negative feedback to control glucose levels

[theonlytycrane]

If blood glucose levels are too high, insulin is released by the pancreas to signal cells to take in glucose for energy or storage.
If blood glucose levels are too low, glucagon is released by the pancreas to signal cells to break down glycogen into glucose for the blood.

Both instances are examples of negative feedback in that the hormone being released reverts the blood glucose level back to within the homeostatic range. Am I thinking about this correctly?

I was confusing the second case with positive feedback as I thought that since glucagon increases blood glucose levels it would be positive.

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[bee17]

They are both negative feedback mechanisms. Low blood sugar triggers release of glucagon. Glucagon increases blood glucose, which then decreases the need for more glucagon. If it was a positive feedback mechanism, the levels of glucagon would just keep increasing and increasing. Make sense?

 

[RyanLJ]

The same kind of confusion occurs with Behaviorism in Psychology. Negative Reinforcement and Positive Punishment are not always intuitive concepts.
Giving someone headphones as a reward to increase the frequency of a behavior would normally be assumed to be an act of positive reinforcement. However, if a passage emphasizes that the purpose and use of the headphones is to block out noxious background noise, the best answer becomes Negative Reinforcement - reinforcing a behavior by removing an aversive stimulus.

What you're reducing with glucagon is the 'state of lowness' of blood glucose. While it might sound like wordplay, the 'state of lowness' is the stimulus that triggers the release of glucagon.

Another way of looking at it would be setting an arbitrary zero point for blood glucose at which pancreatic endocrine function is minimal. As the concentration of glucose increases, you get a positive number of increasingly large magnitude, and insulin secretion acts to counter that (reducing the magnitude of the positive number). As the concentration of glucose drops, you get a negative number of increasingly large magnitude, and glucagon secretion acts to counter that (reducing the magnitude of the negative number).

 

[nomdeplume1234]

I think it helps to think of it in terms of homeostasis. If the system deviates from homeostasis (either high or low blood sugar) then if some process acts in order to return the system to homeostasis then it is called negative feedback.

Also I think there may be a difference between increase/decrease in the product produced and an increase/decrease in some effect that product will have. maybe that was the source of the confusion?

 

[David513]

This part of the Oxford dictionary definition for negative feedback is very useful: "...where the result of a certain action may inhibit further performance of that action." So by increasing insulin in the body, you inhibit the need for more insulin (you're successfully storing away excess glucose but don't want to take too much out of circulation); by increasing glucagon, you inhibit the need for more glucagon (you're successfully putting more glucose in the blood but don't want to add too much into circulation).

The more each hormone acts, the less of a need there is for more of that hormone. Negative feedback!

Make sense?