Special Senses: Hearing, Taste, Smell

1. Special Senses: Hearing, Taste, Smell Peripheral Nervous System Chapter 8

2. 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 Senses

3. 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 Crash Course: Hearing & Balance

4. Anatomy of Ear HEARING & BALANCE HEARING ONLY

5. Anatomy of Ear Why do we need earwax??? Earwax protects delicate lining of meatus (auditory canal) and helps prevent microorganisms from entering the ear • Divided into 3 regions: • External, Middle, Internal • External Ear • Auricle (pinna) and Auditory Canal • Ceruminous Glands in canal secrete earwax • Tympanic membrane - eardrum

6. 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

7. Otitis media • 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 http://www.petearclinic.com/images_video.htm http://apps.uwhealth.org/health/hie/2/19596.htm

8. 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

10. Hearing Sound waves > external acoustic meatus eardrum vibrates > ossicles set into motion > oval window on vestibule > set fluid in motion > vibrations stimulate “hair cells” in cochlea> vestibulocochlear nerve transmits impulse to midbrain > auditory cortex of temporal lobe Within Cochlear duct, membranous labyrinth is Spiral Organ of Corti – hearing receptors or “hair cells” Figure 8.15

11. Cochlear HAIR CELLS Determine volume and pitch Volume = the higher the volume, the more hair cells are stimulated Pitch = the higher the pitch, the faster they move and the lower the pitch, the slower they move

12. How the ear works… http://www.youtube.com/watch?v=dCyz8-eAs1I What is a cochlear implant? https://www.youtube.com/watch?v=zeg4qTnYOpw Cochlear implants https://www.youtube.com/watch?v=6FhgYcfZZY8

13. 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.

14. 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 Crash Course: TASTE & SMELL

15. Facts About Smelling • 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

16. How the nose works… http://www.youtube.com/watch?v=dIDBG-UPRUI

17. Olfactory epithelium Olfaction Olfactory tract Olfactory bulb Nasal conchae Route of inhaled air (a) Figure 15.21a

18. 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

19. Mitral cell (output cell) Olfactory tract Glomeruli Olfactory bulb Cribriform plate of ethmoid bone Filaments of olfactory nerve Lamina propria connective tissue Olfactory gland Axon Basal cell Olfactory receptor cell Olfactory epithelium Supporting cell Dendrite Olfactory cilia Mucus Route of inhaled air containing odor molecules (b) Figure 15.21a

20. 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

24. Taste Buds and Taste • Most pleasurable sense • Approx. 10,000 taste buds, most on tongue • Papillae – projections that hold taste buds • Circumvallate papillae – back of tongue; taste buds on sides • Fungiform papillae – top of tongue; taste buds on sides; more numerous • Filiform papillae – sides of tongue; taste buds on top Figure 8.18

25. How the tongue works… https://www.youtube.com/watch?v=KuP-Kj7MHes

26. Taste Buds Filiform papilla Fungiform papilla Circumvallate Papilla Tongue epithelium Connective tissue

28. Taste Buds • Chewed food mixes with saliva • solution slides down to sides of papillae • enters taste pore • stimulate gustatory hairs • stimulate gustatory receptor cells • impulse travels by nerves to brain • Gustatory cells – respond to chemicals • Gustatory hairs – microvilli, protrude through taste pore Figure 8.18

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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

35. Flavor Lab See instructions on worksheet

36. Homeostatic Imbalancesof the EAR & NOSE