Illustrate a) Resting Potential, b) Action Potential, c) Depolarization and d) Repolarization in detail with neat sketch. Elaborate half cell potential in detail. Elaborate with neat sketch electrode-electrolyte interface and electrode circuit model in detail. State the electrical properties of microelectrodes.

Resting Potential

Resting potential, the imbalance of electrical charge that exists between the interior of electrically excitable neurons (nerve cells) and their surroundings. 

If the inside of the cell becomes less negative (i.e., the potential decreases below the resting potential), the process is called depolarization.

If the inside of a cell becomes more electronegative (i.e., if the potential is made greater than the resting potential), the membrane or the cell is said to be hyperpolarized. 

Action Potential

An action potential is defined as a sudden, fast, transitory, and propagating change of the resting membrane potential. Only neurons and muscle cells are capable of generating an action potential; that property is called the excitability.

Depolarization

In biology, depolarization is a change within a cell, during which the cell undergoes a shift in electric charge distribution, resulting in less negative charge inside the cell. Depolarization is essential to the function of many cells, communication between cells, and the overall physiology of an organism.

Repolarization 

repolarization refers to the change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential which has changed the membrane potential to a positive value.

half cell potential

Half-cell potential refers to the potential developed at the electrode of each half cell in an electrochemical cell. In an electrochemical cell, the overall potential is the total potential calculated from the potentials of two half cells.

The measurement of half-cell potential is used to evaluate:

Presence of corrosion

Potential vulnerability of element surface area to corrosion

The half-cell potential measurement can only indicate the corrosion probability at a given location and time, but long-term monitoring of the half-cell potential reading is necessary to correctly assess and predict the corrosion severity.

Electrode-electrolyte interface

The current crosses it from left to right. The electrode consists of metallic atoms C. The electrolyte is an aqueous solution containing cations of the electrode metal C+ and anions A–.

Oxidation reaction causes atom to lose electron Reduction reaction causes atom to gain electron Oxidation is dominant when the current flow is from electrode to electrolyte, and reduction dominate when the current flow is in the opposite.

Electrode is made up of same atoms of the same material as the cations

electrical properties of microelectrodes.

Metal Microelectrode

The tungsten filament or stainless steel wire made into minute structure forms the tip of the microelectrode. This technique is electropointing. The insulating material covers the entire electrode for safety purpose.

Few electrolytic processing is done to reduce the impedance. Measurement of bioelectric potentials requires two electrodes. The resulting voltage potential is the difference between the potential of microelectrode and reference electrode. The total sum of the three potentials is as follows.

E= EA + EB + EC

Where,

EA – metal electrode-electrolyte potential at microelectrode tip.

EB – Reference electrode-electrolyte potential.

EC – Variable cell membrane potential.