12 Visual System

Question 1

The wall of the eye consists of three concentric layers?

Answer 1

fibrous tunic

vascular tunic

neuroepithelial (or inner) tunic

Question 2

These maintain pressure within the eyeball, thus preventing the eyeball from collapsing

Answer 2

vitreous body

aqueous humor

Question 3

fibrous tunic consists of

Answer 3

sclera

cornea

Question 4

It provides mechanical support and protection of the eye

Answer 4

Fibrous tunic

Question 5

-covers the entire outside surface of the eye except for the cornea

-consists of dense connective tissue and provides rigidity, helping to maintain the shape of the eyeball.

Answer 5

Sclera

Question 6

-is a transparent layer covering the iris, the colored portion of the front of the eye.

-is curved and therefore helps bend light toward the retina.

Answer 6

Cornea

Question 7

The vascular tunic consists of

Answer 7

iris

ciliary body

choroid

Question 8

-contains dilator and sphincter muscles.

Answer 8

Iris

Question 9

Contraction of the sphincter muscle results in a ____ in pupillary size (miosis) while Contraction of the dilator muscle results in pupillary dilation (mydriasis).

Answer 9

decrease

Question 10

____ reflects the general state of sympathetic tone, and certain emotions such as pain, fear, and anger

Answer 10

Pupillary dilation

Question 11

consists of the ciliary processes and ciliary muscles

Answer 11

Ciliary body

Question 12

-are folds of tissue containing capillaries that secrete aqueous humor.

-Extending from this to the lens are zonular fibers (suspensory
ligaments).

Answer 12

ciliary processes

Question 13

-are a bundle of smooth muscles that alter the shape of the lens to allow for near or far vision.

-plays a key role in accommodation. This process involves the change in the curvature of the lens when focusing on near or far objects. When focusing on near objects, it contracts resulting in a more convex lens.

Answer 13

ciliary muscles

Question 14

-this consists of loose connective tissue with numerous vasculature and melanocytes.

-It serves a nutritive function for ocular tissue.

Answer 14

choroid

Question 15

-is an additional layer in the choroid found in many species of domestic animals, including cats, dogs, horses, and ruminants

-This causes the animal’s eyes to appear to glow when shined with light.

-this reflects light toward the retina so that the animal can see in low light.

Answer 15

tapetum lucidum

Question 16

What is the innermost tunic of the eye

Answer 16

retina

Question 17

What are the two layers of the retina

Answer 17

outer pigmented layer

inner neural layer

Question 18

layer of the retina that is one cell- a thick layer of melanin-containing epithelial cells, similar to the choroid. These cells also act as phagocytes and store vitamin A

Answer 18

pigmented layer

Question 19

The neural layer has three major layers?

Answer 19

photoreceptor layer

bipolar cell layer

ganglion cell layer

Question 20

What do you call the layers that separate the three major layers of the neural layer from each other

Answer 20

outer and inner synaptic layers

Question 21

Before reaching the photoreceptor layer, light must first pass through the ____

Answer 21

ganglion and bipolar cell layers

Question 22

two types of photoreceptor cells

Answer 22

rod cells (95%)

cone cells

Question 23

photoreceptor cells consist of two portions?

Answer 23

outer segment

inner segment

Question 24

portion of the photoreceptor cells wherein the photosensitive region contains photopigments that convert light stimulus to receptor potential

Answer 24

outer segment

Question 25

portion of the photoreceptor cells that is the metabolic region

Answer 25

inner segment

Question 26

-the photochemical in rod cells

-responsible for the perception of shades of gray.

-has a low threshold of excitability and is easily stimulated by low intensity light.

Answer 26

Rhodopsin

Question 27

-have a higher threshold of excitability than rod cells

-photochemical iodopsin requires relatively high-intensity light to be stimulated.

-less sensitive to light than rod cells.

-provide color.

Answer 27

Cone cells

Question 28

In primates, each cone cell has one of three opsins:

Answer 28

a pigment primarily sensitive to blue, green, or red colors

Question 29

In the dog, each cone has one of two opsins:

Answer 29

a pigment sensitive to light with a wavelength of either violet or yellow-green

Question 30

cells that convert the physical energy of light signals into electrical impulses

Answer 30

Photoreceptor cells (rods and cones)

Question 31

in the retina, this give rise to axons of the optic nerve

Answer 31

Ganglion cells

Question 32

Optic nerve fibers terminate in three nuclei:

Answer 32

lateral geniculate nucleus of the thalamus (that projects fibers to the visual cortex

rostral colliculus (which mediates such visual reflexes as turning the head in response to a sudden visual stimulus or pupillary dilation; and

the pretectal nucleus (which is responsible for pupillary constriction)

Question 33

Opsins serve as G-protein coupled receptors and they contain chromophore ____ that undergo photoisomerization when struck by photons.

Answer 33

11-cis-retinal

Question 34

Cones contain a photosensitive pigment called _____ whereas rods contain ____

Answer 34

opsins

rhodopsin