2. Scala vestibuli
Scala media
Scala tympani

4. Stereocilia with mechanically-gated K+ channels
Open K+ channels
Depolarize
Open Voltage-gated Ca++ channels
Release of NT from synaptic vesicles

5. Activity of Hair Cells Depolarization leads to more NT release
Bend toward basal bodie or Kinocilium .....depolarization.
Note baseline level of activity.
Note action potentials in first order sensory neurons.
Depolarization leads to more NT release
Hyperpolarization leads to less NT release

6. All hair cells nearly identical
Basilar membrane thickens toward the apex

7. Base
Apex

8. Coding for Pitch = _________ = _______ & Intensity
Base .... high pitch (treble)
Apex .... low pitch (bass)
Pitch coded by _____________________________________________________________________________________________________________________________
Intensity coded by ____________________________________________________________________________________________________

9. Auditory Range
Humans: __________________Hz; optimal ____________ Hz

10. Audiogram
Decibel = unit for expressing relative loudness on a log scale
“Nerve deafness” cause by _____________________.

11. Fourier Analysis of Complex Waves
                     
Pure sine waves

12. Pathway to Temporal Lobe
In Brainstem
Organ of
Corti Hair
Cells
Cochlear
Ganglion =
Spiral
Ganglion
Superior
Olive
Cochlear
Nuclei
MG of
Thalamus
Auditory
Cortex

13. Sound Localization Low frequency by : High frequency by :
Practical Applications?

14. Tonotopy in Auditory Cortex

15. Organs of Equilibrium

16. Semicircular Canal

17. Utricle and Saccule

18. Vestibular Apparatus Hair cells
NT release dependent upon degree of bending of kinocilium and microvilli
For ampula of semi-circular canals: cupula
For utricle and saccule: otolith membrane
Stereocilia in Endolymph (Hi K+, low Na+)
A generalized hair cell
Specialized epithelial cell for transducing mechanicl to electrical
Has synaptic vesicles with basal level of release
also recieves synapses
Stereocilia bathed in endolymph (High K+, low Na+) secreted by
stia vascularis
Gradient favors K+ entry
Tips of stereocilia embedded in a gelatinous matrix.
Mechanical channels, at rest partially open, change degree of opening depending upon degree of bending of stereocilia.