Question

Are these positive or negative feedback loops?
•FSH and estrogen production by the
follicle
•Estrogen increases the thickness of the
uterine lining
•LH and progesterone production
•Effect of fertilization on LH levels
•Effect of progesterone on maintaining
pregnancy

Answer 1

Are they all positive? I'm a little bit confused at the difference.

Answer 2

Are you having trouble understanding the difference between negative and positive feedback, or how feedback applies to the examples you have been given?

Answer 3

Positive feedback happens when the presence of some molecule, A, somehow up-regulates itself and results in the body making more A. Negative feedback happens when the presence of a molecule B some how tells the body to make less of molecule B, so eventually it all disappears.

The effect of progesterone on maintaining pregnancy is certainly a positive feedback loop. In pregnancy, progesterone makes the body produce another hormone, human chorionic gonadotropin (which I have almost certainly misspelled) and that hormone tells the body to make more progesterone.

*If* human chorionic gonadotropin had told the body to make less progesterone, it would have been an example of negative feedback.

Answer 4

So would the first one (FSH-estrogen) be negative? I'm a little confused with these specific examples because I don't know much about the hormones.

Answer 5

FSH stimulates estrogen.

So at this point, the question is whether estorgen turns around and up regulates or down regulates FSH. If more estrogen means less FSH, then it is negative feedback. If more estrogen means more FSH, then it is positive feedback.

Answer 6

And in this case yes, estrogen does inhibit production of FSH so it is negative feedback.