The Ear S2M1

  1. Sensory input from the vestibular cochlear apparatus is transmitted to the brain via
    • Vestibulocochlear nerve (CN VIII)
    • (Balance and hearing)
  2. What determines the pitch of sound
    Frequency of waves measured in Hz
  3. What determines the loudness of a wave and how is it measured
    Amplitude measured in decibels
  4. 10 Decibels is how large of an increase
    10 Fold
  5. Safe exposure to sound is suggested to be what
    85 dB for eight hours a day
  6. The external auditory meatus (external acoustic canal) has what covering it
    Skin containing hair follicles, sebaceous glands, and modified sweat glands called ceruminous glands
  7. What do the ceruminous glands secrete
    A waxy material called cerumen
  8. The external surface of the typanic membrane (eardrum) is covered by what
    Thin epidermis derived from ectoderm
  9. The internal surface of the typanic membrane is composed of what type of cells, derived from where
    Simple squamous/cuboidal epithelium derived from endoderm
  10. What lies between the internal and external surface of the typanic membrane
    A thin layer of mesodermal elements (collagen, elastic fibers, fibroblasts)
  11. The middle ear is filled with
  12. The middle ear communicates anteriorly with the pharynx via
    Eustachian tube
  13. The ossicles connect the tympanic membrane to what
    Oval window
  14. What bones make up the ossicles from lateral to medial
    • Malleus
    • Incus
    • Stapes
  15. What is the smallest bone in the body
    Stapes, the size of a grain of rice
  16. What senses sound vibrations
  17. What senses head position (gravity)
  18. What senses head rotations
    Semicircular canals
  19. What is used for balance
    Vestibular apparatus (Vestibule + Semicircular canals)
  20. Bony Labyrinth
    A series of spaces within the temporal bone covered by periosteum that houses the membranous labyrinth
  21. The membranous labyrinth is composed of
    Continuous epithelium lined cavities of ectodermal origin
  22. What lies between the bony labyrinth and the membrane
    Perilymph (similar to extracellular fluids)
  23. What is inside the membranous labyrinth
    Endolymph, composed of low sodium and high potassium (like intercellular fluid)
  24. What is in the membranous labyrinth that detects hearing and balance
    Hair cells
  25. What is the purpose of the Maculae of the vestibule
    They detect vibrations from tilts of the head
  26. What does the maculae contain
    Utricle and a Saccule (2 clumps total)
  27. What areas of the ear are hair cells found
    • Organ of Corti
    • Vestibule
    • Semi circular canals
  28. How are the hair cells distributed in the semicircular canals
    There are three clumps of hair, 1 per semicircular canal in the ampulla
  29. How do the hair cells in the semicircular canals and maculae differ from those in the cochlea
    • Semicircular canals and maculae have one kinocilium and many stereocilia
    • Cochlea have no Kinocilium in the adult hair cell
  30. How are the hair cells organized in the semicircular canals and maculae
    • The one kinocilium has a 9+2 array of microtubules
    • Many Stereocilia, each contain 50-100 actin arranged in rows the longest are next to the kinocilium
  31. Where is the longest stereocilia
    Next to the Kinocilium
  32. How are the hair cells arranged in the Cochlea
    3 rows in the outer layer and 1 row in the inner
  33. What hair cell sprouts first
    Kinocilium, then the stereocilia surround them
  34. What are the two continuous tubes in the Cochlea that contain perilymph
    • Scala vestibuli
    • Scala tympani
  35. What lies between the scala vestibule and scala tympani in the cochlea
    Cochlear duct/Scala media which contains endolymph
  36. What makes up the Organ of Corti
    Tectorial membrane lying on the inner and outer hair cells which are imbedded in supporting cells all of which are sitting on a basilar membrane
  37. The outer hair cells in the Organ of Corti are positioned where and why
    They are in the middle of the Basilar membrane where the movement stimulated by sound is the greatest
  38. Where are the inner hair cells situated and why
    They lie close to the nerves, and they change the movement of the tectorial membrane into nerve impulses
  39. What is the tectorial membrane made up of
    It is essentially a Glycoprotein rich secretion
  40. What happens for the hair cells to open channels allowing an influx of positive charge depolarizing them
    When the rock to the side of the kinocilium due to sound waves, they pull on a thin filament at their tips and tug open the channels
  41. How many hair cells are present in the cochlea at birth
    3500, they are not replaced
  42. Hair cells are not neurons but
    They secrete neurotransmitters (Glutamate) that stimulate nerves
  43. Stria vascularis
    • Found in the Scala media wall
    • Vascularized epithelium containing ion and water transporting cells that give endolymph its unusual composition
  44. High frequency sounds selectively vibrate
    The basilar membrane of the inner ear near the oval window
  45. Low frequencies are detected where
    At the end of the basilar membrane
  46. Where is Endolymph stored
    Endolymphatic sac and the Endolymphatic duct
  47. What does the endolymphatic sac attach to
    One end to the Saccule and the other to the Utricle of the Vestibular apparatus
  48. What are the maculae
    Clusters of hair cells in the saccule and utricle
  49. Otolith organs
    • Saccule and Utricle
    • These detect the force of gravity and tilts of the head
  50. How are the saccule and utricle oriented
    • Saccule - Vertically
    • Utricle - Horizontally
  51. Otoliths (Otoconia)
    • Calcium carbonate crystals that cover the gelatinous membrane, which blankets the Stereocilia and Kinocilium
    • They are like the rocks that force the gelatine towards the pull of gravity
  52. What causes the vestibular nerve fibers to depolarize
    When the hair cells are bent towards the Kinocilium increasing the rate of firing
  53. What causes the vestibular nerve fibers to hyperpolarize
    When the hair cells are bent away from the Kinocilium reducing the rate of firing
  54. What are the hair cells called in the semicircular canals
    Cristae Ampullaris (found in only at the ends of the 3 semicircular canals in the ampulla)
  55. What is the function of the cristae ampullaris
    To sense angular acceleration and deceleration
  56. Cupula
    Gelatinous structure containing the hair cells in the Ampulla of the semicircular canals
  57. Otoliths are not found in the
    Crista Ampullaris or Organ of Corti, but is in the Macula (Saccule & Utricle)
  58. What senses in the ear do not use Otoliths
    • Sound (Organ of Corti)
    • Head rotation (Ampulla)
  59. What connects the endolymph in the saccule to the cochlea
    Ductus reuniens
Card Set
The Ear S2M1