Chapter 51: The Eye: II. Receptor and Neural Function of the Retina

Question 1

The absorption characteristics of the blue-sensitive pigments in certain type of cones show peak absorbencies at light wavelengths of:

Answer 1

445

Question 2

The absorption characteristics of the green-sensitive pigments in certain type of cones show peak absorbencies at light wavelengths of:

Answer 2

535

Question 3

The absorption characteristics of the red-sensitive pigments in certain type of cones show peak absorbencies at light wavelengths of:

Answer 3

570

Question 4

What best describes the electrical response of rods in the retina to photopic conditions?

Answer 4

hyperpolarization

Question 5

This is a discomfort or pain to the eyes due to light exposure; it is a medical condition, not a fear or phobia

Answer 5

Photophobia.

The lack of melanin (black pigment) in the irises of the eyes makes them somewhat translucent, so they cannot block light effectively. The lack of melanin in the pigment layer of the retina causes light to scatter inside the globe of the eye, which decreases contrast and visual acuity

Question 6

The nutrient blood supply for the internal layers of the retina is derived from the _________, which enters the eyeball through the center of the optic nerve and then divides to supply the entire inside retinal surface

Answer 6

central retinal artery

Question 7

The outer layers of the retina, especially the outer segments of the rods and cones, depend mainly on diffusion from the _____ blood vessels for their nutrition, especially for their oxygen.

Answer 7

choroid blood vessels

Question 8

The reconvertion of the all-trans retinal into 11-cis retinal is catalyzed by the enzyme:

Answer 8

retinal isomerase

Question 9

The taste sensation of bitter is cause by many substances that contain ____, as well as by ____

Answer 9

nitrogen

alkaloids

Question 10

A person with loss of red cones is called a _________; the overall visual spectrum is noticeably shortened at the long wavelength end because of a lack of the red cones

Answer 10

protanope

Question 11

A color-blind person who lacks green cones is called a ___________; this person has a perfectly normal visual spectral width because red cones are available to detect the long wavelength red color. However, they can only distinguish 2 or 3 different hues, whereas somebody with normal vision sees 7 unique hues.

Answer 11

deuteranope

Question 12

Which parent it the color blindness carrier?

Answer 12

mother

red-green color blindness

Question 13

Only rarely are blue cones missing, although sometimes they are underrepresented in a genetically inherited condition called

Answer 13

blue weakness

Question 14

These charts are arranged with a mixture of spots of several different colors, and are rapid method for determining color blindness

Answer 14

Color test charts (Ishihara charts)

spot charts

Question 15

This type of cell transmits signals in the retrograde direction from the inner plexiform layer to the outer plexiform layer. These signals are inhibitory and are believed to control lateral spread of visual signals by the horizontal cells in the outer plexiform layer. Their role may be to help CONTROL THE DEGREE of contrast in the visual image.

Answer 15

Interplexiform cell

Question 16

Which cell type(s) have action potentials in the retina of the human eye?

Answer 16

ganglion cells;

The only retinal neurons that always transmit visual signals via action potentials are the ganglion cells, and they send their signals all the way to the brain through the optic nerve. Occasionally, action potentials have also been recorded in amacrine cells, although the importance of these action potentials is questionable.

Question 17

These retinal cells provide a second mechanism for lateral inhibition, in addition to the horizontal cell mechanism.

Answer 17

bipolar cells

**Because depolarizing and hyperpolarizing bipolar cells lie immediately against each other, this provides a mechanism for separating contrast borders in the visual image, even when the border lies exactly between two adjacent photoreceptors. In contrast, the horizontal cell mechanism for lateral inhibition operates over a much greater
distance.

Question 18

These cells, by their lateral connection provides lateral inhibition and helps to ensure transmission of visual patterns with proper visual contrast.

Answer 18

horizontal cells

Question 19

The phenomenon wherein reduction of rhodopsin and cone pigments by light reduces the concentrations of photosensitive chemicals in rods and cones.

Answer 19

light adaptation

Question 20

If a person remains in darkness for a long time, the retinal and opsins in the rods and cones are converted back into the light-sensitive pigments. Furthermore, vitamin A is converted back into retinal to increase light-sensitive pigments, the final limit being determined by the amount of opsins in the rods and cones to combine with the retinal. This process is called:

Answer 20

dark adaptation

Question 21

Arrange the photoreceptors from those with the broadest to narrowest spectrum of wavelengths of light in which they respond to

Answer 21

Red cone receptors
Rod receptors
Green cone receptors
Blue cone receptors