Homeostasis is a dynamic, self-regulating process that allows organisms to maintain internal stability while adjusting to varying external conditions. The homeostasis mechanism is a complex system that consists of three distinct units that work in a specific sequence to balance any given variable. 

The three units involved in maintaining homeostasis are:  

• Receptor or Sensor: This is the sensing component of homeostasis. The receptor is responsible for monitoring and responding to changes in the body or in the external surroundings. On detecting changes in the internal or external environment, the sensor sends the information to the control center. 
• Control Center: The control receives information from the receptor and processes it, tallying the changed value to its normal value. If the values are different, the control center activates effectors to oppose or enhance the stimulus.  
• Effector: The effector is the component that responds to the commands sent by the control center and counteracts the stimulus to annul its effect and bring the value of the variable back to normal. Effectors can be any bodily structure such as organs, glands, or muscles that are activated on receiving a command from the control center. 

An example of how the three units work together to maintain homeostasis:

The cutaneous receptors of the skin comprise the receptor unit. On detecting changes in the temperature, these receptors send signals to the brain (the control center)

On receiving information regarding the change in temperature, the brain sends signals to the effectors – the blood vessels and sweat glands in the skin – to act accordingly. 

If the external temperature is too high, the blood vessels dilate and the sweat glands produce sweat simultaneously, causing the heat to dissipate and the body temperature to drop. If the external temperature is too cold, the sweat glands do not get activated but the blood vessels constrict, enabling the body to retain heat.