Inorganic ions have multiple roles in different biological processes including transmitting nerve impulses, muscle contraction, and regulation of fluid balance in the body. As an example, potassium and sodium ions play a specific role in regulating the resting membrane potential of neurons as well as the relaxation and contraction of muscle fibers. Sodium ions function to regulate fluid balance, specifically in the exterior of cells. Additionally, a small amount of sodium ions are required to conduct nerve impulses between cells to open specialized channels that permit sodium to flood inside the cell. Other inorganic ions include calcium ions, which are involved in blood coagulation and transmitting nerve impulses. Hydrogen ions are crucial inorganic ions which regulate the acid-base balance in the body. Acid-base balance is the process of the balance between the input (formation) and output (elimination) hydrogen. Iron ions are crucial components of hemoglobin and myoglobin. These ions function to regulate the movement, tissue storage, and use of oxygen in the body. Copper ions are cofactors for multiple types of enzymes, and are necessary for processes like respiration, tissue maturation, and protection against oxidative stress. Phosphate ions are responsible for various processes within cells including glycolysis and ammoniagenesis.