What are the components of homeostasis and how does it work?  What role does negative feedback play?

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txmedteach eNotes educator| Certified Educator

Homeostasis encompasses so many things that it would be impossible to answer that in a reasonable amount of time. If you're in physiology, then your textbook is merely an explaination of the bigger concepts of homeostasis! The details have often not fully been discovered!

However, let's look at some of the more basic components. Homeostasis involves your body ensuring that it maintains a condition in which it can live. This means ensuring the body has energy to power processes, is at the right temperature, pH, solute balance, etc., and delays as long as possible its equilibrium state (death).

In general, the maintenance of homeostasis relies on sensing changes in the body's ideal conditions, and working to restore those conditions to ideal. This is where negative feedback comes in! Negative feedback is everywhere, in every system, and you really can't avoid it!

Negative feedback is based on the concept of a set-point, a sensor, and a corrective mechanism. For example, in a house, an air conditioning/heating system has a temperature set point set by the owner, a sensor in the thermostat that determines if the temperature is correct, and a corrective mechanism in the A/C or heater depending on which way the temperature needs to change in order to be back at the set point.

A great biological example of this system is that which regulates blood pressure. I won't go too deeply into it, but I'll give you some of the examples of negative feedback that you often see. An important "set point" for blood pressure is going to be the mean arterial pressure (MAP), which is the time-averaged blood pressure in, say, the aorta. This is generally set like the A/C temperature arount 100 mmHg. There are receptors throughout the body analagous to the thermostat that determine whether or not the MAP is where it should be, like baroreceptors in the arteries or the juxtaglomerular apparatus in the kidneys. Each of these controls a separate corrective mechanism. If MAP becomes too high, then baroreceptors sense this and signal the brain to cut cardiac output and to increase urine output (less fluid = less pressure). If MAP becomes too low, then the cardiac input is increased, while urine output is decreased!

Now, that's not by any means a detailed description of BP regulation, but I hope that it was illustrative for you in terms of a negative feedback mechanism!