Feedback Mechanisms and the Oestrous Cycle
- 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.
- If a parameter increases, negative feedback will decrease it and vice versa.
- 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 corrective measures stay switched on causing the system to deviate from the original levels even more.
- 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).
- LOW concentrations
- 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.
- Produced by the corpus luteum in the ovary.
- FSH
- 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.
- ovary continues to produce progesterone
- 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
- Progesterone production stops
- Hormones.
- Negative Feedback
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