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EXCI 360 > Ch. 11: Visual System > Flashcards

Ch. 11: Visual System Flashcards

1
Q

Where is the visual cortex located?

A

In the occipital lobe

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2
Q

What does the visual system provide (3)?

A
  1. Recognition and location of objects (sight) [Size, shape and texture of objects]
  2. Eye movement control: Through reflexes and voluntary command
  3. Information used in posture and limb movement control (anticipatory control) : Peripheral vision to orient our body motion
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3
Q

Which photoreceptor is responsible for colour discrimination and requires more light overall?

A

CONES: colour discrimination and require more light.

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4
Q

What are the two neural photoreceptors in the retina?

A

Cones (colour) and Rods (dark / dim illumination)

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5
Q

Information from ____(How many?)___ photoreceptors is transmitted to _(How many?)____ optic nerve fibers (integrated)

A

From 126 million photoreceptors to 1 million optic nerve fibers.

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6
Q

Latin for ‘Pit’.

A

FOVEA

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7
Q

What is the area of the retina where the photoreceptors (cones) are the MOST dense?

A

The Fovea

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8
Q

Which area of the eye is responsible for the fine discrimination and high visual acuity in humans?

A

The FOVEA

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9
Q

The fovea is dense with which photoreceptor?

A

CONES

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10
Q

Are there more RODs inside or outside the FOVEA?

A

The FOVEA is CONE dense, and there are more RODS found OUTSIDE The fovea.

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11
Q

When talking about a blind spot on the eye… Why does that happen? Where is the blind spot?

A

The blind spot refers to the optic disk (devoid of photoreceptors) therefore if image land on optic disk – it can’t actually be seed.

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12
Q

What is found at the optic disk in the eye?

A

Optic nerve and blood vessels

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13
Q

Is the image inverted on the retina?

A

YES and then it is inverted again by the time it reaches the visual cortex in the occipital lobe.

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14
Q

What is the pathway of the light on the Retina cells to the Visual cortex?

A
  • Retina cells: AP travels via……
  • -> Optic Nerve
  • -> Optic chiasm
  • -> Optic tract then….

–> –>SYNAPSE IN THE LATERAL GENICULATE (LG) nuclease of the THALAMUS

  • -> –> –>To the Geniculocalcarine tract (GT)
  • -> –> –> Visual Cortex (VC)
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15
Q

When information in the visual field is transmitted to the visual cortex does the signal travel an ipsilateral pathway or a contralateral pathway?

A

Contralateral pathway – The information from a visual field is transmitted to the contralateral visual cortex

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16
Q

What is the name of the pathway/ tract which transmits visual information that reaches conscious awareness?

A

The retinogeniculocalcarine pathway

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17
Q

If an image is viewed on a person’s left, what is the pathway to the visual cortex?

A

If on left, there is a signal pathway via TR (temporal retina) of the Right eye and NR (Nasal Retina) of the Left eye –> Optic Nerve –> Optic Chiasm –> Optic Tract –> SYNAPSE in LATERAL GENICULATE LG Thalamus –> GT Geniculocalcarine tract –> Visual cortex

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18
Q

What is the visual association cortex?

A

Information in the visual occipital lobe before being sent to other areas of the brain for. Interpretation of Colours and movement.

19
Q

When information has been taken from the Retina through optic nerve, chiasm , tract, then the LG (thalamus ) to GT and is processed through the visual cortex what are the two streams the information takes?

A

There is:
1. The Action stream (dorsal) –> Posterior Parietal Cortex –> specifies how to move (visual guidance)

  1. The Perception Stream (ventral) –> Occipitotemporal region –> Visual identification of objects

What are the 2 objectives of eye movements?

  1. Keep gaze FIXED on a target during head movements
    a. Vestibulo-ocular reflex
    b. Optokinetic reflex
  2. Directing the gaze at visual targets
    a. Saccades
    b. Smooth pursuits
    c. Vergence movements
20
Q

What is the role of the vestibulo-ocular reflex and how does it fulfil that role?

A
  1. The role is to stabilize visual images during head movements (visual FIXATION) – Prevent bouncing in semicircular canal(s)
  2. Move the eyes in the direction opposite to the head movement to maintain stability of the visual field and visual fixation of objects
21
Q

What is the role of the optokinetic reflex and how does it fulfil that role?

A

The role is to keep the gaze fixed on a target during slow head movements and allow the eyes to follow large objects in the visual field. It is elicited by moving visual stimuli and has direct influence on the perception of movement and on postural control

22
Q

What is the reflex that deals with both the movement of the body and vision?

A

OPTOKINETIC REFLEX

23
Q

What is the name of the eye movement which is a quick simultaneous movement of both eyes between two or more phases of fixation in the same direction without moving the head?

A

SACCADE (French for jerk), can be horizontal and vertical

24
Q

Are Saccades reflexive or voluntary?

A

Saccades can be reflexive or voluntary

25
Q

What is meant by smooth pursuit when discussing direction of gaze?

A

A person is following object with eyes, not moving head. In both horizontal and vertical direction.

26
Q

Which eye movement / gaze is slower? (Saccades or smooth pursuit)

A

Smooth pursuit is slower than saccades at a maximum of 100°/ sec

27
Q

When discussing smooth pursuit with the eyes, should the image being tracked, remain sharp or would one expect to have blurry vision?

A

The image of the tracked image will remain SHARP.

28
Q

When discussing the neural control of eye movement, which is the only one of the five systems that does not conjugate reflexively or voluntarily in its movement?

A

VERGENCE – Eyes don’t move the same direction . (voluntary disconjugate)

29
Q

What are the five neural control systems?

A
  1. Vestibulo-ocular
  2. Optokinetic
  3. Smooth pursuit
  4. Saccadic
  5. Vergence
30
Q

What neural control system’s purpose is to hold the gaze on a target during FAST head movement?

A

VESTIBULO-OCULAR

31
Q

What neural control system’s purpose is to hold the gaze on a target during SLOW head movement?

A

OPTOKINETIC

32
Q

Which neural system is used to maintain the gaze on a MOVING TARGET?

A

SMOOTH PURSUIT

33
Q

Which neural system control will RAPIDLY MOVE EYES to a new target?

A

SACCADIC

34
Q

What neural system is used to ALIGN THE EYES on a near target?

A

VERGENCE

35
Q

Where is the origin of command for the vestibulo-ocular system?

A

SEMI-CIRCULAR CANALS

36
Q

What type of movement is considered vestibulo-ocular?

A

Reflex conjugate

37
Q

Where is the origin of command for optokinetic neural control system?

A

Moving object on the retina

38
Q

What type of movement is considered Optokinetic?

A

Reflex Conjugate

39
Q

Where is the origin of command for Smooth pursuit neural system?

A

VISUAL CORTEX

40
Q

What type of movement is considered Smooth pursuit?

A

VOLUNTARY CONJUGATE

41
Q

Where is the origin of command for the saccadic neural system?

A

FRONTAL EYE FIELDS

42
Q

What type of movement is considered Saccadic?

A

VOLUNTARY CONJUGATE

43
Q

Where is the origin of command for the VERGENCE neural control system?

A

VISUAL CORTEX

44
Q

What type of movement is considered VERGENCE?

A

VOLUNTARY DISCONJUGATE

EXCI 360 (4 decks)

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