Inner Ear Physiology - Fitz Flashcards
Which type of hair cells have lateral cisternae?
Type 2
Which type of hair cells are the true snesory receptors?
Why?
The type 1 cells
-they recieve 90% of afferents
-each primary afferent goes to 1 hair cell
-1 hair cells has mutliple afferents
efferents go through dendrite of primary afferent
Type 2 hair cells act a lot like:
Muscle or contractile cells
-only have 10% of afferents
Stretching the tip link between stereocilia causes:
Depolarization
This occurs when the short sterocilia bend toward the taller ones. When there is not tensiosn in the tip link, its hyperpolarized
How does adaptation occur in ahir cells?
Maintaining the tip link tnesion at proper tension to create a “set point”
Some channels always open - can always hyperpolarize
Actin/myosin unit is the mechansim by which this can be maintained
The semicircular canals detect…?
Head rotation
The otilith organs detect?
Gravity!
When inputs disagree about balance, what does thebody use as a reference?
Vestibular input!
Conflict in the body position systems will produce:
Nystagmus
Vertigo
Nausea
SEmicicrular canals are dynamic which means there is not input when….
You are at rest or in constant motion
KInocilia are found where?
NOT in the auidotry system (lose after development)
still found in the vestibular system
The orward and backward nod, with no head rotation, will activate how many semicircular canals?
4
both ant and both post
Which one of the following results from overstimulation of one semicircular canal?
Light headedness
Motion sickness
Syncope
Vertigo
Vertigo
Why does the human cochlea have the lowest thresholdsbetween 500 Hz and 5 kHz?One best answer!
1) The basilar membrane vibration has the lowest amplitude at those frequencies.
2) The basilar membrane has mass and stiffness characteristics that cause it to resonate only at those frequencies.
3) The impedance of the middle ear limits transmission of higher and lower frequencies.
4) Bone transmission is greater than air transmission at higher and lower frequencies.
3) The impedance of the middle ear limits transmission of higher and lower frequencies.
(so it’s the middle ear that allows you to hear or not hear something)
What does it mean when I say that inner ear transduction is directional?
Displacement toward the tallest sterocilia, called positive deflection, results in depolarization.
In the cochlea this happens when the basilar membrane moves toward the scale vestibuli.
When the basilar membrane moves toward the scala tympani this is called negative deflection and results in hyperpolarization!
Which of the following would be decreased in type II cells compared to type I cells?
1) Ability to generate receptor potentials
2) Influx of K+ when transduction channels open
3) Number of primary afferent fibres per hair cell
4) Number of hair cells innervated by a single primary afferent
5) Size and number of efferent fibres contacting each hair cell
Number of primary afferent fibers per hair cell
In horizontal canals, which direction does depolarization occur in reference to the way you turn your head?
Depolarization occurs in the same direction as head rotation.
REMEMBER: The opposite canal will hyperpolarize
Overstimulation of one semicircular canal will cause what?
Vertigo!!!!
What will occur the left horizontal canal as your head turns right?
At these points:
Head begins turning
Head reaches constant velocity
Head stops turning
Head begins turning - Hyperpolarization
Head reaches constant velocity - no response
Head stops turning - depolarization
What will occur the right horizontal canal as your head turns right?
At these points:
Head begins turning
Head reaches constant velocity
Head stops turning
Head begins turning - depolarization
Head reaches constant velocity - no response
Head stops turning - Hyperpolarization
What is the pairing like in reference to the anterior and posterior canals?
Right posterior paired to left anterior
Left posterior paired to right anterior
<p>
| What happens in the anterior and posterior canals when you tip your head forward?</p>
<p>
Hyperpolarization in left posterior SC canal Hyperpolarization in right posterior SC canal Depolarization in left anterior SC canal and right anterior SC canal</p>
A patient with suspected benign paroxysmal positional vertigo is being tested with the Dix-Hallpike procedure: Her head is turned 45o to the left and she is rapidly moved from a sitting to a supine position. What is the response to this maneuver in a NORMAL person?
Hyperpolarization in right anterior SC canal;depolarization in left posterior SC canal
A patient with suspected benign paroxysmal positional vertigo is being tested with the Dix-Hallpike procedure: Her head is turned 45o to the left and she is rapidly moved from a sitting to a supine position. What is the response to this maneuver in a person with this problem?
delayed nystagmus
Why does the human cochlea have the lowest thresholdsbetween 500 Hz and 5 kHz?
The impedance of the middle ear limits transmission of higher and lower frequencies.
Just remember the middle ear is really important for this. That’s why middle ear infections can really affect the clarity of your hearing.
You wont go deaf, but it will be real annoying
What is the resting membrane potential of a hair cell?
-40mV (so more depolarized than a normal neuron)
Purpose of the middle air in regard to energy:
minimize energy loss at air water interface
When you do the Renne hearing test, you are proving the rule that:
Air conduction is better than bone conduction
What happens when something happens to the force amplifiers?
Force amplifiers
1 - Tympanic membrane bigger than Oval window
Malleus bigger than incus
2 - handel of malleus much bigger than handle of incus
3- Tympanic membrane buckles to put force in center
Anything affecting these three processes will affect the conduction, and can create conductive hearing loss
AKA - tear in tympanic membrane
middle ear bones separate due to pressure on a plane etc.
Resonance depends on 2 things
What diseases can change resonance properties
Mass - more mass is a lower freq (mass of ossicles)
Stiffness - high stiffness is high freq (size of middle ear space)
Otosclerosis - increase mass of stapes - this will decrease response to high freq
Otitis Media - starts with increased stiffness, so lose low freq hearing
later, will have increased in mass due to goop, so high freq are lost too!
The traveling wave travels the length of the cochlea. Which frequencies are trasnduced at the base and which are transduced at the apex?
Base - high frequencies!
Apex - low frequencies!
What do the outer hair cells use their afferent fibers for?
The are actually an amplification system
The sounds stimualtion causes them to contract and icnrease basilar membrane movement to move inner hair cells more. This imporves their threshold
(Like pumping while you sswing, nice!)
Whats the phenomenon that produces tones in your ear, that aren’t halllucinations…
OTOACOUSTIC EMISSIONS
Good way to test for hearing problems, especially for infants who can’t respond to “did you hear that”
What is the specialized system that brings potassium back into the stria vascularis without going back into the scala media
It’s a special gap junction system
Genetic probs with this cause a lot of hearing problems
Why can loop diuretics cause hearing problems?
Some specialized channels are very similar between kidneys and inner ear
The Na/K/Cl channel is targeted by loop diueretics can cause hearing problems because the same channels exist in the inner ear.
