What is/are effect on membrane when extracellular concentration of K is decreased?
Active Transpo of Sodium and Potassium Ions Through the Membrane--The Sodium-Potassium (Na+-K+) Pump. First, let us recall from Chapter 4 that all cell membranes of the body have a powerful Na+-K+ pump that continually transpos sodium ions to the out- side of the cell and potassium ions to the inside, as illus- trated on the left-hand side in Figure 5-4. Fuher, note that this is an electrogenic pump because more positive charges are pumped to the outside than to the inside (three Na+ ions to the outside for each two K+ ions to the inside), leaving a net deficit of positive ions on the inside; this causes a negative potential inside the cell membrane. The Na+-K+ pump also causes large concentration gra- dients for sodium and potassium across the resting nerve membrane. These gradients are the following: Na+ (outside): 142 mEq/L Na+ (inside): 14 mEq/L K+ (outside): 4 mEq/L K+ (inside): 140 mEq/L The ratios of these two respective ions from the inside to the outside are Na+ inside/Na+ outside = 0.1 K+ inside/K+ outside = 35.0 Leakage of Potassium Through the Nerve Membrane. The right side of Figure 5-4 shows a chan- nel protein, sometimes called a "tandem pore domain," potassium channel, or potassium (K+) "leak" channel, in the nerve membrane through which potassium can leak even in a resting cell. The basic structure of potassium chan- nels was described in Chapter 4 (Figure 4-4). These K+ leak channels may also leak sodium ions slightly but are far more permeable to potassium than to sodium, normally about 100 times as permeable. As discussed later, this dif- ferential in permeability is a key factor in determining the level of the normal resting membrane potential. Ref guyton and hall textbook of medical physiology 12/e p 59
| Magnitude of RMP
| Negativity of the membrane
| Magnitude of RMP
| Negativity of membrane
General physiology