Hearing - Dec 4th

Question 1

Sounds Waves

Hearing
Pitch (tone) of sound
Intensity (loudness)
Timbre (quality)

Answer 1

Sound waves are the zones of atmospheric rarefaction and compression that initiate the sequence leading to audition.

Hearing
Pitch (tone) of sound
Depends on frequency of air waves
Intensity (loudness)
Depends on amplitude of air waves
Timbre (quality)
Determined by overtones

Question 2

Ear Structures

Outer Ear

Middle ear

Inner ear

Answer 2

Outer Ear
Pinna
* visible ear
External auditory meatus
* Ear canal
Tympanic membrane
* Ear drum
* Entry to middle ear

Ear Structures
Middle ear
Amplifies sound by 20-30 x
Ear ossicles
* Malleus
* Incus
* Stapes
Eustachian tube
* Equalizes ear pressure
To oval window

Inner ear
Cochlea
* contains Organ of Corti, endolymph, perilymph
* Transduction from waves (ripples) to AP’s

Question 3

Organ of Corti
Receptors
Basilar membrane
Tectorial membrane

Answer 3

Receptors
- Hair cells
Basilar membrane
- Contains hair cells. Vibrate at same frequencies as bulging waves coming in.
Tectorial membrane
- stiff
- Tips of hair cells imbedded here

Question 4

Transmission of Sound

what do sound waves hit? membrane? ear moves? oval window? perilymph?

standing waves form where then go where? basilar membrane? Hairs? Potential type? the potential type goes where? locations determine what?

Answer 4

Sound waves hit tympanic membrane
- membrane oscillates
- Moves ear ossicles – amplified waves
- Oval window moves in and out
* Sets perilymph in motion

Standing waves form in perilymph, transfer
into endolymph
Basilar membrane will then oscillate
Pushes hair cells against tectorial membrane
Bends hair cells
* GP’s
AP’s down auditory nerve
Location of bent cells determine pitch

Question 5

Conduction deafness

Sensory deafness

Answer 5

Conduction deafness
- Problem with amplification of sound
* ear ossicles, tympanic membrane
* Hearing aids will help
* Eg. Ear infection, or otosclerosis
Sensory deafness
- Problem with hair cells or auditory nerve
* Hearing aids cannot help
* Eg. Loud music damage

Question 6

Equilibrium
apparatus? part of ear? function? consists of?

deformation of what? created by what? nerve to where? functions?

Answer 6

Equilibrium
- Vestibular apparatus
- Inner ear
- Balance and body position
Consists of
* Semicircular canal
* Utricle and Saccule

Equilibrium
- Mechanical deformation of hair cell
- Created by body movement
- Vestibular nerve to cerebellum
- balance and posture
- motion and orientation
- Eye movement

Question 7

Semi-Circular Canals
what do they detect? what do they use? planes? as body whats? what moves? what lags? bends? gates? potential type?

Answer 7

• Detects acceleration and deceleration
• Uses endolymph and hair cells
  In all planes
• As body accelerates
• Hair cells move
• Endolymph lags behind
• Bends hair cells
• Ion gates altered
  ⬧ AP’s

Question 8

Equilibrium
Deceleration

Bending of stereocilia

Utricle and Saccule
detects? parts? stones? when what moves? heavier goes where? bend? potential type?

Answer 8

Hair cells stop – endolymph continues
Bends hair cells in other direction

Bending of stereocilia in opposite directions has
opposite effects on their membrane potentials

• Detects linear motion
• Endolymph contains otoliths
• Calcium “stones”
• As head moves
• Heavier endolymph moves forward
• Bends hair cells
• AP’s

Question 9

Taste and Smell
type of receptor? binding causes what? smell(nerve)? Taste(nerves)?

Smell
molecules? cells? how many receptors? lifespan? associated with what? what system? response type? related to what?

Answer 9

• Chemoreceptors
• Binding of molecules will trigger GP’s and AP’s
  Smell
• Olfactory nerve
  Taste
• Facial and glossopharyngeal nerves
• Scent molecules must be dissolved in mucous
• Support cells
• 140+ scent receptors identified so far
• 2 month lifespan – then replaced
• Closely associated with taste
• Input to limbic system
• Emotional response
• Related to memories

Question 10

Taste
receptors? lifespan? types? support cells?

facial nerve? Glossopharyngeal nerve? Umami? change between people?

Answer 10

Receptors are taste buds
- Lifespan of 10 days
5 types
* Salty
* Sweet
* Sour
* Bitter
* Umami
Support cells
* mucous

Facial nerve
- Front 2/3 of tongue
- Salty and sweet?
Glossopharygeal nerve
- Back 1/3 of tongue
- Sour and bitter?
Umami
- Central concentration – some in periphery

Some people show regions of sensitivity while others do not