Dictionary of Biological Psychology
Salt can refer to a broad chemical class of substances, but is most often used to refer to the substance known as ordinary table salt: sodium chloride (NaCl). Salt has importance for biopsychology in three distinct ways: as a taste, as the target of SODIUM APPETITE, and as the source of sodium (Na+) and chloride (Cl−) ions that are crucial to normal physiological function.
Unlike sweet or bitter tastes, the tongue does not need specific receptor molecules in order to recognize substances that trigger the sensation of salty taste (see GUSTATION). Instead sodium salts such as sodium chloride appear able to directly activate taste cells in the tongue. In liquid solution, NaCl dissociates into separate sodium (Na+) and chloride (Cl−) ions (see ION). The apical membrane of taste cells contains Na+ channels, through which Na+ ions can enter. Na+ ions appear directly able to trigger the sensation of salt.
Evidence for this comes from the effects of a drug, AMILORIDE, which blocks Na+ channels in cell membranes. When amiloride is applied to the surface of the tongue, it results in a temporary block of the sensation of saltiness produced by sodium salts. This mechanism appears to be the chief way in which salty taste are recognized by the tongue, though there also appear to be secondary mechanisms that operate in a different fashion.
The existence of a specific taste and appetite for salt (see SODIUM APPETITE) may be explained by the crucial role ions play in the normal function of neurons and other cells. The generation of a neuronal RESTING POTENTIAL, the state in which it lies ready to process information, is maintained by active processes in the neuron that control the flow and concentration of Na+, Cl− and other salt ions inside the cell. The generation of an ACTION POTENTIAL, a neuronal signal and unit of information, is produced by a temporary alteration in the control of ion gates and neuron concentration. Without adequate ion supplies, neuronal function is impossible. Thus ingestion of an adequate amount of ion-containing salts is critical to health and function.
KENT C.BERRIDGE
This is the complete article, containing 346 words
(approx. 1 page at 300 words per page).
View More Summaries on Salt
