Module 3.1 Vision

Question 1

What are the five special senses?

Answer 1

Vision, smell, taste, hearing and equilibrium (balance)

Question 2

What are the two parts of the outer layer of the eye?

Answer 2

Sclera and cornea

Question 3

What is included in the middle layer of the eye?

Answer 3

Choroid, the ciliary muscle, and the iris.

Question 4

The pupil is a hole in the ____.

Answer 4

Iris

Question 5

The inner sensory layer is the _____.

Answer 5

Retina

Question 6

What are the two types of photoreceptors and their functions?

Answer 6

The more numerous cells are rods which are stimulated in dim light. Rods are more sensitive to light but do not generate sharp or color images. The cones operate in bright light helping to generate sharp color images.

Question 7

The interior of the eye (posterior to the lens) is filled with_____

Answer 7

Vitreous fluid

Question 8

True or False: The vision pathway begins as the optic tracts, crosses at the optic chiasm and then moves through the optic nerve.

Answer 8

False

Question 9

Where is the LGN located?

Answer 9

Thalamus

Question 10

True or False: The nasal visual field is the visual field on the lateral sides of each eye.

Answer 10

False

Question 11

Why is touch not considered a special sense?

Answer 11

Does not have specialized receptor cells or specialized somatic and visceral afferents.

Question 12

How does the sense of touch function?

Answer 12

Uses general receptors composed of modified dendrites of sensory neurons. General somatic and visceral afferents received combined info on pressure, vibration, pain, and heat.

Question 13

Where is the aqueous humor located?

Answer 13

Space between the cornea and the lens.

Question 14

How many layers does the eye have? What are they?

Answer 14

3 layers: the outer fibrous layer, middle layer, and the inner sensory layer.

Question 15

What are the functions of the choroid?

Answer 15

Its dark color prevents light from dispersing throughout the eye and it is highly vascularized to supply blood to the other layers of the eye.

Question 16

What is the function of the ciliary body?

Answer 16

To change lens shape allowing it to focus.

Question 17

What is the function of the iris?

Answer 17

Uses its muscle fibers to contract or dilate based on the amount of light in the environment, lets more or less light in through the pupil.

Question 18

What is the vitreous body?

Answer 18

The interior of the eye posterior to the lens

Question 19

What is the main function of the vitreous fluid?

Answer 19

To hold the retina in place to the choroid.

Question 20

Where is the lens located?

Answer 20

Posterior to the iris and pupil.

Question 21

What is the pathway of light to the retina?

Answer 21

Through the cornea, aqueous humor, lens, and vitreous humor.

Question 22

What is the pathway of visual info from the retina onwards?

Answer 22

The photoreceptors to the optic nerve, optic chiasm, optic tracts, lateral geniculate nucleus of the thalamus, primary visual area of the occipital lobe.

Question 23

Where is the optic chiasm located?

Answer 23

At the base of the hypothalamus.

Question 24

The medial fibers of the optic nerve ….

Answer 24

Cross over to the other side when they reach the optic chiasm.

Question 25

Where do the optic tracts form and where do they terminate?

Answer 25

They form at the optic chiasm and terminate at the lateral geniculate nucleus (LGN) of the thalamus.

Question 26

What do the optic radiations connect?

Answer 26

The thalamus and the primary visual area of the occipital lobe.

Question 27

What allows for 3-D vision?

Answer 27

Overlapping information in the nasal visual fields allows for 3-D vision, called the binocular visual field.

Question 28

True or false: Only the medial fibers cross at the optic chiasm.

Answer 28

True

Question 29

The left side of the brain receives information from the _________ of the left eye and the ________ of the right eye.

Answer 29

The left side of the brain receives information from the medial side of the left eye and the lateral side of the right eye (bilateral right visual fields).

Question 30

The medial rectus turns the eye _____. The medial rectus is controlled by CN _____.

Answer 30

Medially, CN III, oculomotor.

Question 31

What is a cataract?

Answer 31

Cataracts are lenses that slowly become hardened and cloudy over time.

Question 32

What is another name for double vision?

Answer 32

Diplopia

Question 33

How many muscles control the eye and what are they called?

Answer 33

6 Extrinsic eye muscles.

Question 34

What are the 2 extrinsic eye muscles that are not innervated by the oculomotor nerve?

Answer 34

The lateral rectus and superior oblique.

Question 35

What innervates the lateral rectus muscle?

Answer 35

The abducens nerve CN VI.

Question 36

What innervates the superior oblique muscle?

Answer 36

The trochlear nerve CN IV.

Question 37

How does the superior oblique move the eye?

Answer 37

Depresses, laterally, and internal rotation.

Question 38

How does the inferior oblique move the eye?

Answer 38

Elevates, laterally, and external rotation.

Question 39

How does the inferior rectus move the eye?

Answer 39

Medially and depresses.

Question 40

How does the superior rectus move the eye?

Answer 40

Medially and elevates.

Question 41

What is a common cause of diplopia? How can this be observed and tested clinically?

Answer 41

Damage to the abducens nerve. Patient's eye rests medially from lack of muscle tone; the nasal visual pathway cannot be maintained. If patient is told to look straight ahead and follow finger and one eye cannot move laterally.