Question

Photoreceptors in the retina secrete a large amount of neurotransmitter in

	a.	The presence of light (light phase)
	b.	The absence of light (dark phase)
	c.	Regardless of the light
	d.	Photoreceptors do not secrete neurotransmitter

Answer 1

Option 'b' is correct

Justification: The photoreceptors of retina gets depolarized in the dark phase. So, they secrete a high amount of neurotransmitter called 'glutamate' in the absence of light, which means the dark phase. When the photoreceptors absorb the photons, there will be decrease in the secretion of neurotransmitter glutamate. So, photoreceptors secrete a large amount of neurotransmitter in the absence of light (dark phase).

Justification for incorrect options:

• Option 'a' is incorrect because photoreceptors secrete a decreased amount of neurotransmitter in the presence of light (light phase). If there is an increase in light intensity, there will be decreased secretion of neurotransmitter glutamate by the photoreceptors of retina.
• Option 'c' is incorrect because the secretion of neurotransmitter glutamate by the photoreceptors of retina depends on light.
• Option 'd' is incorrect because photoreceptors secrete neurotransmitter called glutamate.

Thank you!