A). Papillae

Surface structures on the tongue contain taste buds.

B). Taste buds

10,000 taste buds on the tongue, and soft palate.

Contain

1). supporting cells,

2). receptor (gustatory) cells

with sensitive gustatory hairs

3). basal cells: act as stem cells replacing needed parts.

A). Categories

1). Sweet

Responds to sugars and some amino acids (and lead)

2). Sour

Responds to H+

3). Salty

Responds to metal ions & NaCl

4). Bitter

Responds to alkaloids

B). Regions on the tongue

C). Activation of Taste

1). Chemical is dissolved in saliva. We can not taste material that does not dissolve.

2). Molecules bind to receptor proteins.

3). Nerve impulses are generated in associated nerve fibers.

	Different cells have different threshold for activation.
	Bitter is most sensitive than sour than sweet & salty
	Each taste opens up different ion channels.

4). Impulses travel to the medulla and than the thalamus

5). To the gustatory cortex in the parietal lobe.

6). Reflexes for digestion are triggered.

D). Other factors that affect taste

1). Smell

2). Thermoreceptors, pain receptors, mechanoreceptors record the temperature and texture of food.

3). Vision: what food looks like.