Inner Ear Physiology - Fitz

Question 1

Which type of hair cells have lateral cisternae?

Answer 1

Type 2

Question 2

Which type of hair cells are the true snesory receptors?

Why?

Answer 2

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

Question 3

Type 2 hair cells act a lot like:

Answer 3

Muscle or contractile cells

-only have 10% of afferents

Question 4

Stretching the tip link between stereocilia causes:

Answer 4

Depolarization

This occurs when the short sterocilia bend toward the taller ones. When there is not tensiosn in the tip link, its hyperpolarized

Question 5

How does adaptation occur in ahir cells?

Answer 5

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

Question 6

The semicircular canals detect…?

Answer 6

Head rotation

Question 7

The otilith organs detect?

Answer 7

Gravity!

Question 8

When inputs disagree about balance, what does thebody use as a reference?

Answer 8

Vestibular input!

Question 9

Conflict in the body position systems will produce:

Answer 9

Nystagmus
Vertigo
Nausea

Question 10

SEmicicrular canals are dynamic which means there is not input when….

Answer 10

You are at rest or in constant motion

Question 11

KInocilia are found where?

Answer 11

NOT in the auidotry system (lose after development)

still found in the vestibular system

Question 12

The orward and backward nod, with no head rotation, will activate how many semicircular canals?

Answer 12

4

both ant and both post

Question 13

Which one of the following results from overstimulation of one semicircular canal?

Light headedness
Motion sickness
Syncope
Vertigo

Answer 13

Vertigo

Question 14

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.

Answer 14

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)

Question 15

What does it mean when I say that inner ear transduction is directional?

Answer 15

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!

Question 16

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

Answer 16

Number of primary afferent fibers per hair cell

Question 17

In horizontal canals, which direction does depolarization occur in reference to the way you turn your head?

Answer 17

Depolarization occurs in the same direction as head rotation.

REMEMBER: The opposite canal will hyperpolarize

Question 18

Overstimulation of one semicircular canal will cause what?

Answer 18

Vertigo!!!!

Question 19

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

Answer 19

Head begins turning - Hyperpolarization
Head reaches constant velocity - no response
Head stops turning - depolarization

Question 20

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

Answer 20

Head begins turning - depolarization
Head reaches constant velocity - no response
Head stops turning - Hyperpolarization

Question 21

What is the pairing like in reference to the anterior and posterior canals?

Answer 21

Right posterior paired to left anterior

Left posterior paired to right anterior

Question 22

<p>

| What happens in the anterior and posterior canals when you tip your head forward?</p>

Answer 22

<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>

Question 23

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?

Answer 23

Hyperpolarization in right anterior SC canal;depolarization in left posterior SC canal

Question 24

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?

Answer 24

delayed nystagmus

Question 25

Why does the human cochlea have the lowest thresholdsbetween 500 Hz and 5 kHz?

Answer 25

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

Question 26

What is the resting membrane potential of a hair cell?

Answer 26

-40mV (so more depolarized than a normal neuron)

Question 27

Purpose of the middle air in regard to energy:

Answer 27

minimize energy loss at air water interface

Question 28

When you do the Renne hearing test, you are proving the rule that:

Answer 28

Air conduction is better than bone conduction

Question 29

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

Answer 29

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.

Question 30

Resonance depends on 2 things

What diseases can change resonance properties

Answer 30

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!

Question 31

The traveling wave travels the length of the cochlea. Which frequencies are trasnduced at the base and which are transduced at the apex?

Answer 31

Base - high frequencies!

Apex - low frequencies!

Question 32

What do the outer hair cells use their afferent fibers for?

Answer 32

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!)

Question 33

Whats the phenomenon that produces tones in your ear, that aren’t halllucinations…

Answer 33

OTOACOUSTIC EMISSIONS

Good way to test for hearing problems, especially for infants who can’t respond to “did you hear that”

Question 34

What is the specialized system that brings potassium back into the stria vascularis without going back into the scala media

Answer 34

It’s a special gap junction system

Genetic probs with this cause a lot of hearing problems

Question 35

Why can loop diuretics cause hearing problems?

Answer 35

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.