Scala vestibuli Scala media Scala tympani
Stereocilia with mechanically-gated K+ channels Open K+ channels Depolarize Open Voltage-gated Ca++ channels Release of NT from synaptic vesicles
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
All hair cells nearly identical Basilar membrane thickens toward the apex
Base Apex
Coding for Pitch = _________ = _______ & Intensity Base .... high pitch (treble) Apex .... low pitch (bass) Pitch coded by _____________________________________________________________________________________________________________________________ Intensity coded by ____________________________________________________________________________________________________
Auditory Range Humans: __________________Hz; optimal ____________ Hz
Audiogram Decibel = unit for expressing relative loudness on a log scale “Nerve deafness” cause by _____________________.
Fourier Analysis of Complex Waves Pure sine waves
Pathway to Temporal Lobe In Brainstem Organ of Corti Hair Cells Cochlear Ganglion = Spiral Ganglion Superior Olive Cochlear Nuclei MG of Thalamus Auditory Cortex
Sound Localization Low frequency by : High frequency by : Practical Applications?
Tonotopy in Auditory Cortex
Organs of Equilibrium
Semicircular Canal
Utricle and Saccule
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.