Psyc4130 1nd Edition Lecture 4 Outline of Last Lecture I. Basics of NeurophysiologyA. Glial cells, neuron cells, nervous system, CNS matter, neurogliaII. Four Types of Glial CellsA.AstrocyteB.MicrogliaC. OligodendrocyteD.Schwann CellIII. Neurons and TermsA.Neuron partsIV.Different NeuronsA.Bipolar cellsB.Multipolar CellsV.About CellsVI.Eukaryotic CellsVII. General Physiology/Neuron TermsOutline of Current Lecture II. Blood Brain BarrierIII. Important terms/conceptsA. Action PotentialB. Phospholipid IV. Three PotentialsA. Resting potentialB. Graded potentialC. Action potentialCurrent Lecture- Blood Brain Barrier o Keeps most bad stuff out (including large molecules, they get stuck in capillaries unless they specifically get carried across) Plant toxins and bacteria for exampleThese 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.o Imuno-compromise: hard to get rid of if it is bado Selective about which ions it’ll transport across, high sodium concentration o Limits amount of exchange of sodium, chloride, and potassium ionso Formed by tight junctions of the capillaries feeding CNS Less “leaky” Allow for ions to be exchanged easily o Brain gets nutrition from specific transporters, one at a time (very specific)- Pt. 2 Important Terms/Concepts o Selective Permeability (of cell membrane)o Membrane/Resting Potentialo Depolarization and Hyperpolarization EPSPs and IPSPso Threshold of Excitationo Action Potential Electrochemical events, the batteries, based upon ion flow across a membrane Neural communication occurs via action potentials (cells “firing”) Relative balances of positively and negative ions inside and outside of the neuron provide the stored energy that is released during the action potential Think: batteryo Cations and Anionso Extracellular Fluido Intracellular Fluid (aka Cytosol)o Sodium-Potassium Transporters (“Pumps”)o Ion Channels Voltage-Dependent Ligand-Gatedo All-or-None Lawo Saltatory Conduction- Phospholipid o When phospholipids contact water, the hydrophobic (fatty acid) tails automatically align away from water molecules forming a double-layer barrier with water inside and outside. Hydrophobic= tail, hates water Hydrophilic: head, likes water 3 Potentials- Resting potentialo “Membrane potential”- storing the energy to be released during action potential o Big player number 1: the sodium ion (positive charge +1) Higher concentration of sodium outside of axon Graph below = NA+ concentrations during “rest”o Big player number 2: Potassium Ion High concentration of potassium (K+) inside of axon, low outsideo Sodium-Potassium Pump Helps maintain relative concentrations The neuron spends roughly ½ of its energy to run the sodium-potassium pump. It pays a fortune to remain “quiet”o Chloride More concentrated insideo Big player 3: Organic ions More concentrated inside, negatively charged (e.g. proteins)- Important for test!!! o Inside of cell is more – (inside of axon) relative to outsideo Averages ~ -70 mVo More organic ions - Membrane potential conclusionso Concentration Gradient (Ionic) Force Flow is from high concentration to low.o Electrostatic Force Opposites attract.o Inside (cytoplasmic face) of cell is negative with respect to ECF (~ -70mV). Much force wants to push sodium into the neuron at resting potential.- Graded potentialso Threshold of excitation Action potentials are all-or-nothing events. It is absolutely essential that the polarity of the inside of the cell relative to the outside drop from -70 to -55 mV (threshold). Sodium ions rush in, less concentrated inside, more outside, positively charged ions and inside is more negative (opposites attract) drives sodiumto rush in to local area of axon Once this happens at the axon hillock, the action potential occurs automatically. Must depolarize it Ligand molecule that binds and opens up receptor, causes protein to shif Depolarization à excitatory neuron- Action potential o In order to get an action potential, the inside of the cell must be sufficiently depolarized to open voltage-dependent ion (sodium) channels o Brief local transient, reversal of polarity o Inside of the axon during action potential for a fraction of a sec is more positively charged than the outside Na+ channels open, allow sodium in… (going up on hill) (going down on hill) K+ channels eflux, plumits/overshoots -70 before it
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