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Human Physiology (1) > Vision > Flashcards

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

1
Q

What are the main visible features of the eye? (5)

A 
Pupil
Iris - coloured diaphragm
Sclerocorneal junction
Sclera - white bit
Eye lids (palpebra)
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2
Q

What are the 6 muscles in the eye?

A 
Obliques (superior and inferior)
Recti (medial and inferior)
Recti (superior and lateral)
Levator palpeerde superioris
Optic nerve
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3
Q

How many types of cranial nerves are there?

A

CN 2, 3, 4, 6

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4
Q

What are the 3 types of eye movement?

A

Microsaccades (longer)
Drifts (sport, sharp)
Tremors (so small)

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5
Q

What do drifts do in the eye?

A

Move the image across the retina

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6
Q

What do microsaccades do in the eye?

A

Snap the image back to the centre

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7
Q

What are the point of eye movements?

A

Prevent image fading

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8
Q

What processes are involved in the cranial nerve test? (3)

A

Ptosis
Optokinetic nystagmus (rhythmic motion)
Pupillary light reflex

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9
Q

What are the 11 parts of anatomy in the eye?

A 
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
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10
Q

Where are the most cones found?

A

Fovea

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11
Q

Where are the most rods found?

A

Periphery

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12
Q

On a image of the back of thee eye, how do you identify the macula and optic nerve head?

A

Macula = dark red spot in the middle

Optic nerve head = yellow concentrated area

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13
Q

What does accommodation mean?

A

Accommodation means the ciliary muscles and suspensory ligaments act together to focus light onto the retina through the lens

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14
Q

How does the eye react to focusing on something far? (4)

A

Ciliary muscle: relaxed
Ligaments: tight
Lens: flat
Light refraction: small

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15
Q

What is the visual defect for not being able to focus on far objects and how do glasses correct this?

A

Visual defect = near-sighted (myopia)

Glasses: Biconcave

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16
Q

How does the eye react to focussing on something near? (4)

A

Ciliary muscle: contracted
Ligaments: loose
Lens: rounded
Light refraction: large

17
Q

What is the visual defect for not being able to focus on near objects and how do glasses correct this?

A

Visual defect: Far-sighted (hyperopia)

Glasses: Biconvex

18
Q

How do rods detect colour in the darkness? (3)

A

Na+ channels OPEN
Na+/K+ ATPase pump active
Cell at baseline depolarised (-40mV)

19
Q

How do rods detect colour in the light? (3)

A 
Na+ channel CLOSED
Postive ions build up in synapse
Cell hyperpolarised (more -ve)
20
Q

What are photosensitive proteins called and what vitamin do they contain?

A

Opsins, vitamin A

21
Q

What 3 opsin are in the cones?

A

Blue (S) 420nm
Green (M) 534nm
Red (L) 564nm

22
Q

What is the standard mechanism of detecting light in cones? (4)

A

Light
Metarhodopsin detects
Shape change
Na+ channel closed

23
Q

What are the key features of rods? (6)

A 
120 million per eye
Periphery
Monochrome
Low resolution
Many to 1 ganglion cells
2D image
24
Q

What are the key features of cones? (6)

A 
6 million per eye
Fovea
Colour
High resolution
1 to 1 with ganglion cells
3D image
25
Q

What is glaucoma? (3)

A

Fluid out flow is blocked, pressure builds
Constricts optic nerve and artery
Loss of peripheral visual field

26
Q

What is macular degeneration? (3)

A

If the eye stops clearing debris DRUSEN builds up
These block/damage photoreceptors
Effect the fovea so lose central visual field

27
Q

Describe the visual pathway from the eye to the brain? (4)

A

Ganglion cells produce projected AP’s through the optic nerve
Projections from contralateral hemifield switch sides at the optic chasm
Optic tract projects to the lateral geniculate body in there thalamus
Optic radiations project to the visual cortex

28
Q

Describe the focussing in the eye when its dark: (4)

A

Cones adapt in 10mins (not suited for the dark)
Rods adapt in 30mins (suited for the dark)
More rhodopsin must be produced
Sensitivity can increase x10,000

29
Q

Describe the focussing in the eye when its light: (4)

A

Cones adapt in 30mins
Rods adapt in 10mins
Less rhodopsin needs to be produced
Sensitivity decreases

Human Physiology (1) (21 decks)

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