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Neuron; A Simpler Theory

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  • #31
    Hi Cory,

    Thanks for the interest reguarding my passionate madness.

    The original paper needs a huge refinenement. I'm actually collecting clues showing that the actual theory holds failures.

    I'll bring some animations that clearly shows how and why the alternative solution is more effective and "natural".

    I'm asking some biologists with "innocent" questions and I'm amazed with the collected responses => Some refuse to continue the discussion and others recite their lessons without no doubt.

    The main problem with the "original" theory is missing links between very important behaviours in the axon. The transmission is explained by the myelinated axon and thus the theory is extended to the nonmyelinated one.

    But evolution says clearly that low speed fibres were born before these latests.

    Here is an example of a missing link in the reasonning coming from this page: http://en.wikipedia.org/wiki/Action_potential

    The action potential

    When a stimulus arrives at a receptor or nerve ending, its energy causes a temporary reversal of the charges on the neuron cell surface membrane. As a result, the negative charge of 70mV inside the membrane becomes a positive charge of around +40mV. This is known as the action potential, and in this condition the membrane is said to be depolarised. (See depolarization) This depolarization occurs because channels in the axon membrane change shape, and hence open or close, depending on the voltage across the membrane. They are therefore called voltage-gated ion channels. The sequence of events is described below.
    1. At resting potential some potassium voltage-gated channels are open but the sodium voltage-gated channels are closed.
    2. The energy of the stimulus causes the sodium voltage-gated channels in the neuron cell surface membrane to open and therefore sodium ions diffuse in through the channels along their electrochemical gradient. Being positively charged, they begin a reversal in the potential difference across the membrane.
    3. As sodium ions enter, so more sodium channels open, causing an even greater influx of sodium ions. This is an example of positive feedback.
    4. Once the action potential of around +40mV has been established, the voltage gates of the sodium channels, sensitive to the now positive surroundings, close (so further influx of sodium is prevented). While this occurs, the voltage gates on the potassium channels begin to open.
    5. With some potassium voltage-gated channels now open, the electrical gradient that was preventing further outward movement of potassium ions is now reversed, causing more potassium channels to open. This means that yet more potassium ions diffuse out, causing repolarisation of the neuron.
    6. The outward movement of these potassium ions causes the temporary overshoot of the electrical gradient, with the inside of the neuron being more negative (relative to the outside) than usual. This is called hyperpolarisation (hyperpolarization). The gates on the potassium channels now close and the activities of the sodium-potassium pumps cause sodium ions to be pumped out and potassium ions in, once again. The resting potential of -70mV is re-established and the neuron is said to be repolarised.
    and a bit later in the text =>

    Speed of propagation

    Action potentials propagate faster in axons of larger diameter, other things being equal. They typically travel from 10-100 m/s. The main reason is that the axial resistance of the axon lumen is lower with larger diameters, because of an increase in the ratio of cross-sectional area to membrane surface area. As the membrane surface area is the chief factor impeding action potential propagation in an unmyelinated axon, increasing this ratio is a particularly effective way of increasing conduction speed.
    and,

    Detailed mechanism The main impediment to conduction speed in unmyelinated axons is membrane capacitance. In an electric circuit, the capacity of a capacitor can be decreased by decreasing the cross-sectional area of its plates, or by increasing the distance between plates.
    Please find the capacitance in the first five points explanation. :embarasse
    Simplicity is the ultimate sophistication. L VINCI
    We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances. I NEWTON

    Everything should be made as simple as possible, but not a bit simpler.
    If you can't explain it simply, you don't understand it well enough. Albert Einstein
    bernard

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    • #32
      And if you look closely to the capacitor =>

      http://en.wikipedia.org/wiki/Capacitor

      You'll see that energy exists between plates and communication is oriented them inexorably. If membrane acts as a capacitor which has a capacitance then the electric flow is only vertical. There is no way to create a lateral motion as we are seeing it in axons. The wave is going and capacitors haven't such a property.
      Simplicity is the ultimate sophistication. L VINCI
      We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances. I NEWTON

      Everything should be made as simple as possible, but not a bit simpler.
      If you can't explain it simply, you don't understand it well enough. Albert Einstein
      bernard

      Comment


      • #33
        Hi Bernard,
        Glad to hear that you are continuing to refine and pursue. I wish that I understood the intricate mechanics better and could engage in discussion better on your theory.

        On capacitance, I know that I was taught about electrical impluses traveling the membrane. And ranvier nodes (I think that's what the spaces between the myelin are called?) allow for a bit of skipping over for parts of the membrane.

        Could you clarify this quote for me?

        The transmission is explained by the myelinated axon and thus the theory is extended to the nonmyelinated one.
        Are you saying the the existing theory makes sense for myelinated axons, but not nonmyelinated?

        Cory
        Cory Blickenstaff, PT, OCS

        Pain Science and Sensibility Podcast
        Leaps and Bounds Blog
        My youtube channel

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        • #34
          Cory,

          The actual theory doesn't make sense in both scenario.
          The five points cited are perfectly clear and may explain the lateral motion but it doesn't (seems) work for myelinated axons. So they created a theory which explains the saltatory conduction and said it worked also for non myelinated. But doing so has a price, they reject the five points since it does not need a capacitance.

          And if it doesn't need a capacitance it discards also its use with myelinated axons. That is the problem. The capacitance is mandatory in their explanations for myelinated axons.

          They created a circular reference in the theory. An endless loop that is useless. They cite a theory they do not use in non myelinated conduction as the explained process/solution for myelinated.
          Simplicity is the ultimate sophistication. L VINCI
          We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances. I NEWTON

          Everything should be made as simple as possible, but not a bit simpler.
          If you can't explain it simply, you don't understand it well enough. Albert Einstein
          bernard

          Comment


          • #35
            Hi All,

            Reading the old writings I made let me think that a refinement is not only possible but really necessary.

            The works of Professor I TASAKI complete my "vision" about a more subtle theory. It is of course, more complex but so natural and understandable.

            Nature had no choice! We tried to glue some simple thoughts and simple theories on a complex interactive set of properties and constraints.

            They become preponderant in ralation of the size of the axons.

            In a small diameter, the electrostatic behaviour is strong as the elasticity of membrane. Ions have "problems" to come in and ions channels are distant because their repelling forces. slow because the resultant force is largely used to "win" the membrane.
            Membrane, with phase transitions, plays a major role because it acts as a lock and favors an unidirectional travel of the AP.
            Increasing diameter, give more electrostaic/volumic forces and a good compromise. In larger versions, the membrane is too weak and too deformable and the speed is thus limited as it is comfirmed. Nature, with myelinated axons, tried to tighten the membrane to give some "boost" like in small fibres. But, the adopted solution is better => a dual set of forces electostatic/volume that send a pressure wave in a tight tube. Bravo, simple and marvelously efficient.
            Last edited by bernard; 03-07-2006, 07:37 AM.
            Simplicity is the ultimate sophistication. L VINCI
            We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances. I NEWTON

            Everything should be made as simple as possible, but not a bit simpler.
            If you can't explain it simply, you don't understand it well enough. Albert Einstein
            bernard

            Comment

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