Nervous Control of Movement in Cephalopods

Abstract

ABSTRACT Nerve muscle preparations have been made of the mantle and stellar nerves of octopuses and squids. Two motor innervation systems have been found in each. Both have been observed as unit preparations. The possibility of double innervation of the same muscle cells exists but has not been directly checked. The fast innervations produce electrical responses which are maximal to the first stimulus and which have little or no absolute refractory period. They appear to be local rather than spike potentials. Fatigue is very rapid. The mechanical response sums in Octopus, but not in Loligo. The slow innervations produce electrical and mechanical responses which facilitate with repetition. The fast system of Loligo does likewise after fatigue to a low level of response. No evidence was found for a functional nerve net in the mantle. Organizational features of the stellate ganglion have been identified physiologically in Octopus. The ganglion acts both as an integrating motor centre and as a reflex centre.