Sweating

This chapter discusses the anatomy, innervations, and functions of the sweat gland. There are two types of human sweat glands, apocrine and eccrine. The full complement of eccrine sweat glands is present at birth and undergoes a gradual reduction in numbers with increasing age. Regulation of sweating in humans serves an important role in thermoregulation and loss of the ability to sweat can result in thermoregulatory failure, including heat stroke. Eccrine sweat glands are of greater neuroscience interest and the rest of the description will focus on eccrine sweat glands. Surrounding the secretory cells are myoepithelial cells whose contraction is thought to aid the expulsion of sweat. There are a number of factors that affect the sweat response. With repeated episodes of profuse sweating, the salt content of the sweat progressively declines. In individuals that have acclimatized to a hot climate, the salt content is reduced, probably reflecting an increase of mineralocorticoids in response to thermal stress. Innervation is mainly by sympathetic postganglionic cholinergic fibers. In isolated human eccrine sweat gland regulation, the regulation of sweating is cholinergic and muscarinic, being completely inhibited by atropine.