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Special Senses: Hearing, Taste, Smell Peripheral Nervous System Chapter 8 The Senses General senses of touch (tactile) Temperature - thermoreceptors (heat) Pressure - mechanoreceptors (movement) Pain - mechanoreceptors Special senses Smell - chemoreceptors (chemicals) Taste - chemoreceptors Sight - photoreceptors (light) Hearing - mechanoreceptors Equilibrium - (balance) mechanoreceptors The Ear: Hearing and Balance Two functions: Hearing and Balance Hearing: Sound vibrations Equilibrium: Gross movements Mechanoreceptors: respond to physical forces Both respond to different stimuli and activated separately Anatomy of Ear HEARING ONLY HEARING & BALANCE Anatomy of Ear Why do we need earwax??? Divided into 3 regions: External, Middle, Internal Earwax protects delicate lining of meatus (auditory canal) and helps prevent External Ear microorganisms from entering the ear Auricle (pinna) and Auditory Canal Ceruminous Glands in canal secrete earwax Tympanic membrane - eardrum Anatomy of Ear Middle Ear Tympanic Cavity – air filled, mucosa- lined Eustachian Tube – connects to throat Auditory ossicles (tiny bones) – hammer, anvil, stirrup Pressure build up Swallowing yawning “VALSALVA” Eustacian tube THROAT Otitis media http://www.petearclinic.com/images_video.htm http://apps.uwhealth.org/health/hie/2/19596.htm Middle ear inflammation Common with sore throat in children Enlarge, inflamed eardrum Pus, fluid build up requires incision and tubes to relieve pressure and drain Anatomy of Ear INNER EAR This is a cavity Bony labyrinth – bony chamber divided into 3 regions Cochlea Vestibule Semicircular Canals Two fluids: Endolymph Perilymph Labyrinth: an intricate, sometimes confusing, arrangement or pattern Sound waves Hearing > external acoustic meatus eardrum > ossicles > oval window > set fluid in motion > vibrations stimulate “hair cells” >duct, Within Cochlear membranous labyrinth is cochlear nerve transmits Spiral impulse to midbrain Organ of Corti – > receptors auditory cortex ofhearing temporal lobe or “hair cells” Figure 8.15 How the ear works… http://www.youtube.com/watch?v=dCyz8eAs1I What is a cochlear implant? https://www.youtube.com/watch?v=zeg4qTnYO pw Cochlear implants https://www.youtube.com/watch?v=6FhgYcfZZ Y8 Hearing Loss The following factors contribute to age-related hearing loss: Family history (tends to run in families) Repeated exposure to loud noises Smoking (smokers are more likely to have such hearing loss than nonsmokers) Certain medical conditions and medications also contribute to age-related hearing loss. About half of all people over age 75 have some amount of age-related hearing loss. Chemical Senses: Taste and Smell Chemoreceptor – respond to chemicals in solution OLFACTORY = smell GUSTATORY = taste Five types of receptors for taste Olfactory receptors much more sensitive Complement each other, respond to same stimuli Smell not as good as animals; however, some people are wine tasters, perfumers If you smell a particular odor all day, you won’t recognize its presence, you become accustomed, ex. garbage men During old age, people lose sense of smell- lots of perfume Humans can distinguish 10,000 or so chemicals What we really smell is pain: ex. chili, ammonia, menthol (cold) Specific chemicals cause specific patterns of neurons to fire How the nose works… http://www.youtube.com/watch?v=dIDBGUPRUI Olfactory epithelium Olfactory tract Olfactory bulb Nasal conchae (a) Route of inhaled air Figure 15.21a Olfactory Receptors: Smell 1000’s of olfactory receptors roof of nasal cavity Sniffing intensifies sense of smell Olfactory receptor cells have olfactory hairs – long cilia – in mucus layer Chemicals in mucus layer stimulate hairs -> filaments -> nerve Olfactory impressions long lasting – memories, adaptive Figure 8.17 Olfactory tract Mitral cell (output cell) Glomeruli Olfactory bulb Cribriform plate of ethmoid bone Filaments of olfactory nerve Olfactory gland Lamina propria connective tissue Axon Basal cell Olfactory receptor cell Olfactory epithelium Supporting cell Mucus (b) Dendrite Olfactory cilia Route of inhaled air containing odor molecules Figure 15.21a Pathway of smell Nostril > nasal cavity > olfactory receptors (sensory neurons) in membrane (top of nasal cavity) > through ethmoid (bone) > olfactory neurons in olfactory bulb > brain Taste Buds and Taste Most pleasurable sense Approx. 10,000 taste buds, most on tongue Papillae – projections, taste buds found on sides Circumvallate papillae – sides of tongue Fungiform papillae – top, more numerous Figure 8.18 How the tongue works… https://www.youtube.com/watch?v=KuPKj7MHes Taste Buds Filiform papilla Fungiform papilla Circumvallate Papilla Connective tissue Tongue epithelium Taste Buds Gustatory cells – Chewed food mixes with saliva respond to chemicals solution slides down to sides of papillae Gustatory hairs – enters taste pore microvilli, protrude through taste stimulate gustatory hairs pore stimulate gustatory receptor cells impulse travels by nerves to brain Figure 8.18 Five Taste Sensations SWEET – sugars, saccharine, salts SOUR -- acids BITTER – alkaloids SALTY – metal ions in solution UMAMI– glutamate, “beef taste” and MSG Only slight differences in receptor location. Most buds respond to 2+ stimuli http://pactlab-dev.spcomm.uiuc.edu/classes/08SP/280blogs/first_weblog3/2008/02/digitizing-your-taste-buds.html Taste Homeostatic role Tastes for salt or sugar – minerals or carbs Sour – Oranges, lemons – Vitamin C Umami – protein intake Bitter – most poisons and spoiled food bitter, protective Factors of Taste Temperature, texture Spicy food excites pain receptors in mouth Taste and Smell Complementary Eating when you have cold Ghost chile pepper from India Heat Exceptionally hot Scoville rating 330,000–1,000,000 liquid Oleoresin Capsicum Loss of Taste & Smell Beginning in 60’s ability to taste and smell diminishes Decrease in # of receptors About 50% over 80 cannot smell Sense of taste is poor Loss of Taste & Smell Various other factors also can contribute to loss of taste and smell, however, including: Nasal and sinus problems, such as allergies, sinusitis or nasal polyps Certain medications, including beta blockers and angiotensin-converting enzyme (ACE) inhibitors Tooth decay or poor dental hygiene Cigarette smoking Head or facial injury Alzheimer's disease Parkinson's disease Impact of LOSS Quality of life, often leading to decreased appetite and poor nutrition Contributes to depression Might tempt you to use excess salt or sugar on your food to enhance the taste — which could be a problem if you have high blood pressure or diabetes Homeostatic Imbalances of the EAR & NOSE Disorder Otitis media (292) Conduction deafness (297) Sensorineural deafness (297) Anosmias (300) Cause Effect Skip 3-4 lines