Biol 642 - The Auditory System

Front 1

What kind of energy is sound

Back 1

Mechanical Energy, by rarefaction and compression as a series of pressure waves

Front 2

What kind of energy is sound

Back 2

Mechanical Energy, by rarefaction and compression as a series of pressure waves

Front 3

What is the measurement of sound

Back 3

Hertz (no. of cycles/sec)

Front 4

What is the range of sound perception for humans

Back 4

20-20,000Hz

Front 5

Where is sound processed in the brain

Back 5

Sound is processed in the Medial Geniculate Nucleus (MGN)

Front 6

Ear anatomy: What are the parts that make up the outer, middle, and inner ear

Back 6

Outer ear: Pinna, Ear canal / Middle: tympanic membrane, ossicles / Inner: Oval window, cochlear and vestibular system

Front 7

What is Impedence Matching and where does it take place

Back 7

Impedence matching is the action by the ossicles to match the air frequency and the liquid frequency in the ear

Front 8

What is the Attenuation Reflex

Back 8

The acoustic reflex (also known as the stapedius reflex, attenuation reflex, or auditory reflex) is an involuntary muscle contraction that occurs in the middle ear of mammals in response to high-intensity soundstimuli.

Front 9

What is the the Cochlea and where is it located

Back 9

The Cochlea is the organ where sound waves are converted into fluid waves and then ionic signals and finally into action potentials

Front 10

What is the process of Sound Transmission

Back 10

1. Sound strikes the tympanic membrane, 2. Wave energy transferred from bones in the middle ear which vibrate, 3. Vibrations are transmitted via oval window to the scala vestibuli and creates a fluid wave in the cochlea, 4. Fluid waves push on membrane of scala media, 5. Sound waves then trasnferred to scala tympani and then dissipated into the air by the round window, 6. Deformation of the scala media causes the tectorial membrane to move and activate the stereocilia of the hair cells

Front 11

What is Tonotopy

Back 11

Tonotopy is the coding of sound information by the Basilar Membrane

Front 12

How does the Basilar Membrane distinguish sounds

Back 12

Different areas of the Basilar Membrane determine what frequencies it can hear. Thicker part senses high frequency, thinner part senses low frequency

Front 13

What is the difference between the Oval Window vs. Round Window

Back 13

They are both intersections between the middle and inner ear. The Oval Window is connected directly to the stapes and how vibrations from from the ossicles are transferred into the fluid of the scala vestibuli, the scala media, the scala tympani, then finally out the Round Window which allows the vibrations to dissipate and ultimately the moving of the stereocilia on the basilar membrane

Front 14

What are the parts of the Cochlea (8)

Back 14

1. Bony Cochlear Wall, 2. Scala Vestibuli, 3. Scala Media, 4. Scala Tympani, 5. Tectorial Membrane, 6. Organ of Corti, 7. Basilar Membrane, 8. Cochlear Nerve

Front 15

What is Sensory Transduction, and where does it take place

Back 15

The conversion of one form of stimulus to another. In the auditory system, that is the conversion of mechanical energy into electrical energy through the hair cells. Auditory ST takes place in the Organ of Corti, more specifically in the hair cells

Front 16

What are the parts of the Organ of Corti (4)

Back 16

1. The inner hair cells (1 row), 2. The outer hair cells (3 rows), 3. Tectorial Membrane, 4. Basilar Membrane

Front 17

How does sound displace the basilar membrane

Back 17

1. Movements in the S. Vestibular causes movements in the S> Media, 2. This moves the Tectorial Membrane, which moves the Outer and Inner Hair Cells, 3. The Hair Cells will displace and cause a firing of the receptor potential depending on the amount of displacement (nm)

Front 18

What are the parts of the Hair Cells (12)

Back 18

1. Stereocilia, 2. Kinocilium, 3. Microvilli, 4. Cuticular Plate, 5. Basal Body, 6. Tight Junction, 7. Belt Desmosome, 8. Nucleus, 9. Supporting Cell, 10. Basal Membrane, 11. Afferent Nerve Ending, 12. Efferent Nerve Ending

Front 19

What are the steps of Sensory Transduction in the Hair Cells

Back 19

1. Mechanical stimulation opens the K+ channels at the Stereocilia, 2. K+ flows into the Hair Cell at the Stereocilia due to the high concentration of K+ in the Scala Media, 3. The influx of K+ causes a Depolarization down the Hair Cell, 4. The Depolarization causes the VG Ca2+ channels to open, 5. This causes the influx of Ca2+, 6. This signals the cell to release the Neurotransmitters to the Auditory Nerve Synapse

Front 20

What are the different fluids of the cochlea and what are the eq potentials of each

Back 20

The S. Vestibular and Tympani are filled with Perilymph, and the S. Media is filled with Endolymph. The Perilymph has an electrical measurement of 0 mV due to low K+, and the Endolymph has 80 mV due to high K+

Front 21

Do Hair Cells fire Action Potentials

Back 21

No, the depolarization only leads to Neurotransmitter release

Front 22

Describe the interaction of the Inner Hair Cells with the brain

Back 22

A single row of IHCs are all Sensory Receptors, of which about 95% of the hair cells are connected to Afferent Fibers towards the Auditory Cranial Nerve VIII (8)

Front 23

Describe the interaction of the Outer Hair Cells with the brain

Back 23

Comprised of 3 rows of OHC, these can actively contract/relax, stiffen or unstiffen the Tectorial Membrane at certain locations. They are connected to mostly Efferent Fibers (thus giving rise to such outputs like Tinnitus, and IHC sensitivity)

Front 24

Describe Amplification in the ear

Back 24

This is most important for low-intensity sounds, motor protein, called Prestin, located in the OHC walls will change its lengths. This will change the stiffness of the cochlear membranes. Prestin is inactivated (causing compression) by Furosemide

Front 25

Describe Conductive Hearing Loss

Back 25

Damage to the Outer/Middle Ear (e.g: Tympanic Membrane), which causes a reduction in the efficiency of transmission of sound form outside to the inner ear.

Front 26

What are the symptoms and treatment of Conductive Hearing Loss

Back 26

Symptoms: Lack of directionality, flat amplification curves, Treatment: Use of a hearing aid (eg: Cochlear implants)

Front 27

Describe Sensorineural Hearing Loss

Back 27

Damage to the Inner Ear, (eg: Hair Cells or Auditory Nerve)

Front 28

What are the symptoms and treatment of Sensorineural Hearing Loss

Back 28

Symptoms: Invasive, not good resolution, Treatment: Cochlear Implant IF auditory nerve is intact