Class 10

  1. Basic Chemistry

    A.   ISSUE: All neural membrane potentials are the product of basic physics and chemistry

    B.    Atoms and Binding

    1.                 The atom

    a)                 The nucleus

    b)                The electron shell or cloud

    (1)              A full ring

    (2)              A partially full ring

    2.                 Binding

    a)                 Ionic binding and ions:

    (1)              Electron from one atom joins other atom, both become charged.






    (6)              In solution, ions will tend to wander a part

    b)                Covalent binding and "sharing electrons":

    (1)              Electrons are shared - tightly bound -

    (2)              Generally, atoms cannot separate until bond is broken

    C.   Concentration: amount of substance per volume.

    1.                 Atoms do not move purposively

    2.                 Chemicals will flow from high concentrations to low with effect of evening out concentration: by random movements: Diffusion

    D.   Entropy

    1.                 A definition of entropy: no differences anywhere

    2.                 That entropy increases is the second law of thermodynamics

    3.                 Thus diffusion increases entropy

    4.                 Enthalpy: DEF: forces that can lead to organization

  2. Application of Chemistry to Membrane

    1. Channels in the Membrane

    2. What channels are there

  3. Charging the membrane: The Resting Potential

    1. Charge gradients vs. diffusion gradient.

      1. E.g. potassium

      2. The Nernst Equation for potassium EK = 58log([K]o/[K]i) = -93 mV

      3. Nernst Values for other ions

        1. ENa = + 56 mV

        2. ECl = - 66 mV

      4. Getting to -70 mV

        1. The Goldman equation Em =

        2. Permeability = the ability of an ion to reach equilibrium

        3. Gets us to -67

        4. The Sodium Potassium Pump
          1. 3 NA/2K
          2. gets us to -70

          3. Uses energy