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chemosensory system

chemosensory system - Chemosensory Systems Although the...

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Chemosensory Systems Although the body can detect chemicals internally (changes in oxygen or carbon dioxide), we will focus on chemicals detected by the tongue and the nose. Taste and smell add a lot to our lives. We make a lot of associations with taste and smell. Flavor = Perception of olfaction (smell) + gustation (taste). Perception of flavor is a combination of taste and smell, mostly smell. Taste: the stimulation of receptor cells in taste buds. Taste buds are receptive organs found on the tongue and parts of the throat. There are many receptor cells each contains 50-100 cells. Each taste bud has capsule cells, which form an outer protective layer. At the surface of the taste bud there is a taste pore through which tastants (chemicals that can be tasted) enter. Within each taste bud, there are sensory receptor cells and basal stem cells. Sensory, receptor cells (taste buds) have microvilli at their surface to increase surface area for detecting tastants. Taste transduction occurs in the microvilli. Taste receptor cells are not neurons (they are specialized epithelial cells) innervated by cranial nerves. If taste buds lose innervations, they disappear but can regenerate with new innervations and stem cell differentiation. They are found mostly on folds of skin called papillae: 1.Fungiform 2.Vallate (Circumvallate) 3.Foliate 4.Filiform (no taste buds on these), like cats tongue Taste Bud Innervations: The tongue in innervated by cranial nerves VII, IX, and X: 1. The facial nerve (cranial nerve VII, chorda typani is one branch of facial nerve) innervates the anterior tongue. 2. The glossopharyngeal nerve innervates the posterior tongue. 3. The vagus nerve innervates the epiglottis. Sensory System Theories: 1. Labeled Line Theory: Each receptor responds to a limited range of stimuli with a direct line to the brain.
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