Human A&PBIO 304 · American River College ← Week 05 pre-work

BIO 304 · Week 05 · Interactive Workbook

Hearing & Equilibrium

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Part 1 of 4 · Recall

Fill in the blanks

Type the term that completes each statement, using the word bank. Pull it from memory first.

Word bank

AmpullaSacculeBasilar membrane variesStapes → oval windowCochleaHair cells bend → depolarizeHair cellsVestibulo-ocular reflex (VOR)Auricle (pinna)MixedLow-frequency soundsCochlear duct (scala media)BPPVRinne testTympanic membrane (eardrum)

  1. collects and funnels sound
  2. vibrates with sound waves
  3. transmits to fluid-filled inner ear
  4. snail-shaped fluid-filled tube; coiled 2.5 turns
  5. middle chamber; contains organ of Corti
  6. mechanoreceptors; bend → depolarize → release NT
  7. narrow & stiff at base, wide & flexible at apex
  8. displace apex
  9. enlarged base of each canal; contains crista ampullaris (hair cells in cupula)
  10. detects vertical linear acceleration
  11. NT release modulates afferent firing
  12. eyes move opposite head movement to keep gaze stable
  13. both components
  14. air vs bone conduction; AC > BC normally and in sensorineural; BC > AC in conductive
  15. displaced otoliths in semicircular canal; brief positional vertigo

Define it: high-yield vocabulary

Write a clear definition in your own words for each term.

  1. Tympanic membrane
  2. Auditory ossicles
  3. Cochlea
  4. Organ of Corti
  5. Hair cells
  6. Oval window
  7. Eustachian tube
  8. Semicircular canals
  9. Utricle and saccule
  10. Otoliths
  11. Conductive hearing loss
  12. Sensorineural hearing loss

Part 2 of 4 · Anatomy lab

Draw and label

Box A. Outer, middle, and inner ear

Directions

  1. Draw an ear in cross-section from outside to inside. Divide into three regions with vertical lines.
  2. Outer ear (left): pinna (the visible external ear) and external auditory canal leading to the tympanic membrane (eardrum). Label.
  3. Middle ear (center): air-filled space behind the eardrum, containing three tiny bones (the ossicles): malleus, incus, stapes. Label each. Show the stapes contacting the oval window of the cochlea.
  4. Inner ear (right): draw the cochlea as a snail-shell spiral (fluid-filled, handles hearing). Above it, draw the three semicircular canals (orthogonal loops) and the vestibule (linear motion). Label all four structures.
  5. Add the Eustachian tube connecting the middle ear to the throat (pressure equalization).
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Box B. Organ of Corti close-up

Directions

  1. Draw a cross-section of the cochlear duct showing the organ of Corti sitting on the basilar membrane.
  2. Label the basilar membrane (under the hair cells, vibrates at different frequencies along its length).
  3. Draw hair cells: a single row of inner hair cells (the main sensory cells) and three rows of outer hair cells (amplifiers). Label.
  4. Show stereocilia (hair-like projections) on top of each hair cell, contacting the tectorial membrane above. Label both.
  5. Show the cochlear nerve fibers leaving the base of the hair cells.
  6. Note the principle: when the basilar membrane vibrates, the stereocilia bend against the tectorial membrane, opening ion channels in the hair cell, leading to neurotransmitter release.
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Structures to label

Label each on your drawing.

  1. Pinna
  2. External auditory canal
  3. Tympanic membrane
  4. Malleus
  5. Incus
  6. Stapes
  7. Oval window
  8. Cochlea
  9. Vestibule
  10. Semicircular canals
  11. Eustachian tube
  12. Basilar membrane
  13. Tectorial membrane
  14. Inner hair cell
  15. Outer hair cell
  16. Stereocilia
  17. Cochlear nerve

Part 3 of 4 · Physiology lab

Reason it through

A. Trace: sound wave to action potential

Explain the main structure-function relationship for this topic.

B. Synthesis

1. A patient has conductive hearing loss (e.g., a fluid-filled middle ear from an infection). Explain mechanistically why sound transmission fails, and contrast with sensorineural hearing loss (damaged hair cells or cochlear nerve).
2. A passenger gets out of a spinning teacup ride and feels dizzy. Explain what is happening in their semicircular canals during and just after the spin, and why the world appears to keep moving even after they've stopped.
3. High-frequency sounds are detected near the BASE of the cochlea, while low-frequency sounds are detected near the APEX. Explain how the basilar membrane's structural properties produce this 'tonotopic' map.

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