How is rmp established and maintained

The pump protein is phosphorylated by ATP. To understand how the concentration differences for sodium and potassium maintained by the membrane pumps create membrane potentials, let us consider the following situation: let us assume that the membrane is permeable only to potassium but not to sodium.

Therefore, potassium can diffuse through the membrane but sodium cannot. Initially there is no potential difference across the membrane because the two solutions are electrically neutral; i. There is also a concentration gradient favouring sodium diffusion in the opposite direction but the membrane is not permeable to sodium.

Accordingly, after a few potassium ions have moved out of the cell, the cell will have an excess of negative charge, whereas the outside solution will have an excess of positive charge; i. In some cells, the RPM is always changing. For such, there is never any resting potential , which is only a theoretical concept. Other cells with membrane transport functions that change potential with time, have a resting potential. This can be measured by inserting an electrode into the cell.

Transmembrane potentials can also be measured optically with dyes that change their optical properties according to the membrane potential. WikiLectures WikiLectures. Figure 2. The magnitude of this depolarization is generally small less 5 mV and depends on the presence of other ionic pathways in the membrane i. In some cells, no initial depolarization is observed when the sodium pump is inhibited because the input resistance is low due to the high permeability of other ionic pathways.

The gray bar represents a long break in time, indicating that it takes a long time tens of seconds or minutes for the membrane potential to completely dissipate to the zero level 4. Physiology Web at www. Test Questions. Resting membrane potentials are maintained by two different types of ion channels: the sodium-potassium pump and the sodium and potassium leak channels.

Firstly, there is a higher concentration of the potassium ions inside the cell in comparison to the outside of the cell. This creates an unequal distribution of potassium ions, or more accurately, a potassium ion gradient is created. Therefore, following the concentration gradient, the potassium ions will diffuse from the inside of the cell to outside of the cell via its leaky channels.

As the potassium ions leave the cell, it increases the number of anions trapped inside the cell, hence accumulating the negative charges and the positive charges are accumulated outside of the cell.