Question 1

During photoreception all of the following increase except:&#10;A)cGMP phosphodiesterase&#10;B)Transducin&#10;C)Metarhodopsin II&#10;D)Sodium influx into the outer segment of the rod

Accepted Answer

During photoreception, sodium influx into the outer segment of the rod decreases, rather than increases, due to closure of the cGMP-gated ion channels. A, B, and C all increase during photoreception.

Question 2

Which of the following cell types in the retina have axon potentials?&#10;A)Ganglion cells&#10;B)Amacrine cells&#10;C)Bipolar cells&#10;D)Horizontal cells

Accepted Answer

Ganglion cells are the only retinal cells that have axon potentials, which transmit visual information to the brain via the optic nerve. Amacrine cells, bipolar cells, and horizontal cells act as interneurons within the retina and do not transmit information outside of the retina.

Question 3

Which of the following vitamins is essential for preventing night blindness?&#10;A)A&#10;B)B&#10;C)C&#10;D)D&#10;E)E

Accepted Answer

Vitamin A is essential for the proper functioning of the retina and the prevention of night blindness.

Question 4

Which of the following best describes the central fovea of the eye?&#10;A)Cones only, highest visual acuity&#10;B)Cones only, lowest visual acuity&#10;C)Rods only, highest visual acuity&#10;D)Rods only, lowest visual acuity

Accepted Answer

The central fovea contains only cones, which are responsible for high visual acuity and color vision.

Question 5

Which of the following substances is responsible for activation of transducin during photoreception?&#10;A)cGMP&#10;B)All-trans-retinal&#10;C)Rhodopsin&#10;D)Metarhodopsin II

Accepted Answer

Metarhodopsin II is responsible for activation of transducin during photoreception. It is formed by the absorption of photon by rhodopsin, which causes isomerization of all-trans-retinal to 11-cis-retinal, leading to the activation of metarhodopsin II and subsequent activation of transducin. cGMP and rhodopsin are part of the phototransduction cascade, but they are not directly responsible for the activation of transducin.

Question 6

Visual acuity is highest at the fovea centralis partly because each cone cell synapses with multiple ganglion cells in the fovea centralis.&#10;A)Both the statement and the reason are correct and related.&#10;B)Both the statement and the reason are correct but not related.&#10;C)The statement is correct but the reason is not.&#10;D)The statement is not correct, but the reason is correct.&#10;E)Neither the statement nor the reason is correct.

Accepted Answer

The statement is correct, as visual acuity is highest at the fovea centralis due to the high concentration of cone cells present. However, the reason given is not accurate, as cone cells in the fovea centralis actually synapse with only one ganglion cell, resulting in high spatial resolution.

Question 7

Rhodopsin decomposes on exposure to light, causing which of the following in rods of the retina?&#10;A)Depolarization, decreased sodium conductance&#10;B)Depolarization, increased sodium conductance&#10;C)Hyperpolarization, decreased sodium conductance&#10;D)Hyperpolarization, increased sodium conductance

Accepted Answer

Rhodopsin decomposes on exposure to light, causing hyperpolarization of the rod cell membrane, which leads to a decrease in the release of neurotransmitter, and decreased sodium conductance.

Question 8

Which area of the retina is responsible for the greatest visual acuity in humans?&#10;A)Fovea&#10;B)Optic disc&#10;C)Pigment layer&#10;D)Central fovea

Accepted Answer

The central fovea, located within the fovea, contains a high density of cone cells and is responsible for the greatest visual acuity.

Question 9

Which of the following best describes cones of the retina?&#10;A)Black and white&#10;B)Blue, green, violet&#10;C)Blue, yellow, orange&#10;D)Red, blue, green&#10;E)Red, blue, yellow

Accepted Answer

Cones in the retina are responsible for color vision and are sensitive to light in three different wavelength ranges, which roughly correspond to the colors blue, green, and red. Therefore, the best choice is D - red, blue, green.

Question 10

In the retina, the activation of adjacent rods and cones is prevented by the phenomenon of lateral inhibition. Which cell type is thought to be responsible for this process?&#10;A)Bipolar cells&#10;B)Horizontal cells&#10;C)Ganglion cells&#10;D)Amacrine cells

Accepted Answer

Horizontal cells are thought to be responsible for lateral inhibition in the retina. They make synaptic contact with photoreceptor cells and with bipolar cells. They receive signals from multiple photoreceptors and, in turn, suppress the activity of neighboring photoreceptors via inhibitory synapses. This enhances the contrast between light and dark stimuli and contributes to visual acuity.

Question 11

A 45-year-old woman with a vitamin A deficiency is most likely to have increased levels of which of the following substances in rods of the retina?&#10;A)Activated transducin&#10;B)Cyclic guanosine monophosphate&#10;C)Rhodopsin&#10;D)Scotopsin

Accepted Answer

The answer of A 45-year-old woman with a vitamin A...

Question 12

Which of the following factors has a direct action to control sodium channel gating in rods of the retina?&#10;A)Acetylcholine&#10;B)Cyclic adenosine monophosphate&#10;C)Cyclic guanosine monophosphate&#10;D)Norepinephrine&#10;E)Transducin

Accepted Answer

The answer of Which of the following factors has a...

Question 13

Under low or reduced light conditions, which of the following is responsible for the inward-directed sodium current in the outer segments of the photoreceptors?&#10;A)Metarhodopsin II&#10;B)cGMP&#10;C)cis-retinal&#10;D)cAMP

Accepted Answer

The answer of Under low or reduced light conditions, which...

Question 14

Males have a higher incidence of color blindness compared with females because of a genetic disorder passed along by which of the following?&#10;A)X and Y chromosome&#10;B)X chromosome only&#10;C)X or Y chromosome&#10;D)Y chromosome only

Accepted Answer

The answer of Males have a higher incidence of color...

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