Sensory Physiology (hearing)

Question 1

Anatomy of the ear

Answer 1

Outer ear: allows entry of sound waves
Middle ear: amplification of sound waves
Inner ear: convert wave energy into nerve impulses

Question 2

sound waves

Answer 2

Cause air molecules to alternate being compressed and expanded
Intensity of sound: amplitude of wave (decibels)
Pitch: frequency (hertz)

Question 3

Sound amplification in the middle ear

Answer 3

Converts wave energy in gas (air) to wave energy in fluid (ear)
How?
Sound waves strike tympanic membrane
Causes movement of ossicles
Causes movement of oval window
Amplification achieved since surface area of tympanic membrane > oval window

Question 4

Signal transduction for sound

Answer 4

Location: cochlea
Process
Stapes vibrates oval window
Vibrates fluid in scala vestibuli → scala tympani
Wave arrives at round window
During process basilar membrane of cochlear duct vibrates
Cochlear duct contains receptor cells for sound

Question 5

Inner structures of the cochlea

Answer 5

Location: in cochlear duct, on basilar membrane
Structure
Hair that serve as sound receptors
Stereocilia of hair embedded on tectorial membrane
Organ of corti
Functional process
Stereocilia bend as basilar membrane bounces up and down
Bending → depolarizes hair cells → release NT
NT activates afferent neuron → cochlear nerve

Question 6

coding for the qualities of sound

Answer 6

Determined by portion of basilar membrane activated
High pitch → closer to oval window
Low pitch → further away from oval window
Volume
Louder the sound → greater vibrations → more AP

Question 7

balance

Answer 7

Semicircular canals

Otolith organs

Question 8

semicircular canals

Answer 8

Structure: canals with hair and stereocilia
Function:
Detects head rotation along 3 axes
Nodding
Shaking
Side to side
Functional process
Hair with stereocilia that moves as head rotates
Fluid remains stationary, bending stereocilia

Question 9

otolith organs

Answer 9

Location: inner ear
Structure:
Sheets of hair surrounded by calcium carbonate crystals (otoliths) in gel
Function:
Detect linear movement of head
Functional process
Otoliths remain stationary and pull stereocilia during linear movement
Organs
Utricle
Hairs straight up → detect forward and backward acceleration
Saccule
Hair horizontal → detect up and down movements