EFFECTS OF GRAVITY AND HYDROSTATIC PRESSURE ON ANGULAR ACCELERATION CODING SENSORY NEURONES IN THE CRAB AND DOGFISH

摘要

Linear accelerations have been known to affect vestibular afferent activity in vertebrate semicircular canals and are known to affect angular acceleration detectors in the crab. Recently these receptors have been shown to be modulated by hydrostatic pressure. Resting and oscillation derived activity in crab thread hair neurones are modulated by tilt, with a small range of positions which maximize oscillation derived activity. We present an order of magnitude calculation which shows that thresholds for hydrostatic pressure detection are likely to be less than 1kPa. We further present a relationship between spike frequency and pressure for a small group of horizontal canal units in the dogfish. Since reported that the position of the head affected the level of the resting discharge in all three canals of the frog labyrinth, similar effects have been seen in a variety of vertebrates (see [12]). Cephalopoda and crabs amongst the invertebrates have the best angular acceleration detectors, and linear acceleration (gravity) effects on such receptors in octopus were shown by. In the crab, which has a statocyst shaped into semicircular canals, thread hairs interneurones which respond to angular acceleration have their responses modulated by angular position. Afferent neurones coding angular acceleration in crab and dogfish are affected by hydrostatic pressure in addition to gravity.