Ears 3

Question 1

conduction deafness

Answer 1

When there is a problem conducting sound waves along outer ear (cerumen build up, otitis externa), tympanic membrane (perforated), or middle ear (otitis media with effusion, ossicles stiffening).

Question 2

Nerve Deafness

Answer 2

(sensorineural hearing loss)
When problem occurs in inner ear (tumor), cochlea (presbycusis), auditory nerve, or the brain.
Cause in cochlea: Death of hair cells or distorted / destroyed stereocilia from loud noise, disease, or toxins (quinine, some antibiotics).

Question 3

noise-induced hearing loss

Answer 3

2nd most common hearing loss after Presbycusis.
85 dB for 8 hrs causes permanent hearing loss (for every increase by 5 dB, noise exposure time cut in half to cause hearing loss)
Loud sounds bend the stereocilia, but they can recover. However, repeated bending can cause destruction or permanent bending.
Audiograms (hearing test) – trouble hearing treble tones and higher frequencies. Shape of Pinna has natural resonance at higher frequencies, which amplifies sounds at higher frequencies, leading to more hearing loss in these higher frequencies. Tinnitus is a side effect (Ex. After loud concert)

Question 4

tinnitus

Answer 4

Hearing a ringing, buzzing, or other sounds when no external sound is present.
Phantom noise can be in one or both ears, present all the time or it may come and go. Annoyance or very disruptive.
Cause may not be found, age related hearing loss and brain forms a sound, exposure to loud noises, earwax blockage that irritates the eardrum, otosclerosis of ear ossicles, head or neck injuries, some medications, or turbulence in the carotid artery or jugular vein.
If stereocilia are damaged they may move randomly, sending electrical impulses to your brain which is interpreted as noise.
Treat using device that constantly produces sound in the affected ear.

Question 5

cochlear implant function and parts

Answer 5

medical device that replaces the function of the inner ear, acts like cochlea for sound transduction.
Does not restore hearing but allows person to get a representation of the sounds in their environment.
Microphone
Speech processor
Transmitter and Receiver & Stimulator
Electrode array

Question 6

Microphone cochlear implant

Answer 6

picks up sound

Question 7

Speech processor cochlear implant

Answer 7

– selects, filters, and arranges sounds picked up by microphone to prioritize speech

Question 8

Transmitter and Receiver & Stimulator cochlear implant

Answer 8

– receives signals from speech processor and converts them into electric impulses

Question 9

Electrode array cochlear implant

Answer 9

– electrodes embedded into many sites along the cochlea that collect the impulses from the stimulator and then stimulates the auditory nerve at various places for perceiving differences in frequency.

Question 10

vestibular system functions

Answer 10

Balance, equilibrium, posture, head, body, eye movement

Question 11

Vestibular Labyrinth

Answer 11

Otolith organs –
Semicircular canals
Use hair cells, like auditory system, to detect changes

Question 12

otolith organs

Answer 12

help detect gravity and tilt of head
Detect changes in head angle, linear acceleration
Movement of tiny calcium rocks pushes hairs around
We have many, fish have 1/ear
Detect position of the head in space, changes in head angle and linear acceleration (straight line changes in speed and direction). Sensory receptor structure is a macula.

2 Parts:
Utricle – macula horizontal
Saccule – macula vertical

Question 13

semicircular canals

Answer 13

head rotation

detect turning movements of the head, shaking head side to side or up and down by sensing angular acceleration.

Question 14

sensory transduction by macula

Answer 14

Tilted head or change in linear acceleration, gravity causes otolithic membrane to slide backward or forward over the hair cells, bending the stereocilia.
When stereocilia and kinocilium bend, TRPA1 channels open, K+ enters, hair cell depolarizes, glutamate is released into the synapse stimulating the vestibular nerve fiber. (same as auditory hair cells)
Bending toward the kinocilium causes depolarization (increased impulse frequency) and bending away from the kinocilium causes hyperpolarization (decreased impulse frequency).

Question 15

When head rotated one direction, hair cells in one plane

Answer 15

depolarize but in the the other planes they hyperpolarize. Because semicircular canals are in all planes, all possible head rotation angles can be detected.

Question 16

When you stop twirling, inertia of endolymph causes

Answer 16

cupula to bend in the other direction and firing of nerve fibers gives you the sensation of counter-rotation and the dizziness you feel.

Question 17

vertigo

Answer 17

sensation of spinning, tilting, pulled to one side, dizzy spells, can cause nausea, vomiting, headaches, sweating, nystagmus, and tinnitus that lasts for few minutes or hours. Affects nearly 40% of people over 40 yrs.
Caused by inner ear problems:

Question 18

motion sickness

Answer 18

Motion sickness experienced while riding a boat for example is due to the conflicting messages that are sent from the eyes and the vestibular structures.
If your eyes detect that your body is fixed relative to a stationary environment but your vestibular organs detect that you are moving, then the brain becomes confused by the conflicting messages.
Leads to excessive salivation, pallor, rapid deep breathing, profuse sweating, and then nausea and vomiting.
Medications depress the vestibular inputs and work best when taken before riding in the moving object.

Question 19

interaural time delay

Answer 19

Sound reaches one ear faster than the other and the time delay can be used to localize the sound source.
Sound directly from one side will have a 0.6 msec time delay due to the 20 cm distance between ears
Sound in front of you has no time delay
Sound between straight ahead and to your side will have between a 0 msec – 0.6 msec delay

Question 20

Interaural Intensity Difference –

Answer 20

Because the head causes a shadow effect on sound waves, then one ear will receive a lower intensity sound wave than the other and the brain can detect the difference in volume to locate the sound source.

Question 21

Inner ear is home of

Answer 21

sound and balance transduction