4) Membrane Potentials
4) Membrane Potentials
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This 2 page Class Notes was uploaded by Andrea Starkman on Monday February 15, 2016. The Class Notes belongs to at George Washington University taught by Dr. Randall Packer in Spring 2016. Since its upload, it has received 26 views. For similar materials see Human Phisiology in Biological Sciences at George Washington University.
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Date Created: 02/15/16
(4) Membrane Potentials Class Notes 02/01/2016 ▯ ▯ Integral to nerve and muscle mechanisms. Muscles innervated by neural cells (skeletal and smooth). ▯ ▯ Can be measured by microelectrode in cells. -9 to -100 mv ▯ ▯ Basic Electricity Rules: Positive (+) and Negative (-) Charges. Like charges repel and Differing charges attract. Energy is required to move against the charge gradient. Voltage (E): potential of separated charges to do work. Current (I): Measure of the number of charges moving or the work being done. Resistance (R): Ohms law I = E/R ▯ ▯ Sources of Membrane Potential: Concentration of sodium + concentration of chloride = concentration of potassium + concentration of proteins. o No osmotic processes. o Potassium leak out of the cell down its concentration gradient. Stop at equilibrium point. o ICF Side become negative and ECF becomes positive. Diffusive force acting on potassium will become equal to electrical forces causing the leak to stop because the two are opposing each other equally. o Equilibrium Potential: Diffusing Force = Electrical Force At rest cells are more permeable to potassium. Equilibrium potential -88.3mV. Hard for it to reach this so always some leakage because always some sodium leaking in. o Sodium goes down concentration gradient and pulled in by charge force. o When sodium rushes into the cell it changes the equilibrium potential. Chlrodie has -71.1mV equilibrium. ▯ ▯ Ion Channels: Ion flows are contributing to the trans membrane potential. Ligand Gated: Opened by ACH (excitatory) and GABA (inhibitory). Depend on ions. Electrically Gated: Open or close in response to membrane potential. Mechanically Gated: Change in the membrane of the neuron will change the membrane potential. Skin and touch. ▯ ▯ GHK Equation: Trans membrane potential difference. Use permeability. ▯ Nernest Equation: ▯ ▯ Move fastest when moving down a charge and a concentration gradient. Sodium and potassium will usually be the ones moving the fastest. ▯ ▯ ▯
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