Na+/K+ Handling

• normal concentration of Na+ and K+ outside and inside the cell

  K+ ICF = 150 mM

  K+ ECF = 5 mM

  Na+ ICF = 15 mM

  Na+ ECF = 145 mM

  
• anything above 5 mM and depolarization of K+ resting membrane potential

  hyperkalemia - high K+
• harder to reach threshold and hyperpolarization of K+ resting membrane potential

  hypokalemia - low K+
• larger, steeper upstroke; increased Na+ excitability

  hypernatremia

  
• shorter, flatter upstroke; decreased Na+ excitability

  hyponatremia