Topic 3: senses - hearing Flashcards
Define frequency
- Number of waves that pass a certain point at given time
Define pitch
- High pitch = shorter waves moving in and out quickly
- Low pitch = slower fluctuations
Define amplitude
- Difference between high + low pressures created in air by sound wave
- Loudness depends on amplitude
What are the frequency humans can hear?
Between 20Hz and 20kHz
Define + describe decibel
- Used to measure intensity of sound
- 0dB = near silence
- 10dB = 10x power
- 20dB = 100x power
- Sounds above 85 dB can cause hearing loss = depending on power of sound + length of exposure
- 8 hours of 90 dB = damage to ears
- Any exposure to 140 dB = immediate damage + pain
What are the 3 parts of the ear?
1) Outer ear
2) Middle ear
3) Inner ear
Describe the outer ear
- Pinna = protection for delicate inner part of ear + shape detects where sound is coming from in vertical plane
- External auditory meatus = air canal = collects sounds + directs towards ear drum
Describe the middle ear
- Air filled cavity in skull’s temporal area
- Parts = eardrum + tympanic membrane + ossicles + eustachian tube
Describe the tympanic membrane
- Concave area 60-90mm + thickness 700th of mm
- Rich blood supply
- Sound waves in ear canal strike membrane = vibrates = more loud more membrane movement
Describe the ossicles
- 3 small bones
- Malleus = hammer
- Incus = anvil
- Stapes = stirrup
- Connected in chain from tympanic -> cochlea entrance = oval window
- When membrane moves = ear drum moves malleus moves = moves incus = moves stapes
- Footplate moves in/out of oval window = transfers energy endolymph fluid in cochlea
Describe the inner ear
- Vestibular portion = balance
- Auditory portion = cochlea = hearing
Describe the vestibular portion
- Made of 3 semicircular canals
- End of canal = ampulla + 2 membranous sacks = utricle + saccule
- Sacks = contain fluid + sensory cells = move in response to head movement = indicate bodies status
- Works with eyes + receptor cells in body joints = maintain balance
Explain the importance of the vestibular system in dizziness/vertigo
- Dizziess = light headed or unsteady
- Vertigo = type where self or surrounds feel like they are moving
- Vestibular -> lead to dizzy die to mismatched sensory information
CAUSES: - BPPV = crystals dislodged in canals
- Vestibular neuritis = inflammation of nerve due to viral infection
- Meniere’s disease = abnormal ear fluid pressure
Describe the cochlea
- Coiled tube in shape of snail shell
- Wrapped around acoustic portion of auditory nerve
- 3 parts = scala vestibule/media/tympani
- Scala vestibule+tympani = perilymph fluid
- Scala media = endolymph fuid
- Reissner’s membrane separate vestibule + media
- Basilar membrane separates media + tympani
- Basilar membrane = 2 sensory cells = outer/inner hair cells = arranged in rows according to frequency + pitch
- Each hair = projections called stereocilia
Describe the function of cochlea in interpreting sound
When sound energy transferred to cochlea = basilar vibrates up/down = outer hair stereocilia sheer on tectorial membrane above = causes stereocilia to bend = open ion gates = electrical charge in cells = neural impulses travel along auditory nerve to brain = sound
