In systems with a negative feedback mechanism, the effector response cancels or negates the effect of the original stimulus.In the human body, temperature is regulated by a negative feedback mechanism. The mechanism is similar to that of a domestic heating system.
In a domestic heating system, the thermostat detects changes in room temperature. It is connected to the boiler control unit which controls the boiler. The thermostat compares the room temperature with that of the pre-set and makes necessary adjustments to keep the room temperature constant. When the room temperature is low, the boiler control unit switches the boiler on, which warms the room. When the pre-set temperature is reached, the system gets reversed. The thermostat detects that the room temperature is high and sends a signal to the boiler control unit and turns it off. As a result, the room cools down due to loss of heat to surroundings. This is a negative feedback mechanism which enables continuous regulation of a variable within a specific range.
In the human body, when the temperature falls below a certain level, specialized nerve endings detect this and send signals to a group of cells in the hypothalamus of the brain. The hypothalamus activates various mechanisms to increase the body temperature. These mechanisms include:
- Stimulation of skeletal muscles which causes shivering
- Narrowing down of blood vessels in the skin to reduce blood flow and loss of heat
- Behavioural changes such as curling up of the body or covering the body with protective clothing
When the body temperature rises to the normal level, the nerve endings stop stimulating the hypothalamus and the mechanisms which increase body temperature stop.
Most of the mechanisms for maintaining homeostasis in the body use negative feedback.