Feedback Loops in the Endocrine System

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  • 0:05 Review of the Endocrine System
  • 1:30 Feedback Mechanisms
  • 3:30 Endocrine System Feedback
  • 6:34 Lesson Summary
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Lesson Transcript
Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

Your endocrine system regulates many important bodily functions. To do this, it relies on a constant source of information from chemical messengers in your body. This feedback is essential to proper cellular function, most of which goes on without you even noticing.

Review of the Endocrine System

By now, you should have a good understanding of your endocrine system, which is made of hormone-producing glands that help regulate your energy levels, growth, emotions, ability to reproduce, and more. There are over a dozen glands that make up your endocrine system, including your pancreas, adrenal glands, thyroid, and pituitary gland. Hormones are important because they are substances that act as chemical signals in your body. They are like microscopic messengers, carrying important information with them as they travel through your bloodstream.

Hormones may be very small, but they are invaluable to you because the messages they carry help your body maintain proper functionality. You don't notice it, but your body is working all the time to maintain stable internal conditions. This stable internal environment is called homeostasis. The word originates from 'homeo' meaning 'similar' and 'stasis' meaning 'staying the same,' which very nicely describes what your body is trying to do all the time - maintain itself in a certain state!

Homeostasis refers to any number of regulated conditions in your body - temperature, calcium levels, immune health, blood sugar levels, and so much more. As you can imagine, this constant internal regulation takes a lot of work.

Feedback Mechanisms

In order to make sure the conditions in your body are just right, the endocrine system uses feedback mechanisms, which are responses that trigger other activities or processes. There are two types of feedback mechanisms: negative and positive. Negative feedback mechanisms are the most common because they attempt to maintain a target level. In contrast, positive feedback mechanisms are amplifications away from a target level.

Don't let these names fool you though - negative feedback is a very good thing when it comes to homeostasis. Your body does not often employ positive feedback because it doesn't like extreme conditions. Therefore, since negative feedback maintains appropriate conditions in your body, it's the most common type of feedback mechanism. Let's look at an example to see how this works.

Say you're driving down the road, daydreaming about what you'll have for dinner that night. All of a sudden, you see one of those electronic speed monitors, and it tells you that you are going way above the posted limit. This triggers a response from you - you slow down to match the speed limit, which we could call the 'target level.' Negative feedback in action!

Now, let's say that you see that same speed monitor, but instead of slowing down you slam your foot down on the accelerator to see just how far above that speed limit you can go. This is amplification of your speed away from the target level (the speed limit). Positive feedback in biological systems works the same way. Can you see why this wouldn't be a good mechanism for your body to employ when it comes to say, temperature or growth?

The reason we say 'negative' feedback is because what we're really talking about is a 'negative increase.' 'Positive' feedback, on the other hand, instills a 'positive' increase or output. It really has nothing to do with whether or not the feedback mechanism itself is good or bad; it just describes types of responses that occur.

Endocrine System Feedback

Negative feedback regulation works much the same way in your body as it does on the road. For example, your pancreas (an important gland in your endocrine system) relies on negative feedback to regulate blood glucose levels. An influx of glucose, say from a carbohydrate-heavy dinner, triggers your pancreas to produce a hormone called insulin. Insulin's message to your body is to take up that extra sugar into cells in order to bring your blood sugar back to the target level. Once enough glucose has been taken up by your cells, your pancreas stops secreting insulin. It's negative feedback!

Negative feedback also helps you if your blood sugar gets too low. When this happens, your pancreas excretes a different hormone called glucagon. This hormone carries the opposite message of insulin. It tells your cells to release their glucose stores so that you can bring your blood sugar back up - again, to the target level.

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