Feedback Mechanisms and the Oestrous Cycle

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  • Created by: Keryn
  • Created on: 14-05-13 13:04
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  • Feedback Mechanisms and the Oestrous Cycle.
    • Negative Feedback
      • If a parameter increases, negative feedback will decrease it and vice versa.
        • This restores the parameter to its original/preferred level.
      • Parameters
        • Temperature
        • Blood glucose level.
    • Positive Feedback
      • The corrective measures stay switched on causing the system to deviate from the original levels even more.
        • e.g. Na+ channels are opened to initiate an action potential. The movement of Na+ into the membrane opens more channels so the membrane is even more permeable.
        • e.g. hypothermia and hyperthermia.
    • The Menstrual Cycle.
      • Hormones.
        • FSH
          • stimulates the development of an ovum in one ovary.
          • stimulates the production of oestrogen by the ovary.
        • Oestrogen
          • LOW concentrations
            • Inhibits FSH and LH production by negative feedback.
          • HIGH concentrations
            • Stimulates FSH and LH production by positive feedback.
          • ALWAYS
            • Stimulates the thickening of the uterine wall.
            • Stimulates the development of the secondary sexual characteristics, (breasts and wide hips).
        • LH
          • Initially inhibits oestrogen production so that its levels return to normal by negative feedback.
          • Stimulates progesterone production by the ovaries.
          • Stimulates ovulation.
        • Progesterone
          • Produced by the corpus luteum in the ovary.
            • Corpus luteum is the remains of the follicle in which the egg developed.
          • Inhibits FSH and LH production by negative feedback.
      • If pregnant.
        • ovary continues to produce progesterone
          • Uterine wall stays intact so a foetus can develop. (Blood vessels).
          • FSH is inhibited so no more ova can devlop.
      • If not pregnant.
        • Progesterone production stops
          • Uterine wall loses stability and is lost in menstruation
          • FSH isn't inhibited so another ovum can develop and be released


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