|"Physiology basically focuses at functions of various systems, that are dependent on the presence of the certain factors such as ions, molecules, protons.
Their concentration plays a very important role in normal and abnormal physiological functioning, which further has a negative effect over the other pathways that are dependent on the product of the former ones. An example for this can be depicted as Calcium, the most abundant mineral in vertebrates is an essential ion. It plays an important role in a variety of physiological functions including structural (skeletal and teeth) and signaling functions (muscle contraction, nerve impulse conduction, hormone and enzyme secretion, and as a secondary messenger in several pathways). Therefore, the control of calcium concentrations in the blood and extracellular fluid is necessary to maintain the normal functions of the cells as well as the prevention of calcium accumulation in the cells. Normally, the input and output of calcium is adjusted to the physiological needs of the body. Either in normal or disturbed calcium homeostasis, cells will have a way to control events to protect them from cytotoxicity. 1,25(OH)2D3 is one of the active metabolites if vitamin D and has been reported to maintain calcium homeostasis.
(Sakara Tunsophon and Ilka Nemere- Role of PKCb in Signal Transduction for the 1,25D3-MARRS Receptor (ERp57/PDIA3) in Steroid Hormone-Stimulated Calcium Extrusion)."