Question

13. Photoreceptors in vertebrate retinas respond to light stimuli by:

A. Firing action potentials in various patterns, depending on the stimulus intensity

B. Graded hyperpolarization of the membrane (stimulus intensity-dependent)

C. Reducing the amount of acetylcholine (Ach) exocytosed

D. Increasing the amount of glutamate exocytosed

E. B and C

14. In terms of color responses, how many types of cones are there in the human eye?

A. One – responds equally well to all colors

B. Three – red, blue and green based on the spectral sensitivities of the three different cone opsins

C. Two – with maximum absorbances in the UV and infrared wavelengths

D. None! Color vision is mediated solely by the rod photoreceptors

15. What is responsible for the depolarized state of the photoreceptor membrane in the dark?

A. The open cGMP-gated sodium (cation) channels

B. The open leak potassium channels

C. The influx of positive charge known as the “dark” current

D. The increased activity of the enzyme phosphodiesterase

E. A and C

16. What are some factors that contribute to visual acuity in the central retina?

A. The lateral displacement of retinal cells - other than photoreceptors - in the fovea (light scatter reduction)

B. One-to-one communication between photoreceptors and next order neurons – bipolar cells

C. The lack of large blood vessels in front of the foveal region

D. All of the above

Answer 1

MCQ with Explanation