Lecture11-2009W - Excitable Membrane Currents flow so memb...

Info icon This preview shows pages 1–3. Sign up to view the full content.

Excitable Membrane barb2right Currents flow, so memb. potential changes head2right Cell membranes have passive electrical properties barb2right resistance & capacitance head2right Measuring memb. potential Electrochemical Potentials (1) Chemical gradient, conc.-dependent (2) Electric potential difference barb2right selectivity to ions 1 2 checkbld Chemical gradient checkbld Electromotive force (emf) Assumption barb2right memb. is selective only to K +
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

3 Equilibrium potential, when Chemical gradient = emf barb2right E K , equilibrium potential of K+ in this case barb2right But, it is really steady-state (energy expenditure is required) The Nernst equilibrium : Calculating Eq. potential for single ions Chemical work (W C ) to oppose the chemical gradient W C = 2.3 RT log [K + ] out /[K + ] in Electrical work (W E ) to oppose the electrical force W E = FE (E, electrical potential difference) @ Equilibrium, W E = W C barb2right barb2right E = 2.3RT/F • log [ion] out /[ion] in Examples: 1. If [K+]out = 20mM, [K+]in = 400mM, then E K ? E K = 0.058 log (20/400) = -0.075V = -75mV 2. If [Na+]out = 460mM, [Na+]in = 50mM E Na = 0.058 log (460/50) = +0.055V = +55mV
Image of page 2
The Goldman equation (=GHK eq.) : barb2right calculating the steady-state potential for multiple ions
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern