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Special Senses

Special Senses. Ch 17. The Special Senses. Taste Smell Vision Hearing Balance. Taste. Taste and smell are involved with specific receptor cells called chemoreceptors  . respond to chemicals in an aqueous solution. food dissolved in saliva.

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Special Senses

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  1. Special Senses Ch 17

  2. The Special Senses Taste Smell Vision Hearing Balance

  3. Taste Taste and smell are involved with specific receptor cells called chemoreceptors   respond to chemicals in an aqueous solution food dissolved in saliva airborne chemicals dissolved in mucous membrane

  4. The Tongue

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

  6. Taste Buds

  7. Taste Buds

  8. Five Basic Tastes Why are they important? Salty- metallic ions Umami- savory/meaty Bitter- alkaloid Sour- H+ Sweet- sugar

  9. Experiment Dry tongue with a paper towel and place a little sugar on surface. What do you taste?

  10. Gustatory pathway Facial nerve (afferent) 2/3 anterior portion of tongue Glossophyngeal posterior 1/3 of tongue Vagus nerve- few taste buds on epiglottis an pharynx These afferent fibers synapse in medullathalamus gustatory cortex in parietal lobes and fibers to hypothalamus in limbic system

  11. Tastetriggers reflex involved in digestion; causes an increase of saliva in mouth (amylase) and gastric juice in stomach acids cause strong salivary reflex bad tasting food causes gagging or reflexive vomiting taste can change over time taste is 80% smell Mouth also contains: Thermoreceptors Mechanoreceptors Nociceptors- sensitive nerve fibers that are aware of painful stimuli

  12. Olfaction 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 Old 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

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

  14. Olfaction 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

  15. Cortical Regions Associated with Olfactory Information

  16. Anosmias loss of sense of smell Lose sense of smelllose taste May be genetic or a cold (mucus), allergy, zinc deficiency Uncinate- olfactory hallucinations; may be psychological ex. rotting meat smell Olfactory auras- prior to epileptic attack

  17. sclera tear drainage canal iris pupil The Eye palpabre cornea Lacrimal caruncle lateral commisure Medial commisure palpabre

  18. Pupil bright light normal light dim light

  19. Lacrimal Apparatus FLOW OF TEARS Lacrimal gland Lacrimal ducts Sup. or inf. lacrimal canal Lacrimal sac Nasolacrimal duct Nasal cavity

  20. Extrinsic Eye Muscles Superior oblique Superior rectus opticnerve Medial rectus Inferior oblique Lateral rectus Inferior rectus

  21. Fibrous Tunic Fibrous tunic- sclera and cornea (outer most layer) Composed of dense avascular connective tissue

  22. Vascular Tunic • Vascular tunic- uvea: choroid, cilliary body, iris, pupil (middle layer) • Choroid- rich vascular nutritive layer; contains a dark pigment • that prevents light scattering within the eye • Cilliary body- lens is attached; contains muscles that change the • lenses shape • Iris- pigmented ring of muscular tissue composed of circular • and radial muscles • reflex contraction of circular muscle in bright light (small dia of pupil) • reflex contraction of radial muscle in dim light (large dia of pupil) • Pupil- central hole in iris 

  23. Sensory Tunic • Sensory tunic- retina (inner most layer) • Photoreceptors: • rods (dim light, contains pigment rhodopsin) and • Cones (color vision, not evenly distributed, concentrated in fovea) • Optic disc- blind spot because its where optic nerve leaves the eyeball (no rods or cones) • Macula lutea- yellow spot, area of high cone • Fovea centralis- in center of macula lutea, contains only cones, area of greatest visual acuity

  24. Eye Interior

  25. Vitreous Humor • Vitreous humor- behind lens, gel-like substance with fine collagenic fibrils imbedded in as viscous ground substance- binds with water • transmits light • supports the posterior surface of the lens and holds the neural retina firmly against pigmented layer • contributes to intraoccular pressure, helping to counter act the pulling force of the extrinsic eye muscles

  26. Aqueous Humor • Aqueous humor- in front of lens, anterior segment, watery fluid • Supplies cornea and lens with nutrients • Helps to maintain the shape of the eye • Produced and renewed every 4 hrs by the cilliary body

  27. Aqueous Humor

  28. Lens • Lens- transparent biconvex structure, flexible • Attached by suspensory ligaments to ciliary body • focuses image onto retina • changes lens thickness to allow light to be properly focused onto retina

  29. Focusing the Image • Coarse Fixed Focusing • Cornea Shape • Accommodation- adjust configuration of • Lens Shape • Pupil Size

  30. Properties of Light refraction

  31. Accomodation Focusing on a Near Object

  32. Accomodation Focusing on a Far Object

  33. Refraction Abnormalities • Emmetropia- normal 20:20 • Hyperopia- farsighted • Myopia-near sighted • Presbyopia- mature eyes • Astigmatism 20 ft:20 ft You see Normal vision

  34. Snellan Eye Chart What condition does this person have? What condition does this person have? 20/10

  35. Vision & Corrective Lenses

  36. Vision & Corrective Lenses

  37. Astigmatism

  38. Astigmatism

  39. Cataract Clouding of lens (hardening or thickening causes: diabetes mellitus, smoking, UV damage

  40. Glaucoma

  41. Red-Green Color Blind Test

  42. The Retina blind spot macula

  43. Optic Nerve

  44. photoreceptive cells light Retina Ganglion Amacrine Bipolar neuron Horizontal cells Choroid Schlera

  45. Retina

  46. Retina Rod cell membrane photoreceptors

  47. Formation & breakdown of rhodopsin

  48. Operation of Rod Photoreceptors

  49. Primary Visual Pathway Binocular vision

  50. Primary Visual Pathway

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