These are all receptors that react to certain kinds of stimuli. The chemoreceptors react when there are changes in chemical concentrations within the body; the mechanoreceptors detect pressure or distorted stimuli; and the nocioreceptors send signals of pain to the spinal cord and brain.
Spicy food actually does not have a specific location in the taste buds of the tongue. This is the reason why it is not considered a flavor but rather a sensation. Spicy food stimulates the release of chemicals and signals to the brain which are detected by these different kinds of receptors.
