Special Senses - Taste & Olfaction .docx

5 Pages
93 Views
Unlock Document

Department
Anatomy and Cell Biology
Course
Anatomy and Cell Biology 3319
Professor
Kem Rogers
Semester
Fall

Description
Special Senses: Taste & Olfaction • Receptors for general senses are widely distributed • Special sensory receptors are localized & confined to head region • Receptors for special senses are not free endings of sensory neurons but distinct receptor cells • Neuron-like epithelial cells or small peripheral neurons that transfer information • Special sensory receptors are housed either in complex sensory organs (eye or ear) or in distinctive epithelial structures (taste buds or olfactory epithelium) • Sensory information travels to brain via cranial nerve The Chemical Senses: Taste & Smell • Receptors for taste (gustation) & smell (olfaction) are classified as chemoreceptors Taste (Gustation) Taste Buds • Location of taste receptors in mucosa of the mouth & pharynx • Majority of the 10,000 or so taste buds are on surface of the tongue • Few others occur on posterior region of palate (roof of mouth), on inner surface of cheeks & on posterior wall of the pharynx and on the epiglottis (leaf-shaped flap behind tongue) • Most taste buds occur in peglike projections of the tongue mucosa called papillae • Taste buds occur within epithelium that covers papillae • In small fungiform papillae scattered over entire surface of tongue –buds are on apical surface • In small filiform papillae scarred over entire surface of tongue • In large (circum)vallate papillae arranged in inverted V near back of tongue –buds are in side walls • In foliate papillae on posterolateral surface of tongue – taste buds are in the side walls • Each taste bud - globular collection of 50-100 epithelial cells that resembles bud on tree or closed tulip • Each contains two major cell types: o Gustatory epithelial cells o Basal epithelial cells • Long microvilli: gustatory hairs project from gustatory epithelial cells & extend through taste pore to surface of the epithelium • Microvilli then are bathed in saliva containing dissolved molecules that stimulate taste • Molecules bind to plasma membrane, inducing gustatory epithelial cells to generate impulses in nerve • Cells in taste buds are replenished every 7-10 days by division of basal epithelial cells, replacing ones that are scraped & burned off during eating • Entire bud is destroyed – new one will form after nerve ending grows back into regenerating epithelium Taste Sensations & Gustatory Pathway • Taste sensation can be described in terms of 5 basic qualities: o o Sweet o Sour o Bitter o Salty o o Umami (deliciousness)  Elicited by substance: glutamate that is found naturally in meat, aged cheeses & tomatoes • Combination of activated cells + pattern of activity = specific tastes • Exception: bitter receptors found on many cells • Maps that assign specific taste sensations to specific areas of the tongue are common • Mapped areas are dubious & all modalities of taste can be elicited from all areas that contain taste buds • Taste information reaches brain stem & cerebral cortex through gustatory pathway • Sensory fibres carrying taste information occurs in 3 nerves: o Facial (VII) transmits impulses from taste receptors from anterior 2/3 of tongue o Glossopharyngeal (IX) carries sensations from tongue’s posterior 1/3 & few taste buds in pharynx o Vagus (X) carries taste impulses from few taste buds on epiglottis & lower pharynx o Overlap – facial & glossopharyngeal • Thalamic relay: ventral posteromedial nucleus of thalamus • All sensory neurons that carry taste information synapse in medullary nucleus: solitary nucleus • Impulses are then transmitte
More Less

Related notes for Anatomy and Cell Biology 3319

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit