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Senses and Sensibility I. Sensory modalities II. Physiology of sensation III. Thermal homeostasis IV. Physiology of taste V. Physiology of smell Sensory Modalities • Chemoreceptors (e.g., taste, smell, O2 level in blood) Sensory Modalities • Chemoreceptors (e.g., taste, smell, O2 level in blood) • Mechanoreceptors (e.g., touch, hearing, equilibrium, proprioreception) Sensory Modalities • Chemoreceptors (e.g., taste, smell, O2 level in blood) • Mechanoreceptors (e.g., touch, hearing, equilibrium, proprioreception) • Photoreceptors (vision, photoperiod) Sensory Modalities • Chemoreceptors (e.g., taste, smell, O2 level in blood) • Mechanoreceptors (e.g., touch, hearing, equilibrium, proprioreception) • Photoreceptors (vision, photoperiod) • Thermoreceptors Communication by Sensory Neurons • Sensory stimuli cause graded potentials Axon Hillock Communication by Sensory Neurons • Sensory stimuli cause graded potentials • AP triggered in sensory neuron if graded potentials reach threshold Axon Hillock Communication by Sensory Neurons • Sensory stimuli cause graded potentials • AP triggered in sensory neuron if graded potentials reach threshold • Sensory neurons synapse onto neurons of CNS Axon Hillock Properties of Sensory Neurons • Selectivity Vision Hearing Taste Properties of Sensory Neurons • Selectivity • Transduction – convert stimulus into graded potential – Na+ channels open or close – AP created in sensory neuron Senses and Sensibility I. Sensory modalities II. Physiology of sensation III. Thermal homeostasis IV. Physiology of taste V. Physiology of smell Range of Sensory Perception • Sensory Adaptation Thalamus filters out some stimuli Range of Sensory Perception • Range Fractionation - neurons differ in range of sensitivity Senses and Sensibility I. Sensory modalities II. Physiology of sensation III. Thermal homeostasis IV. Physiology of taste V. Physiology of smell Thermoreceptors • Peripheral Thermoreceptors - epithelial tissue • Central Thermoreceptors - hypothalamus Thermal Homeostasis Stimulus: Cold Air Stimulus: High Core Temp Peripheral Thermoreceptor Central Thermoreceptor Hypothalamus Motor Neuron Sympathetic NS Muscle (Shivering) Sweat Glands Senses and Sensibility I. Sensory modalities II. Physiology of sensation III. Thermal homeostasis IV. Physiology of taste V. Physiology of smell Chemoreceptors • Chemoreceptors respond to chemicals in an aqueous solution The Chemical Senses: • Taste – 5 receptor types – cells are highly generalized Taste Buds are Located in Papillae Taste Buds are Located in Papillae Gene Simmons has LOTS of papillae! Taste Buds are Located in Papillae Taste buds line the papillae of your tongue. Taste Buds are Located in Papillae Taste buds line the papillae of your tongue. I Rock & Roll all Night and Party Every Day! Anatomy of Taste Buds Taste cell Support cell Basal cell Anatomy of Taste Buds Taste cell Support cell Basal cell 1) Taste cells form receptor surface and synapse with cranial nerves Anatomy of Taste Buds Taste cell Support cell Basal cell 1) Taste cells form receptor surface and synapse with cranial nerves 2) Supporting cells provide support for taste buds Anatomy of Taste Buds Taste cell Support cell Basal cell 1) Taste cells form receptor surface and synapse with cranial nerves 2) Supporting cells provide support for taste buds 3) Basal cells produce new _________ Hypothetical Distribution of Taste Cells Hypothetical Distribution of Taste Cells Distribution of Taste Taste cell Support cell Basal cell • Most taste cells respond to only 1 of the 5 tastes Transduction in Taste Cells • Salty & Sour flavors - Na+ or H+ ions enter cells through existing channels Transduction in Taste Cells • Sweet , Bitter & Umami more complicated – Bind to receptors and activate secondary messengers, which open Na+ channels Senses and Sensibility I. Sensory modalities II. Physiology of sensation III. Thermal homeostasis IV. Physiology of taste V. Physiology of smell Jerry made the ice cream but Ben would test all the new flavors because Ben has hardly any sense of smell JERRY GREENFIELD: He kept making me put in these bigger and bigger pieces of chunks. BEN COHEN: Jerry always wanted to make them smaller so that there would be better chunk distribution in each scoop, or in each pint, and I insisted that it was critical that the chunks be really, really huge. And he said, “but Ben, somebody might take a spoonful and they won't get a chunk at all.” And I said, “that's OK, that's a sacrifice you have to make. It's worth it, for the big chunk they'll get in the next spoon.” Olfaction (Smell) • Smell enhances the sense of Taste Olfaction (Smell) • Smell enhances the sense of Taste Olfaction (Smell) • Smell enhances the sense of Taste Olfaction (Smell) • Smell enhances the sense of Taste • Olfactory cells Olfaction (Smell) • Smell enhances the sense of Taste • Olfactory cells • Mucus Anatomy of Olfaction Olfactory nerve olfactory bulb Ethmoid olfactory epithelium basal cell olfactory cell support cell Chemoreceptors • Chemoreceptors respond to chemicals in an aqueous solution The Chemical Senses: • Taste – 5 receptor types – cells are highly generalized • Smell – Thousands of receptor types – cells are highly specialized Olfactory Cells Are Specialists • The nose can distinguish ~10,000 odors Olfactory Cells Are Specialists • The nose can distinguish ~10,000 odors 10,000 Odors! How does your nose knows? Olfactory Cells Are Specialists • Nose can distinguish ~10,000 odors! • Each olfactory cell expresses a different receptor protein (only one type per cell) Olfactory Cells Are Specialists • Nose can distinguish ~10,000 odors! • Each olfactory cell expresses a different receptor protein (only one type per cell) • Cells with a given receptor are randomly distributed in the olfactory epithelium Olfactory Cells Are Specialists • Nose can distinguish ~10,000 odors! • Each olfactory cell expresses a different receptor protein (only one type per cell) • Cells with a given receptor are randomly distributed in the olfactory epithelium • All neurons of a given type converge in the olfactory bulbs of the brain Convergence of Olfactory Cells nasal epithelium point of convergence (in olfactory bulb) Ethmoid Bone Physiology of Olfaction 1. Volatile odor enters nasal cavity Physiology of Olfaction 1. Volatile odor enters nasal cavity Physiology of Olfaction 1. Volatile odor enters nasal cavity 2. Odor dissolves in mucus lining Physiology of Olfaction 1. Volatile odor enters nasal cavity 2. Odor dissolves in mucus lining 3. Bind to receptor protein Physiology of Olfaction 1. Volatile odor enters nasal cavity 2. Odor dissolves in mucus lining 3. Bind to receptor protein 4. Na+ channels open Physiology of Olfaction 1. Volatile odor enters nasal cavity 2. Odor dissolves in mucus lining 3. Bind to receptor protein 4. Na+ channels open 5. AP sent to Olfactory Bulb Physiology of Olfaction 1. Volatile odor enters nasal cavity 2. Odor dissolves in mucus lining 3. Bind to receptor protein 4. Na+ channels open 5. AP sent to Olfactory Bulb 6. To the Brain Hmmm… That smells like bacon The Dirty Secret Behind Flavor • So why do McDonald’s fries taste soooooo good? New Jersey Smells Great! McDonalds French Fries: Potatoes, partially hydrogenated soybean oil, natural flavor (beef, wheat and dairy sources), dextrose, sodium acid pyrophosphate (to preserve natural color). Cooked in partially hydrogenated vegetable oils (may contain partially hydrogenated soybean oil and/or partially hydrogenated corn oil and/or partially hydrogenated canola oil and/or cottonseed oil and/or sunflower oil and/or corn oil). Contains derivatives of wheat and dairy.
