Control Systems of the Body
The human body has thousands of control systems. The most intricate of these are the genetic control systems that operate in all cells to help control intracellular function and extracellular functions. This subject is discussed in Chapter 3.
Many other control systems operate within the organs to control functions of the individual parts of the organs; others operate throughout the entire body to control the interrelations between the organs. For instance, the respiratory system, operating in association with the nervous system, regulates the concentration of carbon dioxide in the extracellular fluid. The liver and pancreas regulate the concentration of glucose in the extracellular fluid, and the kidneys regulate concentrations of hydrogen, sodium, potassium, phosphate, and other ions in the extracellular fluid.