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Nervous System > Vision > Flashcards

Vision Flashcards

1
Q

What is the most powerful bender of light?

A

Cornea

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2
Q

What is accommodation?

A

The ability of our eyes to change the focus from distant objects to close objects

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3
Q

What three things comprise accomodation?

A

Lens changes shape - becomes thicker and more spherical
Pupil constricts
Eyes converge

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4
Q

What happens when the lens thickens?

A

Ciliary muscles become thicker on both side which means the lens is no longer under strength. This creates a thicker lens

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5
Q

How does parasympathetic information get to the ciliary body?

A

Cranial nerve 3 - oculomotor

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6
Q

What happens when the pupil constricts?

A

Pupillary constrictor is a concentric muscle around the border of pupil which gets parasympathetic innervation

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7
Q

What happens when the eyes converge?

A

Medial rectus muscles used

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8
Q

Why are our medial rectus muscles thicker than our lateral rectus muscles?

A

We spend a lot of time looking at things close up

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9
Q

What is myopia?

A

Short sighted

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10
Q

What happens in myopia?

A

Image is formed in front of the retina

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11
Q

What is the most common cause of myopia?

A

Eyeball is too long for strength and power of lens and cornea

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12
Q

What are the symptoms of myopia?

A

Headaches
Infants and preverbal children with a divergent squint
Toddlers experience loss of interest in things far way
May notice child losing interest in class

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13
Q

How can myopia be corrected?

A

Bending power needs to be decreased so biconcave lenses

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14
Q

What is hyperopia?

A

Long sighted

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15
Q

What causes hyperopia?

A

Eyeball too short

Cornea and lens too flat

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16
Q

What happens in hyperopia?

A

Light rays form image behind the retina so lens is made thicker so image forms on retina this mean they use all the power so can’t see objects close up

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17
Q

What are the symptoms of hyperopia?

A

Eyestrain after reading or working on a computer

Convergent squint - needs immediate correction

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18
Q

How can hyperopia be corrected?

A

Biconvex glasses

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19
Q

What is astigmatism?

A

Multiple vision

20
Q

What happens?

A

Multiple images are formed because axis of refraction are not the same

21
Q

How can astigmatism be corrected?

A

Special glasses called cylindrical glasses
Laser eye surgery
Toric lenses

22
Q

What is presbyopia?

A

Long sighted in old age

23
Q

What happens?

A

With age the lens gets less mobile and so is not as capable at changing shape

24
Q

How can presbyopia be corrected?

A

Biconvex reading glasses

25
Q

What is phototransduction?

A

Conversion of light energy to an electrochemical response by photoreceptors

26
Q

What is lamellae made up of ?

A

Cell membrane

27
Q

What are the pigments in rods and cones?

A

Rhodopsin in rods

Cone opsins

28
Q

What happens to the opsin element of rhodopsin when light hits?

A

11-cis retinal isomerises to become all-trans retinal

This bleaches the opsin

29
Q

How are photoreceptors cell kept?

A

Depolarised state by open sodium and calcium channels

30
Q

What happens when rhodopsin becomes activated?

A

Triggers a cascade which results in sodium channel closing and hyper polarisation of cell
This is transmitted by a flux of calcium ions

31
Q

What is the function of intrinsic ocular muscles?

A

Control pupil diameter and helps alter lens curvature to enable us to see near objects

32
Q

What is the function of extrinsic ocular muscles?

A

Move the eye

33
Q

What are the extrinsic ocular muscles?

A

Medial, lateral, inferior and superior rectus

Superior and inferior oblique

34
Q

What is the attachment of the recti muscles?

A

Sclera anteriorly

35
Q

What are the attachment of the oblique muscles?

A

Sclera posteriorly

36
Q

What is the origin of the superior oblique?

A

Lesser wing of sphenoid

37
Q

What is the origin of the inferior oblique?

A

Medial part of orbit floor

38
Q

What is the origin of the recti muscles?

A

Tendinous ring

39
Q

What is the function of the elevator palpebrae superioris?

A

Elevates upper eyelid

40
Q

What is the origin of the elevator palpebrae superioris?

A

Roof of orbit

41
Q

What is the action of the medial rectus muscle?

A

Adduction

42
Q

What is the action of the lateral rectus muscle?

A

Abduction

43
Q

What are the actions of the superior rectus muscles?

A

Elevation, adduction, intorsion

44
Q

What are the actions of the inferior rectus muscles?

A

Depression, adduction, extorsion

45
Q

What are the actions of the superior oblique muscles?

A

Intorsion, depression, abduction

46
Q

What are the actions of the inferior oblique muscles?

A

Extorsion, elevation, abduction

47
Q

Where do the optic nerves cross?

A

Optic chiasma which sits just above the pituitary gland

Nervous System (16 decks)

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