Taste

1. Taste Amanda Song, Caity McMahon, Pariis Yi, & Tobi Owoyemi

2. Sensory Organ/Structures The mouth is responsible for tasting It contains receptors that distinguish taste

3. Sensory Organs/Structures Papillae - small peg-like projections that cover the dorsal tongue Taste buds are found on sides of circumvallate papillae and on the tops of fungiform papillae Gustatory Cells - Specific epithelial cells that respond to chemicals dissolved in the in the saliva Gustatory Hairs - long microvilli that protrude through taste pore; when stimulates, they depolarize and send impulses to the brain. Surface of the tongue

4. Epithelium of tongue Epiglottis Palatine tonsil Taste bud Connective tissue Lingual tonsil Surface of the tongue Gustatory (taste) cell Circumvallate papilla Basal cell Sensory nerve fiber Fungiform papillae Taste buds Gustatory hairs (microvilli) emerging from a taste pore

5. Taste Sensory Receptors • Taste buds are the receptors for taste • Scattered in the oral cavity: on the tongue, soft palate, and inner surface of cheeks • Respond to different taste sensations (taste buds can respond to more than one) • Gustatory cells are the cells that receive taste sensation • Chemicals dissolved in the saliva bind to their microvilli and trigger an action potential

6. Taste Sensory Receptors Taste buds receive taste based on what food triggers • Sweet receptors - respond to sugars, saccharine, some amino acids, and some lead salts • Sour receptors - respond to hydrogen ions and acidity • Bitter receptors - respond to alkaloids • Salty receptors - respond to metal ions • Umami receptors - respond to glutamate (amino acid responsible for "beef taste")

7. Pathway of Taste Sensory Information • Different tastes change the flow in ions across the membrane of taste cells • Sweet & Bitter tastes - bind into receptor sites which release other substances into the cell • Sour tastes - contain H+ ions that block channels in the membrane • Salty tastes - break up into Na+ ions which flow through the membrane directly into the cell

8. Electrical Signals • Ion changes result in an action potential • Gustatory hair (microvilli of cell that protrudes through taste pore) are stimulated and depolarize • Cranial nerves VII, IX, and X carry the impulses from taste buds to gustatory cortex in the brain • Connected to the brain stem • Chorda tympani nerve - conducts signals from the front and sides of the tongue • Glossopharyngeal nerve - conducts signals from the back of the tongue • Vagus nerve - conducts taste signals from the mouth and the larynx

9. Causes of Taste Disorders • Upper respiratory and middle ear infections • Radiation therapy for cancers of the head and neck • Exposure to chemicals or medications • Head injury • Some surgery to the ear, nose, and throat • Poor oral hygiene • Dental problems • Aging

10. Common Taste Disorders • Hypogeusia: reduced ability to taste sweet, sour, bitter, or salty • Caused by serious burns, drug use, smoking • Ageusia: inability to detect any tastes Thought to be caused by damage to taste buds (which causes an inability of nerves to transmit taste to brain)