Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Neuroscience and Mental Health > 13. Neurology of the visual system > Flashcards

13. Neurology of the visual system Flashcards

1
Q

Describe the path of a signal from the eye to the visual cortex (i.e. the visual pathway)

A
  • Optic nerve - ganglion nerve fibres
  • Optic chiasma - nasal half cross over
  • Optic tract
  • Lateral geniculate nucleus - ganglion nerve fibres synapse
  • Optic radiation - 4th order neurone
  • Primary visual cortex (aka Striate Cortes) - in occipital lobe
  • Extra-striate cortex - helps with vision and other related functions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where are the cell bodies of the optic nerve?

A

Retina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where do the ganglion nerve fibres from the retina synapse with the next order?

A

Lateral geniculate nucleus (relay centre in the thalamus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the first and second order neurones in the visual pathway?

A
  • First - rod and cone retinal photoreceptors

* Second - retinal bipolar cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the third order neurones in the visual pathway?

A 
Retinal ganglion cells
• Optic nerve (II)
• Partial decussation at optic chiasma (53% of fibres)
• Optic tract
• LGN
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

When do the fibres in the visual pathway become myelinated?

A

After entering the optic nerve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the receptive field of a neurone?

A

Retinal space within which incoming light can alter the firing patter of a neurone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is ‘convergence of receptive field’?

A

Number of lower order neurones field synapsing on the same higher order neurone
i.e. • low convergence: cone= bipolar cell = ganglion cell
• high convergence: cones > bipolar cells > retinal ganglion cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How is convergence different in the cone system and rod system?

A

Rod system convergence > cone system convergence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How is the convergence different in the central and peripheral retina?

A

Central retina convergence > peripheral retina convergence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the receptive field, visual acuity and sensitivity of low convergence?

A

(Cones or peripheral)
• small receptive field
• fine visual acuity
• low light sensitivity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the receptive field, visual acuity and sensitivity of high convergence?

A

(Rods or centre)
• large receptive field
• coarse visual acuity
• high light sensitivity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are on-centre ganglion cells?

A
  • Stimulated by light at the centre of the receptive field

* Inhibited by light on the edge of the receptive field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are off-centre ganglion cells?

A
  • Inhibited by light at the centre of the receptive field

* Stimulated by light on the edge of the receptive field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are on and off-centre ganglion cells important for?

A
  • Contrast sensitivity

* Enhanced edge detection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How many eyes do lesions, anterior and posterior to the optic chiasm, affect?

A
  • Anterior - one eye

* Posterior - both eyes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which visual field are crossed fibres (at the optic chiasm) responsible for?

A
  • Originate from nasal retina

* Responsible for temporal visual field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Which visual field are uncrossed fibres (at the optic chiasm) responsible for?

A
  • Originate from temporal retina

* Responsible for nasal visual field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Which hemisphere of the brain does information of the right visual field go to?

A

Left hemisphere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What visual disorder does a lesion at the optic chiasma cause?

A
  • Damaged crossed ganglion fibres (nasal retina - temporal field)
  • Bitemporal hemianopia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What does a (right/left sided) lesion posterior to the optic chiasma cause?

A
  • Right sided - left homonymous hemianopia in both eyes

* Left sided - right homonymous hemianopia in both eyes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What usually causes a bitemporal hemianopia?

A

Enlargement of pituitary gland tumour (sits under optic chiasma)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What usually causes a homonymous hemianopia?

A

Stroke

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is a quadrantanopia?

A

Visual field loss in same quadrant of both eyes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What is macular sparing?
Visual field loss that preserves vision in the centre of the visual field
26
Where is the primary visual cortex located?
* Along the calcarine sulcus, within the occipital lobe * Characterised by a distinct stripe derived from the myelinated fibre of the optic radiation projecting into the visual cortex
27
How are the different visual fields represented in the primary visual cortex?
* Disproportionately large area representing the macula * Area above the calcarine fissure represents the inferior visual field * Area below the calcarine fissure represents the superior visual field * Right hemifield from both eyes projects onto Left PVC * Left hemifield from both eyes projects onto right PVC
28
How is the primary visual cortex organised (at a more microscopic level)
* Functional columns * Each column is sensitive to visual stimuli of a particular orientation * Right and left dominant columns
29
What does the brain compare information from the left and right eye for?
Understand depth
30
What usually causes a macula sparing homonymous hemianopia and how?
* Stroke * Leads to contralateral homonymous hemianopia (loss on both sides) with macula sparing * Area representing macula receives dual blood supply from PCA from both sides * Good protection and blood supply allows sparing
31
What is the extra-striate cortex and its function?
* Area around the PVC within the occipital lobe * Converts basic visual information (position + orientation) into complex human precepts (motion + object representation)
32
What is the dorsal pathway involved with?
* aka the How Pathway * Relays information from the PVC to the posterior parietal lobe * Deals with motion detection
33
What is the ventral pathway involved with?
* aka the What Pathway * Relays information from the PVC to the temporal visual cortex * Handles detailed object representation and face recognition
34
What could damage to the ventral pathway lead to?
Cerebral Achromatopsia - inability to perceive colour despite normal functioning cone photoreceptors
35
How does pupil constriction change vision and how is it mediated?
* Decreases spherical aberrations and glare * Increases depth of field and reduces amount of light entering the eye * Reduces bleaching of photo-pigments • Parasympathetic nerve (in CN III)
36
How does pupil dilatation chance vision?
• Increases light sensitivity in the dark * Radial muscle contracts * Mediated by sympathetic nerve
37
Describe the afferent pathway of the pupillary reflex
* Rod and cone photoreceptors => bipolar cells => retinal ganglion cells * Pupil-specific ganglion cells exit at the posterior third of optic tract before entering the LGN * Synapses at dorsal brain stem (Pretectal Nucleus) * Synapses on Edinger-Westphal nuclei on both sides in the brainstem * Nerves from left side of each eye go to left half of brainstem
38
Describe the efferent pathway of the pupillary reflex
* Edinger-Westphal Nucleus => Oculomotor nerve efferent * Synapses at ciliary ganglion (anterior to the optic chiasm) * Short posterior ciliary nerve => pupillary sphincter (parasympathetic)
39
What is direct and consensual light reflex?
* Direct - refers to the constriction of the pupil of the light-stimulated eye * Consensual - refers to the constriction of the pupil of the fellow eye
40
What is the neurological basis of the consensual light reflex?
Afferent pathway on either side alone will stimulate the efferent pathway on both sides
41
How will a right afferent defect affect pupil constriction?
* When right eye is stimulated with light, no pupil constriction * When left eye is stimulated with light, normal pupil constriction in both eyes
42
How will a right efferent defect affect pupil constriction?
* No right pupil constriction at all | * Left pupil constricts, whether right or left eye is stimulated with light
43
How can you test for pupillary reflex damage?
Swinging torch test
44
What is duction?
Eye movement in one eye (without making any reference to the movement of the fellow eye)
45
What is version?
Movement of both eyes in the same direction • Gazing to the right: dextroversion • Gazing to the left: levoversion
46
What is vergence?
Movement of both eyes in opposite directions simultaneously
47
What is convergence?
Simultaneously adduction (inward) movement in both eyes when viewing a near object
48
What is saccade and what are the different types?
``` Short fast burst movement (up to 900deg/sec) • reflexive saccade • scanning saccade • predictive saccade (track objects) • memory-guided saccade ```
49
What is smooth pursuit?
* Sustained slow movement (up to 60deg/sec) * Driven by motion of a moving target across the retina * Used for hunting to locate and follow the object more clearly
50
What are the 6 extraocular muscles?
* Superior rectus * Inferior rectus * Lateral rectus * Medial rectus * Superior oblique * Inferior oblique
51
Which general parts of the orbit do the extraocular muscles come out from?
* 5/6 from the back | * Inferior oblique comes in nasally
52
What kind of motion do the vertical rectus muscles produce when the eye is adducted and abducted?
* Adducted (towards midline) - anterior-posterior axis not aligned, torsion motion produced * Abduction - anterior-posterior axis is aligned, maximal elevation and depression * Small amount of rotation nasally due to angle of attachment of vertical rectus muscles
53
Where is the superior oblique muscle attached and what movement does it produce?
* Travels through the trochlea * Attached high on the temporal side of the eye * Passes under the superior rectus * Down + out
54
Where is the inferior oblique muscle attached and what movement does it produce?
* Attached low on the lateral side of the eye * Passes over the inferior rectus * Moves the eye in a diagonal pattern - up + out
55
What does the oculomotor nerve (III) control in the eye?
* Superior rectus * Lid levator - raises eyelid * Inferior rectus * Medial rectus (adducts eye) * Inferior Oblique (elevates and abducts) * Parasympathetic nerve - constricts pupil
56
What does the trochlear nerve (IV) control in the eye?
Superior oblique (depresses and abducts)
57
What does the abducens nerve (VI) control in the eye?
Lateral rectus (abducts eye)
58
What is supraversion?
Elevation of both eyes i.e. simultaneous right and left eye supraduction
59
What is infraversion?
Depression of both eyes i.e. simultaneous right and left eye infraduction
60
What is the difference between supraduction and supraversion?
* Supraduction - one eye moving up | * Supraversion - both eyes moving up
61
What is torsion?
Rotation of the eye around the anterior-posterior axis eye
62
What is third nerve palsy?
* Oculomotor nerve palsy * Only muscles not innervated by CN III are working - lateral rectus + superior oblique muscle * Eye moves down and out * Droopy eyelid (ptosis)
63
What is sixth nerve palsy?
* Abducens nerve palsy * Deficit in abduction of affected eye (by lateral rectus) * Affected eye deviates inwards * Double vision worsens on gazing to the side of the affected eye
64
What is optokinetic nystagmus?
* Form of physiological nystagmus, triggered by the presentation of a constantly moving grating pattern * Smooth pursuit + fast phase reset saccade
65
What is the optokinetic nystagmus reflex useful for testing?
* Visual acuity in pre-verbal children * Observing presence of nystagmus movement in response to moving grating patterns of various spatial frequencies * Presence of optokinetic nystagmus in response to moving grating signifies that that patient has sufficient visual acuity to perceive the pattern

Neuroscience and Mental Health (17 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions