Topic 6 - Hearing & Balance Flashcards
What is the 2 main waves for sound?
- Frequency (Hz)
- Loudness (dB)
What are the 3 main parts of the ear?
- outer ear
- middle ear
- inner ear
What parts of the outer ear are there & what are functions of the outer ear?
- 2 main functions of outer ear = channel sound wave & protect inner ear
- 2 parts; Pinna & ear canal
- Ear canal creates distance b/w environment & eardrum = protection
- ear wax = barrier
What parts of the middle ear are there & what are functions of the middle ear?
- Tympanic membrane (eardrum) = boundary b/w outer & middle ear. It vibrates when responding to sound
- Has 3 middle ear bones (malleus, incus & stapes)
How does the sound differ in the middle ear compared to the outer ear?
There’s greater amplification in the middle ear than the outer ear - 2 reasons
1. eardrum bigger than stapes (3rd M.B)
2. The 3 M.B act like lever & push stapes onto oval window (start of inner ear)
What is the Eustachian tube?
- It’s connected to pharynx (back of nose & mouth)
- normally closed to prevent debris from nasal area entering middle ear
How does the Eustachian tube open?
- Opens by sneezing, yawning, swallowing, breathing out etc.
- Occurs since actions contract muscle called tensor tympani muscle running along side Eustachian tube
Why is opening the Eustachian tube important?
- When changing pressures, important as it being closed results in potential unequal air pressure b/w middle ear & environment
- This could cause eardrum to bend leading to pain
*NOTE: It can be blocked with mucus if respiratory tract infection e.g common cold
What is the stapedius muscle?
- responds to chronic sounds (loud music)
- it moves the stapes slightly away from oval window (inner) to decrease sound transmission
- ONLY protect for chronic loud sounds X sudden sounds.
*Note: hearing may not go back to normal if exposed to loud sound for too long as loud sound can cause permanent damage
What is the inner ear composed of?
- Filled with fluid
- Cochlea (where sensory cells like hair cells/neurons for hearing are)
- Semicircular canal & otolith organs (where sensory cells like hair cells/neurons for balance are)
What are the 3 main chambers of the cochlea?
- Scala vestibuli
- Cochlear duck
- Scala tympani
How far do frequencies travel in the cochlea?
- Higher frequency travels little along the cochlea
- Low frequency travels far along the cochlea
What is the vestibular apparatus & what does it do?
- It detects changes in motion and position of the head
- It is a series of fluid filled tubes that all connect
- Has 3 semicircular canals = provide sense of rotational/angular acceleration & help maintain balance when turning head/spinning/tumbling
- Has 2 otolith organs = utricle & saccule (both provide info. about linear acceleration & head tilting
What do the hairs in semicircular canals & otolith organs do?
- One major hair at end called kinocilium
- if hairs bend towards kinocilium, ion channels open & + ions move into cells = depolarising them -> increase transmitter released -> activate receptors on assoc. afferent sensory neurons
- if hairs bend away from kinocilium, ion channels close & hyperpolarisation occurs -> decrease transmitter thus few action potentials produced etc.
What is the connection between the nasopharyngeal region & middle ear called?
Eustachian tube
What is diff. frequency detection most dependent on?
point of displacement on the basement membrane
