Resting membrane potential

• What is membrane potential?

  The potential difference across a cell membrane
• What is resting membrane potential?

  The membrane potential in a resting excitable cell
• What do ion channels in cell membranes do?

  They allow specific ions to pass through
• Which ions have selective ion channels in cell membranes?

  K+, Na+, Ca$^{2+}$, and Cl-
• What is the voltage reference point for membrane potential?

  Extracellular fluid is the voltage reference point
• What is the charge distribution at rest inside and outside the cell?

  Inside is negatively charged, outside positively charged
• How is membrane potential expressed when the inside is negatively charged?

  As a negative value compared to outside
• What happens when electrical current changes in a cell?

  The cell is no longer in a resting state
• Why does resting membrane potential exist?

  Due to excess negative ions inside and positive outside
• What attracts positive ions in the cell?

  Excess negative charges inside the cell
• Where do excess charges collect in relation to the plasma membrane?

  In a thin shell against the inner and outer surfaces
• Which ion primarily contributes to resting membrane potential?

  K+
• What factors determine the magnitude of resting membrane potential?

  Ion concentration differences and membrane permeabilities
• What happens when potassium ion channels open in a solution with NaCl and KCl?

  K+ diffuses into compartment 1, creating excess positive ions
• What is the effect of an electrical potential on ion movement?

  It can cause net movement of ions across a membrane
• What is the electrochemical gradient?

  The combined effect of concentration and electrical gradients
• What is the equilibrium potential for an ion?

  The membrane potential where net ion movement is zero
• What happens at the equilibrium potential for an ion?

  No net movement of the ion occurs
• What does the Nernst equation describe?

  The equilibrium potential for any ion
• What is the formula for the Nernst equation?

  E ion = 61/z log (C out/C in)
• What does the constant 61 in the Nernst equation represent?

  A constant value for gas and temperature
• How does membrane permeability affect ion contribution to membrane potential?

  Greater permeability increases the ion's contribution
• What is the resting membrane equation?

  Vm = 61 log (Pk (K out) + PNa (Na out) + PCl (Cl in)/ Pk (K in) + PNa (Na in) + PCl (Cl out)
• How is the resting potential generated across the plasma membrane?

  By K+ moving out of the cell through channels
• Why is the resting membrane potential not equal to K+ equilibrium potential?

  Na+ channels slightly influence the membrane potential
• What does the ATPase pump do in a resting cell?

  Moves ions to maintain resting membrane potential
• How does the ATPase pump affect Na+ and K+ movement?

  Moves three Na+ out for every two K+ in
• What happens to K+ and Na+ flux during resting potential?

  K+ flux is greater than Na+ flux
• What is the state of ion flux in a steady state resting neuron?

  K+ is highly permeable, Na+ has low permeability
• How do chloride ions behave in excitable cells?

  Chloride concentrations shift with equilibrium potential
• What happens to chloride ions in cells without pumps?

  Equilibrium potential equals resting membrane potential
• How does chloride ion diffusion occur in cells with active transport systems?

  Net Cl- diffusion contributes to excess negative charge
• What is the effect of chloride ion diffusion on membrane potential?

  It makes the membrane potential more negative