Biology Unit 5 Flashcards - Feedback mechanisms

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Name the stages of 'Homeostatic control'
Set point - Desired level, Receptor - Detects deviation, Controller - Coordinates information, Effector - Brings about change, Feedback loop - Tells receptor to cancel effector
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When does Negative Feedback occur?
When feedback causes the corrective measures to be turned off
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What is Positive Feedback?
When feedback causes the corrective measures to remain turned on
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Name the 4 hormones in the control of the Oestrous cycle
FSH, LH, Oestrogen and Progesterone
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What does FSH do?
Simulates the development of follicles in the ovary, which contains eggs, and stimulates the follicles in the ovaries to produce oestrogen
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What does LH do?
Causes ovulation to occur, and stimulates the ovary to produce Progesterone from the corpus luteum
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What does Oestrogen do?
Causes the rebuilding of the uterus lining after menstruation and stimulates the pituitary gland to produce LH
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What does Progesterone do?
Maintains the lining of the uterus in readiness to recieve the fertilised egg and inhibits the production of FSH from the pituitary gland
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What happens on day 1 on the Oestrous cycle?
The pituitary gland releases FSH into the blood which stimulates follicles in the ovary to grow and mature
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What happens after the growing follicles grow long enough?
They secrete small amounts of oestrogen into the blood, this causes the uterus lining to build up again and inhibits the release of FSH and LH from the pituitary gland (negative feedback)
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What happens at day 10 of the oestrous cycle?
The level of oestrogen increases until it reaches a critical point where it stimulates the pituitary gland to release more FSH and LH (positive feedback)
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What does a surge in LH cause?
One of the follicles in the ovary to release its egg, this is called ovulation on day 14
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What happens after ovulation?
LH stimulates the empty follicle to develop into a structure called the corpus luteum which secretes progesterone
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What happens if the egg is not fertilised?
The corpus luteum degenerates and so no longer produces progesterone
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What happens when less progesterone is produced?
The lining of the uterus is no longer maintained and breaks down, less progesterone also means that FSH release in no longer inhibited so the cycle releases itself
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Other cards in this set

Card 2

Front

When does Negative Feedback occur?

Back

When feedback causes the corrective measures to be turned off

Card 3

Front

What is Positive Feedback?

Back

Preview of the front of card 3

Card 4

Front

Name the 4 hormones in the control of the Oestrous cycle

Back

Preview of the front of card 4

Card 5

Front

What does FSH do?

Back

Preview of the front of card 5
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