Chapter 10 phys part 2 - ears

human ranges for frequency and loudness

20-20,000, 0-80 decibels

Bones of the ear in order

Malleus, incus, stapes

Layers of the cochlea from upper to lower and fluid in each

Scala vestibuli (perilymph), scala media (endolymph), scala tympani (perilymph)

Where are steriocilia located

On basilar membrane in cochlear duct

inner hair cell numbers and function

Each one is innervated by 6-20 sensory neurons from nerve VII, one row is 3500, they relay sound

Outer hair cell numbers and function

11,500 arranged in rows with 3 rows per turn, innervated by motor neurons that make them shorten when depolarized and elengate when hyperpolarized, they amplify sound

Where are low frequency vs high frequency sounds transmitted through cochlea

Low frequency go deeper to apex, high frequencies are closer to the base

What are steriocilia embedded in

Tectorial membrane

How hearing works steps

Tectorial membrane vibrates which bends steriocilia, opens K+ channels facing endolymph, K+ influx depolarizes cell, the cell releases glutamate to neuron, K+ passively returns to perilymph

what does more bend in steriocilia and more displacement in basilar membrane do

Increases frequency of AP’s, increases amount of glutamate released

How does pitch perception work

hair cells closest to where vibrations are displaced into scala media are stimulated more often

Neural pathway of hearing

Vestibulocochlear nerve, cochlear nuclei in medulla and pons, inferior colliculi, medial geniculate body of the thalamus, auditory cortex of temporal lobe

Which areas of hearing neural pathway are tonotopic

Cochlear nuclei and auditory cortex

When sound waves are not conducted from outer to inner ear

Conduction deafness

When nerve impulses are not conducted from cochlea to auditory cortex

Sensorineural deafness

Age related hearing impairment

Presbycusis