Ocular Anatomy and Physiology TS1

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Questions and Answers

What is the purpose of phosphorylation in the phototransduction cascade?

  • To amplify the signal
  • To activate rhodopsin
  • To inactivate rhodopsin (correct)
  • To reform cGMP

What is the result of the decrease in intracellular cGMP in photoreceptors?

  • Increase in glutamate release
  • Activation of transducin
  • Opening of CNG channels
  • Closure of CNG channels (correct)

What is the role of transducin in the phototransduction cascade?

  • To activate rhodopsin
  • To activate phosphodiesterase 6 (correct)
  • To hydrolyze cGMP
  • To release glutamate

What is the effect of light on rhodopsin?

<p>It causes rhodopsin to change into metarhodopsin II (B)</p> Signup and view all the answers

What is the purpose of guanylyl cyclase in the recovery phase of the phototransduction cascade?

<p>To reform cGMP (A)</p> Signup and view all the answers

What is the conformational change in the chromophore of rhodopsin upon photon absorption?

<p>From 11-cis-retinal to 11-trans-retinal (A)</p> Signup and view all the answers

What is the primary function of phosphodiesterase 6 (PDE6) in the phototransduction cascade?

<p>To hydrolyze cGMP to 5'-GMP (B)</p> Signup and view all the answers

What is the role of arrestin in the phototransduction cascade?

<p>To inactivate rhodopsin (B)</p> Signup and view all the answers

What is the effect of lower intracellular Ca2+ levels in the recovery phase?

<p>Activation of guanylyl cyclase (C)</p> Signup and view all the answers

What is the result of the activation of several hundred transducin molecules by metarhodopsin II?

<p>Amplification of the signal by guanosine triphosphate (GTP) (B)</p> Signup and view all the answers

What is the primary function of the retinal pigment epithelium (RPE)?

<p>To nourish and collect waste products from the photoreceptor layer (C)</p> Signup and view all the answers

What is the structure that provides the highest visual acuity?

<p>Fovea centralis (B)</p> Signup and view all the answers

What is the approximate number of cones in the human retina?

<p>6 million (A)</p> Signup and view all the answers

What is the purpose of the Henle's fiber layer in the retina?

<p>To process signals from foveal and parafoveal photoreceptors (C)</p> Signup and view all the answers

What is the function of the inner segment of photoreceptor cells?

<p>To synthesize components for outer segment renewal (A)</p> Signup and view all the answers

Flashcards

Phosphorylation purpose?

To inactivate rhodopsin.

cGMP decrease result?

Leads to closure of CNG channels.

Transducin's role?

To activate phosphodiesterase 6 (PDE6).

Light's effect on rhodopsin?

Changes into metarhodopsin II.

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Guanylyl cyclase purpose?

To reform cGMP.

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Chromophore change?

From 11-cis-retinal to 11-trans-retinal.

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PDE6 function?

To hydrolyze cGMP to 5'-GMP.

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Arrestin's role?

To inactivate rhodopsin.

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Effect of lower Ca2+?

Activation of guanylyl cyclase.

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Metarhodopsin II's effect?

Amplification of the signal by GTP.

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RPE primary function?

To nourish and collect waste products from the photoreceptor layer.

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Highest visual acuity?

Fovea centralis.

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Number of cones?

6 million.

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Henle's fiber layer?

To process signals from foveal and parafoveal photoreceptors

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Inner segment function?

To synthesize components for outer segment renewal.

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