位– Inhibitory postsynaptic potentials (IPSPs)抑制性 更不容易產生動作電位• After release, the neurotransmitter– May diffuse out of the synaptic cleft– May be taken up by surrounding cells– May be degraded by enzymes
  36. 36. Summation總和, 神經細胞的訊息處理• Through summation, an IPSP can counter theeffect of an EPSP• The summed effect of EPSPs and IPSPsdetermines whether an axon hillock will reachthreshold and generate an action potential© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.
  37. 37. Figure 48.17Terminal branchof presynapticneuronPostsynapticneuronAxonhillockE1E2E1E2E1E2E1E2I I I I070Membranepotential(mV)Threshold of axon ofpostsynaptic neuronRestingpotentialActionpotentialActionpotentialIE1 E1 E1 E1 E1 E2 E1 ISubthreshold, nosummation(a) (b) Temporal summation (c) Spatial summation Spatial summationof EPSP and IPSP(d)E1
  38. 38. Neurotransmitters• There are more than 100neurotransmitters, belonging to five groups:acetylcholine, biogenic amines, aminoacids, neuropeptides, and gases• A single neurotransmitter may have more than adozen different receptors© 2011 Pearson Education, Inc.
  39. 39. Table 48.2
  40. 40. Acetylcholine• Acetylcholine is a common neurotransmitterin vertebrates and invertebrates• In vertebrates it is usually an excitatorytransmitter
  41. 41. Biogenic Amines• Biogenic amines includeepinephrine, norepinephrine, dopamine, andserotonin• They are active in the CNS and PNS
  42. 42. Amino Acids• Two amino acids are known to function asmajor neurotransmitters in the CNS: gamma-aminobutyric acid (GABA, -氨基丁酸) andglutamate谷氨酸
  43. 43. Neuropeptides• Several neuropeptides, relatively short chains ofamino acids, also function as neurotransmitters• Neuropeptides include substance P (物質P) andendorphins腦內啡, which both affect ourperception of pain• Opiates鴉片類bind to the same receptors asendorphins and can be used as painkillers
  44. 44. LECTURE PRESENTATIONSFor CAMPBELL BIOLOGY, NINTH EDITIONJane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson© 2011 Pearson Education, Inc.Lectures byErin BarleyKathleen FitzpatrickNervous SystemsChapter 49授課老師: 曾昭能第一教學大樓 N914分機2692cntseng@kmu.edu.tw
  45. 45. Topics• Evolution of nervous system– Vertebrate nervous system– PNS• Brain– Sleep & arousal, Biological clock– Emotion, Language, Learning & Memory– Neurological Disease
  46. 46. • Each single-celled organism can respond tostimuli in its environment• Animals are multicellular and most groupsrespond to stimuli using systems of neurons© 2011 Pearson Education, Inc.Concept 49.1: Nervous systems consist ofcircuits of neurons and supporting cells
  47. 47. Nerve net(a) Hydra (cnidarian)RadialnerveNervering(b) Sea star (echinoderm)Nerve net:a series ofinterconnectednerve cells, nonerveNerves: bundlesof nerve fibersRadially symmetrical
  48. 48. EyespotBrainNervecordsTransversenerveBrainVentralnerve cordSegmentalganglia(c) Planarian (flatworm) (d) Leech (annelid)flatworms have a central nervoussystem (CNS) consists of a brainand longitudinal nerve cordsBilaterallysymmetricalGangliasegmentally arrangedclusters of neuronsCephalization & Centralization
  49. 49. (e) Insect (arthropod)SegmentalgangliaVentralnerve cordBrainAnteriornerve ringLongitudinalnerve cords(f) Chiton (mollusc) (g) Squid (mollusc)GangliaBrainGangliaBrainSpinalcord(dorsalnervecord)Sensoryganglia(h) Salamander (vertebrate)Nervous system organization correlateswith lifestyleSessile molluscs (e.g., clams andchitons) have simple systems,More complex molluscs(e.g., octopuses and squids) have moresophisticated systemsIn vertebratesCNS: brain and spinalcordPeripheral nervous system(PNS): nerves and ganglia
  50. 50. Organization of the Vertebrate NervousSystem• The spinal cord– conveys information from and to the brain– produces reflexes independently of the brain• A reflex is the body’s automatic response to astimulus– For example, a doctor uses a mallet to triggera knee-jerk reflex© 2011 Pearson Education, Inc.
  51. 51. QuadricepsmuscleCell body ofsensory neuron indorsal rootganglionGraymatterWhitematterHamstringmuscleSpinal cord(cross section)Sensory neuronMotor neuronInterneuronFigure 49.3
  52. 52. • Invertebrates– Ventral腹 nerve cord• Vertebrates– Dorsal背 spinal cord• The spinal cord and brain develop from theembryonic nerve cord• The nerve cord gives rise to the central canaland ventricles of the brain© 2011 Pearson Education, Inc.
  53. 53. Figure 49.4Central nervoussystem (CNS)BrainSpinal cordPeripheral nervoussystem (PNS)Cranial nervesGanglia outsideCNSSpinal nerves骨頭包覆
  54. 54. • Cerebrospinal fluid, CSF– Filtered from blood– Cushion the brain and spinalcord– central canal of the spinalcord– ventricles of the brain• Gray matter– neuron cell bodies, dendrites, andunmyelinated axons• White matter– bundles of myelinated axons
  55. 55. Glia in the CNS• Ependymal cells室管膜細胞 promote circulation ofcerebrospinal fluid• Microglia微膠細胞 protect the nervous system frommicroorganisms• Oligodendrocytes寡突細胞 and Schwann cells form themyelin sheaths around axonsOligodendrocyteMicroglialcellSchwann cellsEpendy-malcellNeuron AstrocyteCNS PNSCapillaryVENTRICLE
  56. 56. • Astrocytes 星狀細胞– structural support for neurons– regulate extracellular ions andneurotransmitters– induce the formation of a blood-brain barrier that regulates thechemical environment of the CNS• Radial glia play a role in theembryonic development of thenervous system
  57. 57. The Peripheral Nervous System• Transmits information to and from CNS• afferent neurons transmit information to theCNS• efferent neurons transmit information away fromthe CNS• Cranial nerves• Spinal nerves
  58. 58. • The PNS has two efferent components– The motor system• carries signals to skeletal muscles and is voluntary– The autonomic nervous system• regulates smooth and cardiac muscles and isgenerally involuntary• The sympathetic regulates arousal and energygeneration (―fight-or-flight‖ response)• The parasympathetic system has antagonisticeffects on target organs and promotes calming anda return to ―rest and digest‖ functions• The enteric division controls activity of thedigestive tract, pancreas, and gallbladder© 2011 Pearson Education, Inc.
  59. 59. Efferent neuronsAfferent neuronsCentral NervousSystem(information processing)Peripheral NervousSystemSensoryreceptorsInternaland externalstimuliAutonomicnervous systemMotorsystemControl ofskeletal muscleSympatheticdivisionParasympatheticdivisionEntericdivisionControl of smooth muscles,cardiac muscles, glandsFigure 49.7
  60. 60. Parasympathetic divisionAction on target organs:Constricts pupilof eyeStimulates salivarygland secretionConstrictsbronchi in lungsSlows heartStimulates activityof stomach andintestinesStimulates activityof pancreasStimulatesgallbladderPromotes emptyingof bladderPromotes erectionof genitaliaCervicalThoracicLumbarSynapseSacralSympatheticgangliaSympathetic divisionAction on target organs:Dilates pupil of eyeAccelerates heartInhibits salivarygland secretionRelaxes bronchiin lungsInhibits activity ofstomach and intestinesInhibits activityof pancreasStimulates glucoserelease from liver;inhibits gallbladderStimulatesadrenal medullaInhibits emptyingof bladderPromotes ejaculationand vaginal contractions
  61. 61. Table 49-1
  62. 62. Concept 49.2: The vertebrate brain isregionally specialized• Specific brain structures are particularlyspecialized for diverse functions• These structures arise during embryonicdevelopment© 2011 Pearson Education, Inc.
  63. 63. Embryonic brain regions Brain structures in child and adultForebrainMidbrainHindbrainTelencephalonDiencephalonMesencephalonMetencephalonMyelencephalonCerebrum (includes cerebral cortex, whitematter, basal nuclei)Diencephalon (thalamus, hypothalamus,epithalamus)Midbrain (part of brainstem)Pons (part of brainstem), cerebellumMedulla oblongata (part of brainstem)MidbrainForebrainHindbrainTelencephalonDiencephalonMesencephalonMetencephalonMyelencephalonSpinalcordCerebrum DiencephalonMidbrainPonsMedullaoblongataCerebellumSpinal cordChildEmbryo at 5 weeksEmbryo at 1 monthFigure 49.9b
  64. 64. Figure 49.9dDiencephalonThalamusPineal glandHypothalamusPituitary glandSpinal cordBrainstemMidbrainPonsMedullaoblongata
  65. 65. Figure 49.9cAdult brain viewed from the rearCerebellumBasal nucleiCerebrumLeft cerebralhemisphereRight cerebralhemisphereCerebral cortexCorpus callosum
  66. 66. Arousal and Sleep• The brainstem and cerebrum control arousaland sleep• The core of the brainstem has a diffuse networkof neurons called the reticular formation• This regulates the amount and type ofinformation that reaches the cerebral cortexand affects alertness• The hormone melatonin is released by thepineal gland and plays a role in bird andmammal sleep cycles© 2011 Pearson Education, Inc.
  67. 67. Figure 49.10EyeReticular formationInput from touch,pain, and temperaturereceptorsInput from nervesof earssuprachiasmaticnucleus (SCN)
  68. 68. • Sleep is essential and may play a role in theconsolidation of learning and memory• Dolphins sleep with one brain hemisphere at atime and are therefore able to swim while―asleep‖© 2011 Pearson Education, Inc.
  69. 69. Figure 49.11Low-frequency waves characteristic of sleepHigh-frequency waves characteristic of wakefulnessKeyLocation Time: 0 hours Time: 1 hourLefthemisphereRighthemisphere
  70. 70. Biological Clock Regulation• Cycles of sleep and wakefulness are examplesof circardian rhythms, daily cycles of biologicalactivity• Mammalian circadian rhythms rely on abiological clock, molecular mechanism thatdirects periodic gene expression• Biological clocks are typically synchronized tolight and dark cycles© 2011 Pearson Education, Inc.
  71. 71. • In mammals, circadian rhythms are coordinatedby a group of neurons in the hypothalamuscalled the suprachiasmatic nucleus (視交叉上核SCN)• The SCN acts as a pacemaker, synchronizingthe biological clock© 2011 Pearson Education, Inc.
  72. 72. Emotions• Generation and experience of emotions involvesmany brain structures including theamygdala, hippocampus, and parts of thethalamus• The structure most important to the storage ofemotion in the memory is the amygdala, a massof nuclei near the base of the cerebrum• The limbic system also functions inmotivation, olfaction, behavior, and memory© 2011 Pearson Education, Inc.
  73. 73. Figure 49.13HypothalamusThalamusOlfactorybulbAmygdala杏仁核 Hippocampus海馬迴
  74. 74. Concept 49.3: The cerebral cortex controlsvoluntary movement and cognitive functions• The cerebrum, the largest structure in thehuman brain, is essential for awareness 察覺, language, cognition, memory, andconsciousness 意識• Four regions, or lobes(frontal, temporal, occipital, and parietal) arelandmarks for particular functions© 2011 Pearson Education, Inc.
  75. 75. Figure 49.15Motor cortex(control ofskeletal muscles)Frontal lobePrefrontal cortex(decision making,planning)Broca’s area(forming speech)Temporal lobeAuditory cortex (hearing)Wernicke’s area(comprehending language)Somatosensory cortex(sense of touch)Parietal lobeSensory associationcortex (integration ofsensory information)Visual associationcortex (combiningimages and objectrecognition)Occipital lobeCerebellumVisual cortex(processing visualstimuli and patternrecognition)
  76. 76. Language and Speech• Broca’s area– in the frontal lobe– is active when speech is generated• Wernicke’s area– in the temporal lobe– is active when speech is heard• These areas belong to a larger network ofregions involved in language• All in the left brain© 2011 Pearson Education, Inc.
  77. 77. Figure 49.16HearingwordsSpeakingwordsSeeingwordsGeneratingwordsMaxMin
  78. 78. Lateralization of Cortical Function• The two hemispheres make distinct contributionsto brain function• The differences in hemisphere function arecalled lateralization• Lateralization is partly linked to handedness• The two hemispheres work together bycommunicating through the fibers of the corpuscallosum 胼胝體© 2011 Pearson Education, Inc.
  79. 79. • The left hemisphere is more adept at– language, math, logic, and processing ofserial sequences– dominant• The right hemisphere is stronger at– pattern recognition, nonverbal thinking, andemotional processing© 2011 Pearson Education, Inc.
  80. 80. Information Processing• Somatosensory receptors provide informationabout touch, pain, pressure, temperature, andthe position of muscles and limbs• The thalamus 丘腦 directs different types ofinput to distinct locations© 2011 Pearson Education, Inc.
  81. 81. Figure 49.17Frontal lobe Parietal lobePrimarymotor cortexPrimarysomatosensorycortexGenitaliaToesAbdominalorgansTongueJawHipKneeTonguePharynxHeadNeckTrunkHipLeg
  82. 82. Information Processing in the CerebralCortex• Input and processing of sensory informationin the brain1. sensory organs2. somatosensory receptors3. specific primary sensory areas of the brain4. adjacent association areas process and integrateinformation from different sensory areas• In the primary cortices, neurons are distributed accordingto the body part that generates sensory input or receivesmotor input
  83. 83. Frontal Lobe Function• Frontal lobe damage mayimpair decision making andemotional responses but leaveintellect and memory intact• The frontal lobes have asubstantial effect on ―executivefunctions‖• 執行功能是一系列高層次的認知過程,可以控制、整合、組織和維持其他認知能力© 2011 Pearson Education, Inc.
  84. 84. Evolution of Cognition in Vertebrates• Previous ideas that a highly convolutedneocortex is required for advanced cognitionmay be incorrect• The anatomical basis for sophisticatedinformation processing in birds (without a highlyconvoluted neocortex) appears to be theclustering of nuclei in the top or outer portion ofthe brain (pallium)© 2011 Pearson Education, Inc.
  85. 85. Human brainAvian brainThalamusMidbrainHindbrain CerebellumAvian brainto scaleThalamusMidbrainHindbrainCerebellumCerebrum (includingcerebral cortex)Cerebrum(including pallium)Figure 49.18
  86. 86. Concept 49.4 Changes in synapticconnections underlie memory and learning• Two processes dominate embryonicdevelopment of the nervous system(連結形成時)– Neurons compete for growth-supporting factorsin order to survive– Only half the synapses that form during embryodevelopment survive into adulthood© 2011 Pearson Education, Inc.
  87. 87. Neural Plasticity可塑性• Neural plasticity describes the ability of thenervous system to be modified after birth• Changes can strengthen or weaken signaling ata synapse© 2011 Pearson Education, Inc.
  88. 88. Figure 49.19N2N1N2N1(a) Synapses are strengthened or weakened in response toactivity.(b) If two synapses are often active at the same time, thestrength of the postsynaptic response may increase atboth synapses.
  89. 89. Memory and Learning• The formation of memories is an example ofneural plasticity• Short-term memory is accessed via thehippocampus• The hippocampus also plays a role in forminglong-term memory, which is stored in thecerebral cortex• Some consolidation of memory is thought tooccur during sleep© 2011 Pearson Education, Inc.
  90. 90. Long-Term Potentiation (LTP)• As a form of learning, LTP increases thestrength of synaptic transmission• If the presynaptic and postsynaptic neurons arestimulated at the same time, the set of receptorspresent on the postsynaptic membraneschanges© 2011 Pearson Education, Inc.
  91. 91. Long-Term Potentiation (LTP)• LTP involves glutamate receptors– AMPA receptor: mostly internalized– NMDA receptor: needs depolarization to remove Mg2+block, permeable to Ca2+ (gated by both ligand andvoltage)– Ca2+ signaling enhances synapse strength bytargeting AMPA receptors to membrane© 2011 Pearson Education, Inc.
  92. 92. Figure 49.20aPRESYNAPTICNEURONGlutamateMg2Ca2NaNMDAreceptor(closed)StoredAMPAreceptorNMDA receptor (open)POSTSYNAPTICNEURON(a) Synapse prior to long-term potentiation (LTP)
  93. 93. Figure 49.20b(b) Establishing LTP123AMPAreceptorNMDA receptorMg2Ca2Na
  94. 94. Figure 49.20c(c) Synapse exhibiting LTPDepolarizationActionpotentialAMPAreceptorNMDA receptor1342
  95. 95. • 同時活化的神經元之間的連結會被強化– 同時滿足打開NMDA receptor 的條件• 作用頻繁的突觸也會被強化– 突觸溝充滿glutamate, 藉由少數可活化的AMPA或NMDA receptor 產生去極化, 進而活化其他 receptor
  96. 96. Stem Cells in the Brain• The adult human brain contains neural stemcells• In mice, stem cells in the brain can give rise toneurons that mature and become incorporatedinto the adult nervous system• Such neurons play an essential role inlearning and memory© 2011 Pearson Education, Inc.
  97. 97. Concept 49.5: Nervous system disorders canbe explained in molecular terms• Disorders of the nervous system include– Schizophrenia– Depression– Addiction– Alzheimer’s disease– Parkinson’s disease• Genetic and environmental factors contribute todiseases of the nervous system© 2011 Pearson Education, Inc.
  98. 98. Schizophrenia• About 1% of the world’s population suffers fromschizophrenia• Schizophrenia is characterized byhallucinations, delusions, and other symptoms• Available treatments focus on brain pathwaysthat use dopamine as a neurotransmitter© 2011 Pearson Education, Inc.
  99. 99. Figure 49.22Genes shared with relatives ofperson with schizophrenia12.5% (3rd-degree relative)25% (2nd-degree relative)50% (1st-degree relative)100%50403020100Relationship to person with schizophreniaRiskofdevelopingschizophrenia(%)Individual,generalpopulationFirstcousinUncle/auntNephew/nieceFraternaltwinIdenticaltwinGrandchildHalfsiblingParentFullsiblingChild
  100. 100. Depression• Two broad forms of depressive illness areknown: major depressive disorder and bipolardisorder• In major depressive disorder, patients have apersistent lack of interest or pleasure in mostactivities• Bipolar disorder is characterized by manic(high-mood) and depressive (low-mood) phases• Treatments for these types of depression includedrugs such as Prozac (enhances serotoninactivity)© 2011 Pearson Education, Inc.
  101. 101. Drug Addiction and the Brain’s RewardSystem• The brain’s reward system rewards motivationwith pleasure (where dopamine is the majortransmitter)• Some drugs are addictive because theyincrease activity of the brain’s reward system• These drugs includecocaine, amphetamine, heroin, alcohol, andtobacco• Drug addiction is characterized by compulsiveconsumption and an inability to control intake© 2011 Pearson Education, Inc.
  102. 102. • Addictive drugs enhance the activity of thedopamine pathway• Drug addiction leads to long-lasting changes inthe reward circuitry that cause craving for thedrug© 2011 Pearson Education, Inc.
  103. 103. Figure 49.23Nicotinestimulatesdopamine-releasingVTA neuron.Inhibitory neuronDopamine-releasingVTA neuronCerebralneuron ofrewardpathwayOpium and heroindecrease activityof inhibitoryneuron.Cocaine andamphetaminesblock removalof dopaminefrom synapticcleft.Rewardsystemresponse
  104. 104. Alzheimer’s Disease• Alzheimer’s disease is a mental deteriorationcharacterized by confusion and memory loss• Alzheimer’s disease is caused by the formation ofneurofibrillary tangles and amyloid plaques in the brain• There is no cure for this disease though some drugs areeffective at relieving symptoms© 2011 Pearson Education, Inc.Amyloid plaque Neurofibrillary tangle 20 m
  105. 105. Parkinson’s Disease• Parkinson’s disease is a motor disordercaused by the death of dopamine-secretingneurons in the midbrain• It is characterized by muscle tremors, flexedposture, and a shuffling gait• There is no cure, although drugs and variousother approaches are used to managesymptoms© 2011 Pearson Education, Inc.