Hearing, Balance, Taste, & Smell Flashcards
What do the ossicles do?
Concentrate and amplify the vibrations from the tympanic membrane onto the oval window
The three ossicles
Malleus, incus, and stapes
How does the organ of Corti encode the frequencies of sounds?
Tonotopic organization.
High-frequency sounds cause maximal vibration near the base of the cochlea, while low-frequency sounds cause maximal vibration near the apex
Where does the brain integrate signals from the left and right ears?
The superior olivary nucleus.
Auditory pathway
Auditory nerve fibres terminate in cochlear nuclei → superior olivary nuclei → inferior colliculi (primary auditory centres) → medial geniculate nuclei of the thalamus→ auditory cortex
Features of sound localization
- Intensity differences (volume)
- Latency differences (arrival)
- Structure of the ear can diminish and reinforce some frequencies (spectral filtering)
- Specialized for detection of biologically relevant sounds
Hearing loss
Moderate to severe decrease in sensitivity to sound, 3 different types
Deafness
Hearing loss so profound that speech
cannot be perceived even with the use of hearing aids
Three types of hearing loss
Conduction deafness
Sensorineural deafness
Central deafness
Conduction deafness
Disorders of the outer or middle ear, prevents sound from reaching the cochlea
Sensorineural deafness
Hair cells fail to respond to movement of the basilar membrane so no action potential is fired. Caused by genetic mutations
Central deafness
Damage to auditory brain areas from stroke etc.
- Word deafness- difficulty recognizing speech sounds
- Cortical deafness- difficulty recognizing all complex sounds (rare)
Semicircular canals
Connected to utricle and saccule are oriented in three planes
Three planes of vestibular system
- Tilting (roll, x-axis)
- Nodding (pitch, y axis)
- Shaking (yaw, z-axis)
Ampulla
Enlarged chamber at the base of the canals with the hair cells for balance
