Brainscape's Knowledge GenomeTM

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


See full index

BMA1901-Module 7 > Mod7-Obj4: Major structures of the eye and its physiology > Flashcards

Mod7-Obj4: Major structures of the eye and its physiology Flashcards

1
Q

Vision is our…

A

Dominant sense

  • 70% of the body’s receptors are in the eye
  • Visual processing by half cerebral cortex
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Accessory structures

A
  • Eyebrows
  • Eyelids (Palpebrae)
  • Conjuctiva
  • Lacrimal apparatus
  • Extrinsic eye muscles
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Eyebrows

A
  • Protect the eye from perspiration

- Shade from direct sunlight

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

Eyelids (Palpebrae)

A
  • Muscular folds of facial skin fringed with hair
  • Eyelashes are richly innervated (triggers blinking to prevent damage)
  • Glands secret oily lubricant that lubricates eyelid & prevents eyelids from sticking together
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Conjunctiva

A
  • Transparent mucous membrane lining the eyelids and white of the eye
  • Produces lubricating fluid to prevent drying out and friction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Lacrimal (tear) Apparatus

A
  • Secretes dilute saline solution (tears) containing mucus, antibodies &lysozyme
  • Blinking spreads tears
  • Tears provide nutrients and oxygen, cleanse, moisten and protect the surface of the eye
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Movement of the eyeball

A
  • Six extrinsic muscles which are innervated by cranial nerves III, IV and VI
  • These enable the eyes to be fixed on stationary or moving objects and keep both eyes fixed on the same object at the same time
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Lens

A
  • Lens is bioconvex, transparent and flexible
  • Changes shape to focus light
  • Spherical unless and outside force is applied
  • Held in place by ciliary zonules called suspensory ligaments attached to ciliary muscles
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Ciliary muscle

A

Circular muscle surrounding the lens

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

Suspensory ligaments

A

Extend from muscle to lens to hold in place

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

Ciliary muscles contract

flatten the lens

A

Suspensory ligaments relax and the lens becomes spherical

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

Ciliary muscles relax

lens become round

A

Suspensory ligaments tighten, pull at the circumference of the lens. causing it to flatten

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

The lens and ciliary zonules divides the eye into 2 segements

A
  1. ) Anterior segment

2. ) Posterior segment

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

Anterior segment of the lens and ciliary zonules

In front of the lens

A

-Anterior chamber: Between cornea and iris
-Posterior chamber:
Between iris and lens

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

The anterior segment of the lens and ciliary zonules

A

Contains aqueous humour that supplies nutrients and oxygen to the lens and cornea

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

Posterior segement of the lens and ciliary zonules

Behind the lens

A

Contains vitreous humour (gelatinous)

-Maintains the shape of the hollow eyeball and holds the retina into place

17
Q

3 layers of the eyeball

A
  1. ) Fibrous layer (outer layer)
  2. ) Vascular layer (middle layer), three regions
  3. ) Retina (inner layer): nervous layer
18
Q

Fibrous layer of the eyeball

outer layer

A
  • Sclera: Tough opaque connective tissue

- Cornea: Transparent region

19
Q

Vascular Layer (middle layer), supplies blood to the other two layers

A
  • Choroid: Highly vascularised area
  • Ciliary body: Forms muscular rings around lens
  • Iris: Adjustable diaphragm that controls diameter of pupil (coloured area)
20
Q

Retina (inner layer): Nervous layer

A
  • Photoreceptors (cones & rodes)
  • Fovea centralis (cones for visual acuity)
  • Optic disc (no photoreceptors)
21
Q

Rods and cones

Photoreceptors

A

Photoreceptors: light detecting cells (converting it to an action potential)
-Light reflects off objects and travels through our eyes to the photoreceptors of the retina

22
Q

Rods (photoreceptors)

A

Receptors for dim light and peripheral vision

23
Q

Cones (photoreceptors)

A

Receptors for bright light, colour and visual acuity

24
Q

Focusing light on the Retina: 2 processes

A
  1. ) Refraction

2. ) Accommodation

25
Q

Refraction (focusing light on the Retina)

A

Bending of light when it changes speed passing from one medium to another

26
Q

Accomodation (focusing light on the Retina)

A

Changing the shape of the lens to direct light rays to the retina

27
Q

Refraction of light

A

Refractions explains why these objects appear the way they do (why they appear bent)

28
Q

Focussing light on the Retina: Refraction involving 4 changes
(Bending of the light, multiple
refractions before it reaches the retina)

A
  1. ) Air to cornea
  2. ) Cornea to aqueous humour
  3. ) Aqueous humour to lens
  4. ) Lens to vitreous humour
29
Q

Focussing light on the Retina: Refraction

A

The amount of refraction is constant for changes except for the amount of refraction through the lens because the lens is highly elastic and changes shape for focussing (changes the bending of the light ray)

30
Q

Combined effects of the refractions…

A

occur to focus the image on the retina

31
Q

Focussing light on the Retina…Refraction of distant vision

flattened lens

A

An object that is 6 metres or more away from the eye reflects light rays that are virtually parallel to each other. These light rays will focus on the retina with the lens flattened (ciliary muscles relaxed, suspensory ligaments tightened)

32
Q

Distance vision

A

Sympathetic activation

  • Nearly parallel rays from distant object
  • Lens is flattened for distant vision. Sympathetic input relaxes he ciliary muscle, tightening the ciliary zonule, and flattening the lens
33
Q

Focusing light on the Retina: Close vision

rounder lens

A

Objects that are nearer than 6m reflect light rays that are on divergent paths. These requirer greater refraction to bring them into focus at the retina

  • Lens is less thickened (more round) to increase refractory power=accomodation
  • This is achieved through contraction of the ciliary muscle
34
Q

Close vision

A

Parasympathetic activation

  • Divergent rays from close object
  • Lens bulges for close vision. Parasympathetic input contracts the ciliary muscles, loosing the ciliary zonule, allowing the lens to bulge
35
Q

Focussing for close vision

A
  • Convergence of the eyeballs: turning both eyeballs medially e.g.) looking at the tip of your nose
  • Constriction of pupil: by iris sphincter muscle to decrease the diameter of the pupil. This prevents most divergent light rays from entering eye and causing blurred vision
36
Q

Converting light to neural impulses

A

Once an object is focussed light rays are directed on the retina where photoreceptors (rods and cones) are located

37
Q

Rods contain rhodopsin

A
  • Light promotes the breakdown of rhodopsin causing the rod cell membrane to depolarise, which produces and action potential
  • The visual pigments of cones operate in similar fashion
38
Q

Rhodopsin

A

Sensitive to light, found in rods

BMA1901-Module 7 (6 decks)

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