Hall: Guyton and Hall Textbook of Medical Physiology, 12th Edition
Chapter 50: The Eye: II. Receptor and Neural Function of the Retina
Test Bank
1. Which compound is responsible for activation of transducin during photoreception?
A. cGMP
B. All-trans-retinal
C. Rhodopsin
D. Metarhodopsin II
2. During photoreception all of the following increase EXCEPT:
A. cGMP phosphodiesterase
B. Transducin
C. Metarhodopsin II
D. Sodium influx into the outer segment of the rod
3. Which of the following statements is correct?
A. The total number of cones in the retina is much greater than the total number of rods
B. Each individual cone responds to all wavelengths of light
C. Activation of photoreceptors (rods and cones) results in hyperpolarization
D. The central fovea contains only rods
4. Which best describes the function of the horizontal cells of the retina?
A. The horizontal cells prevent the lateral spread of excitation caused by light on the
retina
B. Horizontal cells generate action potentials and transmit this activity to the lateral
geniculate nucleus
C. Horizontal cells connect the photoreceptors to the ganglion cells
D. Horizontal cells begin the analysis of the visual seen
5. Which of the following statements best describes the relatively poor visual acuity in
humans at night compared to daylight?
A. The central fovea is the area of greatest visual acuity and this area contains only rods
B. The central fovea is the area of greatest visual acuity and this area contains only
cones
C. The central fovea contains rods that have a connection ratio of 1:1 with ganglion cells
Test Bank
50-2
D. The central fovea, the area of greatest visual acuity, is the exit point for ganglion cell
axons which results in greater activation of photoreceptors in this area
6. 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?
A. Bipolar cells
B. Horizontal cells
C. Ganglion cells
D. Amacrine cells
7. Which of the following correctly explains the events that lead to the change in receptor
potential in the rod photoreceptor during photoactivation?
A. cGMP dependent sodium channels in the outer segment of the rod open resulting in
hyperpolarization of the receptor
B. cGMP levels increase which results in depolarization of the receptor
C. cGMP levels increase which results in an increase in the sodium influx into the outer
segment of the rod and the receptor hyperpolarizes
D. cGMP levels decrease which results in a decrease in sodium influx into the outer
segment of the rod and the receptor hyperpolarizes
8. Which of the following statements is correct?
A. The total number of rods in the retina is much greater than the total number of cones
B. Each individual cone responds to all wavelengths of light
C. Activation of photoreceptors (rods and cones) results in depolarization
D. The central fovea contains only rods
9. Which of the following statements are true?
A. An individual rod can respond to all wavelengths of light
B. In conditions of normal daylight, the level of cGMP is sufficient to keep open the
sodium channels in the outer segment of the photoreceptors
C. Light causes the outer segments of the photoreceptors to depolarize
D. All of the above
10. Which area of the retina is responsible for the greatest visual acuity in humans?
A. The fovea
B. The optic disc
Test Bank
50-3
C. The pigment layer
D. The central fovea
11. 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?
A. Metarhodopsin II
B. cGMP
C. cis-retinal
D. cAMP
12. Which cell types in the retina exhibit axon potentials?
A. Ganglion cells
B. Amacrine cells
C. Bipolar cells
D. Horizontal cells