What can we infer from the osmotic pressure

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Nerve cell

Donnan diffusion potentials build up on all cell membranes of the organism. The potentials caused by the various ions add up to a total potential, the resting potential of the cell. The resting potential is largely constant in most cells, it is between -50 and -90. Potassium ions are mainly found in the cell, while sodium ions predominate outside the cell.

In the nerve cell, the membrane potential must be changed in order to conduct stimuli. There are also numerous channel proteins for various ions in the membrane. These can be opened or closed as required. The resting potential is -70. When the cell is excited, sodium channels open and sodium ions flow in. The potential becomes positive, around +30. The sodium channels close again immediately. The excitation potential is passed on via the axon and transferred to other nerve cells at the synapse. At the same time, potassium channels open, whereby potassium ions flow out and restore the original potential of -70. The Na / K-ATPase (sodium-potassium pump) is also active in the membrane. It releases sodium ions from the cell to the environment and transports potassium ions into the cell. Since both processes run against the concentration gradient, energy in the form of ATP must be used for this process. When a molecule of ATP is split into ADP and phosphate, 3 ions can be transported out and 2 ions can be transported in.