Neuropsychology

Class 9

I.      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.

(4)              

(5)              

(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

  1. Application of Chemistry to Membrane

    1. Channels in the Membrane

    2. What channels are there

  2. 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

        Ion Concentration [IN] Concentration [Out] Relative Permeability
        Potassium K+ 400 10 1
        Sodium Na+ 50 460 0.04
        Chloride Cl- 40 540 0.45
      4. Getting to -70 mV

        1. The Goldman equation Em =
                   58log((PK*[K]o+PNa*[Na]o+PCl*[Cl]i)/
                           (PK*[K]i+PNa*[Na]i+PCl*[Cl]o))

        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