Topic 8.5 Flashcards
Speed of sound in air
343 m/s
Characteristics of sound (3)
- frequency
- intensity
- phase difference
Types of sound (3)
- Pure tone
- Real sound
- Noise
What is real sound made of?
fundamental frequency (pitch) + overtone
dB equation
dB = 20*log (Pa/Pref)
At which frequency is our hearing the sharpest?
2000 Hz (needs the least intensity to hear it)
Range of human hearing
20-20 000 Hz
What are the ossicles
malleus, incus, stapes
What can reduce the movement of the ossicles?
stapedius and tensor tympani muscles
What does the stapes connect to?
The oval window
What does the inner ear contain?
Cochlea and vestibular apparatus
What are the parts of the cochlea?
Bony and membranous labyrinths
3 compartments of the cochlea
- scala vestibuli
- scala media
- scala tympani
Which part of the cochlea receives vibration first?
scala vestibuli
What comes after scala vestibuli?
scala tympani (loops back around)
What separates the scala tympani and scala media?
basilar membrane
What separates scala vestibuli and scala media?
reissner’s membrane
What is scala tympani connected to?
round membrane
Where is the organ of corti located?
in scala media
What does the organ of corti contain?
rows of inner and outer hair cells
How many inner hair cells?
3500
What do inner hair cells detect?
They detect the actual vibration
Which hair cells have contact with the tectorial membrane?
The outer hair cells
How many outer hair cells?
16 000
Role of outer hair cells (2)
- detect low amplification sound (they are basically amplifiers)
- dampening mechanism
2 mechanisms of amplification in the middle ear
- decrease in area (oval window < tympanic membrane)
- lever system of the ossicles
What is the important plasma membrane protein of the outer hair cells?
prestin
What is prestin?
a motor protein capable of causing contraction without the use of ATP and calcium signaling
What does contraction of the hair cells do?
enhance upward movement of the basilar membrane and cause endolymph to flow out
Sound identification (3)
- intensity : rate coding mechanism
- frequency : place coding mechanism
- spatial localization : phase difference
Which channels open when stereocilia are moved?
transient receptor potential channel type A1
endolymph potential in vestibule and cochlea
- vestibule : 0mV
- Cochlea : 80mV
Em of hair cells
-40mV
Electrical gradient in cochlear hair cells
120mV
K+ and Na+ in scala tympani and scala vestibuli
K+ : 2mM
Na+ : 140 mM
K+ and Na+ in scala media
K+ : 150 mM
Na+ : 1mM
Where is the endolymph generated?
in the stria vascularis
Afferentation of signal
- spiral ganglion
- cochlear nerve
- cochlear nuclei
- superior olivary nucleus
- lateral lemniscus
- inferior collicular nucleus
- nucleus of medial geniculate body
- primary auditory cortex
Primary auditory cortex
in temporal lobe, broadmann area 41
