PC1002 Final: Nervous System Physiology
Document Summary
Osmolarity & tonicity osmolarity the total concentration of solutes, penetrating and non- penetrating. Normal cell osmolarity is approximately 300mosm. tonicity the concentration of only the non-penetrating solutes. Tonicity is always in reference of the extracellular non-penetrating solute concentration compared to the cell"s non-penetrating solutes. A solution can be isotonic, hypertonic or hypotonic with respect to the cell. Osmolarity and tonicity are clinically relevant because replacement fluids that are given to a patient should match the osmolarity and tonicity so that they don"t affect the cell size. Look for all the information when using the formula, do not assume the value of some variables. Know that sodium wants to move into the cell and that potassium wants to move out of the cell. This is the membrane potential of non-excitable cells and excitable cells at rest . More than 90% of resting potential is due to passive diffusion of k+ and na+ down their concentration gradients.
