COM 1 Physiology week 6 Flashcards
Name the layers of the eye
- Outer fibrous layer
- Middle vascular layer
- Inner Neural layer
What does the outer fibrous layer contains
Cornea, corneal epithelium, conjunctiva, sclera
What does the Middle Vascular layer contasij
Iris +choroid
What does the inner neural layer contain
Retina
What is the function of the lens
Focuses light onto the retina
When does refraction occur
It occurs when a wave changes directions a it passses from one medium to another due to a change in speed or medium
What does the refractive index of material determine
How much light is refracted
Name the 4 refractive interfaces which the eye has
-Interference between air to the surface of the cornea
-Posterior surface of the cornea to aqueous humor.
Aqueous humor to the anterior surface of the lens.
Posterior surface of the lens to vitreous humor.
What is the refractive indices of the materials :
-Air
-Cornea
-Aqueous humor
-Lens
-vitreous humor
Air: 1
Cornea: 1.38
Aqueous humor: 1.33
Lens: 1.40 (average)
Vitreous humor: 1.34
How much of the eyes refractivee Power does the cornea provide
The cornea provide 2/3 of the eyes refractive power
What is accommodation
When the interna lens of the eye can change its culture in response to nervous signals form the brain
Explain the processin formation of an imagine on the retina
-Starting from the lens system
-How the brain precieves the image
The lens system of the eye focuses an image on the retina, which is inverted and reversed compared to the object.
The brain perceives the image upright because it is trained to interpret an inverted image as normal.
Explain how/THE MECHANISM of how the lens can change shape in childre
-The lens increases in refractive power
-Then the lens change from moderately convex to very convex
Explain how the ciliary muscle controls the shape of the lens
And the ciliary muscle controls the shape of the lens throgh its meridional and circular muscle fiibers
Explain how the parasympathetic nerves control the cillary in accommodation
+ what happens when it is stimulated
Parasympathetic nerve signals from the third cranial nerve control the ciliary muscle.
When stimulated, these nerves contract the muscle, releasing the tension on the lens, allowing it to thicken and focus on nearby objects.
What is presbyopia
Loss of accommodation
Explain why presbyopia/ loss of accommodation occurs
As a person ages, the lens becomes thicker and less elastic, reducing its ability to change shape.
The power of accommodation decreases with age,
What is the effect of people with presbyopia(loss of accommodation) + what do they require
- They can no longerfocus on both near and far objects, requiring bifocal glasses for clear vision at differnet distances
