Question

@ how is action potential stored in brain and how to know which is signalling a.p.

Answer 1

Action potentials aren't really stored. The resting state for a neuron (a brain cell) is about -70mV (that's a charge of negative milivolts-the lowercase "m" is actually the Greek letter mu). When that charge is changed by particles entering the cell at the synapse, the neuron becomes depolarized (becomes more positive/less negative). If it reaches a certain threshold, usually about -55mV, an action potential is generated. This signal goes to the next neuron and so one. This can be measured with different kinds of electrodes (clamp techniques).