1. CREATED BY: BEN JUDY TEMI OLAFUNMILOYE TOMI JEGEDE PD. 4B Special Senses: Taste

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. Basic Taste Sensations 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”).

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. Burning Mouth Syndrome (BMS) 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.

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.