HEARINGby: Michelle Hwang, Natasha

Kurien, & Cameron ProctorPeriod 4B

Sensory Receptors The receptors of the ear are the

mechanoreceptors. These receptors respond to physical

forces such as gross movements that disturb fluids that are around the balance organs

Even though balance and hearing are housed in the ear, their receptors work independently of each other

Sensory Receptors The Spiral organ of Corti is located in the cochlear duct

The hair cells located in the spiral organ of Corti are the hearing receptors

The cochlear duct has chambers above and below it containing perilymph (extracellular fluid)

Sound enters through the external ear Sound waves are vibrated through eardrums, ossicles and oval

window. They then reach the cochlea and set cochlear fluids in motion.The ossicles increase the amplitude of the sound waves so

that the large force can reach the small window . It cause the three bones, incus(hammer), stirrup(malleus) and stapes(anvil) to span the tympanic cavity or the middle ear

This causes the inner ear’s fluid to vibrate and then the waves of the fluid causes the basilar membrane to vibrate

The vibrations cause the gel-like tectorial membrane to move which then stimulates the hair receptor cells by bending or tweaking them

Cochlear Duct and Spiral Organ of Corti

Sensory Receptors (continued)

The fibers of the basilar membrane “tunes” different regions to reverberate at specific frequenciesHigh pitched frequencies disturb short

fibers that are located close to the oval window, but low pitched frequencies disturb long fibers that are located further along the cochlea

From Hair Receptors to the Brain

The stimulated hair cells send impulses along the cochlear nerve› The cochlear nerve is part of the cranial nerve VIII

or the vestibulocochlear nerve) The impulse is taken to the auditory cortex of

the temporal lobe of the brain This is where interpretation of sound/ hearing

happens Our two ears hear sound at different times or

“in stereo”. This helps us locate the location from which the sound is coming from.

Disorders

Conduction deafness- when something such as ear wax buildup interferes with sound vibrations reaching the fluid of the inner ear

Sensorineurial deafness- when there is some damage to the hair receptor cells in the spiral organ of Corti, the cochlear nerve, or the auditory cortex neurons. This damage can be caused by loud sounds