Touch.

Light touch, a sense of muscle position, and the responses to tissue-damaging levels of pressure all involve mechanosensitive sensory neurons that originate in the dorsal root or trigeminal ganglia. A variety of mechanisms of mechanotransduction are proposed. These ranges from direct activation of mechanically activated channels at the tips of sensory neurons to indirect effects of intracellular mediators, or chemical signals released from distended tissues, or specialized mechanosensory end organs. This chapter describes the properties of mechanosensitive channels present in sensory neurons and the potential molecular candidates that may underlie. Mechanically regulated electrical activity by touch and tissue damaging levels of pressure in sensory neurons seems to involve a variety of direct and indirect mechanisms and ion channels, and the involvement of specialized end organs in mechanotransduction complicates matters even more. Imaging studies are providing useful information about the events in the central nervous system associated with touch pain and allodynia (a pathological state where touch becomes painful this type of activity).