Neuropsychology

Class 10

1. 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

2. Working the Membrane: The Action Potential

   1. A Brief Review of Electricity

      1. Potential

      2. Flow

      3. Resistance

      4. Conductance α 1/Resistance

      5. Ohm's Law:

         1. V=IR= I/G

         2. I = V/R = VG

         3. V = Voltage

         4. I = Current or Flow

         5. R = Resistance

         6. G = Conductance

   2. An Electrical Description of the Action Potential
      

      1. Phases

         1. Depolarization: -70 mV to +30mV

         2. Repolarization: +30 to -70mV

         3. Overshoot: ~-80mV

      2. All-or-None Law

   3. Use Goldman Equation to Figure out why Action Potential Happens and Why All-or-None

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

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

      3. Table of Permeabilities and Concentrations

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