Control of ciliary motion.

Abstract

Three levels of excitable structures are proposed: living ciliated cell; living cilium with ciliary membrane and attached basal granule and contractile element within a cilium. Intrinsic as well as extraneous stimuli modify the activities associated with these structures. The effect is usually not monistic but pluralistic. If there is an excitatory innervation to a certain kind of ciliated tussue, the electrical or chemical events associated with the arrival of the nerve impulse, if any, will cause the innervated membrane of the ciliated cell to depolarize by a process as yet unknown. It is possible that such changes affect not only pluricellular coordination but cause the minor structures to respond directly. Thus, intrinsically determined direction, amplitude, frequency, and beating phase of an individual cilium, as well as syn-chronal and metachronal coordination between the cilia, will be modified as a result of cell excitation and/or excitatory response of a single cilium and/or direct response of contractile elements. All of these may also cooperate with each other within a cilium, induced by the physicochemical action of the impulse. Sometimes these effects may compete with each other, 1 effect overwhelming another. For example, the reversal-inducing effect of KC1 is superseded by the effect of inward transmembrane electric current, which causes an augmentation of ciliary stroke in ciliate protozoa.