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Systems 2 - The Nervous System > Vision 1 > Flashcards

Vision 1 Flashcards

1
Q

What two anatomical structures of the eye have the power to bend light?

A

Cornea (45D)

Lens (15D but can accommodate)

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2
Q

What is the scientific name for the bending of light?

A

Refraction

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3
Q

At what distance is an object too close to focus on?

A

20cm

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4
Q

What three things happen simultaneously during accommodation?

A
  1. Lens changes shape
  2. Pupil constriction
  3. Eyes converge
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5
Q

Describe the changes that occur to the shape the lens as an object gets closer?

A

Thicker and more spherical

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6
Q

Describe the process that allows the lens to thicken?

A
  1. Ciliary muscles contract
  2. Space in the middle decreases
  3. Suspensory ligaments become lax
  4. Lens is no longer under stretch
  5. Lens becomes thicker
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7
Q

What division of the autonomic nervous system governs the ciliary body?

A

Parasympathetic

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8
Q

Why do the pupils constrict when an object gets closer?

A

To only allow a few light rays from the object in question - producing a clearer image

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9
Q

What muscle is responsible for constricting the pupil and what division of the nervous system governs it?

A

Constrictor pupilae - parasympathetic

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10
Q

Where is the constrictor pupilae located?

A

In a concentric ring around the border of the pupil

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11
Q

What muscles allow for convergence of the eye?

A

Medial rectus

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12
Q

What nerve innervates the medial recti muscles?

A

CN III

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13
Q

What is the colloquial word for myopia?

A

Shortsightedness

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14
Q

What is emmetropia?

A

Perfect vision

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15
Q

What feature of the lens produces myopia?

A

Too powerful

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16
Q

What is the most common cause of myopia?

A

Eyeball too long

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17
Q

Where does the image focussing relation to the retina in myopic eyes?

A

Infront of the retina

18
Q

What are some common symptoms of myopia?

A

Headaches, complaints of not being able to see

Infants/preverbal children - divergent squint

Toddlers - loss of interest in activities, more interest in books and pictures

Teachers may notice loss of interest at school

19
Q

How can myopia be corrected?

A

Biconcave lenses (glasses/contacts)

Laser eye surgery

20
Q

What is the colloquial word for hyperopia?

A

Longsightedness

21
Q

What is the most common cause of hyperopia?

A

Eyeball is too short

22
Q

In hyperopia, where does the image form in relation to the retina?

A

Behind the retina

23
Q

What are the symptoms of hyperopia?

A

Eyestrain, convergent squint

24
Q

Why does hyperopia require immediate correction?

A

To avoid lazy eye, ambulopia

25
Q

How can hyperopia be corrected?

A

Biconvex lenses (contacts/glasses)

Laser eye surgery

26
Q

What is presbyopia?

A

Age related long-sightedness

27
Q

How does presbyopia occur?

A

Lens gets less elastic with age

28
Q

When does presbyopia usually present in life?

A

5th decade

29
Q

What is astigmatism?

A

Non-spherical shape of the cornea (or lens) therefore surface has different curvatures in different meridians

30
Q

How is astigmatism corrected?

A

Laser eye surgery

Cylinder adjustments

Toric contact lenses

31
Q

What is the process of phototransduction?

A

The converting of light into a neural impulse and ultimately a mental image

32
Q

What are cones?

A

Photoreceptors which are responsible for colour distinction and which work in high light

33
Q

What are rods?

A

Photoreceptors responsible for low light vision

34
Q

What visual pigments are contained in rods?

A

Rhodopsin

35
Q

What visual pigment is contained in cones?

A

Opsins S, M and L

36
Q

Roughly outline the phototransduciton cascade?

A

Light stimulates visual pigments

Stimulates transducin

Stimulates
Phosphodiesterase

Na+ channels close (hyperpolarisation)

Stimulates retina

37
Q

What is the special feature of the resting potential of photoreceptor cells?

A

Depolarised at resting state, due to open Na+ and Ca+ channels

38
Q

How is visual pigment regenerated?

A

Dietary Vitamin A from the liver regenerates visual pigments

39
Q

Other than visual pigments, what does vitamin A also do in the eye?

A

Maintains healthy epithelium (cornea and conjunctivae)

40
Q

What pathologies can occur as a result of vitamin A deficiency?

A 
Blindness (/night blindness)
Ulceration of cornea 
Bitot's spots 
Corneal melting
Corneal opacification
41
Q

Why does colour blindness occur?

A

Different types of cones are responsible for perception of different colours

Systems 2 - The Nervous System (14 decks)

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