The present review focuses on an emerging Ca²⁺ signal transduction concept that might be applicable to the general operation of all sensory neural networks. The central theme of this concept is that Ca²⁺ signals through a delicately controlled membrane guanylate cyclase (ROS-GC) transduction machinery. This, in turn, generates pulsated levels of cyclic GMP. Cyclic GMP then serves as a Ca²⁺ second messenger.  The delicacy and specificity of the transduction machinery is achieved through its unique composition and structural design.  An extraordinary operational property of these features in the machinery is that in response to the parent Ca²⁺ spike it is able to be stimulated or inhibited.  Thus, it can cause depolarization or hyperpolarization in the plasma membranes of the neurons.  The presence of this machinery has been successfully tested in the three model systems—SIGHT, SMELL, TASTE-- of the sensory neurons and also in the light-regulated pineal gland.