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Year 2- CNS > How We See 2 > Flashcards

How We See 2 Flashcards

1
Q

Phototransduction?

A

Conversion of light energy to an electrochemical response by photoreceptors.

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2
Q

What are the photoreceptors of the eye?

A

Rods and cones

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3
Q

What do phototransduced rod and cones do?

A

Activate the optic nerve by generating an action potential

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4
Q

What is the visual pigment found in rods?

A

Rhodopsin

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5
Q

What is the visual pigment found in cones?

A

Opsin

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6
Q

Do rods or cones help visualise colour?

A

Cones

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7
Q

Cones help to visualise which three colours?

A

Red, blue and green

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8
Q

What do rods do?

A

Help to see in dim light

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9
Q

What is found within the opsin pigment of rods and cones?

A

Vitamin A compound

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10
Q

Which form does the vitamin A compound takes in rods?

A

11-cis Retinal

->this is combined with opsin to make rhodopsin i think

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11
Q

How does bleaching of the visual pigment result in phototransduction?

A

Phototransudction cascade

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12
Q

What role does Vitamin A play in the visual pigment?

A

Visual pigment regeneration

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13
Q

What happens if you have prolonged vitamin A deficiency?

A

Rods affected first (because we have more rods than cones).
Rods get bleached and cannot get reformed affecting vision in dim light.

(this lecture was confusing but she said we didn’t need to know all the details, have another look over if you want to understand more fully).

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14
Q

How does the body get vitamin A?

A

Through the diet

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15
Q

What is vitamin A required for?

A

Healthy epithelium
Vision in dim light

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16
Q

In which other conditions may vitamin A deficiency occur?

A

-Malnutrition
-Malabsorption syndromes e.g. coeliac disease

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17
Q

What are some of the signs of vitamin A deficiency?

A

Bitot’s spots in conjunctiva*
Corneal ulceration

*important to remember that Bitot’s spots remain in conjunctiva for a while so may indicate past vitamin A deficiency rather than current

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18
Q

There are many reaction that take place in response to light but what is the final outcome of these reactions?

A

Results in an action potential which is carried to the brain via optic nerve

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19
Q

What is the visual field?

A

Everything seen with one eye, including the periphery

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20
Q

Fovea?

A

Point of best visual acuity

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21
Q

As the two optic nerves go through the optic foramen, they enter the middle cranial fossa and come together. What is the name of the region in which the two optic nerves come together?

A

Optic chiasm

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22
Q

Which area number is the primary visual cortex centre situated in?

A

Area number 17

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23
Q

Once the optic nerves have met at the optic chiasm, what happens?

A

The optic fibres cross over at the optic chiasm and moves down optic tracts and synapses at the LGB.

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24
Q

What happens once the optic nerve synapses at the LBG?

A

Optic radiation radiates through temporal and parietal lobes until it reaches the occipital lobe.

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25
Q

Images formed by the right half of the visual field go where?

A

Left side of occipital cortex

-> and vice versa e.g. images formed by left side of visual field go to right side of occipital cortex

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26
Q

Okay, bit of information first. Try to understand and answer the question :)
We can describe the fibres coming from the eye as coming from the nasal/temporal region of the right/left eye. The temporal region is lateral while the nasal region in medial. There is a nasal and temporal side to both eyes.
Therefore, a fibre from the temporal AND the nasal side of the right eye will travel down towards to the optic chiasm, as will a temporal AND nasal fibre on the left side.

Only one of the two types of fibre (nasal and temporal) cross at the optic chiasm. Which fibres cross over to go to the opposite tract of the body?

A

Nasal fibres

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27
Q

RECAP- name the intrinsic muscles of the eye.

A

Ciliaris muscle
Constrictor pupillae
Dilator pupillae.

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28
Q

RECAP- name the extrinsic muscles of the eye.

A

Lateral rectus
Superior rectus
Medial rectus
Inferior rectus
Superior oblique
Inferior oblique
LPS

29
Q

RECAP- which CN supplies the superior oblique muscle?

A

CN IV (trochlear)

->remember what the man in anatomy labs said SO=sulphur which has a wee four down below so it’s CN 4 which supplies SO

30
Q

RECAP- which CN supplies the lateral rectus muscle?

A

CN VI (abducent)

31
Q

RECAP- which CN supplies all the muscles of the eye EXCEPT the SO, LR?

A

Oculomotor nerve- CN III

32
Q

Which movement describes looking up?

A

Elevation of the eye

33
Q

Which movement describes looking down?

A

Depression of the eye

34
Q

Which movement describes looking away from the nose?

A

Abduction

35
Q

Which movement describes looking towards the nose ?

A

Adduction

36
Q

What is the name given to looking to the right?

A

Dextroversion

37
Q

What is the name given to looking to the left?

A

Levoversion

38
Q

Therefore, what is looking up and to the left called?

A

Levoelevation

39
Q

What is looking up and to the right called?

A

Dextroelevation

40
Q

What is looking down and to the left called?

A

Levodepression

41
Q

What is looking down and to the right called?

A

Dextrodepression

42
Q

What happens in intorsion?

A

Top of eyeball rotates towards nose

43
Q

What happens in extorsion?

A

Top of eyeball rotates away from nose

44
Q

Intorsion and extorsion cannot happen voluntarily. What may them occur?

A

When twisting or turning the head

45
Q

What is the primary action of the MR?

A

Adduction

46
Q

What is the primary action of the LR?

A

Abduction

47
Q

What are the primary, secondary and tertiary actions of the SR?

A

Primary= elevation
Secondary= adduction
Tertiary= abduction

->mnemonic to remember actions of superior and inferior rectus and oblique muscles= RADSIN
(Recti ADductors, Superiors Introtors).

48
Q

What are the primary, secondary and tertiary actions of the IR?

A

Primary= depression
Secondary= adduction
Tertiary= extorsion

49
Q

What are the primary, secondary and tertiary actions of the SO?

A

Primary= intorsion
Secondary= depression
Tertiary= abduction

50
Q

What are the primary, secondary and tertiary actions of the IO?

A

Primary= extorsion
Secondary= elevation
Tertiary= abduction

51
Q

What is a squint/strabismus?

A

Misalignmentof the eyes

52
Q

What is the name of the squint when one eye rotates or turns inwards?

A

Convergent squint

53
Q

What is the name of the squint when one eye rotates or turns outwards?

A

Divergent squint

54
Q

Give two functional consequences of a squint.

A

Amblyopia- lazy eye
Diplopia - double vision

55
Q

Which types of squint may result in diplopia/double vision?

A

Squints occurring as a result of a nerve palsy

56
Q

What is used to correct amblyopia @(lazy eye) in younger years?

A

Eye patch over normal eye to force squinting eye to work

->whooooooooooooo go me

57
Q

Describe the pupillary reaction to increased illumination.

A

Both pupils constrict via parasympathetic innervation.

58
Q

Describe the pupillary reaction to decreased illumination.

A

Both pupils dilate via sympathetic innervation.

59
Q

How do you assess pupillary reflex in a clinical setting?

A

Use pen torch in each eye to check for constriction.
Then switch the pen to to other eye as both pupils should remain constricted.

60
Q

Afferent?
Efferent?

A

Afferent= sensory
Efferent= motor

61
Q

Nerve fibres destined for the pupillary reflex synapse where?

A

Edinger-Westphal nucleus (EWN)

62
Q

Why is there bilateral constriction of the pupil when the light is only shone in one eye?

A

The pupillary reflex fibres go to the EWN of both sides

63
Q

Anisocoria?

A

When the two pupils are not the same size

64
Q

What can cause anisocoria?

A

Trauma
Horner’s Syndrome

65
Q

If there is a third nerve palsy with an absent pupillary reflex, what should be considered?

A

Cerebral artery aneurysm

66
Q

Why does anisocoria occur in Horner’s Syndrome?

A

Due to damage to the sympathetic innervation of the pupil.

67
Q

In those with Horner’s Syndrome, what else might be noticeable?

A

Ptosis- eyelid droops
Anhidrosis- loss of sweating on affected side

68
Q
A

Year 2- CNS (49 decks)

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