This document discusses sensory receptors and their classification. It begins by outlining the components of the sensory system, including sensory receptors, afferent neurons, and the sensory cortex. Receptors are classified based on their location (exteroceptors, enteroceptors, telereceptors) and type of stimulus detected. The labeled line principle states that specific receptors transmit only one sensory modality along dedicated pathways. Receptor potentials are generated when stimuli open ion channels, allowing intensity encoding. Adaptation causes receptors to stop firing over time to constant stimuli, with tonic receptors transmitting continuously and phasic receptors only at stimulus onset/offset.