Final answer:
Brandon experiences the flavor of his hot cocoa through the receptor cells in his taste buds. Taste buds, which house gustatory receptor cells, are mainly responsible for sensing the basic tastes and are located in different types of papillae on the tongue's surface.
Step-by-step explanation:
Brandon is drinking hot cocoa. Receptor cells in his taste buds produce the flavor he experiences. The primary function of taste buds is to detect the five basic tastes: sweet, salty, sour, bitter, and umami (savory). These taste buds are housed in papillae found on the surface of the tongue. Within these taste buds are specialized cells known as gustatory receptor cells, which transduce the chemical stimuli from food and drink into nerve impulses. These impulses travel through afferent nerves to the central nervous system (CNS), where we perceive the flavors.
There are several distinct types of papillae on the tongue, each with different functions and structures. For instance, fungiform papillae are located mainly on the anterior two-thirds of the tongue and contain one to several taste buds, while the circumvallate papillae are much larger, found near the posterior margin of the tongue, and can house up to 250 taste buds.
The sense of taste closely interacts with the sense of smell, as olfactory receptors also play a role in the perception of taste. However, when it comes to the tasting process via the tongue, it's the taste buds with their gustatory receptor cells that are the key players.