Endocrine: Feedback Systems

[Laraine]

Hey everyone,

So I'm pretty sure that feedback systems are mostly negative except for oxytocin and LH right? My new anatomy teacher is telling us that "every feedback has a positive and negative. The reason for this is that with every reaction there is an opposite reaction. Meaning if something has been turned on to make a change there needs to be something that turns it off. This also hold true for oxytocin- it has both because just as the body requires its release it also need it to be regulated and turned off".

I think he is wrong.

It is negative because if a variable changes then the system responds by making the opposite change. In positive feedback if the variable changes the system responds by continuing the change( to a point). ie: LH stimulates estrogen secretion which enhances LH secretion which stimulates estrogen leading to the LH surge which triggers ovulation.

What have you been taught?

Thanks everyone :)

[Esme12, ASN, BSN, RN]

But the excesses of any hormone of system failure to turn on or off have negative effects. The human body is a delicate balance...it responds to imbalances with illness and disease.

[Laraine]

ok so he's saying that for example with bld Ca+2 levels: if there is high Ca+2 levels, it is a negative feedback and when there is low Ca+2 levels it is a positive feedback.

I say this is completely incorrect.

the system is simply negative feedback, yes?

[Esme12, ASN, BSN, RN]

I must be obtuse today...I have no clue what you mean.

Anyone else?

[i♥words]

ok so he's saying that for example with bld Ca+2 levels: if there is high Ca+2 levels, it is a negative feedback and when there is low Ca+2 levels it is a positive feedback.

I say this is completely incorrect.

the system is simply negative feedback, yes?

I see what you are saying. Let me try an example (and hope I'm not wrong).

The anterior pituitary produces ACTH to stimulate the adrenal cortex to produce cortisol, correct?

Pituitary -> (ACTH) -> Adrenals -> (Cortisol)

When cortisol levels are high, the negative feedback loop tells the pituitary gland to stop producing ACTH. Negative feedback.

Your professor is basically saying that, when the cortisol levels are low, a positive feedback loop tells the pituitary gland to continue producing ACTH. Positive feedback.

But you think there is only negative feedback in this scenario, that there is no feedback until the cortisol levels are high and the pituitary gland is told to stop producing ACTH.

I'm actually thinking that the negative feedback and positive feedback scenario makes sense. Aren't signals always being sent?

Anyone else?

[Laraine]

You know, I appreciate your help here but I can see that even though his logic makes sense, unfortunately I'm pretty sure he is wrong and is just 'making **** up' as the saying goes. please don't get caught up in this erroneous information, I wouldn't want anyone else to get a wrong answer on an exam. It's negative feedback, I'll leave it at :)

[Laraine]

Hey everyone,

I posted this in the student section, but I don't want to mess up peoples' learning so I thought I'd ask the established nurses for help here.

I think my anatomy teacher is wrong about negative feedback, I think he might be making up stuff that isn't accurate.

Here's the issue:

I'm pretty sure that feedback systems are mostly negative except for oxytocin and LH right?

My new anatomy teacher said, "every feedback has a positive and negative. The reason for this is that with every reaction there is an opposite reaction. Meaning if something has been turned on to make a change there needs to be something that turns it off. This also hold true for oxytocin- it has both because just as the body requires its release it also need it to be regulated and turned off".

I think he is wrong.

Here is what I read:

In negative feedback if a variable changes then the system responds by making the opposite change.

In positive feedback if the variable changes the system responds by continuing the change( to a point). ie: LH stimulates estrogen secretion which enhances LH secretion which stimulates estrogen leading to the LH surge which triggers ovulation.

Any help/clarification is appreciated.

Thanks,

Laraine

[i♥words]

How do you know he is incorrect?

[Laraine]

I took anatomy already. I am retaking because I had to change schools and the new school only gave me half a credit even though I've covered all the systems. I had an outstanding teacher before. Frankly, the caliber at this new school is distinctively inferior, but circumstances forced our relocation.

[hi616]

I am just a student in anatomy right now so I am no expert either. But, I do agree with you. The only positive feedback systems I can think of are ovulation, childbirth, and blood clotting. I've never had a teacher explain it the way your teacher did and I've taken several biology classes. For example, why would our body use a positive feedback loop to regulate blood sugar levels? It is regulated by negative feedback; if it had a positive feedback loop you would have diabetes, right? Unless he means that in this case the positive feedback loop is when you eat and your blood sugar continues to go up?? But I don't think you could count that as positive feedback because your body isn't automatically eating; you decide when you want to eat. Maybe he's not completely wrong, but at the very least confusing. I'm not sure, just trying to help you think through it. Good luck!

[Laraine]

ah, yes, thank you. I do think he is confused, and regrettably, he's spreading it. I also asked him if ADH was associated with renin and he said yes! Maybe he's just a little rusty. I certainly feel cautious about asking him anything else going forward.

Thank you for your reply!

[applewhitern, BSN, RN]

Hmmm. You guys are making me glad I am not in school anymore!