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    (Original post by Cleoleo)
    What does all or nothing and refractory period mean anyoneee?
    all or nothing is a term used to say...

    that minimum amount of stimulus is required to start an action potential, the all or nothing effect is beneficial as it prevents a stimulus starting of the smallest of things happening

    By summation effect and/or temporal
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    Going into that paper tomorrow only to have done one past paper lol GOOD LUCK everyone!!!
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    (Original post by nadzzdan)
    Going into that paper tomorrow only to have done one past paper lol GOOD LUCK everyone!!!
    lol do some more now!?
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    Can anyone explain to me what exactly this learning outcome is asking:

    LO 15, Topic 7: explain the principle of negative feedback in maintaining systems within narrow limits.
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    (Original post by Dentistry:))
    Can anyone explain to me what exactly this learning outcome is asking:

    LO 15, Topic 7: explain the principle of negative feedback in maintaining systems within narrow limits.
    I'd suggest it just means negative feedback in terms of homeostasis. As for maintaining systems and it's limits it'll talk about high/low pH levels (too much CO2 in blood) or high/low blood pressure and how negative feedback restores the balance (so receptors to medulla oblongata to effector cells simply). Hope that helps!
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    (Original post by PlatypusPigeon)
    I'd suggest it just means negative feedback in terms of homeostasis. As for maintaining systems and it's limits it'll talk about high/low pH levels (too much CO2 in blood) or high/low blood pressure and how negative feedback restores the balance (so receptors to medulla oblongata to effector cells simply). Hope that helps!
    Ah i get it now. Cheers mate.

    Hows your article prep?
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    ok last min rev !!!
    how does IAA cause cell elongation (5 marks)
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    describe negative feedback mechanism (2 marks)
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    some1 please explain to me how;
    plants sensitivity is brought about in plants? when phytochromes red light Pr is converted into far-red light Pfr..?
    to be honest the plant thingy...?
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    OMG, Gene expression Paragraphs (43-48) fadskjfnhkdsj ??:s

    I just dont understand what they're trying to get to in the Article Paragraphs (43-48).
    I get everything else in the Article but this... :| . Someone care to explain please in a short summary, and what topics id have to read over for this bit

    Thanks
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    I've managed to confuse myself, can someone just clarifiy whether depolarised is being made positive or negative? And same with hyperpolarised. Thanks
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    depolarised is more positive and hyperpolarised is more negative
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    (Original post by iesians)
    describe negative feedback mechanism (2 marks)
    I know it but it's hard to write/explain. I'd probably say something along the lines of a change results in the opposite event occuring to counteract the initial change.
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    (Original post by Dentistry:))
    Ah i get it now. Cheers mate.

    Hows your article prep?
    ****tt, I lost the article so am using an online copy with no synoptic highlights so am completely clueless. I'm just hoping the bio4 resit is still fresh in my head because that may help :P How about you?
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    (Original post by iesians)
    ok last min rev !!!
    how does IAA cause cell elongation (5 marks)
    IAA is a Auxin that causes uneven growth in plants and controls the tropisms, Uneven growth is caused by uneven distrubution of the IAA.

    In shoots it moves to the more shaded parts so that the shoot bends towards the light.

    I may be utterly wrong here, but do we actually need to know about how the cells are actually elongated?!
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    (Original post by iesians)
    describe negative feedback mechanism (2 marks)
    a process of homoeostasis such as Vasolidation or Sweating which maintains constant internal temperature from small deviations in the external environment?
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    (Original post by ConnorB)
    IAA is a Auxin that causes uneven growth in plants and controls the tropisms, Uneven growth is caused by uneven distrubution of the IAA.

    In shoots it moves to the more shaded parts so that the shoot bends towards the light.

    I may be utterly wrong here, but do we actually need to know about how the cells are actually elongated?!
    IAA binds to receptor sites on cell surface membrane
    Activates a pump, which pumps H+ out of the cytoplasm into the cell wall
    Since the conc of H+ changes, pH drops, so the optimum pH for enzymes is reached. These enzymes break the bonds between the cellulose microfibrils
    Cell wall becomes flexible, absorbs water (osmosis) and stretches (woooo elongation)

    I think we need to know that
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    (Original post by platypuspigeon)
    iaa binds to receptor sites on cell surface membrane
    activates a pump, which pumps h+ out of the cytoplasm into the cell wall
    since the conc of h+ changes, ph drops, so the optimum ph for enzymes is reached. These enzymes break the bonds between the cellulose microfibrils
    cell wall becomes flexible, absorbs water (osmosis) and stretches (woooo elongation)

    i think we need to know that :s
    we need to know this???????
    Wtf
    fml
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    (Original post by PlatypusPigeon)
    IAA binds to receptor sites on cell surface membrane
    Activates a pump, which pumps H+ out of the cytoplasm into the cell wall
    Since the conc of H+ changes, pH drops, so the optimum pH for enzymes is reached. These enzymes break the bonds between the cellulose microfibrils
    Cell wall becomes flexible, absorbs water (osmosis) and stretches (woooo elongation)

    I think we need to know that
    w0w ! perfect answer !!
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    (Original post by ConnorB)
    IAA is a Auxin that causes uneven growth in plants and controls the tropisms, Uneven growth is caused by uneven distrubution of the IAA.

    In shoots it moves to the more shaded parts so that the shoot bends towards the light.

    I may be utterly wrong here, but do we actually need to know about how the cells are actually elongated?!
    yup we do !
    someone on this page posted a 100% correct answer chk it out !
 
 
 
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