Most homeostasis pathways follow a similar structure, and for each pathway, we can identify specific actors and functions.

Figure 1:A flow diagram showing the ordered sequence of the process of homeostasis

In homeostatic processes, the sensors, control center and effectors usually form a cycle using anegative feedback loop. The action of the effectors reduce the impact of the intensity of the stimulus, thus the sensors are picking up that the body is not as much off-balance, and will tell so to the control center, which will decrease the action of effectors, and so on.

Stimulus
The variable change that causes homeostatic pathways to be activated is usually called a stimulus. It could be anything from rising temperature, change in hormone concentrations, an injury, or anything out of the ordinary that threatens the delicate balance.

Sensors
The structures able to detect a stimulus are called sensors. Nerves cells and cells with specific chemoreceptors or baroreceptors are examples of sensors. Sensors typically send a signal to the rest of the body that something is going wrong and can potentially be dangerous.

Control Center
The control center is usually at the other end of this signal. The control center is an organ or a tissue able to receive and process the signal from the sensors, then make a decision about the best path to take to react to the stimulus. The brain stem contains a lot of control centers for the body with for example the medulla able to process a signal from sensors in the carotid about a lack of oxygen in the bloodstream. The medulla will then instruct your body to take deeper breaths, bringing in more oxygen to be incorporated in the bloodstream at the interface with the lungs.

Effectors
The control center does not act alone: once it has decided to take action to counter the stimulus, it will communicate this decision to effectors, organs whose specific action will directly affect the output from the stimulus. For example, in case of your body overheating, the hypothalamus in the brain will instruct the sweat glands to start secreting water outside the skin, and blood vessels to dilate to dissipate more heat at the interface with the skin.