Receptors

When the body is touched, receptors in the skin send messages to the brain causing the release of chemicals such as endorphins.

Caffeine is a purinergic antagonist that competitively inhibits adenosine at the sites of P1 receptors.

The brain has no pain receptors.

Having fifty times as many olfactory neural receptors as human beings, dogs have a sense of small that is a hundred thousand times more acute.

That feeling is caused by the capsaicin molecules in the peppers activating the capsaicin receptors on our tongue—the more capsaicin, the hotter the pepper.

Cats have scent receptors in their mouths.