|(Taken from Hole's Anatomy)|
- Receptors: provide information about specific conditions in the internal environment. A receptor may be a molecule or a cell or even a system. The receptor detects the bodies need and then contacts the control center.
- Control Center: includes a set point (target value of a physiological measure maintained automatically in the body), which tells a particular value should be. An example would include human body temperature at 98.6 degrees Fahrenheit. This center gets the information from the receptor, reads where the body is at compared to where it needs to be, and sends the mission to the effectors.