Hearing

Question 1

the external and middle ear are filled with what?

Answer 1

With Air

*inner ear is filled with fuid

Question 2

What two nerves are associate with the inner ear?

Answer 2

facial nerve, Vestibulocochlear nerve

Question 3

Describe the process of sound transduction

Answer 3

• Vibrations of the tympanic membrane are transmitted to the inner ear through the three auditory ossicles: the footplate of the stapes is pushed into the oval window
• This movement displaces the fluid within the scala vestibuli, a tubular structure of the inner ear
• The pressure wave is transmitted through the basilar membrane of the cochlea to the scala tympani
• This causes the round window to bulge into the middle ear

Question 4

what organ is responsible for the transduction of sounds?

Answer 4

The organ of Corti = the epithelium layer

Question 5

What is impedence matching?

Answer 5

amplifying of pressure waves (like during whispering) up to 10-20dB- so we convert pressure waves in air to pressure waves in fluid

it depends on

– Ratio of surface area of tympanic membrane to that of the oval window

–Mechanical advantage of the lever system formed by the ossicle chain

Question 6

Movement of what membrane below the hair cells - allows for signal transduction in the inner ear?

Answer 6

the basilar membrane moves and causes the cilia of the outer hair cells to bend- this causes a change in cation conductance in the apical ends of the hair cells - this causes a change in membrane potential

Question 7

what are some causes of deafness?

Answer 7

conduction deafness= impaired sound transmission due to wax/foreing body or perforated typanic membrane in the external/middle ear

sensorineural deafness= loud sound, vascular lesions, drug toxicity - typically hair cells in certain parts of the cochlea are selectively damaged - diagnosed by audiometry

Question 8

What are the Weber and Rinne tests?

Answer 8

Weber Test = evaluates lateralization - use vibrating tuning fork on top of patient’s head and ask patient where he hears it (one or both sides)- tests bone transduction - in an effected ear your overcompensating for a blockage of some sort and by bypassing air conduction and just using bone conduction, we actually hear better on effected side

Rinne Test = evaluates air and bone conduction - place base of a vibrating tuning fork on the mastoid process til patient can no longer hear sound- then quickly move tuning fork near ear canal - ask patient if he hears it and compare hearing times - if normal, air conduction should be greater than bone conduction- but if there is hearing deficiency, the bone conduction will be greater than air conduciton

Question 9

what part of the cochlea acts as a frequence analyser?

Answer 9

the basilar membrane

it distributes the stimlus along the oran of corti so that different hair cells will respond to different frequencies of sound - high frequencies are best detected at the base, lower frequencies at the apex of the cochlea

Question 10

the semicircular ducts are responsible for what acceloration?

Answer 10

horizontal, superior and posterior acceleration

Question 11

what are the otolith organs responsible for?

Answer 11

utricle and the saccule are important for your linear accelerations- they contain calcium crystals that effect hair cells

Question 12

describe the depolarization/hyperpolaization trends of the hair receptors in your inner ear

Answer 12

movement in opposite directions exibit opposite polarization effects leading to decaresed or incrased frequency of the nerve impulses - giving signal

Question 13

What is Meniere’s Disease?

Answer 13

• unilateral nerve deafness
• tinnitus = ringing in affected ear
• abnormal eye movements (nystagmus)
• vertigo, ataxia, vomiting
• caused by buidup of endolymph and/or reduction in blood flow to the ear