Negative feedback in homeostasis describes a process by which bodily systems maintain their normal environments or states. Homeostasis describes the body's overall regulation of its internal systems. When changes in a state such as body temperature occur, negative feedback responses are triggered to bring the temperature back to its normal point. For example, if the body becomes too hot, sweating occurs to cool it. If the body becomes too cold, shivering is one response that helps to warm it up.
The typical or ideal state of a bodily system is called the set point, but negative feedback in homeostasis can't keep systems exactly at the set point. Instead, negative feedback in homeostasis acts to keep body temperature, for instance, within what is called a normal range of values. The value of a system that changes due to different circumstances is called a variable.
There are often three parts to a negative feedback response, which are called the receptor, control center, and the effector. The receptor is the part of the feedback response that simply detects changes in the value of the variable. This information is passed along to the control center, which monitors the changes and begins a negative feedback response when the changes fall too far outside of the normal range of values. When that happens, the control center signals an effector to take action that will help return the system toward its set point.
One example of negative feedback in homeostasis is the way the body regulates blood pressure. The receptors in this case are pressure-sensitive veins located near the heart and the head. These receptors send nerve impulses to the part of the brain, here the control center, that regulates heart rate. The control center then sends signals to the effector, which in this case is the heart. In response to the brain's messages, the heart speeds up or slows down to regulate the blood pressure.
The concept of negative feedback in homeostasis is also used in psychology. In psychology it can be a useful way of understanding basic drives and motivations. For example, a person who has been deprived of food typically becomes hungrier as time passes. The feeling of hunger is a negative feedback mechanism attempting to return the body to its nutritional set point. When that person eats, the mechanism has been successful and the feeling of hunger dissipates.