Adaptation - the sensory system soon adapts to continued stimulation and doesn't respond to the stimulus. Touch receptors are a type of mechanoreceptor. In humans, the fingertips and tongue are rich with receptors, but there are fewer in the back of the hand and neck. Touch receptors are free nerve endings or nerve endings that are surrounded by a capsule. The hypothalamus processes these nerve impulses.
Prostaglandins sensitize tissue to pain.
Aspirin works by inhibiting prostaglandin synthesis. Stimulus - chemical. Receptor - chemoreceptor. There are four basic tastes - bitter, sweet, salty, and sour. Odors are caused by the response of ciliated receptor cells that line the olfactory epithelium to different molecules.