Hearing Flashcards
What are sound waves?
compression and decompression of the air (rarefaction) that reach your ears and allow to hear sounds
What is amplitude? How is it measured?
depth of the lowering and of the raising of the wave, measured in decibels (dB)
At which decibel levels are we feeling pain?
Above 130dB = pain
What level of decibel can cause hearing loss if heard for a prolonged period of time?
Above 85dB for prolonged time = hearing loss
What level of decibel causes immediate hearing loss?
Near sound above 120dB = immediate hearing loss
What is sensorineural hearing loss?
type of deafness caused by high-decibel sounds
What is frequency? How is it measured?
cycles per second that the wave has, measured in Hertz(Hz)
What is the range of frequencies that humans perceive?
Humans perceive sounds between 20 and 20,000 Hz (outside of this we don’t hear the sounds)
How is amplitude perceived?
Amplitude is perceived as the loudness of the sound
How is frequency perceived?
Frequency is perceived as the pitch of the sound
Are frequency and amplitude dependent?
No
What is the pinna? What does it do?
visible part of the ear (Collects sound from the environment and localizes them)
What is the auditory canal?
Conducts sounds energy from outer to middle ear
What are the parts of the middle ear?
Eardrum (tympanic membrane) and ossicles (3 bones)
What are the ossicles’ names?
- Malleus, incus, and stapes (amplify sounds coming from outside to transfer them to the cochlea)
- Stapes connects to inner ear at the oval window
What are the parts of the inner ear?
- Cochlea (contains receptors responsible for transducing energy from sound waves to electrical impulses)
- Semicircular canals (play a role in balance)
what are the 3 chambers of the cochlea?
- Scala timpani (Lower part)
- Scala media (middle part - organ of Corti)
- Scala vestibuli (upper part)
What does the cochlea coils around?
Coils around a bony pillar called the modiolus
What are the 2 types of fluids in the cochlea chambers?
- Endolymph (scala media)
* Perilymph (scala tympani and scala vestibuli)
How is called the membrane separating the organ of Corti from the scala tympani?
Basilar membrane
How is called the membrane separating the organ of Corti from the scala media?
Tectorial membrane
What are hair cells? Where are they located?
- Includes tectorial membrane
- Hair cells connect to ganglion cells, which carry info to the brain
- Outer hair cells closer to tectorial membrane and inner hair cells closer to basilar membrane
How is the basilar membrane differentially affected by the different wavelengths of sounds?
Because of its shape
• Thick at the base: high-frequency cannot move pat the beginning of the structure (peaks are observed early on)
• Low frequency waves are less affected by the thickness (tend to peak further down the apex)
What are mechanoreceptors?
activated when subjected to deformation (they are modified epithelium and not neurons)
What are stereocilia and what do they do?
- Stereocilia are embedded in the tectorial membrane and bend towards the kinocillium (positive direction) during the peak of a wave, depolarizing the membrane (increased afferent fiber firing)
- Bend away from kinocillium (negative direction) - cells hyperpolarize (no action potential) (decreased afferent fiber firing)
Stereocilia and ____ form the hair bundle
Cilium (true cilium or kinocilium)
Do hair cells have dendrites and axons?
No
What are the roles of inner and outer hair cells?
- Inner: relay info related to the frequency of waves, through afferent fibers to the brain
- Outer: play a role in the amplification of sounds and receive the info related to the location of sounds from the brain through efferent fibers
Which is more present in the ear: inner or outer hair cells?
About 3x more outer hair cells
The majority of info carried to the brain comes from? Why?
95% of info carries to the brain comes from inner cells - Because 90% of inner hair cells are connected to spiral ganglion cells (ganglion cells receive info from 1 hair only but 1 hair is connected to many ganglions)
What forms the auditory nerve?
Axons of spiral ganglions
How is the auditory nerve also called? 2 names
vestibulocochlear nerve or cranial nerve VIII
Where does info from the auditory nerve ends up?
In the primary auditory cortex in the temporal lobes
What are the 3 cochlear nuclei in the medulla to which the auditory nerve projects?
- Dorsal
- Anteroventral
- Posteroventral
What does it means that the basilar membrane is tonotopically mapped?
high-frequency sounds processed at the base of basilar membrane are processed ventrally and low frequency sounds are processed dorsally
From the chochlear nuclei, where is the info relayed (two pathways)?
to contralateral superior olivary nucleus through the brainstem (Primary pathway)
into to the ipsilateral superior olivary nucleus (Secondary pathway)
From the superior olivary nucleus, where is the info relayed?
info flows through the inferior colliculus of the midbrain to the contralateral and ipsilateral medial geniculate nucleus (MGN) of the thalamus, and then to A1
