Feedback mechanisms
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- Created by: r98
- Created on: 22-04-16 20:38
What are the two types of feedback?
negative feedback & positive feedback.
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What type of feedback is it when the feedback causes the corrective measures to be turned off, so the system returns to its normal level?
Negative feedback.
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How does negative feedback help in temperature regulation when the body is lowering its temperature after it had risen?
The cooler blood returning from the skin passes through the hypothalamus where the thermoreceptors detect that blood temperature is at the set point again and so they cease impulse to the heat loss centre, so vasodilation etc ceases.
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How is negative feedback involved in the control of blood glucose, when there is a fall in the concentraion of glucose in the blood?
After the blood glucose conc has returned to its normal level, (due to production of glucagon etc), this blood circulates back to the pancreas, the a-cells detect the change and stop producing glucagon (=negative feedback).
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What does having separate negative feedback mechanisms that control departures from the norm in either direction, give humans?
A greater degree of homeostatic control.
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When does positive feedback occur?
When the feedback causes the corrective measures to remain turned on.
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What are the four main hormones that control the menstrual cycle?
Follicle-stimulating hormone (FSH), luteinising hormone (LH), oestrogen, and progesterone.
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What 2 hormones are released from the pituitary gland?
Follicle-stimulating hormone (FSH) & luteinising hormone (LH).
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What 2 hormones are produced by the ovaries?
Oestrogen & progesterone.
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What are the two roles of FSH?
It stimulates the development of follicles in the ovary, which contain eggs, and stimulates the follicles in the ovaries to produce oestrogen.
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What are the two roles of LH?
It causes ovulation to occur, and stimulates the ovary to produce oestrogen.
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What are the two roles of oestrogen?
It causes the rebuilding of the uterus lining after menstruation, and stimulates the pituitary gland to produce LH.
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What are the two roles of progesterone?
It maintains the lining of the uterus in readiness to receive the fertilised egg, and inhibits the production of FSH from the pituitary gland.
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How are the hormone levels & the uterus affected when the growing follicles secrete small amounts of oestrogen into the blood? What type of feedback does this cause?
This causes the uterus lining to build up again and also inhibits the release of FSH and LH from the pituitary gland (=negative feedback)
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What happens at around day 10, of the menstrual cycle, when oestrogen levels reach a critical point? What type of feedback does this cause?
It stimulates the pituitary gland to release more FSH and LH (=positive feedback).
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How does ovulation occur, at day 14 of the menstrual cycle?
There's a surge in FSH and LH production. The surge in LH causes one of the follicles in the ovary to release its egg.
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What does LH stimulate, after ovulation?
It stimulates the empty follicle to develop into a structure called the corpus luteum, which secretes progesterone (and some oestrogen).
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How is progesterone involved in negative feedback?
It inhibits the release of FSH and LH by the pituitary gland.
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What happens if the egg is not fertilised, during the menstrual cycle?
The corpus luteum degenerates and so no longer produces progesterone.
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How does the degeneration of the corpus luteum affect the lining of the uterus and the production of FSH?
As there is less progesterone, the lining of the uterus is no longer maintained and so breaks down (menstruation). Less progesterone also means that FSH release is no longer inhibited.
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What hormones does FSH stimulate & what hormones does it inhibit?
Stimulates production of oestrogen, in ovary. Doesn't inhibit any of the four main hormones involved in the menstrual cycle.
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What hormones does LH stimulate & what hormones does it inhibit?
Stimulates production of progesterone, in the ovary. Doesn't inhibit any of the four main hormones involved in the menstrual cycle.
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What hormones does oestrogen stimulate & what hormones does it inhibit?
Stimulates production of LH, in the pituitary gland. Inhibits production of FSH, in pituitary gland.
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What hormones does progesterone stimulate & what hormones does it inhibit?
Doesn't stimulate production of any of the four main hormones involved in the menstrual cycle. Inhibits producton of FSH & LH, in pituitary gland.
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Other cards in this set
Card 2
Front
What type of feedback is it when the feedback causes the corrective measures to be turned off, so the system returns to its normal level?
Back
Negative feedback.
Card 3
Front
How does negative feedback help in temperature regulation when the body is lowering its temperature after it had risen?
Back
Card 4
Front
How is negative feedback involved in the control of blood glucose, when there is a fall in the concentraion of glucose in the blood?
Back
Card 5
Front
What does having separate negative feedback mechanisms that control departures from the norm in either direction, give humans?
Back
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