Cyclic amp is produced by a membrane bound enzyme which is activated by the binding of a hormone and ligand on the other side of that membrane. When a door bell is rung, an electric pulse is sent to a bell which is located within the house. The bell ringing alerts the occupant that someone is at the door and that they must do something. The similarity is that both systems send a signal across a barrier to stimulate an action within a closed space.
METAMIA is a free database of analogy and metaphor. Anyone can contribute or search. The subject matter can be anything. Science is popular, but poetry is encouraged. The goal is to integrate our fluid muses with the stark literalism of a relational database. Metamia is like a girdle for your muses, a cognitive girdle.