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    (Original post by InItToWinItGetIt?)
    I thought that whenever the baroreceptors are stretched (hence detecting an increase in pressure?) they will send impulses to the CVC which will then send impulses down the PARASYMPATHETIC nerve to lower the heart rate.
    Sorry if I am being really dumb here.

    And I thought it's chemoreceptors that play more of a role. They detect a drop in pH due to an increase in CO2 as there is more aerobic resp taking place. That's what it says in the CGP book and in the purple edexcel revision guide anyway.
    Hey,

    You're right but those are the baroreceptors located in carotid arteries. However, the stretch receptors in the heart muscle walls respond to increased stretching (more than usual due to greater venous return) by stimulating the sympathetic nerve to increase heart rate. Essentially, this is also a negative feedback system which I think chemdweeb mentioned somewhere before about the heart trying to reduce the volume received to the normal volume by contracting more and harder.

    Yup, both are important. I think they both work together in the end so might as well write both if you have time but knowing edexcel, we're not likely to have much spare time :P
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    (Original post by chemdweeb1234)
    i would still mention chemoreceptors because ultimately chemoreceptors do detect the fall in pH associated with increased respiration (and subsequntly increased blood CO2 levels)

    but i agree with what you've said before...

    i think the distinction was in why baroreceptors in the vessels lead to an INCREASED heart rate in response to lower pressure, and why the baroreceptors in the atrial walls lead to an INCREASED heart rate in response to an INCREASED pressure
    Ok yeah, I agree..mentioning both would be good

    Yup..kind of confusing that the receptors in the heart walls seem to have a positive feedback system but ultimately, it's to reduce the overall volume of blood..so would you say that's negative or positive feedback? cause the direct effect is to magnify the change so it seems like positive but...:confused:
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    (Original post by sparkle*92)
    Ok yeah, I agree..mentioning both would be good

    Yup..kind of confusing that the receptors in the heart walls seem to have a positive feedback system but ultimately, it's to reduce the overall volume of blood..so would you say that's negative or positive feedback? cause the direct effect is to magnify the change so it seems like positive but...:confused:
    like i said before

    it is negative feedback... the only positive feedback examples i can think of are oxytocin release during labour, and sodium ions opening voltage gated sodium ion channels during the all or nothing response..... most biological process are negative feedback.... it is negative because the heart walls care about venous pressure, they dont care about the pressure of the blood vessels, they are worried about the pressure of blood returning to the heart... their response ultimately leads to the reduction of pressure of the blood returning to the heart (as blood is drawn out faster) ... therefore, negative feedback i would think
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    (Original post by tkoki1993)
    sorry I havent finished.. I had to stop doing biology for a while and focus solely on chemistry... there was so much in chemistry that I hadnt revise and my exam is today.. I'll start again today.
    sorry for the delay
    No worries, it's fine, thanks for replying!
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    (Original post by sparkle*92)
    Hey,

    You're right but those are the baroreceptors located in carotid arteries. However, the stretch receptors in the heart muscle walls respond to increased stretching (more than usual due to greater venous return) by stimulating the sympathetic nerve to increase heart rate. Essentially, this is also a negative feedback system which I think chemdweeb mentioned somewhere before about the heart trying to reduce the volume received to the normal volume by contracting more and harder.

    Yup, both are important. I think they both work together in the end so might as well write both if you have time but knowing edexcel, we're not likely to have much spare time :P
    I think I get it now. I kept imagining as them as the same thing, so was confused as it essentially contradicted itself. But they are quite obviously two different and separate mechanisms. Thanks

    Do we have to learn about the venous pressure one? It's not in any of the books I have.
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    how is everyone finding the article? im finding it really confusing!
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    (Original post by shanshine)
    how is everyone finding the article? im finding it really confusing!
    It was a lot to take in the first time I read it, but give it a couple more goes over the next day or two and it will sink in

    It did seem to get a bit complicated towards then end as it talks on about erg1a erg1b etc, but I think you just need to revise hard on topics that will likely be suggested from the material such as explaiing Gene therapy (Germ line/Somatic therapy and the different methods of application - using viral vectors/plasmids etc). I have a feeling they might also ask how transcription factors/gene expression works and the method of action of hormones/steroids etc. Maybe how genetic mutations occur too and how they can be inherited (punnet squares/monohybrid inheritance)?

    Let's just hope that the paper isn't as much of a nightmare as Monday's Unit 4
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    Can someone explain respiration?

    I get the whole proton pumping thing, but I don't get the ETC. In the book it has nothing about what actually happens when the ETC accepts the electron. I am guessing they go through a series of redox reactions, but is there energy released when this occurs? Is this used to phosporylate ADP? I don't get it.
    In the book it just mentions the ETC and then talks about chemiosmosis, completely ignoring the ETC giving the impression that ATP is only formed by chemiosmosis.

    thanks
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    (Original post by Ihategcse)
    Can someone explain respiration?

    I get the whole proton pumping thing, but I don't get the ETC. In the book it has nothing about what actually happens when the ETC accepts the electron. I am guessing they go through a series of redox reactions, but is there energy released when this occurs? Is this used to phosporylate ADP? I don't get it.
    In the book it just mentions the ETC and then talks about chemiosmosis, completely ignoring the ETC giving the impression that ATP is only formed by chemiosmosis.

    thanks
    When the electrons gets accepted by the primary electron acceptor, they get passed down the ETC, through a series of redox reactions like you said.

    As they are passed down the ETC. the electrons keep going from a higher energy level to a lower energy level and this releases energy. The energy is then used to pump protons (H+) into the space between the inner membrane and outer mitochondrial membrane.

    This creates an electrochemical gradient and protons move down this gradient via ATPsynthase, and when this happens ADP gets phosphorylated to ATP

    http://www.youtube.com/watch?v=mfgCc...feature=relmfu
    this video is really good^
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    Does anyone know what the importance of synaptic divergence and synaptic convergence is?
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    Lots of resources here.

    http://www.scribd.com/Raaga92
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    (Original post by InItToWinItGetIt?)
    Does anyone know what the importance of synaptic divergence and synaptic convergence is?
    divergence allows the wave of depolarisation to distributed from one neurone to multiple nuerones, therefore these impulses are distibuted around the body.
    Convergence causes multiple neurone's electrical impluses to be amplified into one neurone, making the action potential more likely to occur.
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    (Original post by Meesta)
    divergence allows the wave of depolarisation to distributed from one neurone to multiple nuerones, therefore these impulses are distibuted around the body.
    Convergence causes multiple neurone's electrical impluses to be amplified into one neurone, making the action potential more likely to occur.
    Oh yeah *doh*

    Thanks
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    http://www.facebook.com/pages/Protes...30890383657523


    Everyone like it!! and spread it around!!
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    Will all the questions based on the article be from topics that are in Unit 5, or might they ask completely different things?
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    (Original post by InItToWinItGetIt?)
    When the electrons gets accepted by the primary electron acceptor, they get passed down the ETC, through a series of redox reactions like you said.

    As they are passed down the ETC. the electrons keep going from a higher energy level to a lower energy level and this releases energy. The energy is then used to pump protons (H+) into the space between the inner membrane and outer mitochondrial membrane.

    This creates an electrochemical gradient and protons move down this gradient via ATPsynthase, and when this happens ADP gets phosphorylated to ATP

    http://www.youtube.com/watch?v=mfgCc...feature=relmfu
    this video is really good^
    I used that video as well earlier in the year, it's really good and his accent sucks you in :P If you get what I mean...haha
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    (Original post by Phenylethylamine_)
    I used that video as well earlier in the year, it's really good and his accent sucks you in :P If you get what I mean...haha
    lol never really concentrated on his accent. His videos are amazing though. Wish the guy covered all our spec lol
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    Could someone shed light on what we need to know on how plants react to stimuli?
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    (Original post by InItToWinItGetIt?)
    Could someone shed light on what we need to know on how plants react to stimuli?
    LOL... shed light

    haha... erm...
    You should know about phytochromes and how they respond to light ... they detect light ... where they are found? possible mechanism? the two types.... and certain functions / consequences of phytochromes like germination... etiolation.... etc.

    and then there is shedding unilateral light on plants... phototropism and how this is controlled by IAA
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    (Original post by chemdweeb1234)
    LOL... shed light

    haha... erm...
    You should know about phytochromes and how they respond to light ... they detect light ... where they are found? possible mechanism? the two types.... and certain functions / consequences of phytochromes like germination... etiolation.... etc.

    and then there is shedding unilateral light on plants... phototropism and how this is controlled by IAA
    Haha I didn't even realise I put that

    Yeah got phytochromes and Pr and Pfr. Found in leaves, seeds, roots and stem is what I have in my notes.

    Got phototropism and uni-lateral light. Should I add geotropism and photopriodism?

    Thanks
 
 
 
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