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
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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
The process is often expressed as the Parallel Conductance Model: -- 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.