6. Renal physiology 3 - Collins

• Driving force behind simple diffusion is?

  Brownian motion - random thermal motions of atoms
• Simple diffusion stops - when particles reaches equilibrium
• Driving force behind electrodiffusion is?

  Brownian motion and voltage
• Electrodiffusion is net movement of ions due to concentration gradient and electrical field
• facilitated diffusion

  • does not require energy - it is movement down gradient
  • but it uses membrane carrier
• What can disrupt facilitated diffusion?

  Higher concentration will cause carriers to become saturated
• ion channel - movement of ions through ion channel down an electrochemical gradient

  • requires no ATP
  • can't be saturated
• primary active transport - solutes will move against gradient

  • needs ATP
• secondary active transport - downhill movement of another solute provide energy for uphill movement of another solute

  • indirect usage of ATP
• tubular reabsorption is transport of substances out of the nephron tubules into the blood stream via peritubular capillaries
• tubular secretion is transport of substances into the nephron tubule from the blood stream via peritubular capillaries