How electrical signal exist related with membrane potential and and action potential?

Answer 1

Resting potential and action potential are both names for the measure of electrical voltage within the membrane of a cell. Specifically, these terms are used in describing the transfer of information along neural pathways. Resting potential is a state where cells are at rest. However, if an electrical response or depolarization reaches threshold, then ion channels open, allowing sodium ions to rush into the membrane and increase the voltage measure, firing an action potential along the length of this membrane.

Answer 2

In order to understand how electrical signal exist and how a membrane potential is generated we must take into account the charge inside the neuron and outside the neuron. Inside the neuron (intracellular) the charge is negative compare to outside (extracellular) which is possitive.

The major ions that contribute to this difference in electrical potential is potassium(intracellular) and sodium (extracellular).. When the membrane potential is set to be in a resting state (known as the resting potential where sodium is abundant outside and potassium inside) then an electrical signal has the potential to be form and generate an action potential.

An action potential is initiated mostly by chemical transmission (there's also electrical transmission but ill explain chemical) in which a neurotransmitter binds to its recepto at the synapse.

Now before the neurotransmitter binds to its receptor on the post-synaptic membrane the membrane potential is in its resting state (as said above). Once it binds it opens specialized receptors that will allow the sodium ions (which are abundant outside) to enter the cell and change the charge. This change in charge generates an electrical signal that in combination with possitive feedbacks will increase up to the point where an action potential is generated.

So the bottom line is membrane potential differs depending in which state the neuron is (resting or excited) and the contribution of the major ions involved (sodium and potassium) in order to achieve these states. The electrical signal exist either the neuron is in its resting state or not, the only difference is that it fluctuates based on the movement of the ions in and out of the cell.