The principles of feedback mechanisms
Negative feedback = when the feedback causes the corrective measures to be turned off, and so it retunes the system to its original level.
Positive feedback = when the feeback causes the corrective measure to remain turned on, and so causing the system to deviate even more from the original level.
Control of the oestrous cycle
- Begins early teens and ends with menopause at late 50s.
- Length varies between 25 - 25 days, but the average is 28 days.
- The following occurs in each cycle:
- Egg is released.
- Lining of the uterus is made ready for an egg to be implanted.
- If egg is not fertilised and planted in the uterus, menstration occurs.
- There are four main hormones involved:
- FSH (follicle stimulating hormone) - this is produced in the pituitary gland. It stimulates the development of follicles in the ovarym which contains eggs, and stimulates the follicles in the ovaries to produce oestrogen.
- LH (lutenising hormone) - this is produced in the pituitary gland. It causes ovulation to occur, and stimulates the ovary to produce progesterone from the corpus luteum.
- Oestrogen - produced in the ovaries. It causes the rebuilding of the uterus lining after menustration and stimulates the pituitary gland to produce LH.
- Progesterone - produced by the corpus luteum. It maintains the lining…