Light produces a depolarizing generator potential and an increase in spike activity in both type A and B photoreceptors (Dennis, 1967; Alkon and Fuortes, 1972).
Rotation or gravity causes the statoconia to press against the motile cilia of hair cells in front of the centrifugal or gravitational force vector, resulting in a depolarizing generator potential and an increase in spike activity (Alkon, 1975).
Rotation of the statocyst has been shown to be an adequate stimulus for evoking depolarizing generator potentials and an increase in spike activity in Hermissenda hair cells (Alkon, 1975).
Generator potential responses induced by light flashes of constant duration but increasing intensity were recorded extracellularly from the epistellar body photoreceptors of the octopus, Eledone cirrhosa [ILLUSTRATION FOR FIGURE 6A OMITTED].
As already seen for the extracellular compound generator potentials, the time-to-peak depolarization for individual photoreceptor cells decreased with increasing stimulus intensity [ILLUSTRATION FOR FIGURE 10C OMITTED].
While perfusing the slice with modified Limulus Ringer (first trace), the light flash evoked a burst of [approximately]7 action potentials at the leading edge of the generator potential, followed by 34 action potentials yielding a steady-state firing rate of [approximately]4.5 impulses/s for the last 4 s of the response.
The decrease in steady state response, from 4.0 to 0 impulses/s, was associated with a partial hyperpolarization of the generator potential from 10 to 5 mV depolarization.
He covers cellular processes, cell membranes, channels and control of membrane potential, sensory generator potentials
, action potentials, synapses and muscles, and includes a practice examination with answers.