HAP- Vision

Vision

What are the two kinds of photoreceptors? 

Rods and cones. 

What are rods? 

Photoreceptors distributed all over the retina. They are responsible for vision in low light and are extremely sensitive.

What are cones? 

Photoreceptors concentrated in the center of the retina. They are responsible for detection of colors and are less sensitive than rods.

Where are rods located in the retina? 

Rods are distributed all over the retina. 

Where are cones concentrated in the retina? 

Cones are concentrated in the center of the retina. 

What is the function of rods?

Responsible for vision in low light; extremely sensitive. 

What is the function of cones? 

Responsible for detection of colors; less sensitive than rods. 

What is the pathway of an image from light entering the eye to reaching the brain? 

Light passes through the eye and hits the retinal pigment epithelium (RPE). Light causes molecular changes that begin an impulse. The impulse travels through rods and cones, then bipolar neurons, then ganglion cells before traveling to the brain via the optic nerve. 

What is the fovea centralis? 

A tiny pit in the retina that contains only cones, so it is the point that provides the sharpest image.

What is the blind spot? 

The point where the optic nerve meets the eye. There are no photoreceptors in this area. 

Why do we not regularly notice our blind spot? 

Because the blind spot affects different parts of each eye, and the brain "fills in" the missing images.

What is myopia?

Near-sightedness. It occurs when the eye is too long, causing light to focus in front of the retina.

What is hyperopia? 

Far-sightedness. It occurs when the eye is too short, causing light to focus behind the retina. 

How do corrective lenses help with vision problems?

Corrective lenses help to refract the light so it accurately converges on the retina. 

What is the summary statement for vision? 

Two kinds of photoreceptors (rods and cones) are found in the retinal pigment epithelium. The optic nerve channels impulses from these receptors to the brain but causes a blind spot in the retina where it attaches. If light does not correctly focus on the retina, corrective lenses may be required.