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    Not sure if this has already been discussed but what topics do people think are likely to crop up? Usually my teacher gives us a list of things that havent been in recent exam papers but she hasnt this time :/
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    Can anyone define refractory period??
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    (Original post by boxr01)
    Not sure if this has already been discussed but what topics do people think are likely to crop up? Usually my teacher gives us a list of things that havent been in recent exam papers but she hasnt this time :/
    I'm certain hormones(pep-tide and steroid) and transcription factors will come up.
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    (Original post by jojo1995)
    branches are dendrites right ?

    also nerones that dont have action potenials passing along them weaken and disintergrate right ?

    thanks for everything
    yes and yes and you're welcome
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    Anyone else think the habituation practical will come up? It's only been in one of the past papers I think whereas the other 2 have been in a few of them. Also does anyone know if we need to know the core practicals from the other units for this exam? I hope not!
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    (Original post by RnTf)
    Can anyone define refractory period??
    Period of time after an action potential passes during which the axon cannot be stimulated, as the concentration of sodium ions in the axon is very high
    There are 2 types:
    1) Absolute refractory period: no action potential can be generated in the axon whatsoever
    2) relative refractory period: an action potential can be generated, but the threshold level is very high
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    (Original post by thegreenchildren)
    Anyone else think the habituation practical will come up? It's only been in one of the past papers I think whereas the other 2 have been in a few of them. Also does anyone know if we need to know the core practicals from the other units for this exam? I hope not!
    No, but things like DNA profiling/gel electrophoresis do revise. It may come up for the article.
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    Would somebody be able to clarify how heart rate and breathing rate is controlled by the medulla? I am a bit confused about the chemoreceptors for the heart rate. Is it just the cardiovascular control centre in the brain or is it also the carotid and aortic bodies or is this for the breathing rate? ahhh confused! Each book says different
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    (Original post by ViolentMind)
    Guys im still worried aboout the scientific article. What do you think the main points are for it

    Help please
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    hi does anyone know whether id use the same snail for my habituation experiemnt ... throughout it or would i tap one snail for 10 gtimes and then reapeat the tewst using a differnt snail of the same species ?
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    (Original post by thegreenchildren)
    Would somebody be able to clarify how heart rate and breathing rate is controlled by the medulla? I am a bit confused about the chemoreceptors for the heart rate. Is it just the cardiovascular control centre in the brain or is it also the carotid and aortic bodies or is this for the breathing rate? ahhh confused! Each book says different
    Prior to exercise, adrenaline is released. It stimulates the SAN to increase the frequency of waves of depolarisation it generates, so the heart rate increases. As a result, blood pressure in arteries increases. This is detected by baroreceptors in sinuses of carotid artery and aorta, that send impulses to the CVCC, causing vasodilation to occur.

    During exercise, the rate of respiration of cells in active muscles increases, so oxygen demand increases to supply the cells with more energy in the form of ATP. Also, the levels of carbon dioxide increase in the blood, stimulating chemoreceptors, which send impulses to the CVCC. The cardioaccelerator centre send stimulatory impulses ti the sympathetic nerve to the heart, stimulating the SAN, so heart rate increases further more. Again, blood pressure and vasodilation occur (don't refer to blood pressure and vasodilation if they don't ask for it. pay attention to what they ask)

    When exercise stops, oxygen demand starts to decline as the rate of cellular respiration decreases . Also, the levels of carbon dioxide decrease in the blood, so the chemoreceptors are stimulated less. Less impulses are sent to the cardioaccelerator centre in the CVCC, so less impulses travel to the heart via the sympathetic nerve, the SAN is stimulated less, the heart rate decreases, so blood pressure decreases, barorecptors are less stimulated , so less vasodilation occur. these are examples of negative feedback.

    PS: adrenaline doesn't cause a decrease in pressure as far as I know. It has fight or flight effects on the body, meaning that the heart rate increases.
    If the heart rate increases, the input of blood into the heart increases. Take a minute and think about this point.
    When input of blood increases, ventricular walls stretch. When they stretch, they're recoil is more powerful, increasing the stroke volume.
    Heart rate and stroke volume have both increased, so cardiac output has increased, meaning that blood pressure has increased.


    As for the breathing rate, when levels of carbon dioxide rise, this is detected by chemoreceptors which send impulses to the respiratory centre in the medulla., which in turn send stimulating impulses to the respiratory muscles, so tidal volume and breathing rate increase
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    (Original post by jojo1995)
    hi does anyone know whether id use the same snail for my habituation experiemnt ... throughout it or would i tap one snail for 10 gtimes and then reapeat the tewst using a differnt snail of the same species ?
    a different snail, because this one has habituated (it has learned, and it's behaviour is adjusted). Keep in mind the the snail you use at the beginning should be bred in the lab so it has not been exposed to waves and habituated
    For trials, use snails of the same species, size and age
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    Instead of snails, can we use tortoise?? (CGP prefers tortoise...)
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    (Original post by Lujain Al Omari)
    a different snail, because this one has habituated (it has learned, and it's behaviour is adjusted). Keep in mind the the snail you use at the beginning should be bred in the lab so it has not been exposed to waves and habituated
    For trials, use snails of the same species, size and age
    thank you <3 !!
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    (Original post by RnTf)
    Instead of snails, can we use tortoise?? (CGP prefers tortoise...)
    of course YOU can #
    yeah but really, you can
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    (Original post by RnTf)
    Instead of snails, can we use tortoise?? (CGP prefers tortoise...)
    In the exams they use snail as an example so I think you should learn habituation of a snail. I don't think it will be a problem though.
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    what do we need to know about dopamine ?

    ive jotted these down is that all, excluding the drugs and treatment and stuff ?

    - parkingsons is the death of dopaminer producing cells in the region of the brain known as the substantia nigra in mid brain
    - parkinsons is charicaterised with low levels of dopamine
    - loss of control of movement , stiffness of movement and muscles, depression, tremors
    - dopamine is a neurotransmitter that is used in the brain .. in neurones rfesponsible for activities such as movement

    and depression:


    - depression is casued by lack of the / low levels of serotonin in the brain

    - serotionin is a neurotransmiteer in the brain

    - so overall brain activity is supressed

    - mood, is bad

    - can be caused by external factors ie family break down
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    (Original post by thegreenchildren)
    Would somebody be able to clarify how heart rate and breathing rate is controlled by the medulla? I am a bit confused about the chemoreceptors for the heart rate. Is it just the cardiovascular control centre in the brain or is it also the carotid and aortic bodies or is this for the breathing rate? ahhh confused! Each book says different
    Heyyy this was a question that came up in the june 2010 paper.
    "Describe how the cardiovascular centre, in the medulla oblongata, affects the SAN during exercise."

    the answer was
    That increased impulses sent via the sympathetic nervous system to the SAN which stimulates frequent depolarisation which in turn increases the heart rate.

    Does that help?
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    (Original post by ViolentMind)
    Help please
    someone earlier posted this which i thought was very helpful
    Attached Images
  1. File Type: pdf Article questions and answers.pdf (820.0 KB, 162 views)
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    what are people thinking bout the article? I had a look and I'm wondering if there will be a lot on cell division mechanisms because of the emphasis on cancer?
 
 
 
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