part3BME314finalreview2010

part3BME314finalreview2010 - Lecture 13 Membrane Potential:...

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Lecture 13 Membrane Potential: created by separation of charged ions across a cells external membrane regulated by: ion pumps/channels critical in: muscle cells/nerve cells Resting Potential: vm = vi - vo where vo = 0(ground) for convention; potential difference across a membrane at rest key exterior ions: salty out (Na+) key interior ions: salty - K in (Na+ and K+) ion conc of cell: in out Na+ 12 120. K+ 125 5 Cl- 5 125 ion gradients are used to: *make ATP *drive transport processes *generate electrical signals hyperpolarization: makes the inside more negative depolarization: makes the inside more neutral how do ions move across memb? active-regulated by ATP, opened or closed in response to stimulus, selective and allows only specific ions to pass passive - open channels allow ions to flow through, ion specific, only one type of ion can pass Rest memb controlled by?Cl-, K+, Na+ channels Passive channels are responsible for resting membrane potential Active channels are responsible for action potentials Ficks Law J = Ohms Law J = J = flow of ions due to drift in E field mu = ion mobility (L 2 /sV) Z = ionic valence dv/dx = voltage gradient [i] = ion concentration Einsteins: D = relationship of diffusivity and mobility; drift of particles in an E field under osmotic pressure
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k = 1.38 E-23 J/K q = 1.61E-19 C = magnitude of electric charge Nerst Equation: v m = v i - v o = Assume only permeability to: one ion species Nerst Equation: Fundamental biophysical description of: membrane pot. arising due to charge separation; only separation of one ionic species Derivation of Nerst Equation using Ficks’ Law: J(diff) and Ohm’s Law: J(drift) Lecture 14 Donnan Equilibrium: membrane potential of a cell is due to the presence of all ions At equilibrium the Nerst potentials for K+ and Cl- must be equal. Ek =Ecl faster 0 < # slower 0 > # Goldman Hodgkin Katz Equation: P is the permeability find J then use space charge neutrality when perm. of one ion is high compared to others, Vm predicted by Goldman equation
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Electrical components of cell: concentration gradient across a channel for an ion gives rise to an emf that drives ions across the channel (modeled as a battery) R = 1/G : resistance given in conductance G (conductance) measured in Siemens G measure of ease of flow of ions through channel Lecture 15 Biomedical Instrumentation: Measurand: variable you measure examples: blood glucose, blood flow, blood pressure, pH, respiratory rate, temperature Instrumentation systems consist of: a sensor that measures a desired property, components that convert the analog output signal from the sensor into an electrical signal. components used to process the data (e.g., signal processing techniques to filter the data), and to store and display the digital and/or analog data. Feedback control: when a control system action opposes changes
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This note was uploaded on 02/01/2011 for the course BME 314 taught by Professor Frey during the Spring '08 term at University of Texas at Austin.

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part3BME314finalreview2010 - Lecture 13 Membrane Potential:...

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