Hearing and Taste/Smell Flashcards
Sound waves
Sound waves are the zones of atmospheric rarefaction and compression that initiate the sequence leading to audition
Sound waves = decompression and compression
Amplitude = loudness
Number of cycles per second = frequency = pouch
- Sound wave air to electrical impulses
Hearing
Pitch (tone) of sound
Depends on frequency of air waves
Intensity (loudness)
Depends on amplitude of air waves
Timbre (quality)
Determined by overtones
Ear structures: outer ear
Pinna
* visible ear
External auditory meatus
* Ear canal
Tympanic membrane
* Ear drum
* Entry to middle ear
Ear structures: middle ear
Ear ossicles
- func is to amplify sound by 20-30 x
* Malleus
* Incus
* Stapes
Eustachian tube
* Equalizes ear pressure (what plugs on planes)
To oval window
Ear structures: inner ear
Cochlea:
* contains Organ of Corti, endolymph, perilymph
- Transduction from waves (ripples) to AP’s
Organ of corti
Receptors
-Hair cells
Basilar membrane
-Contains hair cells
- moves up and down (amplifying) as waves push through
-bends hair, give sound wave
- AP, sodium gates open
Tectorial membrane
-stiff
-Tips of hair cells
imbedded here
Transmission of sound
Sound waves hit tympanic membrane
-membrane oscillates
-Moves ear ossicles – amplified waves (sound)
-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
Location of bent cells determine pitch
- which region, where the hair is bent gets interpreted as a certain sound
Deafness (not genetic)
Conduction deafness:
Problem with amplification of sound
* ear ossicles (middle ear), tympanic membrane
* Hearing aids will help
* Eg. Ear infection, or otosclerosis
(building up of pressure or stiffen over time)
Sensory deafness:
-Problem with hair cells or auditory nerve (not working)
* Hearing aids cannot help
* Eg. Loud music damage
Equilibrium
Vestibular apparatus
-Inner ear
-Balance and body position
Consists of
* Semicircular canal (3 of them)
* Utricle and Saccule (hair cells too)
Mechanical deformation of hair cell (bending)
-Created by body movement
Vestibular nerve
-to cerebellum
-balance and posture
-motion and orientation
- Eye movement
Semi-Circular Canals
Detects acceleration and deceleration
-Uses endolymph and hair cells
-In all planes
As body accelerates
* Hair cells move
* Endolymph lags behind (keeps moving, fluid slosh)
* Bends hair cells
* Ion gates altered
⬧ AP’s
Deceleration
Hair cells stop – endolymph continues
Bends hair cells in other direction
-Skull moving, endolymph (fluid) lag behind
Utricle and Saccule (balance)
Detects linear motion
Endolymph contains otoliths
-Calcium “stones”
As head moves
-Heavier endolymph moves forward
-Bends hair cells
* AP’s
Taste and Smell
Chemoreceptors
-Binding of molecules will trigger GP’s and AP’s
Smell
-Olfactory nerve
Taste
- Facial and glossopharyngeal nerves
Smell
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
-Brain has to learn small, different firing for different smells
Taste
Receptors are taste buds
-Lifespan of 10 days
5 types
* Salty
* Sweet
* Sour
* Bitter
* Umami (savoury)
Support cells
* mucous
