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Download Sense of smell- olfaction
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Sense of smell- olfaction • Olfactory receptor neurons have olfactory cilia which mix the mucus covering of olfactory epithelium. • Mucus covered to dissolve airborne liquid molecules • Located in most superior part of nasal cavity-that’s why we must sniff to detect delicate odors. • 4,000 – 10,000 odor molecules detected by humans Anosmia • Complete lack of smell • Results in depression– worse than in patients with other sensory losses • Causes: – Damage to frontal lobe – Nasal congestion – Viral infections – Genetic disorder Rats with Anosmia • Blind rat can survive • Rats with anosmia won’t mate or eat die Taste and Smell are related • The receptors share several common pathways in the brain • Odor molecules give us 70-75% of overall taste – flavor Sense of Taste-- Gustation • Taste buds contain chemoreceptors called gustatory cells with cilia that project into taste pores bathed in saliva • Most taste buds are found in between papillae: elevated projections of differing shapes • Fungiform papillae- large, anterior 2/3 tongue, contain one or a few taste buds • Circumvallate papillae- huge, transverse row at back of tongue, thousands of buds • Foliate papillae- red ridges of mucosa on lateral edges of posterior tongue, 100 buds • Filiform papillae- bumps with tiny projections, scattered, experience food TEXTURE Primary tastes • Each receptor cell responds most effectively to only 1 of the 5 “primary tastes”: – Sweet – Sour – Salty – Bitter – Umami/savory– this taste is perceived when proteins are cooked and release amino acids • What else influences our perception of taste? Taste and location on tongue • Can we “map” the tongue? Taste and location on tongue • Current research shows that all tastes can be detected in all areas of tongue– regional differences may not really exist • ALL 5 taste receptor cells are in every taste bud Taste Preferences • Prenatal tastes exposed to fetus – Fetus swallows 200-760 mL of amniotic fluid daily • Taste forms at early stage of gestation • Flavors from maternal diet reach amniotic fluid Importance of taste • Taste is the only special sense with 3 different cranial nerve routes (VII, IX, X– facial, glossophayngeal, and vagus) to the brain– indicates taste important to survival (why?)
