What does chemoreceptors respond to?

An example of direct chemoreceptors are the cells located on the tongue. When people taste food, it is because these cells respond to the chemicals in the food, sending a signal to thebrain to let the brain know about what's happening in the mouth. Specific regions of the mouth have areas which are targeted towards specific tastes, such as salty and sweet. This explains why foods can taste different as they are chewed and swallowed, and also why some foods have an aftertaste, as certain chemicals can take longer to stimulate the chemoreceptors.