Homeostasis

If you missed the first post, there is still time to catch up. This is week 1 of a 6 week college biology course prep plan. This week’s focus is on homeostasis.

Homeostasis is the ability to maintain balance around a controlled condition. Your own body works to maintain equilibrium constantly. Homeostatic mechanisms determine your body temperature, blood pressure, and urine output. This is accomplished through a balancing system namely, a feedback system.

Feedback Systems

What are feedback systems? Feedback systems have three parts: receptor, control center, effector. The receptor receives information about a condition like body temperature and sends that information to the control center. The control center has three jobs: receives the information, generates a response, sends the response command to the effector. In more common terms: takes the information, makes a decision, and delegates the task to the workers to complete. The effector does its job, because it is signaled to do so by the control center. The temperature rises in your body and you sweat or the temperature drops and you shiver. These mechanisms are precise in order to attempt to maintain your body temperature within a very narrow range that we call normal.

Negative and positive feedback systems

A negative feedback system is the type of system that I discussed with body temperature. A negative feedback system reverses (or negates) the change in the controlled condition. For example, body temperature is the controlled condition and when we get cold we shiver in order to get warmer (reverse or negate the change).

There are also positive feedback systems. A positive feedback system reinforces a change until a major event occurs in order to ultimately restore homeostasis, but these are not very common. One example is blood clotting. When blood clotting starts, a signal is produced that reinforces clot production, causing a more stable clot and resulting in loss of blood being stopped. If the signal that reinforced clotting wasn’t produced, the clot would be washed away. By reinforcing the change (clotting) we are able to regain homeostasis (stopping the blood loss).

Negative feedback systems are more common, but each type of feedback system is necessary for survival. A specific range of acceptable values for a condition is typical, rather than a culminating event. For example, your thermostat usually controls the temperature in your home versus getting a new unit.