The Eye

Question 1

Which type of cells are better for night vision? Why?

Answer 1

Rods - converge into one single bipolar cell

Question 2

Which cells are concentrated to the fovea?

Answer 2

Cones

Question 3

What are cones good for?

Answer 3

High acuity
Day vision
Colour vision

Question 4

What is the path of light from the eye to the visual cortex?

Answer 4

Eye
Optic nerve
Optic chiasm
Optic tract
Lateral geniculate nucleus
Optic radiation
Visual cortex

Question 5

What are the three major functional classes of neurones in the retina?

Answer 5

Photoreceptors - made of rods and cones

Interneurones - bipolar, horizontal and amacrine cells

Ganglion cells - magnocellular (M) and parvocellular (P)

Question 6

Features of magnocellular (M) pathway sensitivity?

• colour contrast
• luminance contrast
• fine detail
• motion

Answer 6

• colour contrast: none (black and white)
• luminance contrast: high
• fine detail: low
• motion: high

Question 7

Sensitivity of parvocellular pathway?

• colour contrast
• luminance contrast
• fine detail
• motion

Answer 7

• colour contrast: yes
• luminance contrast: low
• fine detail: high
• motion: low

Question 8

What is the function of interneurones?

Answer 8

Combine the signals from photoreceptors

Question 9

What do the ganglion cells do?

Answer 9

They are the output cells of the retina

Their axons converge and leave the eye to form the optic nerve

Question 10

When looking through an ophthalmoscope, where does the optic nerve leave the eye?

Answer 10

At the optic disc, slightly medial to the posterior pole of the globe

Question 11

Which fibres cross in the optic chiasm?

Answer 11

Fibres from the nasal retina of each eye

Question 12

Where do fibres in the right optic tract carry information from? Which visual field?

Answer 12

From the right half of each retina

Carry images seen on the left hemifield

Question 13

Where do fibres in the left optic tract carry information from? Which visual fields?

Answer 13

The left half of each retina

Images from the right hemifield

Question 14

What are the names of the right and left visual fields?

Answer 14

Temporal and nasal

Question 15

Where is the lateral geniculate nucleus?

Answer 15

In the thalamus

Question 16

Where does the LGN receive projections from?

Answer 16

The optic tract
Reticular formation
Brainstem
Cortex

Question 17

What is the magnocellular pathway most important for?

Answer 17

Motion and depth

Question 18

What is the parvocellular pathway most important for?

Answer 18

Fine detail and colour

Question 19

Where is the primary visual cortex located?

Answer 19

Medial aspect of occipital lobe

Question 20

Where can information from the primary visual cortex be relayed to?

Answer 20

Secondary visual cortex (V2)

Tertiary visual cortex (V3)

Question 21

How are the visual cortex neurones arranged?

Answer 21

Highly organised columns

Fovea has the largest representation compared to peripheral areas

Question 22

What happens to the retina as it develops?

Answer 22

Increases in thickness

Question 23

What is the pathway in the pupillary reflex?

Answer 23

Axons from retinal ganglion project along optic nerve to pretectal area of midbrain

These cells synapse bilaterally with interneurones and pass to the Edinger-Westphal nucleus

Here, they synapse with preganglionic parasympathetic neurones in the oculomotor nerve

Pre-ganglionic neurones synapse with post-ganglionic parasympathetic pathway in the ciliary ganglion

Innervate the ciliary muscle, causing constriction

Question 24

What allows the consensual pupillary reflex to occur?

Answer 24

There are bilateral projections in the Edinger-Westphal nucleus

Question 25

What are the three events that happen in accommodation and which nerve is involved?

Answer 25

Convergence of the eye Constriction of the pupil Fixation of the lens - brought about by activation of the parasympathetic component to CNIII acting on circumferential muscles of the ciliary body

Question 26

What would damage to the left optic nerve cause?

Answer 26

Complete loss of vision in the left eye

Question 27

What would damage to the optic chiasm cause?

Answer 27

Compression of nasal hemiretinae of both eyes as these are the ones which cross Lose temporal vision - non-homonymous bitemporal hemianopia

Question 28

What can cause non-homonymous bitemporal hemianopia?

Answer 28

Pituitary tumour compressing the optic chiasm

Question 29

What would a lesion to the right optic tract cause?

Answer 29

Damage to right temporal hemiretinae -> loss of right nasal vision Damage to left nasal hemiretinae -> loss of left temporal field So lose left half of visual fields in both eyes -contralateral (left) homonymous hemianopia

Question 30

What can cause damage to the optic tract?

Answer 30

Tumour Infection Surgery Stroke

Question 31

Which fibres are found in meyer's loop?

Answer 31

Fibres from inferior retina - vision of upper half

Question 32

Where do fibres from upper and lower retinal quadrants terminate?

Answer 32

Upper retinal quadrant (inferior vision) - medial LGN Lower retinal quadrant - lateral LGN

Question 33

What can damage to upper right optic radiations in the temporal lobe lead to?

Answer 33

Loss of vision in the upper left quadrant - left homonymous superior quadrantopia

Question 34

What can cause a superior homonymous quadrantopia?

Answer 34

Damage to the right temporal lobe | -vascular occlusion in middle cerebral artery

Question 35

What can damage to the right occipital lobe lead to?

Answer 35

Homonymous hemianopia (left)

Question 36

What does macular sparing indicate?

Answer 36

A cortical lesion in the contralateral side

Question 37

What changes in visual fields occur in glaucoma?

Answer 37

Damage to the optic nerve causing a peripheral visual field defect which is not always noticed

Question 38

What is the path of light from its entry into the eye to rods and cones?

Answer 38

Enters through the iris Focused by the cornea and lens Traverses the virtuous humour to reach the retina Regina consists of rods and cones

Question 39

Where do fibres of from the inferior retina pass?

Answer 39

Though the temporal lobe by looping around the inferior horn (Meyer's loop) of the lateral ventricle

Question 40

Where do fibres from the superior retina travel?

Answer 40

Back through the parietal lobe to the occipital lobe in the retrolenticular limb of the internal capsule to the visual cortex