as well known brain are connected to our body by neuronal cells. it transmits and receives its data by action potential during neuronal cells. i wonder if any one can explain to me the properties of this current. can we consider this current as a AC current?


closed as off-topic by Marcus Müller, Olin Lathrop, Trevor_G, brhans, Voltage Spike Aug 4 '17 at 16:53

  • This question does not appear to be about electronics design within the scope defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

  • \$\begingroup\$ Depends what you are considering AC. DC can be considered AC as well. Just having a zero amplitude and a non-zero offset. \$\endgroup\$ – Eugene Sh. Aug 4 '17 at 15:26
  • 2
    \$\begingroup\$ I'm voting to close this question as off-topic because this is a biomedical, not an electrical engineering question. Also, lacks research, since wikipedia explains everything pretty well and OP didn't take any reference to literature. \$\endgroup\$ – Marcus Müller Aug 4 '17 at 15:56
  • 1
    \$\begingroup\$ I gave up at the start of the second sentence. Closing due to sloppiness, and -1 for the disrespect. \$\endgroup\$ – Olin Lathrop Aug 4 '17 at 16:00
  • \$\begingroup\$ @MarcusMüller -- sure, rain on my parade! \$\endgroup\$ – Scott Seidman Aug 4 '17 at 16:09
  • \$\begingroup\$ @ScottSeidman sorry :D yeah, the way you represented it, your answer has a lot of engineering value. Great answer! Not quite sure it makes the question better :) Can you actually enrich the question? That would make it easier to retract my close vote, emotionally! (saying you can would do that, already, no need to hurry) \$\endgroup\$ – Marcus Müller Aug 4 '17 at 16:30

Because of the nature of the cell membrane, which is permeable to some ions and impermeable to others, the cell is at a Nernst equilibrium, which is a chemical engineering concept in which electrical forces on ions balance with those due to concentration gradients. The resting membrane potential is near the Nernst potential of Potassium ion, as at rest the membrane is most permeable to potassium.

The trick behind the action potential is that there are voltage-mediated ion channels. Most specifically, when a small injection of current makes the cell membrane move in a positive direction, it becomes more permeable to sodium ion, which makes the inside of the cell move in a more positive direction, and makes it even more permeable to sodium, and so on and so on, in a positive feedback loop. Eventually, the membrane gets very near the Nernst potential of sodium ion. Then, potassium channel start opening and sodium channels start shutting, bringing the cell back to resting potential

enter image description here -- from http://slideplayer.com/slide/8690401/26/images/18/The+Action+Potential+is+Generated+by+Sequential+Activation+of+gNa+and+gK.jpg

The process is often expressed as the Parallel Conductance Model: enter image description here -- From http://d2vlcm61l7u1fs.cloudfront.net/media%2F915%2F915975a0-b751-48de-9ade-dee95fa25a46%2Fphpot2y0T.png

The values of the batteries correspond to the Nernst potentials of the respective ionic species -- which is the value at which current of the ion due to electrical forces is equal and opposite to current due to the concentration gradient for a given species.

Though resting potential is about -70mV, the action potential is mostly an AC signal, with frequency components well into the kHz range.


Not the answer you're looking for? Browse other questions tagged or ask your own question.