1. Special Senses: Hearing & Balance
Review Ear anatomy
Sensory organs for
Hearing: _____________
Balance: Otolith organs (saccule and utricle) and 3 semicircular canals
Organ of Corti
Fig

2. Sound transmission Sound waves Tympanic membrane vibrations
Ossicles transmit & amplify vibration
Via oval window to perilymph then endolymph 1

3. cont. Vibrations in endolymph stimulate receptor cells
NT release of receptor cell stimulates nearby sensory neuron
Impulse to auditory cortex of temporal lobe via ________________ nerve
Fig 10-18 2

4. Interpretation of Sound Waves: Pitch Perception
Sound wave frequency expressed in Hertz (Hz) = wavelength / sec
Human can hear between 20 and 20,000 Hz
High pitch = high frequency
Low pitch = low frequency
Tone = pure sound of 1 frequency (e.g. tuning fork)

5. Basilar Membrane Pitch perception is function of basilar membrane
BM stiff near oval window
BM more flexible near distal end
Brain translates location on membrane into pitch of sound
→Temporal aspects of frequency are transformed into spatial coding
→ Spatial coding is preserved in auditory cortex

6. Effects of different sound pitches on the basilar membrane
Fig 10-20

8. Interpretation of Sound Waves: Loudness perception
Rate at which APs are fired   loudness 
Sound Intensity Measurement:
Decibel Scale (dB) starts at 0 and is logarithmic
130 dB pain threshold
> 80 dB frequently or prolonged  ?
Examples:
noisy restaurant ~ 70 dB
rock concert ~ 120 dB

9. conductive hearing loss sensorineural hearing loss
Hearing loss that results from damage to the structures of the inner ear is called _________.
central hearing loss
conductive hearing loss
sensorineural hearing loss

10. Three Types of Hearing Loss
Conduction deafness: Damage to _______or _______ear. Many possible etiologies (?)
Sensorineural (perceptive) deafness: Damage _______ear. Most common: gradual loss of receptor cells
Central deafness: Damage to _____________ or cortical cells.
Age related: ________________
Presbycussis
External or middle ear. Otitis media, otosclerosis etc….
Inner ear
Neural pathways
Fig 10-21 3

11. near the stiff and narrow proximal end
Low frequency sound waves create the maximum displacement ______________________ of the basilar membrane.
near the stiff and narrow proximal end
near the flexible and wide distal end
in the middle
near the oval window
both A) and D) are correct b

12. taller more frequent less frequent shorter broader
Louder noises result in ____________ action potentials in the sensory neuron
taller
more frequent
less frequent
shorter
broader

13. Equilibrium = State of Balance
Utricle and saccule (otolith organs) with maculae (sensory receptors) for linear acceleration and head position
Semicircular canals and ampullae with cristae ampullaris (sensory receptors) for rotational acceleration
Important besides inner ear: input from vision & stretch receptors in muscle

14. Motion Sickness Due to sensory input mismatch = Equilibrium disorder
Not in book
Motion Sickness
= Equilibrium disorder
Due to sensory input mismatch
Example?
Antimotion drugs (e.g.: Dramamine):
Depression of vestibular inputs 4