4 - Hearing & How We Do It Flashcards
below what level is hearing damage negligable?
75db
what happens to the ability of a person to hear diff frequencies as they age?
ability to hear higher freqencies decreases
how are ears adapted to hearing + perceiving sounds from different directions?
- two ears - is sound left or right? hits one ear before it hits the other.
- shape of ears - is sound from in front or behind? sound bounces and deflects.
how do the ears “self-clean”?
the skin of the eardrum migrates outwards and grows out of the ear canal - it doesn’t just shed (this would clog the ear)
at what rate does skin grow out of the ear canal?
0.7mm a day
name the two different types of ear wax. what is the difference between the two?
- honey wax - “sticky wax” only found in african or caucasian populations
- flaky wax - only found in asian populations
what is the role of earwax?
waterproofing
* stops water getting into ear and clogging ear
what part of the ear is a human adaption to hearing sound in air instead of water?
the middle ear - amplifies the sound waves in air
how is the middle ear ventilated:
* at atmospheric pressure?
* at abnormal pressure?
- atm - physiological gas exchange across mucosa - middle ear gas is dissolved out into mixed venous blood
- abnormal - eustachian tube opens for acute changes - “popping” ear to level pressure
what type of vibration is air?
what type of vibration is cochlear fluid?
air - low pressure high-displacement
cochlear fluids - high-pressure low-displacement
what is the ratio of the tympanic membrane:oval window?
20:1
what is the function of the middle ear muscles?
pull ossicles and protects your hearing
how many times does the cochlea turn?
2.5 times
what is the purpose of the round window?
allows sound to dissipate out of the cochlear after it has hit the apex - prevents echoing of sound
what is the function of inner hair cells?
transmit information to the brain
what is the function of outer hair cells?
cochlear amplifier that refines the sensitivity and frequency selectivity of the mechanical vibrations of the cochlea
where do the inner hair cells sit?
within the fluid
where do the outer hair cells sit?
they are embedded in the tectorial membrane and so stiffen the basilar membrane so it only vibrates in one frequency
what happens to the hair cells as a person ages?
outer hair cells die off - causes deafness
what is meant by cochlear microphonics?
the ear fine tunes itself to hear certain frequencies
when is cochlear microphonics lost?
when OHCs are poisoned
Label the cochlea
Label the cochlea
what fluid does the scala media contain?
endolymph - high in K+
what fluid does the scala vestibuli contain?
perilymph - high in Na+
