W4 L3 (Vision) Flashcards
What is the retina?
A layer of light-sensitive cells
What is the general path of image transduction?
An image is coded on the retina and transmitted through a series of complex steps
What is the stimulus in vision?
Light waves between 380 and 760nm
Who needs light?
All species need light to see, some can see wavelengths that we can’t
What are the 3 properties of light and what do they impact of what we see?
- Wavelength- Color
- Intensity- Brightness
3 Purity-Saturation
What determines intensity and purity
Intensity- # of photons
Purity- # of wavelengths
What happens at the pupil?
Light is let in
What is the iris?
The colorful part of the eye
What are the 4 protective mechanisms of the eye?
- Sheltered in a bony socket
- Eyelids act like shutters
- Blinking disperses tears
- Eyelashes trap debris
What produces tears and where is this structure located?
The lacrimal gland in the upper lateral corner under the eyelid
Where do tears drain?
The corners of the eye and back into the nasal passageway
What are the 3 layers of the eye from peripheral to the interior?
- Sclera/cornea
- Choroid/Ciliary body/iris
- Retina
What is the sclera?
The visible white part of the eye
What is the cornea?
The clear, anterior most outer layer of the eye through which light rays pass to the interior of the eye
What is the choroid?
The layer under the sclera that is highly pigmented and contains blood vessels that nourish the retina
What is the retina?
The innermost layer in the posterior region of the eye that contains the eye’s photoreceptors, the rods and cones
What is the difference between rods and cones?
Rods- Night vision
Cones- Day vision
What do the photoreceptors of the eye do?
Convert light energy to nerve impulses
What do the pigment in the choroid and retina do?
Absorb light that scatters after striking the retina
What is the lens?
A transparent, biconvex structure of the eye that refracts (bends) light rays and whose strength can be adjusted to accommodate for vision at different distances
What is the vitreous humor and what does it do?
A semifluid, jelly-like substance located in the larger posterior (rear) cavity between the lens and retina; is important in maintaining the spherical shape of the eyeball
What is the aqueous humor and what does it do?
The clear, watery fluid in the anterior chamber of the eye; provides nourishment for the cornea and lens
Why are there no blood vessels in the cornea and lens
Because they would impede the passing of light to photoreceptors
What is the ciliary body?
The portion of the eye that produces aqueous humour and contains the ciliary muscle
What is refraction?
The convex shape of the cornea and lens that bends light inwards
What are the two muscles around the pupil?
- Circular (constrictor)
2. Radial (dilator)
What happens when the radial muscle (dilator) opens up the pupil, and when does this happen?
It increases the number of photons admitted and this is good for dim light
Which of the constrictor or dilator responds to the para and what one responds to the symp?
Para-Constrictor
Symp-Dilator
What does creates a clearer image a large or small pupil in clear light?
Small
What is a sign of arousal with regards to the eye?
Dilated pupil
What structures direct light to the retina?
Cornea and lens
What part of the eye is the basis for eye scanning?
The iris
What is a light ray?
The forward movement of light in a particular direction
What is refraction?
The bending of a light ray
Do convex and concave lens’ diverge or converge rays and what is found in the eye?
Convex-Converge
Concave-Diverge
The lens of the eye is convex
What is astigmatism?
A defect in the eye or lens caused by a deviation from spherical curvature, resulting in distorted images, as light rays are prevented from meeting at a common focus
What is accommodation?
The ability to adjust the strength of the lens in the eye so that both near and far sources can be focused on the retina
What is the ciliary muscle?
A circular ring of smooth muscle within the eye whose contraction increases the strength of the lens to accommodate for near vision
What are the 2 main components of the ciliary body and what are their functions?
- Ciliary muscle-Strengthen lens
2. Capillary network-Produces aqueous humor
