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I just wanted to get a realistic viewpoint of our nervous system. I understand arteries and veins, but I wanted to know how similar our nervous system is to that?

I understand we have neurons (please correct me if I am wrong) all over the surface of body. Whenever we feel a touch a neuron fires a response, and that response travels through axons (myelin sheath).

My main question is what a nerve exactly is. Is it a long axon? How many axons (same thing as neuron body?) are in a nerve? I am sure it depends on different nerves.

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  • $\begingroup$ I vote to re-open - this question is not too broad. On the contrary, it is a set of highly specific questions, basically boiling down to terminology. I edited the question previously when the close-votes were already pouring in, and hence I vote now to re-open without editing any further. I think it is fine as is. Furthermore, there is background info, so there is no ground to 'leave-close' due to homework :-) $\endgroup$
    – AliceD ♦
    Feb 17, 2015 at 12:36
  • $\begingroup$ I forgot to message you, but I edited your question to make it more compatible with Biology Stack Exchange. At Biology we like clear questions. Nice question +1 $\endgroup$
    – AliceD ♦
    Feb 18, 2015 at 11:47
  • $\begingroup$ Chris, this was my first question on this website. I only knew of one rule and that was to be as specific as possible. I tried. I am not very familiar with the format of this website so I am not sure what "close-votes" or "re-open" you were talking about. I barely found out that my question was answered :) which I really appreciate. $\endgroup$
    – Singh
    Feb 20, 2015 at 5:48
  • $\begingroup$ @ChrisStronks I see a number 4 next to my question. What does that mean? Net positive votes I got? Also, can anyone edit my question? Or do you run this website? $\endgroup$
    – Singh
    Feb 20, 2015 at 5:49
  • $\begingroup$ The close-vote and re-open comments were directed to others that close-voted this question. It may help you to read through the help site and see what a good question looks like and what can happen when people not agree with the question content. $\endgroup$
    – AliceD ♦
    Feb 20, 2015 at 7:56

1 Answer 1

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I will go through your list of questions below:

  • I wanted to know how similar is our nervous system to [the circulatory system]?
    They are very different, but as in every comparison of very complex systems, there is some overlap. The circulatory system carries fluids, the nervous system electrical signals so they are functionally not alike. However, both systems run throughout the body and have a more or less central control unit (the brain and heart respectively). So there is a structural similarity. I reckon they are as much alike as a city's sewer system and electricity grid.

  • I understand we have neurons (please correct me if I am wrong) all over the surface of body.
    That is correct

  • Whenever we feel a touch (stimulus arises) a neuron fires a response, and that response travels through axons (myelin sheath).
    Tactile stimulation may result in firing of one or more neurons, dependent on the intensity of the stimulus. Larger stimuli will, obviously, recruit more fibers. Stronger stimuli will evoke stronger responses (increased firing). Axons indeed conduct the neuronal responses, like an electrical wire conducts electrical current. Longer axons are often myelinated (insulated). Not all neurons related to touch are myelinated, however.

  • So my main question is that what exactly is a nerve?
    A nerve is a bundle of axons that carry related functional information. Typically, nerves conduct information originating from locations closely located together in the body, and generally they convey this information to a localized spot in the body as well. For example, the optic nerve carries information from the photoreceptors (related information) from the retina (localized source) to the brainstem (localized target).

  • Is [a nerve] a long axon?
    A nerve contains many axons. 'Long' or 'short' is rather subjective.

  • How many axons (same thing as neuron body?) are in a nerve? I am sure it depends on different nerves.
    Neuronal cell bodies are typically located outside a nerve. Nerves contain varying numbers of fibers. For example, the auditory nerve harbors the axons of the spiral ganglion cells that transmit auditory information from the inner ear to the brain. It contains between 31k - 32k (myelinated) fibers in normal-hearing humans (Spoendlin & Schrott, 1989). In contrast, the optic nerve, which carries visual information from the retina to the brain, contains some 1.3 million (myelinated) fibers in young human adults (Jonas et al., 1992)

References
- Jonas et al., IOVS 1992;33:2012-8
- Spoendlin & Schrott, Hear Res 1989;43:25-38

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