The chemical substance responsible for the taste is freed in the mouth and comes into contact with a nerve cell. It activates the cell by changing specific proteins in the wall of the sensory cell. This change causes the sensory cell to transmit messenger substances, which in turn activate further nerve cells. These nerve cells then pass information for a particular perception of flavor on to the brain.
The numerous wart-like bumps on the mucous membrane of the tongue are where the substance producing the taste is transformed into a nerve signal. These bumps, which are called taste papillae, contain many sensory cells with a special structure: together with other cells they make up a bud that looks a bit like an orange with its sections arranged around a center.
In the middle of the top side is a small indentation filled with fluid. The chemical substances responsible for the taste are washed into this funnel-like hollow. This makes sure that the substances are detected and analyzed by as many sensory cells as possible before being swallowed.