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131%2C+T5%2C+Ch16+Special+Senses

131%2C+T5%2C+Ch16+Special+Senses - The Special Senses...

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9/6/11 1 Special Senses Chapter 16 IB 131 Instructor: Tom Carlson Department of Integrative Biology UC Berkeley The Special Senses Touch —a large group of general senses The Special Senses include : taste, smell, sight, hearing and balance Special sensory receptors Localized —confined to the head region – Receptors are not free endings of sensory neurons – Special receptor cells • Are neuron-like epithelial cells or small peripheral neurons –Transfer sensory information to other neurons in afferent pathways Taste The Superior Surface of Tongue Stratified squamous epithelium Filiform papillae Fungiform papillae Vallate papillae Sulcus terminalis Lingual tonsil Superior Surface of the Tongue Figure 23.12 Epiglottis Palatopharyngeal arch Palatine tonsil Lingual tonsil Palatoglossal arch Vallate papilla Terminal sulcus Midline groove of tongue Filiform papilla Fungiform papilla The Superior Surface of Tongue Tongue papillae Filiform papillae: the most numerous papillae on the tongue are small and conical pointed in shape and line up in parallel rows which enable tongue to grasp and manipulate food; do not contain taste buds Fungiform papillae: mushroom shaped and spread over anterior 2/3rds of tongue surface Vallate papillae: V-shaped row bordering the posterior third of the tongue and directly anterior to the terminal sulcus (sulcus terminalis) groove Fungiform and Vallate papillae contain taste buds Sulcus terminalis : Marks border between mouth & pharynx Posterior 1/3rd of tongue lies in oropharynx & is lined with lingual tonsil
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9/6/11 2 The Chemical Senses: Taste and Smell Taste —gustation Smell —olfaction Receptors—classified as chemoreceptors – Respond to chemicals • Food dissolved in saliva • Airborne chemicals that dissolve in fluids of the nasal mucosa Taste Buds Present on fungiform and vallate papillae on the tongue surface Contain taste receptors Collection of 50–100 epithelial cells Contain two major cell types Gustatory epithelial cells Basal epithelial cells • Contain long microvilli (gustatory hairs) extend through a taste pore to the surface of the epithelium Cells in tastebuds replaced every 7–10 days Taste Buds Figure 16.1 (a) Taste buds associated with fungiform and vallate papillae (b) Enlarged section of a vallate papilla Fungiform papillae Taste bud Vallate papilla Epiglottis Palatine tonsil Lingual tonsil Taste fibers of cranial nerve Connective tissue Gustatory epithelial cells Taste pore Gustatory hair Stratified squamous epithelium of tongue (c) Enlarged view of a taste bud (micrograph, 160 X ) Basal epithelial cells Taste Sensation and the Gustatory Pathway Five basic qualities of taste –Sweet, sour, salty, bitter, and umami –“Umami” is elicited by glutamate The “taste map” is a myth –All taste modalities can be elicited from all areas of tongue containing taste buds Gustatory Pathway
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