Vision

Question 1

Describe:

the conjunctiva of the eye

Answer 1

The conjunctiva is a thin, transparent membrane that covers the front of the eye and the inside of the eyelid; it lubricates and protects the eye.

Question 2

Describe:

the cornea of the eye

Answer 2

The cornea is the transparent, slightly convex covering of the front of the eye; it protects the eye and refracts light.

The cornea directly covers the iris, pupil, and aqueous humour.

Question 3

Describe:

the aqueous humor of the eye

Answer 3

The aqueous humor is a gelatinous, transparent fluid that fills the area between the lens and the cornea; it provides nutrients, maintains optimal eye pressure, and refracts light.

Question 4

Describe:

the pupil of the eye

Answer 4

The pupil is a small hole located in the center of the iris; it allows light to enter the eye.

The pupil appears black because entering light rays are absorbed by tissues in the eye.

Question 5

Describe:

the iris of the eye

Answer 5

The iris is a thin, circular muscle that surrounds the pupil; it controls the diameter of the pupil and thus, how much light enters the eye.

The iris is the structure that gives the eye its characteristic color.

Question 6

Will the pupil diameter be larger when in the light or the dark?

Answer 6

In the dark.

In the dark, pupil diameter will increase to let in more light.

Question 7

Describe:

the lens of the eye

Answer 7

The lens is a transparent structure inside the eye; it changes shape to effectively refract light as it enters the eye, properly focusing the light on the center of the retina.

Question 8

Describe:

the vitreous humor of the eye

Answer 8

The vitreous humor is the gelatinous, transparent mass filling the area between the lens and the retina; it effectively keeps the retina in place.

The vitreous humor is not naturally replenished; therefore, foreign material must be surgically removed.

Question 9

Desribe:

the retina of the eye

Answer 9

The retina is a thin, light-sensitive tissue that lines the inside of the eye; it converts light energy to nerve impulses that are sent to the brain to be processed.

Question 10

Describe:

the sclera of the eye

Answer 10

The sclera is the white, fibrous covering of the eye that is continuous with the cornea; it forms the hard outer protective wall of the eye.

Question 11

Describe:

the choroid of the eye

Answer 11

The choroid is a highly vascularized layer of the eye that sits between the sclera and the retina; it carries nutrients to the iris and retina. With the help of melanin, it also helps prevent reflection of light that could damage the eye.

Question 12

Define:

refraction of light that enters the eye

Answer 12

Refraction is the process by which the rays of light entering the eye bend in order to strike the proper place on the retina.

Question 13

What characteristics of the eye promote the refraction of light?

Answer 13

The following characteristics of the eye promote the refraction of light as it enters the eye:

1. The consistency of the aqeous humor and vitreous humor
2. The curvature of the cornea
3. The shape of the lens

Question 14

Describe:

the ciliary muscles of the eye

Answer 14

The ciliary muscles are a ring of smooth muscle around the inside of the eye; they control the shape of the lens within the eye.

Question 15

Describe:

the suspensory ligaments of the eye

Answer 15

The suspensory ligaments attach the lens of the eye to the ciliary muscles; they force the lens to change shape as the ciliary muscles move.

Question 16

How is the refraction of light affected when the ciliary muscles are relaxed?

Answer 16

When the ciliary muscles are relaxed, there is less refraction of light.

As the ciliary muscles relax, the tension on the suspensory ligaments increases, causing the lens to flatten out and decrease the degree of refraction.

Question 17

How is the refraction of light affected when the ciliary muscles are relaxed/**contracted?

Answer 17

When the ciliary muscles are relaxed, there is greater refraction of light.

As the ciliary muscles contract, the tension on the suspensory ligaments decreases, causing the lens to form a more natural convex shape, which increases the degree of refraction.

Question 18

What occurs when light rays converge at a point past the retina?

Answer 18

If light rays converge at a point past the retina, the person will experience far-sightedness, or hypermetropia, meaning they have difficulty seeing objects close up.

Far-sightedness occurs when the eye is too short from front to back, and can be corrected with eyeglasses that have convex lenses.

Question 19

What occurs when light rays converge at a point in front of the retina?

Answer 19

If light rays converge at a point in front of the retina, the person will experience near-sightedness, or myopia, meaning they have difficulty seeing objects at a distance.

Near-sightedness occurs when the eye is too long from front to back, and can be corrected with eyeglasses that have concave lenses.

Question 20

When are eyeglasses with bifocal lenses prescribed?

Answer 20

Bifocal lenses are prescribed to people with presbyopia, or the hardening of the lens.

Presbyopia causes an inability of the lens to form the shapes needed for adequate vision at all distances.

Question 21

Describe:

bifocal lenses in eyeglasses

Answer 21

Bifocal lenses are lenses in which the top half is concave, for distance vision, and the bottom half is convex, for close-up vision.

Question 22

Define:

the visual field of the eye

Answer 22

The visual field of the eye is the spatial area imprinted on the retina when the eye is focused on a distant point.

Centrally, the two eyes have overlapping visual fields, while the right eye’s visual field extends farther to the right, and the left eye to the left.

Question 23

What is the function of:

the optic nerve

Answer 23

The optic nerve transmits visual information from each eye to the various brain structures that analyze these visual signals.

Question 24

Define:

the optic chiasm

Answer 24

The optic chiasm is the point at which the optic nerves from both eyes intersect and allow some axons to cross over to the other side of the brain.

The optic chiasm is located beneath the hypothalamus, in close proximity to the pituitary gland.

Question 25

What are the five possible relay structures between the optic chiasm and the primary visual cortex?

Answer 25

Five relay structures between the retina and the primary visual cortex are:

1. The LGN of the thalamus
2. The suprachiasmatic nucleus of the hypothalamus
3. The pretectum of the midbrain
4. The superior colliculus of the midbrain
5. The pulvinar nucleus of the thalamus

Question 26

What is the most utilized relay structure between the optic chiasm and the primary visual cortex?

Answer 26

The majority of the visual nerve fibers project to the lateral geniculate nucleus (LGN) of the thalamus.

Question 27

After reaching the LGN of the thalamus, where are the majority of visual nerve fibers projected to?

Answer 27

the primary visual cortex of the brain

Question 28

What is the name given to the visual nerve fibers that project from the LGN to the brain’s cortex?

Answer 28

the optic radiation

Question 29

What is the role of visual signals sent to:

the suprachiasmatic nucleus of the hypothalamus

Answer 29

Visual signals sent to the suprachiasmatic nucleus of the hypothalamus deal with the body’s internal clock. The images it receives keep the body informed about the darkness or lightness of the environment.

This allows the body to coordinate the body’s sleep-wake cycle based on daylight and night.

Question 30

What is the role of visual signals sent to:

the pretectum of the midbrain

Answer 30

The visual signals sent to the pretectum of the midbrain deal with certain eye movements and the opening of the pupil.

Question 31

What is the role of visual signals sent to:

the superior colliculus of the midbrain

Answer 31

The superior colliculus of the midbrain deals with visual signals involved in moving the eye; it allows a stimulus that initially appears in the peripheral vision to be clearly viewed.

Question 32

What is the role of visual signals sent to:

the pulvinar nucleus of the thalamus

Answer 32

Visual signals sent to the pulvinar nucleus of the thalamus are involved in the interpretation of images, visual attention and motion perception.

Question 33

Describe the location and function of:

the primary visual cortex

Answer 33

The primary visual cortex is located in the most posterior portion of the occipital lobe of the brain.

It functions as the brain’s first interpreter of basic visual signal information, such as location, color, and shape.

Question 34

Describe the location and function of:

the secondary visual cortex

Answer 34

The secondary visual cortex is located on the posterior part of the occipital lobe; it surrounds the primary visual cortex.

The secondary visual cortex functions to interpret more complex visual images and make associations with other sensory modalities to create a better picture of the world.

Question 35

What are the two major cortical systems for processing visual information?

Answer 35

1. The ventral pathway
2. The dorsal pathway

Question 36

Describe the function of:

the ventral visual pathway

Answer 36

The ventral visual pathway allows for the perception, recognition, and identification of an object based on the object’s intrinsic characteristics, such as color and shape.

Question 37

Describe the function of:

the dorsal visual pathway

Answer 37

The dorsal visual pathway allows for the integration of visual-motor coordination by interpreting the extrinsic characteristics of an object, such as the object’s size, position, and orientation in space.