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Neurology Year 3 > Occular and Vestibulocochlear systems > Flashcards

Occular and Vestibulocochlear systems Flashcards

1
Q

What is the function of the hair cell?

A

Transduction of the stimuli

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2
Q

If a hair cell is moved what occurs?

A

K+ enter via mechanically gated ion channels

Glutamate is released.

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3
Q

What dictates whether TMC-1 channels are open or closed?

A

Tilt of the cilia

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4
Q

What triggers the movement of the cilia?

A

Vibration of the tectorial membrane

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5
Q

What is the tectorial membrane?

A

One of two membranes within the cochlear.

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6
Q

What happens upon entry of K+ ?

A

Membrane depolarisation as endolymph has v.high K+ concentration.

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7
Q

What is tonotropy?

A

Ability to detect pitch

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8
Q

What membrane enables the detection of pitch?

A

Basal Membrane

Flexible so vibrates in sync with fluid motion.

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9
Q

How is the Basal Membrane able to detect pitch?

A

Width decreases the further along the basal membrane you go as width decreases flexibility increases.
This determines the distance a frequency will travel and in turn activate the afferent neurones specific to that area.

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10
Q

Higher frequency sounds are detected where?

A

Within the thinner regions of the basal ganglia.

Thinner the basal membrane the higher the frequency.

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11
Q

Inner hair cell

A

Main source of afferent signal in auditory VIII nerve

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12
Q

Outer hair cell

A

Efferent input

Controls stiffness to amplify membrane vibration

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13
Q

What is the function of Prestin?

A

Alters the length of the cell, when depolarised it contracts bringing the basal membrane closer to the tectoral membrane.

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14
Q

Contraction of Prestin does what?

A

Amplifies membrane vibration.

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15
Q

Which regions of the brain help locate the source of sound in space

A

Lateral and Medial superior olive

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16
Q

What is the basic understanding of what the lateral and medial superior olive does?

A

Works out from the fact that the ipsilateral side (to the sound) receives sound sooner than the contralateral from this time difference it generates an orientation and distance.

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17
Q

What is the main function of the vestibular system?

A

Where am I going and which way is up?

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18
Q

What do the Semicircular Canals do?

A

Head rotation
Head angle
Acceleration

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19
Q

What do the Saccule Uctricle do?

A

Linear acceleration

Gravity

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20
Q

What are the semicircular canals?

A

3x fluid filled chambers at right angles to each other.

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21
Q

Crista

A

Sheet of cells where hairs are clustered

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22
Q

Ampulla

A

Bulge along the canal where crista are located.

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23
Q

Cilia

A

All orientated in the same direction
Project into the gelatinous cupola
Movement of the fluid shifts the cilia

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24
Q

Vestibular canals - Left Horizontal Turn

A

Excite left horizontal

Inhibit right horizontal

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25
Q

Vestibular canals - Right Horizontal Turn

A

Excite right horizontal

Inhibit left horizontal

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26
Q

Vestibular canals - Left Forward tilt

A

Left anterior excited

Right Posterior Inhibted

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27
Q

Vestibular Canals - Left Backwards tilt

A

Left Posterior Excited

Right anterior inhibited

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28
Q

Vestibular Canals - Right forward tilt

A

Left Posterior Inhibit

Right anterior excited

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29
Q

Vestibular Canals - Right backwards tilt

A

Excite right posterior

Inhibit left anterior

30
Q

Otolith organs

A

Utricle - Horizontal

Saccule - Vertical

31
Q

What is the function of otolith organs

A

Linear Acceleration

Gravity

32
Q

Where can hair cells be found within the otoliths?

A

Within the macula

33
Q

How are hair cells orientated in otolith organs?

A

Multidirectional each otoliths divided by strida with each separate patch having hair cells orientated in a certain and different direction.

34
Q

Otoconia Otoliths

A

Crystals of calcium carbonate on the otolithic membrane.

35
Q

What is the function of the otolithic membrane?

A

Movement of the membrane stimulates the cilia

36
Q

What is the Vestibulo Ocular Reflex?

A

Eyes stay still in space when head moves

37
Q

What is the vestibule colic reflex?

A

Head still in space in space or level when walking

38
Q

What is the vestibulo spinal reflex?

A

Adjusts posture for rapid changes in position

39
Q

Why does alcohol affect your balance?

A

Alters the consistency of the cupola so that in floats more in the endolymph so is far more sensitive to movement.

40
Q

List the cells of the retina from deepest to the shallowest.

A

Photoreceptor cells
Bipolar cells
Ganglion cells

41
Q

In what direction does light pass the cells of the retina.

A

Passes through the ganglion and bipolar cells to reach the photoreceptors.

42
Q

What do photoreceptor cells do?

A

Produce an electrical signal that if the summation is enough will trigger an AP in the ganglion cells.

43
Q

Current is generated by the presence of light? T/F explain.

A

False it is generated in the absence of light

Na+ are open producing a depolarising current -40mV

44
Q

What chemical reaction does the presence of light drive?

A

Converts 11-Cis-Retina to all Trans retinal

45
Q

What does All-Trans-Retinal do?

A

G protein (Transducin) is activated
Increased PDE
PDE hydrolysis cGMP reducing its conc
Na+ Channels close

46
Q

What is the affect of the closure of Na+ channels?

A

Hyperpolarisation which leads to a glutamate release

47
Q

What cells aid in the lateral connection within the retina?

A

Amacrine cells

48
Q

What do Amacrine cells do?

A

Receive input from bipolar cells and project to ganglion bipolar and other Amacrine cells.

49
Q

Why are rod cells more sensitive?

A

As there is a greater convergence as many photoreceptor relay to a single ganglion cell.

50
Q

Why do rod cells have little acuity?

A

As the greater the convergence and the sensitivity the lesser the acuity.

51
Q

What light conditions are the rod cells useful for?

A

Dim light

52
Q

Describe Cone cells.

A

Higher acuity as 1 or 2 photoreceptors converge on 1 ganglion cell, as a result not as sensitive.

53
Q

Where would you find cone cell?

A

Highest concentration around the fovea

54
Q

What are activated by different wavelengths?

A

Opsins

55
Q

What do different wavelength result in?

A

Colour

56
Q

Rods

A

Achromatic - no colour
High Convergence and Sensitivity
Low Acuity

57
Q

Cones

A

Chromatic - colour
Low Convergence and sensitivity
High Acuity

58
Q

M Cells

A

Provide information on movement

59
Q

P Cells

A

Information on colour and shape

60
Q

What is the purpose of Centre Surround Organisation / Lateral Inhibition

A

Emphasises areas of difference and enhance contrast
Ours eyes perceive the difference in light levels not the actual amount of light .
Helps localise the source of the light.

61
Q

How do Bipolar cells react to Glutamate?

A

Either hyper polarise or depolarise depending on the cell.

Two pathways On or OFF pathways

62
Q

In the OFF pathway how do Bipolar cells react to an increase in glutamate due to the dark?

A

Depolarise

63
Q

In the OFF pathway how do Bipolar cells react to a decrease in glutamate due to the light?

A

Hyperpolarising

64
Q

In the On pathway how do bipolar cells react to a decrease in glutamate due to the light?

A

Depolarise

65
Q

In the On pathway how do bipolar cells react to an increase in glutamate due to the dark?

A

Hyperpolarise

66
Q

If the bipolar cells hyperpolarise regardless of whether there is light or not what happens to the ganglion?

A

It is inhibited and hyperpolarised

67
Q

If the bipolar cells depolarise regardless of whether there is light or not what happens to the ganglion cell?

A

It is excited and depolarised.

68
Q

How many layers if the lateral geniculate nucleus divided into?

A

6

69
Q

What layers do M cells relay information into?

A

Bottom 2 layers - 1,2

70
Q

What layers do P Cells relay information into?

A

3,4,5,6

71
Q

The lateral geniculate nucleus sends axons into which layer of the primary visual cortex?

A

4c

72
Q

What area of the eye takes up the largest proportion of the primary visual cortex?

A

Fovea - sight of the highest acuity due to concentration of cone cells.

Neurology Year 3 (29 decks)

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