The Visual Pathway Flashcards
What type of waves of the electromagnetic spectrum are capable of stimulating rods and cons?
Visible light
How are rods and cones specialised to react to light?
Contain opsin which itself contains a vitamin A compound
What occurs when light rays reach the retina?
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
How do light rays stimulate action potentials?
Cascade of reactions within rod/cone (change of shape) -> hyperpolarises -> impulse transmitted -> becomes an action potential in the optic nerve cell
Define the visual field
Everything you see with one eye (including the periphery) is your visual field
Name two tests to determine if a person’s visual field is affected?
- Visual Field Test
* Confrontation Test
What happens in a confrontal test?
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.
What happens in the visual field test?
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.
Are images formed on the retina the right way up or upside down?
Images of objects in your field of vision is formed upside down and inverted of your retina
Where do the fibres from the eye travel to in the middle cranial fossa?
Optic chiasma above the pituitary gland in the pituitary fossa, where the (medial) nasal fibres cross to the opposite side
What is effect of the crossing over of fibres at the optic chiasma?
Each optic tract contain fibres from the (lateral) temporal half of the ipsilateral eye and the crossed-over nasal fibres from the contralateral eye
Where do the fibres in the optic tract travel to?
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.
What side of the visual field does each primary visual cortex see?
The opposite, i.e. the right visual cortex sees the left hand of the visual field
What is optic radiation?
The optic radiation are axons from the neurons in the lateral geniculate nucleus to the primary visual cortex
What occurs to vision if there’s damage to the Right optic nerve?
Blindness in one eye
