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    Really need help on first chapter revision.

    The flowchart in my book says process is stimulus-receptor-coordinator-effector-response

    The coordinator in nervous system is the brain and spinal cord (CNS). Does the impulse physically go to the CNS?

    I think yes, the receptor sends the signal to the CNS through the sensory neurone which which then decides the response which is taken to the appropriate effector through motor neurone which carries out response. (Hope this is right)

    What confuses is me is, in the reflex arc, the impulse never reaches the CNS (in this case the spinal cord). The motor and sensory neurone are just connected by a relay neurone. Why doesnt the impulse go physically to the CNS

    I dont think being autonomic has anything to do with it because control of the heart is also autonomic but impulses are sent to the CNS (the medulla oblongata in the brain)

    Please help im really confused as to the role of the co-ordinator.
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    Yes, you are right - the receptor sends via a sensory neurone an impulse to the CNS, which then coordinates and sends an impulse to the effector using a motor neurone.

    In a reflex arc, the sensory and motor neurones are connected by a relay neurone, which is located in the grey matter of the spinal cord. Therefore, the impulse physically goes to the CNS.
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    Interesting, I just started this unit today in A&P
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    (Original post by helpme456)
    Really need help on first chapter revision.

    The flowchart in my book says process is stimulus-receptor-coordinator-effector-response

    The coordinator in nervous system is the brain and spinal cord (CNS). Does the impulse physically go to the CNS?

    I think yes, the receptor sends the signal to the CNS through the sensory neurone which which then decides the response which is taken to the appropriate effector through motor neurone which carries out response. (Hope this is right)

    What confuses is me is, in the reflex arc, the impulse never reaches the CNS (in this case the spinal cord). The motor and sensory neurone are just connected by a relay neurone. Why doesnt the impulse go physically to the CNS

    I dont think being autonomic has anything to do with it because control of the heart is also autonomic but impulses are sent to the CNS (the medulla oblongata in the brain)

    Please help im really confused as to the role of the co-ordinator.
    Yes, so just to clarify: stimulus-sensory neurone-CNS-motor neurone-response.

    The importance of the reflex arc is basically that after going along the sensory neurone, the impulse doesn't need to travel all the way up to the brain, be directed to other brain regions, then go back down to the motor neurone.
    Instead, it can skip this by going from the sensory neurone to the relay neurone in the spinal cord, to the motor neurone. And so it is a lot faster in producing a response (eg minimises amount of time you touch a hot plate for to reduce damage o your hand). And the impulse always 'physically goes there'.
    Some of the impulse does then go up to the brain so that you realise it hurts and you don't do it again.

    Also, it is the CNS that processes the signal and decides the response, the sensory neurone solely sends the signal there.

    Hope this helped.


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    (Original post by jon_b)
    Yes, you are right - the receptor sends via a sensory neurone an impulse to the CNS, which then coordinates and sends an impulse to the effector using a motor neurone.

    In a reflex arc, the sensory and motor neurones are connected by a relay neurone, which is located in the grey matter of the spinal cord. Therefore, the impulse physically goes to the CNS.
    (Original post by ash92:))
    Yes, so just to clarify: stimulus-sensory neurone-CNS-motor neurone-response.

    The importance of the reflex arc is basically that after going along the sensory neurone, the impulse doesn't need to travel all the way up to the brain, be directed to other brain regions, then go back down to the motor neurone.
    Instead, it can skip this by going from the sensory neurone to the relay neurone in the spinal cord, to the motor neurone. And so it is a lot faster in producing a response (eg minimises amount of time you touch a hot plate for to reduce damage o your hand). And the impulse always 'physically goes there'.
    Some of the impulse does then go up to the brain so that you realise it hurts and you don't do it again.

    Also, it is the CNS that processes the signal and decides the response, the sensory neurone solely sends the signal there.

    Hope this helped.


    This was posted from The Student Room's iPhone/iPad App
    Thanks for taking the time to write this. Would it be right to then assume that the relay neurone is the CNS and the coordinator?
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    (Original post by helpme456)
    Thanks for taking the time to write this. Would it be right to then assume that the relay neurone is the CNS and the coordinator?
    Reflex arcs don't need a CNS/coordinator. Not all stimulus-responses follow that flowchart above. The relay neuron is just a relay neuron.
    Although, many sensory neurons do originally synapse with the relay neuron in the spinal cord, but no actual 'processing' is required. It's just necessary for it to do that so it can "pass" the signal along to the motor neuron.
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    (Original post by Hype en Ecosse)
    Reflex arcs don't need a CNS/coordinator. Not all stimulus-responses follow that flowchart above. The relay neuron is just a relay neuron.
    Although, many sensory neurons do originally synapse with the relay neuron in the spinal cord, but no actual 'processing' is required. It's just necessary for it to do that so it can "pass" the signal along to the motor neuron.
    Reflex arcs do not need a coordinator or the CNS (which the spinal cord is part of)? Hmmm... interesting. An example would be highly appreciated.

    Considering that this is for A-level I think that you are over-complicating things. The examiner has a mark scheme. If you put something which is scientifically correct, perhaps at degree level, but is not in the mark scheme - you will not get any marks. Just give the examiners what they want!
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    (Original post by jon_b)
    Reflex arcs do not need a coordinator or the CNS (which the spinal cord is part of)? Hmmm... interesting. An example would be highly appreciated.

    Considering that this is for A-level I think that you are over-complicating things. The examiner has a mark scheme. If you put something which is scientifically correct, perhaps at degree level, but is not in the mark scheme - you will not get any marks. Just give the examiners what they want!
    Sorry, I know the spinal cord is part of the CNS, but I meant in the sense that it doesn't require any actual "processing". I actually wrote your exact words "(which the spinal cord is a part of)", but got rid of it because I didn't want to overcomplicate it.

    I didn't do A level, so am unsure how much knowledge is necessary, and am also unsure of the terminology used - so I apologise if the synapsing with the interneuron in the spinal cord counts as a co-ordinator.
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    (Original post by helpme456)
    Thanks for taking the time to write this. Would it be right to then assume that the relay neurone is the CNS and the coordinator?
    Sort of...yet not so. A processor/co-ordinator accepts the signal and then decides what to do with and passes it on to a certain area. It does bare some similarity with this, ONLY there is no decision-making required, no choosing where the signal goes. It just innately follows from one neurone to the net, without delay.

    By that last statement, think of it like this:
    the reflex arc is like an F1 car going around a track, from the finish line to the end of the track, without stopping. This is a lot quicker for the car to get to the finish line. If the car has to stop or there is a diversion, it will take longer, but eventually may reach the same place.
    So it's much quicker to get to the finish line (ie produce the response) by taking a straight forward, quick, simple, shorter route.


    I hope this helps.
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    (Original post by ash92:))
    Sort of...yet not so. A processor/co-ordinator accepts the signal and then decides what to do with and passes it on to a certain area. It does bare some similarity with this, ONLY there is no decision-making required, no choosing where the signal goes. It just innately follows from one neurone to the net, without delay.

    By that last statement, think of it like this:
    the reflex arc is like an F1 car going around a track, from the finish line to the end of the track, without stopping. This is a lot quicker for the car to get to the finish line. If the car has to stop or there is a diversion, it will take longer, but eventually may reach the same place.
    So it's much quicker to get to the finish line (ie produce the response) by taking a straight forward, quick, simple, shorter route.


    I hope this helps.
    It does, thanks
 
 
 
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