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UH BIOL 1361 - Neurons and Action Potential
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BIOL 1361 1nd Edition Lecture 23Outline of Last Lecture I. Purpose of Circulatory System: Minimize Diffusion DistanceII. Circulatory SystemIII. Open vs. ClosedIV. Vertebrate Circulatory SystemV. CellsVI. VesselsVII. Flow RateVIII. Fick’s LawIX. Flow CircuitsX. PumpOutline of Current LectureI. Neuron StructureII. Fig 37.2III. Real NeuronsIV. Resting PotentialV. Figure 37.6VI. Description of Ion MovementVII. Electrochemical EquilibriumThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.VIII. Action PotentialIX. GraphCurrent LectureI. Neuron Structure (be able to draw this) (Fig 37.5)a. Dendritesi. Receive signals from other neuronsb. Cell bodyi. Contains nucleus and organellesc. Axoni. Transmits signals to other neurons or musclesII. Fig 37.2a. Synapse – junction of a nerve cell with another cellb. Relative Terms depending on cell location in networki. Presynaptic Neuron – cell sending signal across synapseii. Postsynaptic Neuron – cell receiving signalIII. Real Neurons (Figure 37.3a. Cyan = neuron cell bodiesb. Green = dendritesc. Red = support cells (glia)IV. Resting Potentiala. Resting Potential = charge difference across a cell membrane of ALL body cellsb. Develops because of Na+ & K+ movementc. Ion movement through 3 membrane proteins:i. Na+ -K+ pump (requires ATP)ii. Passive K+ channels (channels are always open, facilitated diffusion)V. Figure 37.6a. There are more potassium channels versus sodium channelsb. The membrane is more permeable to potassiumVI. Description of Ion Movementa. Na+ - K+ Pump: Pumps 3 Na+ out and 2 K+ in to the cellb. Result:i. [Na+] = 15 mM insideii. [Na+] = 150 mM outsideiii. [K+] = 140 mM insideiv. [K+] = 5 mM outsidec. Passive K+ Channel is always openi. K+ leaves the cellii. Cl- and Protein- are stuck inside the celliii. Result: (-) charge now greater inside the celliv. (-) charge attracts (+) charge on outside, electrical gradient limits K+ efflux(outflow)VII. Electrochemical Equilibriuma. [X]∈¿[X]out¿Eion=RTzF∗¿i. Eion – equilibrium potential for a specific ionii. R – universal gas constant, 8.314 J*K-1* mol-1iii. T – Temperature (K) degrees C + 273iv. Z – valence of ionv. Faraday’s constant 96,485 Coulombs*mol-1vi. X – ionVIII. Action Potentiala. Depends on voltage-gated Na+ and K+ channelsi. Passive channels that are closed at restii. Open in response to a change in voltage across cell membraneiii. Like an electrically operated gateb. Description of ion movementi. Stimulus changes membrane potential (voltage)c. If change is large enough that voltage exceeds a threshold, voltage-gated Na+ channels opend. Na+ flows into the celle. Changes in potential CLOSES voltage-gated Na+ channels and OPENS voltage-gated K+ channelsf. K+ leaves the cellg. Na+ - K+ Pump re-establishes gradients of Na+ and K+h. Action potential spreads because Na+ diffuses along the inside of the cell membrane, changing the voltage and opening the next batch of voltage-gated Na+ channels*Graph from MasteringBio will be on finalIX. Graph:a. Resting Potential (1)i. The voltage gated channels are closedb. (2)i. A few are openii. A few are closedc. (3)i. Na+ channels opend. (4)i. Voltage-gated Na+ channels closedii. Voltage-gated K+ channels openiii. Passive Na+ channels openiv. Passive K+ channels opene. (5)i. K+ channels closef. Which ion channels are open during each phase of the action potential?g. What is represented by the dotted line?i. Threshold voltage AKA Threshold


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UH BIOL 1361 - Neurons and Action Potential

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