Question 1

Which of the following best describes astigmatism?

Accepted Answer

A condition caused by irregularities in the lens or cornea that leads to poor focusing of light in certain areas.

Question 2

What is the primary function of rods in the retina?

Accepted Answer

To act as photoreceptors activated by light, converting light into nervous impulses.

Question 3

Which pigment is found in rods and is responsible for their activation by light?

Accepted Answer

Rhodopsin

Question 4

The bleaching reaction in rods involves the conversion of rhodopsin into which two components?

Accepted Answer

Retinal and opsin

Question 5

Which form of retinal binds to opsin in the absence of light?

Accepted Answer

11-cis form

Question 6

What happens to retinal when it is stimulated by light?

Accepted Answer

It changes from the 11-cis form to the all trans form and dissociates from opsin.

Question 7

Which of the following best explains why we see poorly when moving from light to dark?

Accepted Answer

Most available rhodopsin has undergone the bleaching reaction and needs to be regenerated.

Question 8

Dark adaptation involves which of the following changes in the eye?

Accepted Answer

Production of more rhodopsin and increased sensitivity of rods.

Question 9

Which of the following statements about cones is TRUE?

Accepted Answer

Cones provide color vision and greater acuity than rods.

Question 10

In daylight, which photoreceptors are more active, and what is the result?

Accepted Answer

Cones are more active, allowing us to see color and shapes with greater precision.

Question 11

Which wavelengths of light activate the pigment rhodopsin in rods?

Accepted Answer

Approximately 500 nm (green light)

Question 12

Which vitamin is required for the production of retinal, a component of rhodopsin?

Accepted Answer

Vitamin A

Question 13

A patient with astigmatism is most likely to experience which of the following symptoms?

Accepted Answer

Blurred or distorted vision due to poor focusing of light.

Question 14

Which of the following is a multi-step process that occurs in the rods after exposure to light?

Accepted Answer

Bleaching reaction, release of opsin, series of chemical reactions, change in neurotransmitter release.

Question 15

Which equation best represents the bleaching reaction in rods?

Accepted Answer

$$	ext{Rhodopsin} \xrightarrow{	ext{light}} 	ext{Retinal} + 	ext{Opsin}$$

Question 16

If a person is deficient in vitamin A, which process in the eye is most likely to be impaired?

Accepted Answer

Production of retinal, leading to impaired rhodopsin regeneration and night vision.

Question 17

Which of the following best explains why cones allow us to see color?

Accepted Answer

Cones contain three pigments that absorb red, blue, or green light.

Question 18

During dark adaptation, the sensitivity of rods can increase by up to:

Accepted Answer

100,000 fold

Question 19

Which of the following is TRUE regarding the role of opsin in vision?

Accepted Answer

Opsin is released during the bleaching reaction and triggers a series of chemical reactions in photoreceptor cells.

Question 20

A person enters a dark room after being in bright sunlight. Which sequence best describes the adaptation process?

Accepted Answer

Initial poor vision due to bleached rhodopsin, followed by increased rhodopsin production and rod sensitivity.

Visual Physiology: Photoreceptors, Pigments, and Adaptation

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