PHRM 100 Lecture 7: APPP 7: Vestibular/Auditory Systems
7. Vestibular/Auditory Systems
Hearing
External Ear (auricle/pinna)
- Collects sound waves from external acoustic meatus → tympanic membrane
(eardrum)
- Energy of sound wave converted to vibration (Ek)
Middle ear (ear ossicles)
- Amplify vibrations
- Malleus, Incus, Stapes (prevents excess movement)
- Filled with air
- Auditory tube opened during yawning/swallowing (balance pressure)
Inner Ear
- Vestibule: central portion which stapes vibrates again
- Cochlea: transforms sound
Balance
Parts of the inner ear:
Semicircular canals – sense rotation of the head
Utricle & Saccule
- otolith organs: keeps your sense of balance
- sense gravity
and linear movements of the head
Hair cells – bathed in endolymph (potassium rich low sodium fluid)
Vestibular Apparatus: detects head motion
Vestibular Nuclei: maintain body position in space
Vertigo (眩暈): perception of rotation in the absence of actual movement
Vestibulotoxicity: ataxia, dysequilibrium, oscillopsia
Chocleotoxicity: loss of response to high frequency sound (affect outer hair cells more)
Recall: DIE test
Innermost hair cells die before peripheral hair cells.
Central Pathway for Sound
Inferior colliculus → medial geniculate body (thalamus
) → auditory cortex (temporal lobe)
Direction of sound: determined by time difference and loudness
