Resting Membrane potential >Nat and Cl are more concentrated outside the ce ll >Kt and organic anions(organic acids and proteins) are more concentrated inside
12 Resting Membrane Potential ➢Na+ and Cl- are more concentrated outside the cell ➢K+ and organic anions (organic acids and proteins) are more concentrated inside
Intracellular vs extracellular ion concentrations Lon 工 intracellular Extracellular 5-15mM 145mM K 140mM 5 mM Mg2+ 0.5mM 1-2mM ca 10-7mM 1-2mM H 1072M(pH72)10-74M(pH74 C 5-15mM 110mM
13 Intracellular vs extracellular ion concentrations Ion Intracellular Extracellular Na+ 5-15 mM 145 mM K + 140 mM 5 mM Mg2+ 0.5 mM 1-2 mM Ca2+ 10-7 mM 1-2 mM H+ 10-7.2 M (pH 7.2) 10-7.4 M (pH 7.4) Cl- 5-15 mM 110 mM
Resting membrane potential Net negative Net positive Charge Charge 圆 Electric Force K+±K+ Chemical force InsideOutside Potassium ions. concentrated inside the cell tend to move outward down their concentration gradient through nongated potassium channels But the relative excess of negative charge inside the membrane tend to push potassium ions out of the cell
14 Resting Membrane Potential ➢ Potassium ions, concentrated inside the cell tend to move outward down their concentration gradient through nongated potassium channels ➢ But the relative excess of negative charge inside the membrane tend to push potassium ions out of the cell
Potassium equilibrium Selectively 90m Cytoplasm permeable Extrad ellular fluid membrane A K A A Concentration gradient for K moves K out of cell Electrical potential difference moves k into cell
15 Potassium equilibrium -90 mV
Resting membrane Nat is more concentrated Potential outside than inside and therefore tends to flow into the cell down its concentration Net negative Net positive Charge Charge gradient Electric Force Nat Nat Nat is driven into the cell by the electrical potential Chemical force Inside difference across the Outside membrane But what about sodium? Electrostatic and Chemical forces act together on Nat ions to drive them into the cell The Nat channel close during the resting state
16 Resting Membrane Potential • But what about sodium? • Electrostatic and Chemical forces act together on Na+ ions to drive them into the cell • The Na+ channel close during the resting state Na+ is more concentrated outside than inside and therefore tends to flow into the cell down its concentration gradient Na+ is driven into the cell by the electrical potential difference across the membrane