Human Eye Anatomy and Function

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Questions and Answers

What is the visual light spectrum wavelength range?

380 -- 740 nm

Images in the eye are formed by ______________, which is the bending of light rays.

refraction

What is the cornea?

The transparent external surface of the eye that bends incoming light

What is the pupil?

The opening through which light enters the eye Signup and view all the answers

What is the iris? What does it do?

The colored portion of the eye; it can vary the size of the pupil Signup and view all the answers

What does the lens do?

Helps focus light on the retina Signup and view all the answers

What is the retina?

Layer of neurons at the back of the eye; has photoreceptors (rods and cones) Signup and view all the answers

What is the fovea?

The part of the retina with the most cones (highest visual acuity) Signup and view all the answers

What carries visual information from the eye to the brain?

Optic nerve Signup and view all the answers

What do the ciliary muscles do?

Accommodation -- causing nearer or farther images to come into focus by adjusting the shape of the lens Signup and view all the answers

What is the difference between hyperopia and myopia?

Hyperopia is farsightedness when your eyeball is too short. Signup and view all the answers

In the retina, what is the order of cell layers in which light hits first?

Ganglion cell layer, bipolar cell layer, photoreceptor layer Signup and view all the answers

In the retina, what is the order of cells in which light is processed?

Photoreceptors, horizontal cells, bipolar cells, amacrine cells, ganglion cells Signup and view all the answers

Which cells generate action potentials?

Ganglion cells Signup and view all the answers

What do horizontal cells do?

Modify responses of bipolar cells Signup and view all the answers

What do amacrine cells do?

Modify responses of ganglion cells Signup and view all the answers

What pigment is associated with rods and cones?

Rods contain rhodopsin; cones have photopsins Signup and view all the answers

Study Notes

The Visual Spectrum

Human eyes can see visible light in the spectrum from 380 to 740 nanometers
The bending of light rays (refraction) is essential for forming images in your eye

The Eye and its parts

The cornea is the clear outer layer of the eye that helps bend light rays
The pupil is the opening where light enters the eye
The iris is the colored part of the eye that controls the size of the pupil
The lens is a clear structure behind the pupil that further focuses light onto the retina
The retina is a layer of neurons at the back of the eye that contains photoreceptor cells called rods and cones.
The fovea is a small area within the retina with a high concentration of cones, giving us our sharpest vision
The optic nerve carries signals from the eye to the brain

How we Focus

Accommodation is the process of changing the lens shape to focus on objects at different distances
Ciliary muscles are responsible for accommodation
Hyperopia (farsightedness) occurs when the eyeball is too short and objects are focused behind the retina. Convex lenses are needed to correct this.
Myopia (nearsightedness) occurs when the eyeball is too long and objects are focused in front of the retina. Concave lenses are needed to correct.

### The Retina’s Layers

Light passes through the following retinal cell layers:
- Ganglion cell layer
- Bipolar cell layer
- Photoreceptor layer
Processing of light happens in this order:
- Photoreceptors (rods and cones)
- Horizontal cells
- Bipolar cells
- Amacrine cells
- Ganglion cells
Only ganglion cells generate action potentials. All other cell types within the eye generate graded potentials.

Rods vs. Cones

Rods are responsible for low-light vision and contain rhodopsin. They have a large receptive field and are good for peripheral vision.
Cones are responsible for color vision and have a smaller receptive field.

Additional Information

Horizontal cells modify the responses of bipolar cells
Amacrine cells modify the responses of ganglion cells

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Description

Explore the fascinating structure and function of the human eye in this quiz. Learn about the key parts of the eye, how we perceive light, and the process of accommodation for focusing on objects. Test your understanding of the visual spectrum and the components that contribute to our vision.