resting membrane potential

Cards (10)

  • maintaining ion gradients
    sodium potassium pump (NA+/K+ ATPase)
    • needs atp
    • 3NA+ out and 2K+ in
  • membrane potential
    ion concentration gradients result in separation of electrical charge across cell membrane
    • inside more negative than outside
    • Inside voltage (Vi) = -70mV
    • Outside voltage (Vo) = 0mV
    • Membrane potential (Em) = Vi – Vo
  • maintaining resting membrane potential
    sodium potassium pump
    • maintains ion gradients
    • electrogenic - loses one positive on inside making inside more negative
    K+ leak channels
    • pores in membrane
    • K+ moves out cell down conc. gradient
    • net movement positive charge out cell
  • function of membrane potential
    Homeostatic - maintains osmolarity
    rapid signalling and communication
    • action potentials
    • receptor potentials
    • post synaptic potentials
    energy source:
    • drives transmembrane transport processes
  • Polarisation
    Depolarisation - membrane potential more positive
    Hyperpolarisation - potential more negative
  • ion movement across semi - permeable membrane
    concentration gradient - high to low
    electrical gradient - attraction to opposite charge
  • electrochemical equilibrium
    point at which number of ions moving along conc. gradient is equal to number moving along electrical gradient
    • overall no net movement X, where x is a specific ion
    • The membrane potential required to produce this electrochemical equilibrium for a specific ion is known as the equilibrium reversal potential, Ex - x is a specific ion
    REVERSAL POTENTIAL CALCULATED USING NERNST EQUATION
     
  • NERNST EQUATION
    • usually biological systems so temp - 310K
  • if membrane permeable to one type of ion
    membrane potential equals reversal potential
    = Nernstian
  • Permeable to more than one type
    membrane potential does not equal reversal potential
    USE GOLDMAN-HODGKIN-KATZ (GHK) EQUATION
    P = permeability