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Medical How long does it take for the brain to recognize pain?

  1. Mar 30, 2015 #1
  2. jcsd
  3. Mar 30, 2015 #2
    The speed of nerve transmission is measurable, but I don't think there is an equivalent measure for the speed of consciousness.
    (Roughly defining that as the time it takes for the signals to be processed and the person identifies them as having a meaning).
    I think it's likely to be different for different people, or even different for the same person depending on physiology and the total amount of activity their brain is engaged in at the time.
     
  4. Mar 30, 2015 #3

    Doug Huffman

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    Gold Member

    Depends on the impact and its application. An Empire State Building leap would homogenize the brain seat of consciousness.
    Pain alone will not cause unconsciousness.
    Reflex arcs do not even use the brain.
     
  5. Jun 22, 2015 #4
    You might have a point there.
     
  6. Jun 24, 2015 #5
    Let me just say that if you cut of a persons head they remain concious for approximately 10 seconds and that's without any connection to the body or heart to produce blood flow to the head.
     
  7. Jun 26, 2015 #6
    B) Almost at the speed of light . Particles , electricity .... :)
     
  8. Jun 26, 2015 #7
    Yes, electricity travels at the speed of light. But our nerve reaction is not that fast. Less than speed of sound I think.
     
  9. Jul 31, 2015 #8
    A) This has never been measured.
    B) Human response times for a touch stimulous are 100ms.
     
  10. Jul 31, 2015 #9
    The method used for electrical signalling in the body is very different from what we are used to in electrical circuits based on the flow of electrons down wires, and much slower too. The speed with which an electrical signal can pass along a nerve varies from a maximum of around 120 m/s for muscular signals to 1 m/s for non-urgent messages, such as mild pain. As you read this, the message travels at about 20–30 m/s to your brain. Even the highest transmission speeds are several million times slower than an electrical signal travelling down a wire.



    Neural transmission is a process of random diffusion
    An average diffusion coefficient is about 3 x 10^10 m^2/s and an average gap between synapses is about 100nm. It can take about 30 us for neural transmission between synapses.



    Source
    The Open University
    Engineering small worlds: micro and nano technologies
    WORKING WITH NATURE: THE CELL AS AN ENGINEERING SYSTEM





    Loss of consciousness / then death has been measured.
    Its been measured a lot in animals with similar nervous systems and body volumes to humans; the Nazis experimented on prisoners in WW2 and there is anecdotal evidence from executions and accidents from witnesses: severed heads remaining alert and responsive for seconds after decapitation (eyes following the executioner around); organs being shown to disemboweled victims and the victim crying out etc.
    Speed of loss of consciousness depends upon the type of injury and the metabolism and health of the victim. If the injury was catastrophic (i.e.. instantly crushed to a pulp) then your body and brain would be destroyed more quickly than your brain could process the information. For all intents and purposes, for the victim, death would be instant.



    So the answer to the question
    For instance, on fatal impact. Would you feel the impact before losing consciousness

    Yes. Many victims of a fatal impact will remain conscious and alert. Speaking, trying to stay alive, maybe trying to move and free themselves. This could be for a seconds or for hours (or even days) before they slip into unconsciousness and then death.
     
    Last edited: Jul 31, 2015
  11. Jul 31, 2015 #10
    100 ms from toe to top. If we are as big as blue whale, perhaps 1 second?
     
  12. Jul 31, 2015 #11
    well, say a blue whale is 25m in length

    assume it has a very similar nervous system to humans and make the assumption that its nerves take the shortest route from tip to brain.

    if mild pain is felt at 1 m/s it might take as long as 25 seconds for a blue whale to notice anything wrong with its tail; to about a second if the pain is severe.
     
    Last edited: Jul 31, 2015
  13. Jul 31, 2015 #12
    The 100ms includes transmission of the signal, processing it and reacting to it. I doubt that the tranmission represents a large proportion of the time.
     
  14. Jul 31, 2015 #13
    Really? Do you have a scientific source for that? While there are obviously no published experiments on humans, it's known that a precipitous blood pressure drop to zero, which would occur in the brain if it were suddenly cut off from the heart, will cause an immediate loss of consciousness.
     
  15. Jul 31, 2015 #14
    Would it though?
    The blood is there to supply oxygen and nutrients to the nerve/brain cells.
    Some oxygen and nutrients are already existing in the cells, so they *might* continue to function in some way for a few seconds.
    There could be some other reason which would cause immediate unconciousness, but not necessarily oxygen starvation.
     
  16. Jul 31, 2015 #15
    I asked for a scientific source, not more personal speculation.
     
  17. Jul 31, 2015 #16
  18. Jul 31, 2015 #17
    Yes, there are many causes of syncope. My question was regarding the statement quoted in post 13. It claims that consciousness can be maintained for 10 seconds after a beheading. Maybe after a partial beheading (which is undefined and meaningless), but a a complete beheading? It's the kind of claim that really requirers a qualified reference The claim is that the brain functions at rhe conscious level for 10 seconds with zero blood pressure irrespective of arterial blood oxygenation or other factors under normal conditions.
     
  19. Aug 1, 2015 #18
    See also Clinical Death:
    https://en.m.wikipedia.org/wiki/Clinical_death
     
  20. Aug 1, 2015 #19
    This claim has the same scientific validity as the opposite claim.

    Demanding scientific evidence is ridiculous - who will be allowed to do the experiment nowadays? (the nazis did these experiments)

    Doctors attending guilotine executions during the French revolution asked the victims to blink when being spoken to after beheading. There is recorded evidence of this happening. This may not be scientific evidence, but it has as much valdiity as the claim that in all cases of sudden beheading, the victim loses immediate consiousness. (define immediate - is immediate so quick that the victim does not know what happens? Do you mean instantaneous? Nothing happens instantaneously.)
     
    Last edited: Aug 1, 2015
  21. Aug 1, 2015 #20

    PeterDonis

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    Staff: Mentor

    Thread closed for moderation.
     
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