Vision Flashcards
Describe the anatomy of the human visual system Explain some of the functions of the human visual system Describe the visual pathway and how the information gets to the visual cortex Describe some common visual disorders (29 cards)
What are the main visible features of the eye? (5)
Pupil Iris - coloured diaphragm Sclerocorneal junction Sclera - white bit Eye lids (palpebra)
What are the 6 muscles in the eye?
Obliques (superior and inferior) Recti (medial and inferior) Recti (superior and lateral) Levator palpeerde superioris Optic nerve
How many types of cranial nerves are there?
CN 2, 3, 4, 6
What are the 3 types of eye movement?
Microsaccades (longer)
Drifts (sport, sharp)
Tremors (so small)
What do drifts do in the eye?
Move the image across the retina
What do microsaccades do in the eye?
Snap the image back to the centre
What are the point of eye movements?
Prevent image fading
What processes are involved in the cranial nerve test? (3)
Ptosis
Optokinetic nystagmus (rhythmic motion)
Pupillary light reflex
What are the 11 parts of anatomy in the eye?
Anterior chamber Iris Optic Disc Optic Nerve - blind spot Cornea Ciliary body Posterior Chamber Fovea - highest sensitivity Retina - photoreceptor layer Choroid layer - light absorbing pigment Sclera - protection
Where are the most cones found?
Fovea
Where are the most rods found?
Periphery
On a image of the back of thee eye, how do you identify the macula and optic nerve head?
Macula = dark red spot in the middle
Optic nerve head = yellow concentrated area
What does accommodation mean?
Accommodation means the ciliary muscles and suspensory ligaments act together to focus light onto the retina through the lens
How does the eye react to focusing on something far? (4)
Ciliary muscle: relaxed
Ligaments: tight
Lens: flat
Light refraction: small
What is the visual defect for not being able to focus on far objects and how do glasses correct this?
Visual defect = near-sighted (myopia)
Glasses: Biconcave
How does the eye react to focussing on something near? (4)
Ciliary muscle: contracted
Ligaments: loose
Lens: rounded
Light refraction: large
What is the visual defect for not being able to focus on near objects and how do glasses correct this?
Visual defect: Far-sighted (hyperopia)
Glasses: Biconvex
How do rods detect colour in the darkness? (3)
Na+ channels OPEN
Na+/K+ ATPase pump active
Cell at baseline depolarised (-40mV)
How do rods detect colour in the light? (3)
Na+ channel CLOSED Postive ions build up in synapse Cell hyperpolarised (more -ve)
What are photosensitive proteins called and what vitamin do they contain?
Opsins, vitamin A
What 3 opsin are in the cones?
Blue (S) 420nm
Green (M) 534nm
Red (L) 564nm
What is the standard mechanism of detecting light in cones? (4)
Light
Metarhodopsin detects
Shape change
Na+ channel closed
What are the key features of rods? (6)
120 million per eye Periphery Monochrome Low resolution Many to 1 ganglion cells 2D image
What are the key features of cones? (6)
6 million per eye Fovea Colour High resolution 1 to 1 with ganglion cells 3D image
