 Homeostasis is a little like walking up the "down" escalator. |
Have you ever climbed up the "down" escalator? If so, you probably did a lot of work and expended a lot of energy. You might have made it up a few stairs or been carried down a few, but you probably stayed in about the same place most of the time. That experience provides a good way to think about one of the most important properties of the body: homeostasis. Homeostasis is the total of all of the processes the body uses to keep its internal environment (variables like body temperature, amount of sugar in the blood, and so on) about the same. Homeostasis is a dynamic process--the variables it controls fluctuate a little, but overall stay relatively constant.
Read the table below to learn about some important terms associated with homeostasis. As you read, think about how these terms relate to processes that occur within your own body.
| Stimulus | A stimulus (plural: stimuli) is anything that causes a reaction or response. It is a change in the internal or external environment. When your pupil gets smaller in bright light, the stimulus is the bright light, and the response is the action of your iris muscles contracting. |
| Sensor | A sensor is something that detects changes. A thermostat in your home detects the temperature of the air, and acts as a sensor. Sensors in the human body include your eyes, ears, and nerves. |
| Effector | An effector is something that carries out a response. In the human body, an effector may be the muscle that causes you to blink when you get something in your eye. |
| Integrating center | An integrating center is the place where decisions are made. The integrating center in the body is the brain. |
| Set point | The set point is the normal, or target, value for something. For example, the human body temperature is about 37 degrees C (98.6 degrees F) for most people. |
Connect each word or phrase on the left with the correct description on the right. If you don't get them all right, review the content on this page before proceeding in the lesson.
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set point
sensor
integrating center
effector
stimulus
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detects changes
target value
carries out a response
causes a reaction or response
place where decisions are made
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