Unit 3.5.5 - Feedback Systems Flashcards
What is negative feedback?
A mechanism that restores a system to their original level.
What do receptors detect?
When a level is too high or low?
What two things make up the communication system?
Nervous or hormonal system
What does negative feedback work to?
Keep things around the normal level
Why does negative feedback only work within certain limits?
If the change is to big the effectors might not be able to counteract it.
How many negative feedback mechanisms does homeostasis involve and why?
Multiple for each thing being controlled because having more than one mechanism gives you more control over changes to your internal environment.
What would happen if you only had one negative feedback mechanism for homeostasis?
You would only be to actively change a level in one direction.
What does only having one negative feedback mechanism mean in terms of response and control?
Slow response and less control.
What is a positive feedback mechanism?
One that amplifies the change in your internal environment.
How do the effectors respond in a positive feedback mechanism?
To further increase the level away from the normal level.
When is positive feedback useful?
To rapidly activate processes in the body.
When does positive feedback when the homeostatic system breaks down?
As the body temperature falls during hypothermia the brain doesn’t work properly and shivering stops. Positive feedback takes the temperature away from the normal level.
What hormones control the mammalian oestrous cycle?
FSH, LH, progesterone and oestrogen.
Where is FSH produced?
In the pituitary gland
When is FSH first produced and what type of feedback does this show?
When progesterone levels drop - negative feedback.
What is the function of FSH
It travels in the blood stream to the ovaries to stimulate follicle development and mature an egg.
What does FSH cause in terms of hormones and what type of feedback does this show?
It causes the ovaries to start to produce oestrogen - positive feedback.
Where is oestrogen produced?
In the ovaries
When is oestrogen produced and what type of feedback does this show?
When FH levels rise - positive feedback.
What is the function of oestrogen?
Stimulates the uterus lining to thicken, inhibits FSH production (so no more follicles develop), it travels in the blood to the pituitary gland and cause the pituitary gland to start to produce FSH and LH.
What is caused when oestrogen levels high and what type of feedback does this show?
It causes the pituitary gland to produce FSH and LH - positive feedback.
Where is LH produced?
In the pituitary gland
When is LH produced and what type of feedback does this show?
When the oestrogen levels rise - positive feedback.
What happens when there is a sudden surge in LH?
Ovulation
What does LH cause?
It travels in the blood to the ovaries to stimulate ovulation.
What happens during ovulation?
Follicle ruptures and an egg is released
How does LH cause the production of progesterone and what type of feedback is this?
It causes the follicle to rupture, the ruptured follicle turns into a corpus luteum which produces progesterone - positive feedback.
Where is progesterone made?
Corpus Luteum
When do progesterone levels rise?
Once the corpus luteum is produced
What does progesterone cause?
It maintains the uterus lining and it inhibits the production of LH and FSH.
What happens in no embryo implants?
The corpus luteum breaks down and stops producing progesterone.
What happens when the progesterone levels are low and what feedback is this?
The uterus lining is no longer maintained and so menstruation starts, low levels of progesterone cause the levels of FSH to rise - positive feedback
If you are pregnant what continues to produce progesterone and why?
The placenta to maintain the uterus lining and to keep FSH levels low so no further eggs will be matured.
