L24 Auditory System Flashcards
(32 cards)
What is sound?
Physical movement of air particles. They vibrate back and forth
What is frequency?
Number of compressed or rarefied patches of air that pass by our ears each second, expressed as Hertz (Hz)
What is intensity?
Air pressure difference between peaks and troughs, expressed as decibels (dB).
What are the names of the peak and trough of sound waves?
Peak - Compression
Trough - Rarefaction
Out of compression and a rare fraction, which one has a higher air pressure?
compression has a higher air pressure than a rarefaction.
What is the human hearing range?
20 Hz to 20000 Hz.
What difference would you expect to see between a low and high intensity of sound waves?
Low intensity- difference between trough and peak is smaller.
High intensity has a higher difference between trough and peak
What are the major structures of ear involved in hearing? (7)
- Pinna
- External auditory canal
- Malleus
- Incus
- Tympanic membrane
- Stapes
- Cochlea.
What major structures are in the ossicles of the middle ear?
- Malleus (hammer)
- Incus (anvil)
- Stapes (stirrups)
What is the function of malleus and incus?
The malleus and incus are two of the three tiny bones, called ossicles, located in the middle ear. They play a crucial role in hearing by transmitting and amplifying sound vibrations from the eardrum to the inner ear
What is the role of the Tympanic membrane?
Its primary role is to vibrate when sound waves strike it. These vibrations are then passed on to the three tiny bones (ossicles) in the middle ear (malleus, incus, and stapes)
What is the role of the middle ear?
The middle ear amplifies the signal and spread out the vibrations to the inner ear.
How does the middle ear transfer sound?
- The tympanic membrane is pushed by the compression phase of a sound wave. This moves the malleus and incus and the stapes which is connected to the oval window.
- The oval window moves back and forth, creating pressure waves in the fluid of the inner ear (cochlea)
- The vibrations that pass through the ossicles are amplified which overcomes the greater impedance of the cochlea fluid (from air to fluid)
What is the role of the cochlea?
The cochlea converts the mechanical vibrations of sound into neural signals that provide us with our sense of hearing.
What role does the spiral structure of the cochlea do?
Its unique spiral structure and the properties of the basilar membrane allow us to distinguish a wide range of sound frequencies
Where is the basilar membrane found?
It’s found in the cochlea of the inner ear
What is a key structural feature of the basilar membrane?
At the base, it’s narrower and stiffer. This part captures the high frequency sounds
At the apex, it’s wider and floppier. This part captures the low frequency sounds
High to low frequency sounds
What allows us to hear different frequencies of sound?
The basilar membrane allows us to hear different frequency sounds due to having maximal displacement in different regions of the membrane
What are the 3 different compartments within the cochlea?
- Scala Vestibuli
- Scala Tympani
- Scala Media
What is the scala vestibuli and scala tympani filled with?
Filled with perilymph
What is different about the two types of liquids within the cochlea?
Endolymph has a higher K+ ion concentration compared to perilymph
How many OHC’s and IHC’s do we have in an outer hair cell?
3 OHC’s and 1 IHC
What are the functions of IHCs and OHCs?
IHCs are the primary sensory receptors.
OHCs are a cochlear amplifier.
What would happen if you lose your outer hair cells?
Hearing threshold would increase by loads of decibals, therefore it would be harder to hear the low intensity vibrations.
