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Advanced Neuroanatomy 1-8 > Visual Systems > Flashcards

Visual Systems Flashcards

1
Q

What three layers form the eyeball

A

Fibrous
Vascular
Inner layer- Retina

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2
Q

Fibrous Layer

A

Outermost layer
Consists of Sclera and cornea

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3
Q

What is the Sclera of the fibrous layer

A

Makes up most of the fibrous layer, visible as the white part of the eye, provides attachment to the extraoccular muscles (responsible for movement of eye)

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4
Q

Cornea (fibrous layer)

A

transparent and positioned centrally in the front of the eye.
Light entering the eye is refracted by the cornea

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5
Q

Vascular Layer

A

Underneath the fibrous layer, consists of the choroid, ciliary body and iris

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6
Q

Choroid (Vascular layer)

A

layer of connective tissue and blood vessels, which provides nourishment to outer layer of retina

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7
Q

Ciliary Body ( Vascular Layer)

A

comprised of ciliary muscle and processes.
Ciliary muscle consists of smooth muscle fibres which are attached to the eye by ciliary processes

Controls the shape of the lens and contributes to the formation of aqueous humor

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8
Q

Iris ( Vascular Layer)

A

Circular structure with an aperture in the centre (pupil)

The diameter of the pupil is altered by smooth muscle fibers within the iris, which are innervated by the ANS

Situated between the lens and the cornea.

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9
Q

Inner layer= Retina

A

Light detecting component, consisting of two layers

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10
Q

What are the two layers of the Retina

A

Pigmented Outer layer
Neural Inner layer

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11
Q

Pigmented Outer Layer of Retina

A

Formed by single layer cells

Attached to choroid , supports choroid in absorbing light, prevents scaterring of light

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12
Q

Neural Inner Layer

A

Consists of photoreceptors = light detecting cells

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13
Q

Macula

A

Area in the centre of the retina
Yellowish in colour, highly pigmented
Contains a depression called the fovea centralis

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14
Q

Fovea Centralis

A

High concentration of light detecting cells
Responsible for high acuity of vision

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15
Q

Optic Disc

A

Blind Spot
Area where the optic nerve enters the retina
Contains no light detecting cells

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16
Q

Macula Lutea, Fovea Centralis

A

Small yellowish area lateral to the optic disc, highest visual sensitivity

Fewer rods (functions in dim light)

More Cones (bright light)

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17
Q

Vitreous Body/Humor

A

Two fluid filled areas of the eye
- Anterior Chamber (located between the cornea and iris)

-Posterior Chamber (located between iris and ciliary processes)

Filled with aqueos humor

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18
Q

Function of Vitreous Body/ Humor

A

Clear like plasma fluid nourishes and protects the eye

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19
Q

Clinical relevence of Vitreous Body/ Humor

A

glaucoma is when the drainage of aqueous humor is obstructed

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20
Q

Blood Supply of Eyeball

A

Receives arterial blood via the opthalamic artery (branch of the internal carotid)

Venous drainage is carried out by the superior and inferior opthalamic veins

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21
Q

Lens

A

Located between the vitreous humor and pupil

Shape of the lens is altered by ciliary body

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22
Q

Clinical Relevence of the lens

A

old age, the lens can become opaque which is a Cataract

23
Q

Accomodation

A

Ability of eye to change the focal length of lens by changing the curvature of the eye lens

Change in Refractive Power

24
Q

Unaccomodated lens

A

when viewing distant objects the lens is made relatively thin and flat and has the least refractive power

25
Q

Accomodated Lens

A

for near vision the lens becomes thicker and rounder and has the most refractive power

this involves a change in the ciliary muscles surroudning the lens

26
Q

Ametropia

A

a group of visual disorders caused by errors in the refractive power of the eye

27
Q

Emmetropia

A

normal refractice condition of the eye

28
Q

Myopia

A

Nearsightedness
Close up objects look clear but distant objects are blurry

Cause: corneal surface too curved
Correction: concave (-) lens

29
Q

Hyperopia

A

Farsightedness
Distant objects are usually seen more clearly than close ones

Cause: eyeball being too short or refracting system too weak

Correction: convex (+) lens

30
Q

How many layers in the retina

A

8

31
Q

Name 5 types of neurons in the retina

A

Photoreceptors
Bipolar Cells
Ganglion Cells
Horizontal Cells
Amacrine Cells

32
Q

Three neuron chain of the retina

A

photoreceptors- bipolar cells- ganglion cells

Major route of info flow from photoreceptors to optic nerve

33
Q

Photoreceptors of optic nerve

A

rods and cones

34
Q

What do rods and cones both have

A

Outer segment - composed of membranous disks that contain light sensitive photopigment

Inner Segment- contains the cell nucleus and gives rise to synaptic terminals that contact bipolar or horizontal cells

35
Q

How can photoreceptors be distinguished

A

Shape
Type of photopigment
Distribution across retina
Pattern of synaptic connections

36
Q

Rod

A

Low spatial resolution
Extremely sensitive to light

Specialised for sensitivity at the expense of resolution

Photopigment: contain single (RHODOPSIN)

Function: peripheral vision and in vision under low light conditions

37
Q

Cone

A

High spatial resolution
Insensitive to light
Colour vision

Specialised for acuity at the expense of sensitivity

Photopigment : photopsin

Three types of cones that differ in the photopigment they contain

Function: function under bright light and are responsible for the central discriminative vision and for colour detection

38
Q

Cone Cells and Colour Blindness

A

Three types of cones differ in photopigment

Each of these pigments has a different sensitivity to light of different wavelengths, referred to blue, green and red or short, medium and long wavelength cones

39
Q

What is color blindness

A

the inherited failure to make cone pigments

Alteration on absorption spectre of cone pigments

40
Q

Retinis Pigmentosa

A

genetic disorder characterised by progressive vision loss due to a gradual degeneration of photoreceptors

Progressive loss of vision&raquo_space; dark clumps of pigment visible in eye

41
Q

Symptoms of retinis pigmentosa

A

Initially night blindness
Reduced peripheral vision
Pigment migration of disrupted retinal pigment epithelium into the retina, over years cones also degenerate

42
Q

Macular degeneration

A

Loss of cone function
Most commone in people over 55

Risk Factors» cvs disease, smoking, light, nutrition

43
Q

WET AMD

A

10% of all cases
progress rapidly
Abnormal blood vessel growth occurs under the macula
»leak fluid into retina, damaging the photoreceptors

Therapy = laser therapy

44
Q

DRY AMD

A

90% of all cases
Gradual disappearance of retinal pigment epithelium

45
Q

What is the visual pathway

A

Structure that are responsible for the perceiving, relaying and processing of visual info

46
Q

Discuss Visual Pathway

A

look at page

47
Q

Primary Visual Cortex (Brodmann area 17)

A

Also known as calcarine cortex, striate cortex or V1

Main site of input of signals coming from the retina

Located on the medial aspect of the occipital lobe, in the gyrus superior and inferior to the calcarine sulcus.

48
Q

What information does the primary visual cortex extract

A

edges
depth
orientation
motion
color of objects

49
Q

What two pathways transfer info from primary visual cortex to association areas

A

Ventral Stream
Dorsal Stream

50
Q

Ventral Stream

A

passes through the secondary visual cortex and extends downward into the inferior temporal gyrus. The processing
done by neurons in this pathway allows us to recognize faces and objects based on their size, shape, and color (what objects are?)

51
Q

Dorsal Stream

A

passes through the secondary visual cortex and extends upward to the posterior parietal cortex. Neurons in this pathway provide information about the motion of objects (where object are?)

52
Q

Pathway and Visual Field Defects

A

look at last three pages of notes to study this

53
Q
A

Advanced Neuroanatomy 1-8 (8 decks)

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