ABSTRACT
Two of the most salient features of a typical electrotonic synapse are its high speed and bidirectionality. Bidirectionality is undesirable way to couple cells in a nervous system because of the need for high specificity in neural processing. The crayfish solves the problem by employing a variety of gap junction types in its electronic synapses, some of which have voltage-dependent gating properties. The septal junction exhibits no voltage dependence. The chapter discusses why it utilizes gap junctions when intercellular fusion conducts. Gap junctions prevent macromolecules and organelles from moving between cells. Gap junctions uncouple damaged lateral giant axons from their neighbors, thereby limiting the spread of damage. Since lateral axons form a ladder-like network, a local area of damage would not prevent the spread of excitation beyond the injured segment. Coupling by gap junctions may be slowly regulated on a time course of hours or even months, as by hormonal control, thereby adjusting escape reflex excitability to suit environmental needs.
