Answer
A. The five primary taste qualities that are generally recognized are sweetness, sourness, bitterness,
saltiness, and umami (savouriness).
B. The three cranial nerves CN)that serve the sense of taste are the facial ( CN VII); the glossopharyngeal (CN IX), and the vagus (CN X).
Work Step by Step
The five recognized taste qualities are sweetness, sourness, bitterness, saltiness and umami, or savouriness. Umami is a taste quality that was discovered by Japanese researchers. Western food scientists have renamed it savouriness. Some food scientists think that there are distinct taste sensations for fatty substances, as well as for pungent and for astringent substances. However, these ideas have not received general acceptance.
The sweet taste. The following substances are said to impart the taste of sweetness: sugars,
saccharin, alcohols, , some amino acids and lead salts
Sour substances; Acids of various kinds ( acetic acid) impart a sour sensation. This sour taste is due
to the hydrogen ion H+ of acids.
Bitterness: This taste is given by alkaloids: caffeine, morphine, strychnine,reserpine, quinine,
nicotine-- and aspirin.
Salty taste: the salty taste is due to sodium chloride found in table salt, sea salt, rock salt ( inorganic
ions)
The cranial nerves that serve the sense of taste are the facial (CN VII), the glossopharyngeal (CN IX)
an the vagus (CN X).
The facial serves taste buds at the front 2/3 of the tongue --mainly in fungiform papillae.
The glossopharyngeal innervate taste buds in the circumvallate papillae at the junction of the anterior 2/3d and posterior 1/rds of the tongue. it also serves the follate papillae on the rear edges of the tongue
The vagus (CN X), innervates taste buds on the epiglottis of the
larynx.
The efferent nerves from the taste buds travel to the solitary nucleus of the medulla oblongata ; thence they pass through the pons to the ventral posterolateral nucleus of the thalamus and on to the gustatory cortex of the insula. Where tastes impulses are interpreted.
