The Auditory System 08/02/24 Flashcards
(23 cards)
What four components make up the auditory system? State whether the first free consist of Water or air?
Outer ear- Air
Middle ear- Air
Inner Ear- Fluid
Central Auditory Pathways
What is the Structure and function of the Pinna and Ear Canal?
Pinna-Cartilaginous structure
Directs soundwaves towards ear canal
What is the Pinna formed from? (2) What week is it formed from birth?
Pharyngeal arches 1&2
Forms between 10th and 18th week
What is the role of The middle ear? What does this mean?
Acoustic Impedance match
Transference of energy from air to fluid
How much energy is lost when energy is transferred from the air to fluid in the inner ear?
97%
What are two Features of the Middle ear that allow it to amplify sound? How many decibles does the middle ear increase your hearing by?
1.Ratio area of TM:Stapes = 14:1
-Lever action of Ossicles
2. 20-35 dB
How much does the structure of the middle ear increase the energy transfer from air to fluid by?
200 times
What is the role of muscles in the middle ear?
How do they do this?
- Protection of the inner ear
- Stiffen the ossicular chain
How is the Stapedius stimulated? How long does it take for it to react?
Acoustically
25ms
What is the apparatus of the inner ear called? What nerve innervates it?
Vestibulocochlear apparatus
Vestibulocochlear nerve (CN 8)
What are the three sections of the cochlea called? How many turns does the cochlea have?
Scala Tympani, Scala Media and Scala Vestibuli
2.5 turns
What are the two ionic fluids called in the Cochlea? Where is each one found?
Endolymph- Scala media
Perilymph- Scala vestibuli/ tympani
What are the Endolymph and Perilymph rich in respectively?
K+ (Endolymph)
Na+ (Perilymph)
Why is it important gradients are maintained in the Cochlea?
Abnormalities will cause deafness
What is the connecting channel between the scala vesitbuli and the scala tympani called?
What does it allow and why?
Helicotrema
Allows fluid to move between the two which slightly impedes the travel of sound
What separates the scala vestibuli from the scala media?
Basilar membrane
What happens to the Basilar membrane as impulses move up the scala vestibuli?
It moves
What are three properties of the Basilar membrane at the base of the cochlea?
Narrow
Stiff
High frequencies detected
What are three properties of the Basilar membrane at the Apex of the cochlea?
Wide at apex
Floppy at apex
Low frequencies detected at apex
What cells are responsible for Mechanical transduction when the basilar membrane is displaced? Where are they found and what afferent never are they attached to?
Inner hair cells
In the Basilar Membrane
Attached to Auditory nerve
What is the function of Outer hair cells?
Stiffen the Basilar membrane to prevent inner hair cells on other parts of the basilar membrane from getting stimulated
What is the pathway of sound?
Auditory fibre- spiral ganglion - cochlear nerve- central auditory pathway
