SWEAT GLAND ACTIVITY AND CHANGING PATTERNS OF SWEAT SECRETION ON THE SKIN SURFACE

Abstract

Between environmental temps. of 20-35[degree]C, sweat glands on the extensor surface of the forearm are phasi-cally active showing alternating periods in which large and small numbers of glands are successively active in secreting onto the skin surface. The periodicity and the number of glands participating in each cycle of activity are not regular, but are influenced by environmental temp., strong peripheral and visceral stimulation, and by psychic and emotional excitation. With the undisturbed subject resting in a comfortable environmental temp., sweating is characterized by the sudden excitation of a number of sweat glands for a period of a few secs. followed by a period of little or no sweating activity by these glands. The secretory activity of individual glands under these conditions is thus relatively short, but activity may alternate between many glands in a given area and thus prolong the duration of a given sweating cycle. Extraneous excitation may also prolong a period of secretion, and cyclic activity may be superimposed upon the functional activity of large numbers of glands at high environmental temps. When presented with a strong thermal stimulation, the sweat mechanism responds in 2 important stages. 1st, an increase in number of functional sweat glands following a few mins. after presentation of the stimulus. If this stimulus is sufficiently severe and prolonged, a second stage of sweating is marked by a large increase in output of the individual glands. Simultaneous peaks and depressions in number of functional sweat glands on both forearms suggest the presence of a sweat center in the central nervous system discharging periodically and bilaterally to the sweat glands. When radiant heat is applied to one arm, sweating is likely to be localized in the area heated, but if the heating is sufficiently intense, bilateral sweating is observed, with greater numbers of active glands on the heated arm.