Sense Organs: Human Eye Structure, Vision Process and Common Eye Disorders

Item 12 - Your Senses

1 - What are the sense organs and their responsible organs?

Touch (skin), smell (nose), sight (eyes), hearing (ears) and taste (tongue).

2 - How do environmental stimuli reach the nervous system?

Sense organs transform electrical stimuli into impulses that travel through nerve cells.

3 - Identify the parts of the eye

• a) Layer with rich blood vessels: Choroid
• b) Opening through which light enters, after the cornea: Pupil
• c) White part that protects the eye: Sclera
• d) Colored part of the eye: Iris
• e) Central transparent region of the eye: Cornea
• f) Internal light-sensitive layer: Retina (the crystalline lens is the internal transparent structure)

4 - Do we recognize an object when the image is formed on the retina? Correct?

No. The image is only formed when nerve messages from the retina reach the brain, which then produces the correct image.

5 - What is the function of the retina?

It transforms light into nerve messages that are carried through the optic nerve to the brain.

6 - What are rods?

Rods are light-sensitive cells that capture images in places with little illumination. They do not distinguish colors and the images are not very sharp.

7 - What are cones?

Cones are light-sensitive cells that function in well-lit places, providing colorful and sharp images.

8 - What is the difference between animals that see colors and those that do not?

Animals that see colors have three types of cones in the retina, which react to blue, green and red light. Many vertebrates perceive the world in colors, but most fish depend on smell and have only blue cones.

9 - In which region of the retina is the image formed?

In the central fovea.

10 - What is the blind spot in the eye?

It is a region of the retina where the optic nerve passes through and which has no rods or cones.

11 - What is the relationship between vitamin A and image formation?

Vitamin A transforms light impulses into nerve impulses.

12 - Identify the vision problems described below.

• a) Difficulty seeing up close due to loss of lens elasticity: Presbyopia
• b) Difficulty seeing distant objects because the image is formed in front of the retina: Myopia
• c) Blurred vision due to irregularities of the cornea or lens, causing the image to be out of focus: Astigmatism
• d) Difficulty seeing close objects because the image is formed behind the retina: Hyperopia
• e) Difficulty identifying some colors: Color blindness
• f) Clouding of the lens, where the lens loses transparency: Cataract
• g) Increased eye pressure damaging the optic nerve: Glaucoma

13 - A person entered a dark place and one of the parts of their eye dilated. Which one?

The pupil.

14 - Organize the sequence of eye parts through which light passes.

Cornea → Aqueous humor → Pupil → Lens → Vitreous body → Retina.

15 - What are the two light-sensitive cell types and what is the difference between them?

Cones and rods. Cones work best in well-lit environments and perceive colors, while rods function in low light and do not perceive colors.

16 - What can fish not see because they lack retinal cones?

Colors.