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    hi, ive learnt about negative feedback mechanisms and how they actively increase or decrease a level in the human body and give more control in maintaining homeostasis.

    For example with blood glucose concentration, if it’s too high, B cells secrete insulin nd if it’s too low, A cells secrete glucagon. This is to get the blood glucose concentration back to normal.

    But the bit which is causing me confusion is, say if the blood glucose concentration was too low and glucagon was secreted, the negative feedback mechanism will ensure that it keeps secreting glucagon until it theblood glucose returns back to normal, but what happens then?
    Does the negative feedback mechanism turn off? (as its reached its normal blood glucose concentration again)
    Or does the negative feedback mechanism stay on until, blood glucose concentration gets too high again and it would then turn off and then insulin would be secreted and that negative feedback mechanism is then turned on.

    If you have a CGP AQA A2 Revision book (green) there’s a diagram on page 72 at the bottom and it says e.g) A cells stop secreting glucagon nd B cells secrete insulin. Does that mean the A cells were continually secreting glucagon even after it reached the normal level and until the feedback mechanism stopped and the other mechanism was turned on and insulin started to be secreted.

    Sorry for any confusion its just I thought multiple negative feedback mechanisms worked by restoring it to the normal blood glucose level and then they turn off. and lets say if it fell too low, then they would turn on to restore it back to the normal level. And then turn off. And if it fell too low again, then they would again turn on and restore it back. And once again turn off.
    I have a feeling the problem is the bad wording in the CGP book.

    Thanks in advance J
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    (Original post by ryanj18)
    hi, ive learnt about negative feedback mechanisms and how they actively increase or decrease a level in the human body and give more control in maintaining homeostasis.

    For example with blood glucose concentration, if it’s too high, B cells secrete insulin nd if it’s too low, A cells secrete glucagon. This is to get the blood glucose concentration back to normal.

    But the bit which is causing me confusion is, say if the blood glucose concentration was too low and glucagon was secreted, the negative feedback mechanism will ensure that it keeps secreting glucagon until it theblood glucose returns back to normal, but what happens then?
    Does the negative feedback mechanism turn off? (as its reached its normal blood glucose concentration again)
    Or does the negative feedback mechanism stay on until, blood glucose concentration gets too high again and it would then turn off and then insulin would be secreted and that negative feedback mechanism is then turned on.

    If you have a CGP AQA A2 Revision book (green) there’s a diagram on page 72 at the bottom and it says e.g) A cells stop secreting glucagon nd B cells secrete insulin. Does that mean the A cells were continually secreting glucagon even after it reached the normal level and until the feedback mechanism stopped and the other mechanism was turned on and insulin started to be secreted.

    Sorry for any confusion its just I thought multiple negative feedback mechanisms worked by restoring it to the normal blood glucose level and then they turn off. and lets say if it fell too low, then they would turn on to restore it back to the normal level. And then turn off. And if it fell too low again, then they would again turn on and restore it back. And once again turn off.
    I have a feeling the problem is the bad wording in the CGP book.

    Thanks in advance J
    For the first bit, blood glucose concentration is regulated by receptors located on the Islets of Langerhans, so when glucose concentrations return back to normal, glucagon release is inhibited preventing glycogenolysis occurring in the liver. And if the glucose levels rise too high, the pancreatic B cells secrete insulin. These are two feedback systems which work hand in hand with each other, both being able to regulate blood glucose levels.

    I don't have access to the OCR CGP, so I can't help you with that unfortunately. Could you upload the diagram? Or hopefully someone with the CGP can come along and help
 
 
 
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