Tissue liquid electrolytes

Liquid surfaces and liquid-liquid interfaces are very common and have tremendous significance in the real world. Especially important are the interfaces between two immiscible liquid electrolyte solutions (acronym ITIES), which occur in tissues and cells of all living organisms. The usual presence of aqueous electrolyte solution as one phase of ITIES is the main reason for the electrochemical nature of such interfaces. 

Mineral elements play a key role in the human body and especially in the regulation of cell metabolism. They are either incorporated into the tissues or else are present in body liquids in ionic form. They also participate in metabolic processes such as electrolyte and hormone economy, haematopoiesis, and development of the nervous and skeletal systems [1,2]. 

Luigi Galvani (1791) was the first to discover the physiological action of electricity. He demonstrated the existence of bioelectric forces in animal tissue. His experiments led Alessandro Volta to the invention of the first battery, voltaic pile [8]. In 1800, Alessandro Volta described the voltaic pile in a letter to the Royal Society in London [7]. The original voltaic cell used two metal disks as electrodes, namely zinc and silver. Cardboard disks separated the electrodes and seawater was the electrolyte. A current was produced when the silver disk was connected to the zinc disk through an external wire. The voltaic pile established the foundation for the liquid battery type. Many other metals and electrolytes have been tried during the last two centuries [9]. 

For measurements of partial pressures in tissues and in liquids such as serum or blood, sensors according to Severinghaus are used. A membrane separates the external liquid or gas phase from the electrolyte surrounding a glass electrode, the potential of which is measured against an Ag/AgCl electrode (see Sections 23.3 and 23.4). 

Electrodes are the direct interface between the biological structures (auditory neurons) and the electronic system in the CFs. Stimulation electrodes inject charge into the tissue to functionally excite the nerves by electrical stimulation. In other words, electrodes measure the electric potential for charge transfer between solid metal state and electrolyte solution in liquid state inside the cochlea. For better stability implants electrode properties must be evaluated with respect to a biocompatible application for optimum stability, efficacy and life time with a minimum of toxicity. From the material point of view the requirements of an ideal electrode [8-10] might be summarized as follows ... 

An electrolyte is a substance with ionic DC conductivity. Intracellular and extracellular liquids contain ions free to migrate. In pure electroljrtes, the charge carriers are ions, and there is no separate flow of electrons—they are all bound to their respective atoms. Therefore, tissue DC currents are ionic currents, in contrast to the electronic current in metals. This is not contradictory to a possible local electronic conductance due to free electrons (e.g., in the intracellular DNA molecules). New solid materials such as organic polymers and glasses may contain an appreciable amount of free ions with considerable mobility therefore, the materials of an electrolytic measuring cell are not limited to liquid media. Some of these solid media show a mixture of ionic and electronic conductivity. 

Abraham et al. [14] have reported solubility correlations for a wide variety of systems that follow Henry s law. Gas/liquid partition coefficients for biofluids are modelled by a suitable combination of gas/water and gas/oil partition coefficients, thus allowing for the hydrophobicity of a given biological tissue or fluid. This method is furthermore able to provide a measure for the tissue/blood distribution of non-electrolytes (which may also be estimated using octanol-water partition coefficients [15]). 

REGULATION OF WATER AND ELECTROLYTE BALANCE. Basically, water (1) enters the body via the digestive tract as liquid or food, (2) moves into the blood and tissue, and (3) leaves via the kidneys, skin, lungs, or feces. Water entering and leaving the body is under rigid... 

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