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Flashcards in The Visual Pathway Deck (18)
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1
Q

What type of waves of the electromagnetic spectrum are capable of stimulating rods and cons?

A

Visible light

2
Q

How are rods and cones specialised to react to light?

A

Contain opsin which itself contains a vitamin A compound

3
Q

What occurs when light rays reach the retina?

A

Light hits the Vitamin A compound causes it to isomerise (change shape) and becomes straight, causing it to not bind to opsin and its release is a process called bleaching

4
Q

How do light rays stimulate action potentials?

A

Cascade of reactions within rod/cone (change of shape) -> hyperpolarises -> impulse transmitted -> becomes an action potential in the optic nerve cell

5
Q

Define the visual field

A

Everything you see with one eye (including the periphery) is your visual field

6
Q

Name two tests to determine if a person’s visual field is affected?

A
  • Visual Field Test

* Confrontation Test

7
Q

What happens in a confrontal test?

A

Compared your visual field (assuming it’s not impaired) to your patient’s by both of you covering an eye and focusing on a point, whilst moving your hand into you visual field form different directions.

8
Q

What happens in the visual field test?

A

Sit in front of a board with one eye closed and one focused on the centre, and a light will flash on the board and they msut say when they see something.

9
Q

Are images formed on the retina the right way up or upside down?

A

Images of objects in your field of vision is formed upside down and inverted of your retina

10
Q

Where do the fibres from the eye travel to in the middle cranial fossa?

A

Optic chiasma above the pituitary gland in the pituitary fossa, where the (medial) nasal fibres cross to the opposite side

11
Q

What is effect of the crossing over of fibres at the optic chiasma?

A

Each optic tract contain fibres from the (lateral) temporal half of the ipsilateral eye and the crossed-over nasal fibres from the contralateral eye

12
Q

Where do the fibres in the optic tract travel to?

A

Fibres from the optic tract synapse at the Lateral Geniculate Body (LGB).
From here, the optic radiation passes behind the internal capsule (retro-lentiform fibres) to reach the Primary Visual Cortex in the occipital lobe.

13
Q

What side of the visual field does each primary visual cortex see?

A

The opposite, i.e. the right visual cortex sees the left hand of the visual field

14
Q

What is optic radiation?

A

The optic radiation are axons from the neurons in the lateral geniculate nucleus to the primary visual cortex

15
Q

What occurs to vision if there’s damage to the Right optic nerve?

A

Blindness in one eye

16
Q

What occurs to vision if there’s damage to the optic chiasma?

A

Bitemporal hemianopia (nasal fibres cannot cross) - loss of nasal vision

17
Q

What occurs to vision if there’s damage to the Right optic tract?

A

Contralateral homonymous hemianopia (loss of left visual field)

18
Q

What occurs to vision if the Right Optic Radiation is damaged?

A

Contralateral homonymous hemianopia (loss of left visual field)