Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

202: Theme 2, Sensory inputs and motor outputs > Physiology of vision > Flashcards

Physiology of vision Flashcards

1
Q

Focus of the eye

A

Carried out by the lens

  • Changes its shape and power to focus an image
  • 1/3 of ray bending

Also by the cornea
- Does 2/3 of ray bending

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

Function of iris

A

Varies retinal intensity by varying its diameter

- 4x change in diameter= x16 change in retinal intensity

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

Pigment layer

A

Located behind the retina

Absorbs unwanted light.

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

Optic disk

A

The region where the optic nerve leaves the eyes.

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

Fovea

A

Small region in the retina that gives the clearest image
- Densely packed with cones

Appears as a small yellow spot on through an opthalmoscope.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Hypermetropia

  • Cause
  • Treatment
A

Long sightedness

  • Image is focused beyond retina
  • Eyeball too short
  • Lens too weak

Treatment
- Convex corrective lens [spectacle/ contact lens]

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

Myopia

A

Short sightedness

  • Image is focused before normal plane of focus
  • Eyeball too long
  • Lens too strong

Treatment
- Concave corrective lens

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

Measurement for refractive power of lens

A

Diopters

- Reciprocal in metres [e.g 2D = 0.5m]

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

Photoreceptors

A

Rods- dim light
- A lot more present

Cones- bright light and colour

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

Processing layers of retina

A

3 direct layers:

  • Receptors
  • Bipolars
  • Ganglion cells

2 transverse layers

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

Rhodopsin

A

G-protein couple receptor found in rods.
- Very sensitive to light, responsible for seeing dim light

Mechanism:

  • Photon from light hits the molecule—> changes from 11-cis to all-trans
  • Triggers intracellular events that hyperpolarise plasma membrane
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Peak spectral sensitivities of human cones

  • Red
  • Green
  • Blue

Rods

A

Red cones [the most cones]
- 560nm

Green
- 530 nm

Blue [the least cones]
- 420 nm

Rods
- 500nm

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

Colour blindness

A

Loss in modification in one or more of the three cone visual pigments.

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

Reg/green colour blindness

A

X-linked condition

- Mutation in the genes for red and green cone visual pigment/

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

Blue colour blindess

A

Caused by mutation in the blue cone pigment gene
- On chromosome 7

Since the chromosome is paired, it is unlikely for individuals to have it, compared to red/green.

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

Central achromatopsia

A

Colour blindness caused by damage to the colour-processing area in the cortex.

17
Q

Scotoma

A

Blind spot in a normal field of vision

Causes:

  • Retinal damage
  • Lesions in visual cortex
  • Tumour restricting optic nerve/ chiasm/ tract/ radiation
18
Q

Homonymous hemianopia

A

Visual field loss of the left OR right side of the vertical midline.

Caused by lesion in the left or right optic tract.

19
Q

Bitemporal hemianopia

A

Visual field loss of the outer half in both right and left fields.

Caused by lesion at optic chiasm.

20
Q

Left-sided blindness

A

Loss of left vision field

- Lesion on left optic nerve

21
Q

Visual pathway

A
  1. Optic nerve
    - From retina
    - Divides in each eye into left and right halves.
  2. Optic chiasm
    - Left and right halves from each eye combines to form optic tract.
  3. Optic tract
    - Some of it goes to superior colliculus
    - Most of it is relayed in the lateral geniculate nucleus [thalamus]
  4. Lateral geniculate
    - Relays information to the striate cortex in occipital lobe
  5. Striate cortex
    - The halves of each combined visual field [from optic tract] is shown as a half.
  6. Information of image is passed to other areas
    - Foveal region is exaggerated
    - Other regions process depth, motion, colour etc
22
Q

Columnar organisation of visual cortex

A

Three overlapping patterns- columns

  1. Ocular dominance
  2. Smaller orientational
    - Orientation of optimal stimuli varies across the surface [L OR R]
  3. Colour blobs
    - Passed to other regions.

Hypercolumn
- One set of all columns

23
Q

Dorsal stream

A

Occipital —->Parietal cortex

Processes:

  • Location
  • Motion
  • Action
24
Q

Ventral stream

A

Occipital —> Temporal

Processes:

  • Object + face identity
  • Conscious perception
25
Q

Visual agnosia

A

Condition where you can see but not recognise and interpret visual information

Due to lesion in temporal lobe

26
Q

Prosopagnosia

A

The inability to recognise similar faces

Due to specific damage of the temporal
- Mainly fusiform gyrus

27
Q

Blindsight

A

Being able to respond to visual stimuli that you cannot consciously see
- Due to lesion in striate/ primary visual cortex

Mechanism

  • Some projections from the lateral geniculate nucleus and superior colliculus reach areas in cortex involved with movement perceptions [without passing through V1]
  • V1 processing only allows conscious processing
28
Q

Vestibulo-ocular reflex

A

Stabilises the gaze whilst the head moves.
- Produces eye movement in opposite direction to head movement.

CN3 nucleus—> CN8 nucleus—> semi-circular canals

29
Q

Optokinetic reflex

A

Stabilises the image of moving object on the retina

Oculomotor nuclei—-> optic tract nucleus

30
Q

Pupillary reflex

A

Illumination of one eye causes constriction in both pupils

Pretectal and Edinger Westphal nuclei receive signals from both eyes.

Damage in one optic nerve

  • Eye will not constrict
  • Other eye pupil will

Damage to oculomotor nerve

  • Pupil contraction will not occur when that eye is stimulated
  • Pupil contract [in damaged nerve eye] occurs when other eye is stimulated

202: Theme 2, Sensory inputs and motor outputs (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions