1. A solid electric conductor through which an electric current enters or leaves an electrolytic cell or other medium.
2. A collector or emitter of electric charge or of electric-charge carriers, as in a semiconducting device.
3. A conducting element that performs one or more of the functions of emitting, collecting, or controlling the movements of electrons or ions in an electron tube, or the movements of electrons or holes in a semiconductor device.
4. A medium for conducting an electrical current from the body to physiological monitoring equipment.
5. A terminal or surface at which electricity passes from one material or medium to another, as at the electrodes of a battery or electrolytic capacitor.
6. One of the terminals of metal, salts, or electrolytes through which electricity is applied to, or taken from, the body or an electric device or instrument.
7. An electronically conductive structure that provides for an electrochemical reaction through the change of oxidation state of a substance.

It may contain or support the reactant or act as the site for the reaction. The anode and cathode of an electric cell are electrodes.

A conductor which is small and which produces stimulation in a concentrated area or to record from a localized section: An electrode is used to make contact with a nonmetallic part of a circuit; such as, a semiconductor or an electrolyte.

An electrode which has the two terminals attached together and near each other.

1. An electrode that develops a standard electric potential.

The calomel electrode is used as a standard in determining the pH (potential of hydrogen) of fluids which refers to a measure of acidity or alkalinity in which the pH of pure water is 7, with lower numbers indicating acidity and higher numbers indicating alkalinity.

2. An electrode consisting of mercury surrounded by a suspension of calomel (a colorless, white or brown tasteless compound, used as a fungicide or insecticide; formerly, as a purgative for purging the bowels; especially, as a laxative in a solution of potassium chloride of a specified strength.

The calomel electrode gives a highly reproducible potential, and is used as a standard, often as a half cell with a glass electrode for determining pH, or with a platinum electrode for establishing redox (oxidation-reduction) potentials or any chemical reactions in which electrons are transferred.

1. A blood-gas electrode that is used to measure the carbon dioxide level of arterial blood.
2. A glass electrode in a film of bicarbonate solution covered by a thin plastic membrane permeable to carbon dioxide but impermeable to water and electrolytes which is normally used to analyze arterial blood samples.

In electrocardiography, an electrode in which connections from three limbs; for example, right arm, left arm, and left leg, are joined and led to the electrocardiograph to form the indifferent electrode, theoretically at zero potential for the system.

A chemical sensor in some clinical laboratory analyzers that functions similarly to a pH electrode.

A recording electrode consisting of an insulated metal wire inside a hollow stainless steel cannula.

Differences in potential are measured using the needle shaft as a reference and the wire tip as the exploring electrode.

An electrode that is capable of both collecting and giving up chloride ions in neutral or acidic aqueous media, consisting of mercury in contact with mercurous chloride, used as a reference electrode in pH measurements.

An electrode with greater resistance than the part of the human body that is enclosed in the circuit.

An electrode in which a drop of mercury, in the course of its formation, acts as the electrode surface.

It is therefore a fresh surface and of a small area, both advantages in a cathode (terminal or electrode at which electrons enter a system) for polarography or a method for analyzing the composition of a dilute electrolytic solution.

An electrode which is connected to a ground.

A boiler that converts electricity to heat energy, by passing a current between electrodes immersed in water to raise the temperature of the water.

The current that flows in a photodetector when there is no optical radiation incident on the detector and operating voltages are applied.

A jelly used for improving the contact between the skin and an electrode during an examination utilizing electrocardiography and electroencephalography.

1. The potential developed by a metal or other electrode material immersed in an electrolytic solution; usually related to the standard potential of the hydrogen electrode, which is established at zero.
2. The instantaneous voltage of an electrode with respect to the cathode of an electron tube.
3. The voltage existing between an electrode and the solution or electrolyte in which it is immersed.

A metal structure, often with a large area, which is an external extension of an electrode of an electron tube to facilitate the dissipation of heat.

An instrument which measures and/or records blood pressure electronically.

1. In naval mine warfare, a magnetic cable sweep in which the water forms part of the electric circuit.
2. A sweep fitted with cutters or other devices to increase its ability to cut mine moorings.

A sweep refers to the employment of technical means to uncover planted microphones or other surveillance devices and explosive mines in the water.

1. A electrode placed in the esophagus: An esophageal electrode obtains electrocardiographic records from this region or used for electrical pacemaking.
2. A pill electrode that lodges in the esophagus at the level of the atrium: An esophageal pill electrode obtains electrograms and delivers pacing stimuli.

In electrodiagnosis, the electrode, usually small, placed nearest to the site of the bioelectric activity being recorded.

It determines the potential in only that localized area.

The electrode that controls the convergence of the electron beam and permits focusing the spot on the screen of a cathode ray tube.

An electrode in which a gas-permeable membrane of the body separates the test solution from an aqueous electrode solution in contact with an ion-selective electrode.

Gas permeation of the membrane changes the chemical equilibrium within the electrolyte, and the ion-sensitive electrode detects this change.

An electrode for measuring the pH of a solution, based on the fact that a thin sheet of glass is permeable to hydrogen ions but not to other ions.

The device often contains both electrodes of a cell within it; that is, a reference electrode as well as the glass electrode proper, and a salt bridge for connecting them, so that the potential produced by the cell depends on the pH of the solution in which the appliance is immersed.

An electrode that absorbs hydrogen gas; used in pH measurement.

A chemical sensor that is highly selective due to a specific enzyme incorporated into its structure.

In chemistry, the metal electrode inside all chemical-sensing potentiometric (voltage-measuring) electrodes.

1. A chemical transducer that yields a response to variations in the concentration of a given ion in solution.
2. A potentiometric electrode (electromotive force or pressure in an electric circuit measured in volts) that develops a potential in the presence of one ion (or class of ions), but not in the presence of a similar concentration of other ions.

An electrode in which the sensing membrane is made up of a hydrophobic ion-exchange neutral carrier (ionophore) dissolved in a viscous, water-insoluble solvent.

The liquid membrane is physically supported by an inert porous matrix; such as, cellulose acetate.

A needle electrode consisting of a single piece of stainless steel wire coated with insulating material except at the tips.

It must be accompanied by another electrode as a reference.

A stimulating electrode which has the two terminals attached separately and relatively far apart.

An electrode composed of a number of insulated wires inside a metal cannula, with their bare tips at apertures, or openings, flush with the outer circumference of the cannula (small flexible tube inserted into a body cavity for draining off fluid or introducing medication).

It is used to determine the territory of a motor unit.

1. An electrode with many contacts for recording from many sources, as from different depths in the brain.
2. Several sets of terminals providing for the use of several electrodes.

A thin, cylindrical electrode with an outer shaft beveled to a sharp point, enclosing a wire or series of wires which can explore the activity of single motor or nerve units of the body or stimulate them.

A cathode; the pole by which electric current leaves the generating source.

1. A blood gas electrode used to measure the partial pressure of oxygen in arterial blood.
2. A platinum wire electrode used in measuring arterial blood oxygen.

When a current of an appropriate voltage is applied, oxygen flows from the specimen through a gas-permeable membrane and is destroyed at the platinum surface.

A tiny electrode with a blunt tip, used in studies of membrane potentials.

1. An electrode with an insulating handle at one end and a small metallic terminal at the other end for use in applying static sparks.
2. An electrode with a small metallic point to obtain a high electric current density in a small area.

An electrode in which the sensing membrane is an organic polymer containing a hydrophobic ion-exchange neutral carrier (ionophore).

An electrode whose contact surface, through which the current passes to the tissue being stimulated, is porous.

An anode; the pole opposite to a cathode (negative) electrode.

The positive pole of a galvanic battery or the electrode connected with it.

An electrode toward which negatively charged ions migrate.

1. An electrode in the electric potential is generated by the relative proportions of quinone (a class of aromatic compounds found widely in plants, especially the yellow crystalline form used in making dyes, tanning hides, and photography) and quinhydrone (dark green, crystalline, slightly water-soluble solid used in a solution, together with a platinum wire, as an electrode) which are present.
2. One of several oxidation-reduction electrode's in which the ratio of the two forms (quinone-quinhydrone), determined by the hydrogen ion concentration, sets up a potential that can be measured and converted to a pH value (fails above pH 8).
3. Quinhydrone electrode is a redox electrode (inert electrode; such as, platinum, gold, carbon) used for measuring pH (measure of the acidity/alkalinity of a solution).

An inert metal (usually platinum) is immersed into the solution to be analyzed and a small amount of quinhydrone crystals is added to the solution.

Quinhydrone is slightly soluble in water, dissolving to form a mixture of two substances, with each of the two substances easily oxidized or reduced to the other.

The potential at the inert electrode depends on the ratio of the concentrations of two substances, which, in turn, depends on the pH.

An electrode used to measure electric potential changes in body tissue.

When used for recording, two electrodes must be used: the exploring electrode and the reference electrode.

1. A chemical electrode whose cell potential remains fixed and against which an indicator electrode is compared.

The most common reference electrode is the silver electrode or silver chloride electrode.

2. An electrode the placement of which is remote from the source of recorded activity, so that it is presumed to be at either a negligible or a constant potential.

1. An electrode that derives its potential to unit charges of a reversible nature, in contrast to electrodes used in electroplating and destroyed during their use.
2. An electrode; such as, the silver/silver chloride electrode in which the electrochemical reaction is reversible, which results in a low resistance to direct current.

An electrode reaction is considered reversible in the "electrochemical sense" if the reaction is fast, that is, if the exchange current density of the electrode reaction is large.

In contrast, in the "chemical sense", reversibility indicates that the reaction can proceed both in forward and backward (reverse) directions.

One of two practical reference electrodes, used with a mercurous chloride (calomel) paste in pH (measure of the acidity or alkalinity of a solution) and other potentiometric (voltage-measuring) instruments. The other is the silver/silver chloride electrode.

The calomel (mercury compound) electrode has been the standard secondary reference electrode used in the laboratory since the introduction of the pH electrode.

An electrode which is placed on or just below the surface of the scalp.

This is the most common type used in electroencephalography.

A needle electrode with a small recording surface for the recording of individual muscle fiber action potentials.

An electrode in which the sensing membrane is made of a single crystal or a pressed pellet containing the salt of the ion to be sensed.

A metal sphere (ball) mounted at the end of a metal rod with an insulated handle.

An electrode that is used to apply electric current to body tissue.

It must include both a negative terminal and a positive terminal.

For related information, see bipolar stimulating electrode and monopolar stimulating electrode.

An electrode placed under the skin.

A nerve stimulating electrode consisting of a fine glass tube into which a nerve filament can be drawn for the purpose of isolated electronic stimulation.

1. An electrode placed on the surface of the skin or an exposed bodily organ which is used to stimulate or to record electrical activity in the underlying body tissue.
2. An electrode used for the stimulation or for a pickup of electrical activity, applied to the surface of the part being studied.

1. An electrode used for the introduction of medicines through the skin by ionization.
2. An electrode filled with therapeutic agents.

An electrode worn on the palpating index finger (examining the body by touching or pressing with the finger) for rapid localization of motor points or small areas on a muscle where a minimal amount of electrical stimulation will cause the muscle to contract.

An appliance which measures the oxygen tension in the skin without penetrating the body's tissues