Role of hair cells

Differences between IHC and OHCs

• number

• innervation

• function

• vulnerability

Type 1 afferents make up (innervation)

• 95% of all spiral ganglion neurons

Our inner hair cell is innervated by

• 5-30 afferent nerve fibers

Most the information about the acoustic world reaches the brain

• via the inner hair cells

The auditory efferent system

• provides feedback to outer hair cells that helps regulate hearing sensitivity & protects hearing from intense noise

How many outer hair cells does an average person have?

12,500

Otoacoustic emissions

• this pointed to a source of energy being generated inside the cochlea

Function of the IHCs

• Inner hair cell’s primary function is to translate sound waves into electrical signals for the brain to interpret

Inner hair cells main job is to

• send information from the Organ of Corti to the brain

Function of the OHCs

• outer hair cells also generate force to improve auditory sensitivity and frequency selectivity

Inner hair cells primarily make up the

afferent system

Outer hair cells primarily make up the

efferent system

Electromotility

• change in the length of the OHC in response to changes in the electrical potential of the cell

  • increases the displacement of the traveling wave

OHC motion causes an increase in the intensity of sound at the cochlea

• it acts as a cochlear amplifier

OHCs are more susceptible to

• damage from noise exposure and ototoxic medications

Damaged OHCs leads to…

• hearing loss and reduced frequency selectivity

Cochlear amplifier

• it’s amplifying vibrations

Frequency selectivity

• OHC are connected to the basilar membrane tonotopically, if outer hair cells at the spot assigned is moving up and down and creating more energy, it makes the inner hair cell produce more information to the brain

Are Inner hair cells connected to the tectorial membrane?

• No, they are not connected but the outer hair cells ARE connected

What part of the vestibular system is responsible for forward/ backward (horizontal) acceleration?

• Utricle

When calcium crystals (otoconia) get dislodged

• you can become dizzy, have vertigo

Vestibular system

• detects changes in the head (movements)

Vestibular organs also

• have hair cells

Otoconia sit in a

gel like substance