Final answer:
Endocrine signals are slow because they travel through the bloodstream, get diluted, and act at low concentrations over long distances, unlike the quick-acting paracrine signals that diffuse locally and act on nearby cells.
Step-by-step explanation:
Endocrine versus Paracrine Signaling
Endocrine signals are transmitted more slowly than paracrine signals primarily because they travel through the bloodstream. This mode of transport entails that hormones get diluted and are present in low concentrations when they reach their target cells. Paracrine signaling, on the other hand, involves signal molecules that move by diffusion through the extracellular matrix, acting on nearby cells which allows for quick responses. Additionally, endocrine signaling often induces long-lasting effects as hormones are designed to affect regions sometimes far away from their origin.