Characteristics of single mechanoreceptive fibres innervating hairy skin of the human hand.

Unit activity was recorded percutaneously by microelectrodes from 69 nerve fibres innervating the hairy skin of the back of the hand in 6 awake human subjects. Twelve fibres had no receptive field on the skin, twenty-one fibres could be classified as rapidly adapting (RA) and thiry-six fibres as slowly adapting (SA) mechanoreceptive fibres. Four SA fibres has a spontaneous discharge in absence of stimulation. Mechanical thresholds of tra fibres ranged from 0.3 to 1.7 g and those of SA fibres from less than 0.1 to 1.7 g. Conduction velocities of the fibres were 22-41 m/s (RA fibres) and 10-73 m/s (SA fibres). Intensity functions of SA fibres could be described by power functions with exponents varying between 0.31-1.23. Most RA and SA fibres were entrained by vibratory stimuli. The results indicate that the receptors in the human hairy skin do not differ considerably in their characteristics from the receptors in the human glabrous skin or from animal receptors in the hairy skin.