Neuroanatomy of Vision: Retina

Question 1

What are the three layers of the eye and subdivisions of each?

Answer 1

Sclera/Cornea,
Uvea (Ciliary Body, Choroid, Iris)
Retina

Question 2

T/F: The annular sphincter muscle of the iris is controlled by sympathetic innervation.

Answer 2

False, it is controlled by parasympathetic innervation. The annular muscle controls constriction of the iris. Eyes constrict under parasympathetic innervation.

Question 3

T/F: The radial dilator muscle is controlled by sympathetic innervation.

Answer 3

True

Question 4

What structure produces aqueous humor in the eye?

Answer 4

ciliary process

Question 5

Where is aqueous humor reabsorbed?

Answer 5

Canal of Schlemm

Question 6

What is the principle cause of glaucoma?

Answer 6

Glaucoma is blindness caused by increased intraocular pressure. Therefore, obstruction of the canal of schlemm or impeded circulation of the aqueous humor would be a cause.

Question 7

The ability to focus on objects in near vision is controlled by what type of innervation and from where?

Answer 7

Parasympathetic from the ciliary ganglia to the ciliary body.

Question 8

Name the three types of ciliary muscles:

Answer 8

Longitudinal, Annular, Oblique

Question 9

What structure has a densest concentration of photoreceptors?

Answer 9

Macula

Question 10

What structure has the densest concentration of cones?

Answer 10

Fovea

Question 11

Name the five types of neurons in the retina:

Answer 11

Photoreceptors, horizontal cells, bipolar cells, amacrine cells, ganglion cells

Question 12

What type of cell facilitates crosstalk between photoreceptor cells?

Answer 12

Horizontal cells

Question 13

Which photoreceptor carries information between ganglion cells?

Answer 13

Amacrine Cells

Question 14

Which structure improves visual acuity by absorbing light not absorbed by photoreceptors?

Answer 14

Pigmented Epithelium

Question 15

What is the name for the perforated sclera through which the optic nerve passes?

Answer 15

Lamina Cribrosa

Question 16

Visual information from cones enter into which sensory pathway of lateral geniculate nucleus?

Answer 16

Parvicellular pathway

Question 17

Visual information from rods enters into which pathway of the lateral geniculate nucleus?

Answer 17

Magnocellular pathway

Question 18

Give the chemical steps of the phototransduction pathway:

Answer 18

Light converts 11-cis retinal into all-trans retinal. All trans-retinal stimulates transducin to activate phosphodiesterase. Phosphodiesterase hydrolizes cGMP to 5’cGMP. Removal of cGMP closes Na+ channels of the cell.

Question 19

During neural development, the eye develops from what structure?

Answer 19

Neural tube

Question 20

The ciliary body controls the refractive properties of the lens in the eye, but what controls the ciliary body?

Answer 20

The ciliary body is controlled by the ciliary ganglia.

Question 21

Explain the principle of lens accommodation in the eye:

Answer 21

When the ciliary body is relaxed, the suspensory ligaments pull the lens flat. When parasympathetic innervation from the ciliary ganglia is received, the ciliary body constricts allowing the lens to bulge due its natural elasticity. This bulged lens is in an accommodated state.

Question 22

Name the functions of the pigmented epithelium:

Answer 22

Reduces reflected light thereby improving visual acuity. Metabolizes photoreceptor discs that are shedded from photoreceptors. Recycles photopigments.

Question 23

Which kind of photoreceptors are part of convergent circuitry that terminates on ganglion cells? Where do the ganglion cells project?

Answer 23

Rods, Layers 1 & 2 of the Lateral Geniculate Nucleus

Question 24

Which photoreceptor type projects to ganglion cells in a 1 to 1 ratio? Where do these ganglion cells project to?

Answer 24

Cones. Layers 3,4,5,6 of Lateral Geniculate Nucleus

Question 25

Describe how dark current activates ganglion cells:

Answer 25

Glutamate has an inhibitory effect on bipolar cells, once glutamate transmission is stopped (dark current), bipolar cells can fire, activating ganglion cells.

Question 26

Which cells are most responsible from the center surround response of a ganglion cell?

Answer 26

Horizontal cells,