Special Senses: Taste

1. Special Senses: Taste Created by: Ben judy TemiOlafunmiloye TomiJegede Pd. 4b

2. What is Taste? • Taste can be categorized as a gustatory perception. • That is a sensation that is the result of the taste buds giving off information about the chemical properties of food and liquid substances. • Humans perceive taste through sensory organs on the tongue called taste buds. • Taste buds act as specific receptors in the oral cavity. • They are widely scattered throughout the tongue, soft palate, and inner surface of cheeks.

3. The Tongue • The dorsal tongue surface is covered with papillae, which are small peglike projections. • Taste buds are found on the sides of the big, rounded circumvallate papillae and the fungiform papillae. • Cells that respond to chemicals dissolved in the saliva are called gustatory cells. • They are epithelial cells with gustatory hairs that project from the taste pores.

4. The Gustatory Cells • The gustatory cells are composed of microvilli, long gustatory hairs, that protrudes through the taste buds. • When stimulated, the microvilli depolarize, which sends impulses to the brain. • Three cranial nerves carry taste impulses. • The facial nerve (VII), the glossopharyngeal nerve (IX), and the vagus nerve (X). • Gustatory cells are subject to a lot of friction, so they are replaced every few days with basal cells.

5. Anatomy of the Taste Buds

6. There are 5 five basic taste sensations that correspond with the 5 main types of taste buds. • Sweet receptors sense sugars, saccharine, some amino acids, and some lead salts • Sour receptors recognize hydrogen ions. • Bitter receptors respond to alkaloids. • Salty receptors sense metal ions in solutions. • Umami receptors respond to the amino acid glutamate (savory “beef taste”). Basic Taste Sensations

7. Sensory Pathway • There are 3 different pathways for taste impulses. They travel from the taste buds to the gustatory cortex. • The facial nerve conducts electrical signals from the anterior sides of the tongue. • The glossopharyngeal nerve conveys signals from the posterior on the tongue. • The vagus nerve sends taste signals from the mouth and the larynx. • The 3 pathways join the brain stem in the nucleus of the solitary tract (NST). • They go to the thalamus before heading to 2 frontal regions: the insula and the frontal operculum cortex.

8. BMS is a very painful condition that feels as if your tongue, gums, and mouth are on fire. • A person with this syndrome often feels a scalding sensation throughout his or her entire mouth. • The symptoms are a dry and sore mouth, numbness of your lips and mouth, loss of taste, or only a bitter sense of taste. • BMS is referred to as a neuropathic condition, for most BMS victims’ nerves are not sending or processing information correctly. • This is due to short circuiting of taste and sensory nerves of both the central and peripheral nervous systems. • This short circuit causes the brain to not be able to turn off the pain receptors, which result in the chronic pain.  Burning Mouth Syndrome (BMS)

9. Bell's Palsy • Bell Palsy's is a disorder of the cranial facial nerve (VII). • Symptoms include loss of the sense of taste, partial impairment of taste, facial pain, difficulty eating, running of a fever, and one-sided facial paralysis or two-sided facial paralysis • It temporarily paralyzes the facial nerves, and disrupts sensory receptors in the face, causing extreme numbness.