BMS 300 1st Edition Lecture 18 Outline of Last Lecture I. The neuron doctrine-the neuron as the fundamental structural functional unit of the nervous systemII. Source of the doctrine -Santiago Ramon cajal-Camillo Golgi -the golgi stain -cellularists and reticularists -law of dynamic polarization III. Structural description of nutritional organization -dendrite -cell body-axon, axon terminal IV. Functional organization model -input -conductible -output V. Distribution of ion channels VI. Cell body of neurons These 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.-logistical problems of asymmetric cells -axoplasmaic transport 1. fast 200-400 mm/day >vesillos & microtubules 2. slow -0.1-2mm/ day >intermittent movement Outline of Current Lecture VII. Cells of the nervous system -Glia -Glia 1. maintain the environment for neural function -Gliac cells in the nervous system1. astrocytes >regulation of extracellular environment2. oligondondrocytes >lay down myelin sheaths/wraps 3. Glia of the peripheral nervous system >schwann cells VIII. Neurons as electrically excitable cells -storing energy in an electrical gradient1. the potassium battery >role of K+ selective leak channels >role of impermeant anions2. the nervous potential >role of the [ko]/[ki] ration IX. The Na+ channel of switching polarity 1. the gate 2. inactivation 3. voltage/charge sensitivity Current LectureGlia-as glue -nothing more than cells holding the nervous system together - in the central nervous system glia are essential for regulating the environment in which neurons function -come in two varieties >astrocyte 1. regulates the extracellular K+ concentration (at about 4-5mmol)2.regulates the neurotransmitter concentration at synapses -we touched on synapses when we talked about how there are synapse the go from the output region to the input region -the output region releases a neurotransmitter into the synaptic cleft -basically bind neurotransmitters at the input site and vacuum them together >oligodendrocyte1.milanation: they wrap conductile regions of neurons with concentric rings (layers) of plasma membrane that we call myelin (laid down in layers) -happens early -the oligodendrocyte sends out a process that allows it to stick to the plasma membrane of the axon but it doesn’t stop, it then continues to send an extension around the cell-the leading edge insinuates itself under the first layer -breaks the bonds between the two membranes -after a while there is a structure that goes around and around -if we go around and around the circles it will go back around to the oligodendrocyte -we use it to send out a process to generate an insulating layer -schwann cell does pretty much the same thing -multiple scrosis: all manner of problems with the nervous system >disease of the oligodendrocytes>you recover and it is a progressive degenerative disease because your body won’t fully heal after each attack >the longer the interval in between each attack the better the diagnosis isNeurons as electrically excitable cells -generation if a potassium battery >separate electrical (ions) charge across a membrane to generate an electrical potential that stores energy and can do work>aka “putting a battery in your phone”-biology does it differently -on the inside of a plasma membrane place 100mmol K+ ions -on the outside we have 10mmol K+ -we put some transmembrane proteins “potassium leak channels” -we not have a selective hydrophilic pathway -it won’t be very long until we reach equilibrium -diffusion of potassium down its concentration gradient -the reality is that on the inside of the membrane there are large impermant anions >can be proteins, acids etc.>negatively charged>big>can’t leave the cell -potassium is a cation -the large anion is negative -the potassium will start running down concentration gradient until their movement is held in check by the anions -the potassium equilibrium potential >Nerust -the nerust potential: the equilibrium potential for potassium is -equilibriums for potassium is 61.5 log (K+(outside)/K-(inside))-in bio the numbers aren’t that simple**we have generated a battery across a membrane in a way that there is more negative on the inside **storing energy across a membrane **we have made a battery that is stable and doesn’t change so it’s not very useful for
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