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CNS > The eye > Flashcards

The eye Flashcards

1
Q

Where does the optic nerve take action potentials?

A

To the visual cortex

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2
Q

Where do the optic nerves develop from?

A

Optic cups of the embryonic diencephalon

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3
Q

What are the 3 layers of the eye?

A

Fibrous
Vascular
Neural

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4
Q

Where is the aqueous humour located?

A

Anterior segment

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5
Q

Which nerve controls movement of the eyelids?

A

Facial nerve - VII

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6
Q

Where is the lipid component of the tear film produced?

A

Tarsal gland of the eyelid

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7
Q

What is the conjunctiva?

A

Mucous membrane covering the eyelids and front of the eye, except the cornea

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8
Q

What do goblet cells in the conjunctiva produce?

A

Mucin component of the tear film

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9
Q

What are the 7 muscles surrounding the eyeball?

A
  1. Dorsal rectus
  2. Lateral rectus
  3. Ventral rectus
  4. Medial rectus
  5. Ventral oblique
  6. Dorsal oblique
  7. Retractor bulbi/oculi
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10
Q

Where is the aqueous component of the tear film produced from?

A

3rd eyelid and an extra gland called the lacrimal gland

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11
Q

What is the fucnction of the Descemets membrane in the fibrous tunic?

A

Last defence in the eyeball

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12
Q

What happens when the endothelium of the eye is damaged?

A

Cells don’t replicate so they get increasingly thinner and spread

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13
Q

Where is the vascular tunic located?

A

Sits between the fibrous tunic and neural layer in the caudal part of the eye.

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14
Q

What makes up the anterior and posterior uvea?

A 
Anterior = iris and ciliary body
Posterior = choroid
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15
Q

What is the function of the iris?

A

Iris is a sphincter with constrictor and dilator muscles which alter the size of the pupil to vary the amount of light entering the eye

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16
Q

What is the term for:
1) Constriction of the eye?
2) Dilation of the eye?
What control are they under?

A

1 = miosis = parasympathetic

2 = mydriasis = sympathetic

17
Q

What is the function of the choroid?

A

Provides blood supply to deep layers of retina

18
Q

Name the structure that reflects light back to the retina to give improved night vision?

A

Tapetum lucidum

19
Q

What is the function of the lens?

A

Refracts light, and can change depth of focus by accommodation (limited in veterinary species)

20
Q

What are the 4 main cell types that make up the retina?

A
  1. Retinal pigment epithelium (RPE)
  2. Photoreceptor cells (rods & cones)
  3. Bipolar ganglion cells
  4. Multipolar ganglion cells
21
Q

Describe the field of view in prey species?

A

Very wide vision

Blind spot at the front

22
Q

What determines the shape of the pupil?

A

Shape of constrictor muscles

23
Q

What is the name of the corners of the eyelids?

A

Canthi

24
Q

What are the 2 types of photo receptors? What do each allow you to see?

A 
Rods = black and white
Cones = colour
25
Q

What is the name of the photopigment that rods and cones contain?

A

Rhodopsin

26
Q

What makes up the photo-pigment rhodopsin?

A

opsin (protein) + retinal (vitamin A)

27
Q

Which species cannot convert B-carotene into vitamin A?

A

Cats

28
Q

What % of a cat/dogs photo-receptors are rods/cones?

A

95% rods

5% cones

29
Q

Which molecule keeps sodium channels open meaning the photoreceptors stay active and release glutamate?

A

Cyclic GMP

30
Q

When is cyclic GMP released?

A

In the darkness

31
Q

What are the 5 steps in signal transduction?

A
  1. Light energy is “trapped” by cis-retinal and the molecule changes conformation
  2. This causes the large opsin molecule to loose its “retinal” and become active
  3. Active opsin causes the alpha subunit of transducin (a G-protein) to activate cGMP phosphodiesterase
  4. Results in an elevation of GMP but a reduction of cGMP
  5. Sodium channels close and the cell hyperpolarises
32
Q

What is released when photoreceptors are active?

A

Glutamate

33
Q

What are the effects of glutamate being excitatory or inhibitory?

A

There are on and off bipolar cells

34
Q

What are the 2 other types of retinal neurons, what are they involved in?

A

Horizontal cells and Amacrine cells

- involved in visual processing

35
Q

How does the monocular and binocular vision vary in carnivores vs herbivores?

A 
Carnivores = restricted monocular, large central binocular
Herbivores = wide monocular lateral field, narrow binocular area
36
Q

What is the name of the visual cortex in the brain, in which species is this large?

A

Tectum

- in birds

37
Q

What process is the thalamus involved in?

A

Sensory processing

38
Q

Through which part of the thalamus does the optic nerve pass?

A

lateral geniculate nucleus

CNS (12 decks)

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