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    (Original post by ghogho)
    the chemoreceptors are resposible for the ventilation rate not the heart rate when it detect that there is an increase in the co2 and decrease in the ph it sends to the inspiratory center in the medulla
    you're getting confused with breathing rate dear.
    stretch receoptors and diapragm are stimulated when inhaling

    inspiratory centre is also related to breathing rate, not heart rate
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    (Original post by ConnorB)
    You're pretty much bang on Though i'm nitpicking a bit here, where are the chemoreceptors located which detect the lower Ph caused by the increase in Co2?
    Thanks
    aortic bodies, carotid bodies and medulla...i'm 100% it's the first two
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    (Original post by This Honest)
    Thanks
    aortic bodies, carotid bodies and medulla...i'm 100% it's the first two
    You Sir, are ready for this exam :cool:
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    How do you calculate the heart rate from an ECG ?
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    i feel like this is a really stupid question but can someone explain phytochromes to me please? There was a question on how plants use photoreceptors and i had absolutely no idea
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    (Original post by This Honest)
    you're getting confused with breathing rate dear.
    stretch receoptors and diapragm are stimulated when inhaling

    inspiratory centre is also related to breathing rate, not heart rate
    my teachers notes say that the main stimulus that controls breathing rate is the concentration of carbon dioxide in the blood
    blood concentration is detected by the chemoreceptors present in the carotid arteries they are sensitive to co2 conc and PH of the blood.
    while what controls the heart rate he wrote:
    stretch receptors in the walls of the aorta send nerve impulses to the cardiovascular center when changes in the blood pressure occur then the cardiovacular center in the brain either send sympathatic or parasympathatic nerve impulses to the SAN
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    (Original post by This Honest)
    more co2 produced
    chemoreceptors detect increase in co2 and send nerve impulses to medulla
    medulla sends nerve impulses to heart via sympathetic nervous system to depolarise SAN
    depolarisation of SAN increases which increases the heart rate
    ???
    Literally just seen this question on an oldish paper, a few things I reckon could be added to make sure you get all the marks:
    State the obvious: aerobic respiration increases during exercise (I know it sounds stupid but they do often give one mark for that)
    State the location of the chemoreceptors.
    And in the markscheme I looked at, it said 'increases the frequency of impulses down the sympathetic nerve to the sinoatrial node' The heart is myogenic so no impulses would be sent from medulla to the SAN, but I think I'd add that little extra phrase to be on the safe side.

    Hope that helps!
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    (Original post by This Honest)
    .
    heart muscle is myogenic, what is meant by myogenic (3 marks)
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    (Original post by ConnorB)
    You Sir, are ready for this exam :cool:
    Thanks still have lots to do though


    (Original post by ghogho)
    my teachers notes say that the main stimulus that controls breathing rate is the concentration of carbon dioxide in the blood
    blood concentration is detected by the chemoreceptors present in the carotid arteries they are sensitive to co2 conc and PH of the blood.
    while what controls the heart rate he wrote:
    stretch receptors in the walls of the aorta send nerve impulses to the cardiovascular center when changes in the blood pressure occur then the cardiovacular center in the brain either send sympathatic or parasympathatic nerve impulses to the SAN
    My book says what your teacher says but at the end, they mention rate and depth of breathing increases so i assumed it was breathing rate they were on about

    I'm gonna pop off enough to wokr on the article, has your tutor sent you the answers to the questions he gave you btw?
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    (Original post by DH3498)
    Literally just seen this question on an oldish paper, a few things I reckon could be added to make sure you get all the marks:
    State the obvious: aerobic respiration increases during exercise (I know it sounds stupid but they do often give one mark for that)
    State the location of the chemoreceptors.
    And in the markscheme I looked at, it said 'increases the frequency of impulses down the sympathetic nerve to the sinoatrial node' The heart is myogenic so no impulses would be sent from medulla to the SAN, but I think I'd add that little extra phrase to be on the safe side.

    Hope that helps!
    Thanks, I'll remember that. Stating the obvious is very important :lol:


    (Original post by wam-bam)
    heart muscle is myogenic, what is meant by myogenic (3 marks)
    self exciting, heart has SAN depolarises and heart and can initiate its own heartbeat without impulses from any where else
    contract spontaneously, doesn't fatigue

    lol i'm just writing everything i know
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    (Original post by pandoraclaire)
    i feel like this is a really stupid question but can someone explain phytochromes to me please? There was a question on how plants use photoreceptors and i had absolutely no idea
    phytochrome is a photoreceptor in plants. it is protien in nature. it is responsible for varitey of responses to light
    phytochrome is present in two forms:
    phytochrome red (PR) and phytochrome far red (PFR) naturally daylight contain alot of FAR RED LIGHT so in daylight PR is rapidaly converted toPFR whlie in prolonged hours of dark PFR is slowly converted to PR
    so what is the role of phytochrome in seed germination? most seeds germinate in the dark, below the ground however some seeds dnt contain enough food reserves to sustain them until they reach light. such seed =s only germinate if they are exposed to light, this ensures that they germinate only if near the surface of the soil .
    expousre of light causes PR to be converted to PFR which initiatesgermination.
    also it has been dicovered that the wavelenght to which the seeds were last exposed to has the greatest effect on the % of germination so whenever the last expouser was to red light it was PFR that was left in the seed.

    well that is all what i know about phytochrome wish that u did understand it
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    why is there a delay in action potential arrival at presynaptic neurone and action potential trigger in post synaptic neurone ??! (2 marks)
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    (Original post by pandoraclaire)
    i feel like this is a really stupid question but can someone explain phytochromes to me please? There was a question on how plants use photoreceptors and i had absolutely no idea
    Phytochrome

    Phytochrome is a pale-blue pigment which is important in plant growth and development. It exists in two interconvertible forms. P660 has a maximum light absorption peak in the red end at 660 nm, whereas P730 has maximum absorption in the far red at 730 nm. When P660 is exposed to light at 660 nm, it is converted to P730. When P730 is exposed to light at 730 nm, it is converted to P660, and it slowly decays to P660 in the absence of light. Thus during daylight the plant accumulates P730 since daylight contains more red light. P730 is believed to be enzymatically active and influences a number of light-related processes, for example, photoperiodism, leaf lamina unfolding and seed germination. During the night the P730 slowly converts back to P660, which is then ready to respond to the daylight again.

    Thus, in summary:
    · Red light is absorbed by P660 which converts it to P730.
    · Far red light is absorbed by P730 which converts it to P660.
    · P730 in the dark slowly converts to P660 and it is this slow conversion

    That is the ‘clock’ by which the plant measures night length.

    Flowering in long day plants (henbane, snapdragon, cabbage, spring wheat and barley) is stimulated only if the level of P730 stays above a critical value. Flowering in short day plants (cocklebur, chrysanthemum, soya bean, strawberry and tobacco) is stimulated only if the level of P730 falls below a critical value. The levels of P730 are governed by the duration of dark periods (night).
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    (Original post by ghogho)
    phytochrome is a photoreceptor in plants. it is protien in nature. it is responsible for varitey of responses to light
    phytochrome is present in two forms:
    phytochrome red (PR) and phytochrome far red (PFR) naturally daylight contain alot of FAR RED LIGHT so in daylight PR is rapidaly converted toPFR whlie in prolonged hours of dark PFR is slowly converted to PR
    so what is the role of phytochrome in seed germination? most seeds germinate in the dark, below the ground however some seeds dnt contain enough food reserves to sustain them until they reach light. such seed =s only germinate if they are exposed to light, this ensures that they germinate only if near the surface of the soil .
    expousre of light causes PR to be converted to PFR which initiatesgermination.
    also it has been dicovered that the wavelenght to which the seeds were last exposed to has the greatest effect on the % of germination so whenever the last expouser was to red light it was PFR that was left in the seed.

    well that is all what i know about phytochrome wish that u did understand it
    u r wrong over there
    natural sunlight contains a lot of RED light ! which is absorbed by Pr which then changes into Pfr.
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    (Original post by ghogho)
    phytochrome is a photoreceptor in plants. It is protien in nature. It is responsible for varitey of responses to light
    phytochrome is present in two forms:
    phytochrome red (pr) and phytochrome far red (pfr) naturally daylight contain alot of far red light so in daylight pr is rapidaly converted topfr whlie in prolonged hours of dark pfr is slowly converted to pr
    so what is the role of phytochrome in seed germination? Most seeds germinate in the dark, below the ground however some seeds dnt contain enough food reserves to sustain them until they reach light. Such seed =s only germinate if they are exposed to light, this ensures that they germinate only if near the surface of the soil .
    Expousre of light causes pr to be converted to pfr which initiatesgermination.
    Also it has been dicovered that the wavelenght to which the seeds were last exposed to has the greatest effect on the % of germination so whenever the last expouser was to red light it was pfr that was left in the seed.

    Well that is all what i know about phytochrome wish that u did understand it
    thankyouuu :d
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    (Original post by d_94)
    Phytochrome

    Phytochrome is a pale-blue pigment which is important in plant growth and development. It exists in two interconvertible forms. P660 has a maximum light absorption peak in the red end at 660 nm, whereas P730 has maximum absorption in the far red at 730 nm. When P660 is exposed to light at 660 nm, it is converted to P730. When P730 is exposed to light at 730 nm, it is converted to P660, and it slowly decays to P660 in the absence of light. Thus during daylight the plant accumulates P730 since daylight contains more red light. P730 is believed to be enzymatically active and influences a number of light-related processes, for example, photoperiodism, leaf lamina unfolding and seed germination. During the night the P730 slowly converts back to P660, which is then ready to respond to the daylight again.

    Thus, in summary:
    · Red light is absorbed by P660 which converts it to P730.
    · Far red light is absorbed by P730 which converts it to P660.
    · P730 in the dark slowly converts to P660 and it is this slow conversion

    That is the ‘clock’ by which the plant measures night length.

    Flowering in long day plants (henbane, snapdragon, cabbage, spring wheat and barley) is stimulated only if the level of P730 stays above a critical value. Flowering in short day plants (cocklebur, chrysanthemum, soya bean, strawberry and tobacco) is stimulated only if the level of P730 falls below a critical value. The levels of P730 are governed by the duration of dark periods (night).
    thank you so much never understood any of that until now XD
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    Explain how the structure of the axon cell membrane is related to the conduction of nerve impulses?! (3 marks)

    help?! aha.
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    (Original post by iesians)
    u r wrong over there
    natural sunlight contains a lot of RED light ! which is absorbed by Pr which then changes into Pfr.
    :oops: oh ya u r ryt about that point... sorry i got mixed up:shy2::shy2:
    but i mentioned that PR is converted to PFR.......
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    (Original post by pandoraclaire)
    thankyouuu :d
    ur welcome
    but there is something to correct!!!
    natural daylight contain mainly RED light!!!
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    How do you calculate the heart rate from an ECG ?
 
 
 
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