Feedback Mechanisms

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Feedback Mechanism

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

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