Physiology of Hearing and Balance Flashcards
What is the normal human hearing range?
20-20,000 Hz
Which part of ear acts as receiver of sound
External ear
Which part of ear acts as mechanical amplifier of sound
Middle ear
Explain the amplification mechanism of the middle ear
- Tympanic membrane: OW ratio is 18:1 –> higher pressure
- Ossicle decrease in size which concentrates energy (malleus:incus ratio)
What is the theoretic mechanical gain in energy from the amplifier mechanism in middle ear?
34 dB
What acts as the transducer/analyser of sound in the ear?
Curved spiral lamina
Describe the coiled tubes of liquid in cochlea
Scala media (endolymph) suspended in between scala tympani & scala vestibuli (perilymph)
What is the functional unit of transduction mechanism in ear?
Inner hair cells in the Organ of Corti
(takes pressure wave and transforms into electrical energy)
Where is oval window and round window located?
Cochlea and middle ear
What is the function of oval and round windows?
Permit transmission of pressure waves in enclosed canal + vibration of the basilar membrane
Which cranial nerve gets stimulated after depolarization of the tectorial membrane?
CN VIII (vestibulo-cochlear nerve)
What is the function of eustachian tube?
keeps ear at atmospheric pressure
Electrical signals culminate in the _____ of the _____ within the ______ gyrus
- Brodman areas 41-42
- primary auditory cortex
- superior temporal
Dysfunction of eustachian tube leads to ____
negative middle ear pressure
What muscles open eustachian tube?
tensor veli palatini
levator palatine
Name the otolith organs
utricle, saccule
Name the specialised sensory structures found on hair cells of inner ear?
kinocilium, stereocilia
What are otoconia
calcium carbonate crystals found in the gelatinous matrix within the otolithic organs (specifically, the utricle and saccule)
What is the function of otoconia
lend weight and due to gravity – brain perceives position and movement when tilting the head or linear motion
What is the vestibulo-ocular reflex?
The deflection caused by the movement of perilymph.
‘Bending’ causes stereocilia to deflect.
How does right vestibular damage cause vertigo?
- Lack of firing in the right ear (right vestibular nerve damage)
- Increased firing (++) in left ear
- Brain interprets that as turning left, causing vertigo
Vestibulospinal tract is responsible for _____?
posture
Medial longitudinal fasciculus & ocular muscles are responsible for ____
gaze stabilisation
Medial lemniscus and thalamus to cerebrum is involved in ____
awareness
