lecture 28 - auditory physiology

Question 1

What is the function of the middle ear?

Answer 1

To amplify sound to the inner ear via bones

Question 2

What are the 3 bones of the middle ear?

Answer 2

Malleus, incus, stapes

Question 3

What is the function of the Eustachian tube?

Answer 3

Maintains equal pressure on either side of the tympanic membrane

Question 4

What is the process of sound transmission to the cochlea?

Answer 4

Sound waves cause tympanic membrane to vibrate, vibrations transfer through malleus/incus/stapes to the oval window where they are concentrated, sound waves pass to the cochlea

Question 5

Where are sounds transmitted to in the cochlea?

Answer 5

Basilar membrane

Question 6

What structure in the cochlear transduces vibrations into action potentials?

Answer 6

Organ of Corti

Question 7

How does the organ of Corti transduce vibrations into neural signals?

Answer 7

Sound passes through the basilar membrane, causing it to vibrate. Hair cells are anchored to the basilar membrane at one end and the stereocilia are rigidly anchored to the tectorial membrane. Hair cells are moved by the vibrating basilar membrane which triggers the release of neurotransmitter and AP conduction

Question 8

What are the 2 types of hair cells in the organ of coti, and what is their function?

Answer 8

Inner hair cells - transduce sound
Outer hair cells - increase sensitivity

Question 9

What is the place theory of audition?

Answer 9

Different frequencies of sound activate different areas of basilar membrane in the cochlea

Question 10

What is the auditory pathway from cochlear to auditory cortex?

Answer 10

cochlear, vestibulocochlear nerve, cochlear nucleus, superior olivary nucleus, inferior collicullus, medial geniculate body (thalamus), auditory cortex (transverse temporal gyrus)

Question 11

What is conduction deafness?

Answer 11

Interruption of sound being conducted from the pinna to the cochlear - i.e. damage/blockage of the canal, drum, middle ear, bones, etc.

Question 12

What is sensorineural deafness?

Answer 12

Dysfunction of auditory pathway from the cochlear to the brain, e.g. damage to hair cells, vestibulocochlear nerve damage, raised ICP

Question 13

What property of the basilar membrane allows for tono-topicity?

Answer 13

Width changes throughout the cochlea (gets wider). This allows for different parts to vibrate at different pitches

Question 14

What are the symptoms of auditory/ear dysfunction?

Answer 14

hearing loss, tinnitus, discharge, pain, vertigo

Question 15

How is Rinne’s test performed?

Answer 15

Tuning fork placed on the mastoid process horizontally. When patient can no longer hear, tuning fork moved in front of the external auditory meatus

Question 16

What does Rinne’s test measure?

Answer 16

Compares bone conduction with air conduction

Question 17

What is a normal finding on Rinne’s test?

Answer 17

Air conduction > bone conduction

Question 18

What is the finding in Rinne’s test in conduction hearing loss?

Answer 18

Bone conduction > air conduction

Question 19

What is the finding in Rinne’s test in sensorineural hearing loss?

Answer 19

Appears normal - air conduction > bone conduction, however the hearing overall will be diminished.

Question 20

How is Weber’s test performed?

Answer 20

Tuning fork is pressed to the forehead and patient says which ear they hear the sound louder in.

Question 21

What does Weber’s test measure?

Answer 21

Measures relative bone conduction of each ear

Question 22

What is the normal result of Weber’s test?

Answer 22

Sound from tuning fork is heard equally in both ears

Question 23

What is the finding in Weber’s test in conductive hearing loss?

Answer 23

Sound from tuning fork is heard louder in the impaired ear

Question 24

What is the finding of Weber’s test in sensorineural hearing loss?

Answer 24

Sound from tuning fork is heard louder in the better ear