Special senses blog

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Special senses blog

  1. 1. The Special Senses
  2. 2. Vision <ul><li>Our dominant sense </li></ul><ul><li>Estimated 70% of all sensory receptors are in the eyes </li></ul><ul><li>Believed over 50% of cerebral cortex is used for visual processing </li></ul><ul><li>The eye has a diameter around one inch </li></ul><ul><li>Eyebrows …. Function? </li></ul><ul><li>Keep sweat from dripping in your eyes </li></ul><ul><li>Eyelids & eyelashes - protection </li></ul>
  3. 3. Accessory Eye Structures: <ul><li>Tarsal glands: </li></ul><ul><li>Lubricates eyelids/prevents from sticking to eye </li></ul><ul><li>Conjunctiva: </li></ul><ul><li>Transparent mucous membrane; prevents eye from drying out </li></ul><ul><li>Caruncle - produces “Sand Man’s Eye Sand” </li></ul><ul><li>Lacrimal apparatus: </li></ul><ul><li>Lacrimal gland, lacrimal canal, lacrimal sac, nasolacrimal duct </li></ul><ul><li>Lysosyme - destroys bacteria </li></ul><ul><li>Tears - why do we cry?? </li></ul>
  4. 4. The Fibrous Tunic <ul><li>Dense avascular connective tissue </li></ul><ul><li>Sclera: White portion of eye. Dense irregular c.t. </li></ul><ul><li>Cornea: Clear portion of eye. Dense regular c.t. </li></ul><ul><li>Very tough material </li></ul><ul><li>Needs a blood supply….but from where?? </li></ul>
  5. 5. The Vascular Tunic <ul><li>Choroid: Includes blood vessels. Nourishment </li></ul><ul><li>Ciliary bodies - holds suspensory ligaments </li></ul><ul><li>Suspensory ligaments - holds lens </li></ul><ul><li>Iris - colored part of eye; smooth muscle forms pupil </li></ul>
  6. 6. The Sensory Tunic <ul><li>The retina: </li></ul><ul><li>Image we see projected onto it </li></ul><ul><li>Image is upside down, brain must flip it </li></ul><ul><li>Optic disc is blind spot </li></ul><ul><li>Optic nerve attaches here </li></ul>
  7. 7. The Lens <ul><li>Biconvex </li></ul><ul><li>Avascular…why?? </li></ul><ul><li>Contains crystalline proteins (crystallins) </li></ul><ul><li>Convert sugar to energy for use by the lens </li></ul><ul><li>New fibers added continually through life </li></ul><ul><li>Lens gets bigger and harder to see out of </li></ul><ul><li>Cataracts - most occur from age </li></ul><ul><li>Also from diabetes, smoking, UVB radiation </li></ul>
  8. 8. The Humors <ul><li>Vitreous humor: fills most of the space inside the eye </li></ul><ul><li>Posterior to lens </li></ul><ul><li>Made of collagen and ground substance </li></ul><ul><li>Transmits light, supports lens and retina, contributes to good eye pressure </li></ul><ul><li>Formed in embryo, lasts a lifetime </li></ul><ul><li>Aqueous humor: fills space anterior to lens </li></ul><ul><li>Continually drains (and produced back at the same rate) </li></ul><ul><li>Glaucoma can result if drainage is blocked </li></ul><ul><li>Too much pressure damages optic nerve </li></ul>
  9. 9. Rods & Cones <ul><li>Rods: Dim light and peripheral vision receptors </li></ul><ul><li>Cones: Operate in bright light </li></ul><ul><li>Cones provide high-acuity color vision </li></ul>
  10. 10. Homeostatic Imbalances <ul><li>Myopia: </li></ul><ul><li>Also called “nearsightedness” </li></ul><ul><li>Can see close objects without a problem </li></ul><ul><li>Occurs from an eyeball that’s too long </li></ul><ul><li>Hyperopia: </li></ul><ul><li>Also called “farsightedness” </li></ul><ul><li>Can see objects farther away </li></ul><ul><li>Occurs from an eyeball that’s too short </li></ul>
  11. 11. Taste & Smell <ul><li>Why do we taste? </li></ul><ul><li>To test/judge our environment </li></ul><ul><li>Taste & smell are linked together </li></ul><ul><li>Taste vs flavor…? </li></ul><ul><li>Taste is limited to four basic sensations </li></ul><ul><li>Flavor is what we associate with taste </li></ul><ul><li>“ This tastes good!!” … statement is flawed! </li></ul><ul><li>Tasting food = 80% smell. </li></ul><ul><li>Smell/taste is genetically hardwired into us! </li></ul>
  12. 12. Taste Buds <ul><li>Called “papillae” </li></ul><ul><li>Two major types: </li></ul><ul><li>Fungiform papillae- small, mushroom-shaped </li></ul><ul><li>Scattered over entire tongue surface </li></ul><ul><li>Most abundant on tip and sides </li></ul><ul><li>Taste receptors ON TOP OF these papillae </li></ul><ul><li>Circumvallate papillae - largest, least numerous </li></ul><ul><li>Form inverted “V” at back of tongue </li></ul><ul><li>Taste receptors ON THE SIDES OF these papilla </li></ul>
  13. 13. Taste Sensations <ul><li>Sweet - detect carbohydrates; mother’s milk is sweet </li></ul><ul><li>Salty - satisfies body’s need for minerals, helps nervous & muscular system </li></ul><ul><li>Sour - possibly for vitamin detection </li></ul><ul><li>Bitter - poison detector! </li></ul>
  14. 14. Taste Bud Anatomy <ul><li>Each consists of 40-100 epithelial cells of three major types: </li></ul><ul><li>Supporting cells - form majority of taste bud </li></ul><ul><li>Receptor (gustatory) cells - insulated by supporting cells </li></ul><ul><li>Basal cells - act as stem cells </li></ul><ul><li>Taste bud cells shed every 10-14 days! </li></ul><ul><li>Taste buds also include gustatory hairs extending through taste pores </li></ul>
  15. 15. Structures of the Ear <ul><li>Outer Ear: </li></ul><ul><li>Includes auricle (pinna), lobule, external auditory canal, and tympanum </li></ul><ul><li>Canal lined with cerumen </li></ul><ul><li>Tympanum responsible for transmitting vibrations </li></ul>
  16. 16. <ul><li>Middle Ear: </li></ul><ul><li>Includes malleus, incus, stapes </li></ul><ul><li>Small bones which transmit vibrations to inner ear </li></ul><ul><li>Also called hammer, anvil, stirrup </li></ul>
  17. 17. <ul><li>Inner Ear: </li></ul><ul><li>Cochlea - includes spiral organ of Corti, and sensory hairs </li></ul><ul><li>Semicircular canals - help with balance! </li></ul>
  18. 18. Homeostatic Imbalances of the Ear <ul><li>Conduction deafness: </li></ul><ul><li>Ear canal is blocked </li></ul><ul><li>Sensorineural deafness: </li></ul><ul><li>Permanent hearing loss/damage </li></ul><ul><li>Tinnitus: </li></ul><ul><li>Constant ringing in your ears </li></ul>
  19. 19. Frequencies and Loudness <ul><li>Range of hearing is between 20-20,000 Hz </li></ul><ul><li>Most sensitive between 1500-4000 Hz </li></ul><ul><li>Loudness measured in decibels (dB) </li></ul><ul><li>Logarithmic in nature </li></ul><ul><li>Normal conversation = 50 dB </li></ul><ul><li>Noisy restaurant = 70 dB </li></ul><ul><li>Danger zone = 90 dB and above </li></ul><ul><li>Rock concert = 120 dB </li></ul><ul><li>Pain threshold = 130 dB </li></ul>

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