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Cell Biology Block 4 > Inner Ear: Cochlea And Auditory System > Flashcards

Inner Ear: Cochlea And Auditory System Flashcards

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1
Q
  1. Where does the external ear end and middle ear begin?
  2. Middle ear contains?
  3. Inner ear contains?
A
  1. Tympanic membrane
  2. 3 ossicle bones
  3. Cochlea and vestibular apparatus
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2
Q
  1. Cochlea is for
  2. Vestibular apparatus is for
  3. Nerve for cochlea and nerve for vestibular apparatus merge to form?
A
  1. Hearing
  2. Head movement
  3. CN VII (vestibulocochlear nerve)
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3
Q

What 3 things make up the bony labyrinth

A

Semicircular canals, vestibule and cochlea (also make up the inner ear)

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4
Q

Cochlea and vestibular apparatus lie inside which part of which skull bone. This is deep to what fossa

A

Petrous part of the temporal bone; deep to middle cranial fossa

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5
Q

Tympanic membrane is connected to 1st ossicle which is called?

Last ossicle is called? It taps on the __

What induces vibration on all the structures mentioned?

A

Malleus

Stapes - taps on the oval window of the inner ear

Vibration at the tympanic membrane induces vibration on the 3 ossicles and oval window (so vibration travels from outermost to innermost)

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6
Q

Path of vibration:

Stapes contacts oval window -> pressure wave thru __ -> around __ -> back thru __ -> thru __

A

Scala vestibuli -> end of cochlear duct -> scala tympani -> round window

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7
Q

What are the scala vestibuli and scala tympani?

A

2 fluid filled spaces that are continuous with each other and surround the cochlear duct

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8
Q

As the sound wave travels thru the scala tympani, what stimulates sensory neurons?

A

Upward deflection of the basilar membrane (bottom of the cochlear duct)

~~~

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9
Q

Besides the scala tympani and scala vestibuli, what other scala is in the ear?

A

Cochlear duct is also known as scala media

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10
Q
  1. Scala vestibuli and tympani are filled with ?
  2. Scala media is filled with? Which is secreted there by?
  3. Scala media (cochlear duct) contains what? Function?
A
  1. Perilymph
  2. Endolymph secreted by stria vascularis
  3. Hair cells - activate sensory neurons
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11
Q

What is the roof of the cochlear duct?

Floor?

A

Tectorial membrane

Basilar membrane

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12
Q

~~~

  1. Hair cells have stereocilia that are always in contact with __
  2. Upward deflection of basilar membrane causes ?
  3. Deflection of stereocilia leads to transduction mechanism that does what?
  4. What then happens to the hair cells?
A
  1. Tectorial membrane
  2. Shearing movement of hair cell stereocilia relative to tectorial membrane
  3. Opens excitatory ionotropic receptors
  4. Hair cells depolarize (become more positive)
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13
Q

continued:

  1. When do the sensory neurons become activated?
  2. What do hair cells do to make the sensory neurons be activated?
A
  1. When the stereocilia/hairs on the sensory neurons bend in response to the sound wave
  2. Hair cells release a neurotransmitter that binds to a receptor on the cochlear nerve endings and activates them
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14
Q

Continued:

  1. So inner and outer hair cells = ?
  2. Inner and outer hair cells transduce ?
  3. Where do hair cells synapse?
  4. Where does the action potential in sensory processes go?
A
  1. Sensory neurons
  2. Sound (frequency and amplitude)
  3. On sensory processes of spiral ganglion neurons
  4. Action potential BYPASSES the cell body in the spiral ganglion neurons and continues through sensory fiber via CN VII to the brain
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15
Q

Where is the base of the cochlear duct? Apex?

Where is the basilar membrane stiffer?

A

Base of cochlear duct= near attachment to middle ear
Apex= toward the helicotrema

Stiffer near the base; progressively less stiff as you move near the apex

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16
Q

So at the base do you need a higher or lower frequency to activate sound (activate hair cells)? Why?

What about at apex?

A

At base you need a higher frequency; since it is more stiff, a higher frequency (more energy) is needed to deflect the basilar membrane (remember deflection is needed to stimulate the sensory neurons)

So at apex, a lower frequency can deflect the basilar membrane ~ less stiff

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17
Q

Each part of the cochlear duct has a specific frequency, what does this mean?

A

Hair cells will not be activated along the entire duct, only will be activated where the frequencies match up

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18
Q

Analogy to remember that the base is stiffer and apex is more flexible?

A

Think of a diving board - base is stiffer; part where you jump (apex) is more flexible

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19
Q

Can is contained the spiral ganglions

How do signals from hair cells move

A

Cell bodies of sensory neurons

Hair cells -> spiral ganglion -> out thru sensory fiber (nerve)

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20
Q

1st order sensory neurons in more depth:

  1. Hair cells synapse where? Be specific
  2. Where does AP go?
  3. Where do 1st order sensory fibers terminate/synapse?
  4. Then information gets forwarded to?
A
  1. Sensory processes of spiral ganglion neurons
  2. Bypasses cell body in spiral ganglion and continues through sensory fiber via CN VIII to medulla (so into the brain)
  3. In cochlear nuclei in medulla
  4. Cochlear nuclei forwards information ultimately to cerebral hemispheres
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21
Q

Stapedius and tensor tympani muscles

  1. Location
  2. Function
  3. Why is this function necessary?
  4. Innervation
A
  1. Middle ear attached to the ossicles; stapedius is on stapes; tensor tympani is on malleus
  2. Reduce vibration to ossicles
  3. Excessive sound can damage hair cells, so these muscles dampen the sound
  4. Stapedius (CN VII); tensor tympani (CN V)
22
Q

Common pattern of hearing loss in middle age comes from loss of ?

What causes this?

A

Selective loss of higher frequencies (can still hear lower frequencies)

With age, the base of cochlear duct becomes stiffer than normal - so need higher than normal frequencies to deflect the basilar membrane/activate hair cells

23
Q

High frequency hearing loss suggests __ dysfunction, not __ dysfunction

Why?

A

Suggests cochlear dysfunction, not neurological dysfunction

Any damage to nuclei in auditory circuit is very unlikely to produce a frequency specific deficit

24
Q

Conductive hearing loss

  1. Problem with?
  2. 4 things that could cause this?
A
  1. Conduction of sounds through outer and middle ear to cochlea
  2. Ear wax, infection of external/middle ear, tympanic membrane perforation (traumatic injury), or ossicle damage
25
Q

Sensorineural hearing loss:

  1. Problem with ?
  2. 5 things that could cause this?
A
  1. Neural component of the auditory system (cochlea, CN VIII, or cochlear nuclei)
  2. Hair cell loss (age), genetic disorders, inflammation/infection, Rx side effect, tumor or CN 8 or brain
26
Q

Tinnitus:

  1. What is it?
  2. Typical tinnitus is from abnormal activity of what 4 things ?
  3. Idiopathic tinnitus is from abnormal activity where?
  4. Can be a side effect of
A
  1. Constant tone/ ringing or buzzing sound
  2. Tympanic membrane, ossicles, cochlea, or CN8
  3. In the auditory circuit
  4. Known side effect of some Rx
27
Q

Auditory bruits (obstruction):

  1. How will it present to patient?
  2. Anterior inferior cerebellar artery gives rise to? Course?
  3. Can also come from which problem of which other artery? Where does this artery course through?
  4. Other 2 causes?
A
  1. Patient hears blood flow in the ear
  2. Internal acoustic artery; follows CN8
  3. Carotid dissection; through petrous temporal bone
  4. Cranial AV malformations or increased intracranial pressure
28
Q

Auditory hallucinations:

  1. What is it?
  2. Typically from abnormal activity where?
A
  1. Abnormal activation of any part of the auditory system

2. Auditory cortex (brain)

29
Q

~rest is going to be on vestibular system

A

~previous was all cochlea/auditory system

30
Q
  1. What is the vestibular apparatus? Everything except..

2. Location

A
  1. Everything except cochlea

2. Within the petrous temporal bone

31
Q
  1. 3 vestibular components
  2. All components are __; why?

General function of the semicircular canals

A
  1. 3 semicircular canals, utricle, and saccule
  2. Fluid filled; head movement moves fluid and this movement is detected by sensory neurons
  3. Detect rotational movements of the head
32
Q

Utricle and saccule are collectively called the

A

Vestibule

33
Q

How are hair cells of vestibule different than hair cells of the cochlea?

A

Vestibule hair cells are imbedded in a gel mass called the cupula

Cochlea hair cells are attached to the membrane

34
Q
  1. What surrounds the cupula?
  2. What effect does rotational head movement have on cupula?
  3. Cilia bending causes?
A
  1. Fluid called endolymph
  2. Causes endolymph to flow in opposite direction of head movement, pushing on the cupula and causing cilia to bend
  3. Bending in one direction causes hair cells to depolarize (become more positive); bending in opposite direction hyperpolarizes them (becomes more negative)
35
Q
  1. What is kinocilium? Where is it located in relation to other cilia?
  2. What happens to impulse frequency during depolarization?
  3. What happens to impulse frequency during hyperpolarization?
  4. What movement of the cilia causes depolarization
  5. What movement of the cilia causes hyperpolarization
A
  1. The tallest cilium on a hair cell; closest to the utricle
  2. It becomes more increased than resting discharge
  3. It becomes more decreased than resting discharge
  4. Movement of cilia towards kinocilium depolarizes the hair cell
  5. Movement of cilia away from kinocilium hyperpolarizes the hair cell
36
Q

Hair cell depolarization leads to release of __ by the hair cell

What does this cause?’

Where are the hair cells in the vestibule located?

A

Glutamate

Causes activation of the post-synaptic sensory neuron (1st order sensory neuron)

In the semicircular canals

37
Q
  1. Endolymph flowing in what direction with depolarize the hair cell
  2. Depolarizing the hair cell = __ the hair cell
  3. Which direction does endolymph go in relation of head rotation?
A
  1. Towards the ampulla
  2. Exciting
  3. Endolymph goes in the opposite direction of head rotation

~so if head rotation forces the endolymph to flow not towards the ampulla; the hair cell will be hyperpolarized instead of depolarized

38
Q

Horizontal semicircular canal:

  1. So if you are turning your head to the left, endolymph is following __
  2. Which side of hair cells will be excited; which will be inhibited?
A
  1. To the right
  2. Left side hair cells increase in firing; right side hair cells decrease in firing (endolymph is going away from cochlea)
39
Q

3 sequential changes in endolymph flow after sustained rotational movement:

  1. Beginning of rotation
  2. Rotation maintained
  3. Rotation stops
A
  1. Endolymph stays behind; excitation of hair cells
  2. Endolymph catches up; baseline firing rate
  3. Endolymph keeps going; hyperpolarization of hair cells
40
Q
  1. What are the otolith organs

2. What do they detect?

A
  1. Utricle and saccule (vestibule)

2. Linear acceleration (not rotation)

41
Q
  1. Location of utricle
  2. Location of saccule
  3. Which is sensitive to motion in the vertical plane?
A
  1. Adjacent to the ampulla end of each semicircular canal
  2. Connected to the utricle and adjacent to the cochlea
  3. Saccule
42
Q

Structure of otolith organs:

  1. Where are the hair cells (with kinocilium) located
  2. This is covered by?
A
  1. Enveloped in gel-like otolithic membrane

2. Otoconia - rock like objects on top of otolithic membrane

43
Q
  1. How is the movement detected in otolith organs?

2. What causes depolarization of the hair cells of the otolith organs? Hyperpolarization?

A
  1. Gravity/linear momentum make otoconia slide in one direction, taking otolithic membrane and hair cell cilia in same direction
  2. Depolarization if hair cell cilia deflect toward kinocilium; hyperpolarization if hair cell cilia deflect away from kinocilium
44
Q

1st order sensory neurons (basically same as in the auditory circuitry):

  1. Hair cells synapse where? Be specific
  2. Where does AP go?
  3. Where do 1st order sensory fibers terminate/synapse?
  4. Then information gets forwarded to?
A
  1. Sensory processes of VESTIBULAR ganglion neurons
  2. Bypasses cell body in VESTIBULAR ganglion and continues through sensory fiber via CN VIII to medulla (so into the brain)
  3. In VESTIBULAR nuclei in medulla
  4. Ultimately forwarded to cerebral hemispheres
45
Q

Vertigo / true dizziness:

Difference between subjective vertigo and objective vertigo

A

Subjective: patient feels like he/she is spinning

Objective: patient feels like the room (or some other object in environment) is spinning around them

46
Q

Subjective vertigo:

  1. Usually result of stimulation of __
  2. Can also result from __
  3. Brain can interpret this type of damage as?
A
  1. Vestibular system
  2. Unilateral damage/loss of function of vestibular system (CN8 damage or vestibular nuclei damage)
  3. As activation of the intact side of the system
47
Q

Objective vertigo:

  1. Often caused by?
  2. This can result from what kind of damage?
A
  1. Reflexive repetitive eye movements (abnormal stimulation of oculomotor system)
  2. Can result from unilateral damage to vestibular system/inappropriate activation of vestibular-ocular reflex
48
Q

What does the vestibular-ocular reflex allow you to do?

A

Focus on one fixed point while your head is turning

49
Q

Benign paroxysmal vertigo aka canal rocks:

  1. Possibly caused by? Which effects function of
  2. Can lead to
  3. Treatment
A
  1. Otoliths dislodging and migrating into semicircular canals affecting cupula function
  2. Subjective vertigo; also nausea/vomiting
  3. Physical therapy to relocate otoliths out of canals
50
Q

Menieres disease:

  1. Caused by?
  2. Leads to __ which gets worse when?
  3. Unproven Rx strategy?
  4. Other treatment
A
  1. Excess endolymph production and pressure in vestibular apparatus (endolymph hydrops)(activates hair cells)
  2. Subjective vertigo (also nausea/vomiting); worse when moving
  3. Diuretics
  4. Surgery
51
Q

Vestibular neuritis:

  1. Caused by?
  2. Induces
A
  1. Viral infection or inflammation of CN8

2. Abnormal stimulation and subjective vertigo

Cell Biology Block 4 (9 decks)

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