Resting Membrane Potential

Resting Membrane Potential

1. MEASURING RMP

   • Types of electrode
     • Microelectrode
       • You pierce the neurone axon using a small electrode and measure voltage directly
     • Patch Clamp Electrode
   • Types of measurement
     • Intercellular
     • Extracellular
       • Local field potential can be measured

2. DETERMINED BY... OF CHARGED IONS

   • The Permeability
     • Controlled by ion channels
       • Voltage Gated ion channels
         • Generate action potential
       • Non gated(always open leaky) channels
         • Important leak channels are the potassium ones and they set the RMP
       • Ligand Gated
         • Generates potential changes
     • Leak porassium channels mean poassium is 40x more permeable than sodium at RMP
   • Concentration gradient
     • Concentration of cells measured in millimoles per dm3
   • Electrical gradient
     • Caused by increase of same charged particles repelling one another

3. ION PUMPS

   • Sodium- Potassium pumps (ATPase) maintain the concentration gradient
     • It ensures that there is a greater conc of sodium outside and potassium inside (3x Na out, 2x K in)
   • Calcium ion pump
     • Pumps calcium out of the neurone

4. CHARATERISTICS

   • Small changes in the ions causes large changes in membrane potential

5. Equations

   • Goldmann Equation
     • Calculates the RMP of a neurone
   • Nernst Equation
     • Calculates the reverse potential of an ion

6. IMPORTANCE OF K+

   • Membrane sensitive to K+, less K= depolarises membrane

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