10-14-09_neuro_cellsignalingA

10-14-09_neuro_cellsignalingA - Announcements Quiz 4 due...

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Announcements Quiz 4 due today at noon Quiz 5 will become available today and will be due next Monday at noon (gradients, transport, neurobiology) The cell simulation project has been postponed for the time being, so there is nothing due this Friday.
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What are the cellular elements that allow us to think and act? Glia •Myelin •Immune function Brain homeostasis Neurons
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The electrochemical gradients for Na + and K + in resting neurons Vander’s Human Physiology
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Resting Potential Current for a given ion from Ohms law, for example, INa=gNa (Vmem-ENa). At resting potential, INa+IK=0. (assume ICl=0 for simplicity) Therefore, INa=gNa (Vmem-ENa)= -IK= -gK (Vmem-EK), where Vmem is the membran potential. Solving for Vm gives Vmem=(gNaENa+gKEk)/(gNa+gK) If ENa=50 mV and EK=-100 mV and gK/gNa=4/1, Vm= -70 mV, which is near the resting potential of many neurons
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The electrochemical gradients for Na + and K + in resting neurons
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Steps in the generation of an action potential
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Voltage-dependent properties of ion channels involved in the action potential
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Refractory period - the time during which it is not possible to generate a second action potential 1. Absolute refractory period - determined by complete inactivation of voltage- sensitive Na channels - no amount of depolarization can elicit regenerative response 1. Relative refractory period - determined by large g k relative to g na (Na channels starting to recover from inactivation) - a large depolarization can increase g na enough to initiate the regenerative response
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Propagation of action potentials • Action potentials are initiated at the axon hillock • Successive segments of axon regenerate the action potential
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Charge lost across the plasma membrane limits the distance of propagation of changes in V mem Water flowing through hose analogy The spatial spread of a voltage change is proportional to the ratio of r mem /r int , where r mem and r int are the membrane resistance and cytoplasmic resistance
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This note was uploaded on 02/09/2010 for the course BIOL 230 taught by Professor Bartlett,e during the Fall '08 term at Purdue University.

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10-14-09_neuro_cellsignalingA - Announcements Quiz 4 due...

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