Hearing

Question 1

Three functional divisions of the ear?

Answer 1

1.) external ear
2.)middle ear
3.) inner ear

Question 2

What is external ear composed of?

Answer 2

The pinna (auricle or tragus): a cartilaginous sound capturing convoluted funnel
The external acoustic meatus (auditory canal, 2.5 cm long tunnel that ends at eardrum)

Question 3

What is middle ear composed of?

Answer 3

Air filled chamber composed of:
Tympanic membrane (9 mm diameter conical membrane)
The three ossicles malleus, incus, stapes
The tensor tympani and stapedius muscles

Question 4

What does inner ear consist of?

Answer 4

Fluid filled membrane composed of:
Cochlea (auditory system, tube that is spiraling two and a half times around the conical bony modiolus)
Vestibule
Semicircular canals

Question 5

Why does tensor tympani attach to malleus and stapedius attaches to stapes? What is function?

Answer 5

Make the ossicles more rigid in order to dampen very loud sounds.
Does not protect from SUDDEN loud sounds.

Question 6

Tympanic membrane structure and function in middle ear?

Answer 6

Conical shape whose covex portion extends into cavity and onto which malleus is attached. Sound waves cause displacement of membrane which is transmitted to ossicles.

Question 7

Function of stapes in middle ear?

Answer 7

Footplate pistons in and out onto oval window thus transferring tympanic membrane displacement into inner ear.

Question 8

What holds together the malleus, incus, and stapes?

Answer 8

Synovial joints

Question 9

What connects nasopharynx to middle ear cavity?

Answer 9

Eustachian tube (auditory tube) closed by a valve and mastoid air space (antrum) via aditus

Question 10

What is function of middle ear?

Answer 10

To enhance the pressure so that the signal is not lost in its transition from air to fluid

Question 11

What does middle ear due to pressure?

Answer 11

Amplifies it by 22x bc oval window is 17x smaller than that out tympanic membrane and ossicles act as levels and increase force output on oval window

Question 12

Name three fluid filled chambers of cochlea?

Answer 12

Scala vestibuli
Scala media
Scala tympani

Question 13

What is Reissner’s membrane?

Answer 13

Located between Scala vestibuli and Scala media

Question 14

Where is basilar membrane located in cochlea?

Answer 14

Between Scala media and Scala tympani

Question 15

What connects at the helicotrema at apex of cochlea and what does it contain?

Answer 15

Scalas vestibuli and tympani

Question 16

What is stria vascularis responsible for?

Answer 16

Layout of ions secreting potassium while absorbing sodium against concentration gradients

Question 17

What is the organ of corti?

Answer 17

The sensory receptor organ of hearing that consists of inner and outer hair cells, pillar cells, etc. sits on basilar membrane and covered by gelatinous tectorial membrane.

Question 18

Where is organ of corti located?

Answer 18

Scala media

Question 19

Describe hair cell transduction?

Answer 19

When basilar membrane is affected by scala’s fluid movement, structures in organ of corti move up or down, causing stereocilia to bend sideways one way or the other.

Question 20

Upward movement of basilar membrane causes?

Answer 20

Stereocilia bend so that potassium channels open and depolarize hair cells, causing calcium channels to open, provoking neurotransmitters such as glutamate and synapsing between hair cells and densities of spiral ganglion cells.

Question 21

Downward movement of basilar membrane causes?

Answer 21

Hyperpolarization

Question 22

Ventral cochlear nuclei?

Answer 22

Have Stellate cells that encode a variety of frequencies and bushy cells that fire at onset of sound and aid in localization of sound along horizontal axis.

Question 23

Dorsal cochlear nucleus?

Answer 23

Has fusiform cells that get excited or inhibited by a wide variety of frequencies and aid in sound localization along vertical axis and tuberculoventral cells that respond with a delay and inhibit echo interference

Question 24

Rinne’s test?

Answer 24

Tuning fork to pt’s mastoid process. When pt can no longer hear place tuning fork near ear for pt to hear it. If not, conductive hearing loss suspected.

Question 25

Weber’s test?

Answer 25

Placing tuning fork on vertex or nasion so sound lateralizes to ear with conductive deafness or away from ear with sensorineural deafness.

Question 26

Conductive hearing loss?

Answer 26

Results from insult to middle ear. Otitis, otosclerosis.

Question 27

Sensorineural hearing loss?

Answer 27

Results from loss of cochlear hair cells.

Question 28

Otitis media?

Answer 28

Formation of scar tissue that hinders the movement of tympanic membrane or ossicles

Question 29

Otosclerosis?

Answer 29

Results in ossification of attachment between ossicles.

Question 30

Function of cochlear nerve?

Answer 30

From the axons of spiral ganglion cells. Travel to medulla to synapse with cochlear nuclei.

Question 31

What does medial superior Oliverary nucelus function in?

Answer 31

Achieves localization of sound source along horizontal axis by processing info about auditory time delay between two ears. Most striking in low frequencies.

Question 32

What does lateral superior Oliverary nucelus function in?

Answer 32

Involved in sound localization by processing the intensity difference between two ears. Most striking at high frequencies.

Question 33

Where does superior Oliverary nucelus go?

Answer 33

Forms lateral lemniscus. Some fibers synapse with nucleus but most synapse with inferior colliculus.

Question 34

Function of inferior colliculus?

Answer 34

Four layered dorsal nucelus that gathers auditory and somatosensory info as well as multilayered central nucelus that has complete tonotopic map.

Question 35

Function of medial geniculate nucelus?

Answer 35

Receives input from inferior colliculus via inferior brachium. Holds complete somatotropic map.

Question 36

Fibers from medial geniculate nucleus go where?

Answer 36

Go to form auditory radiation and end in primary auditory cortex.

Question 37

Function of transverse temporal gyri of Herschl?

Answer 37

Second point of determining localization of sound source. Has columns responsive to every audible frequency and inter aural relationship. Tonotopically organized.