Light Transduction + Receptive Field

2.

Rods follow the stimulus change closely, whereas cones have a latency in their response.

True
False

Correct Answer

A. False

Explanation

Latency of response for rods is longer- rise time and fall time are longer- and then membrane changes slower in rods whereas cone response follows the stimulus change more closely

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3.

When a photon of light strikes Rhodopsin, phosphodiesterase (PDE) becomes:

Active
Inactive

Correct Answer

A. Active

Explanation

When a photon of light strikes Rhodopsin, it causes a conformational change in the molecule. This conformational change activates phosphodiesterase (PDE). Therefore, the correct answer is "active".

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4.

The definition of a receptive field is only applied to ganglion cells.

True
False

Correct Answer

A. False

Explanation

can be applied to any visual neuron: PR, BP, GC, H, A

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5.

What is the purpose of cGMP in photorecptors?

Closes Na channels
Keeps Na channels open
Inhibits PDE
Regenerates Rho

Correct Answer

A. Keeps Na channels open

Explanation

Decreasing the cGMP in the cytosol results in the CLOSURE of the Na channels when light is around

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6.

What is the voltage potential inside a photoreceptor in the dark? What is it in presence of light?

-60mV; -20mV
-20mV; -50mV
-20mV; -60mV
-50mV; -20mV

Correct Answer

A. -20mV; -60mV

Explanation

In the light, the Na channels in the OS are closed and therefore the Na that's being pumped out of the IS cannot get back into the PR. Since Na is + charged, there will be a decrease in the membrane potential (more negative) when light is present vs in the dark.

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7.

In the dark, Na channels are closed, preventing Na to enter the OS.

True
False

Correct Answer

A. False

Explanation

In the dark, Na channels are open and Na flows into the OS. Light results in a closure of the Na channels so that Na doesn't flow back into the OS.

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8.

As part of the dark current, Na is continuously pumped out of the OS and follows it's concentration gradient and enters the photoreceptor in the IS

True
False

Correct Answer

A. False

Explanation

Opposite is true. Na pumped out of IS and then follows gradient to flow back into the PR through the OS.

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9.

What makes photoreceptors unique?

Only have membrane potential changes
Hyperpolarize when excited
Decrease NT release when excited
2 of the above
All of the above

Correct Answer

A. All of the above

Explanation

Photoreceptors are unique because they exhibit all of the mentioned characteristics. They only have membrane potential changes, meaning that their response to light stimuli is solely based on changes in their membrane potential. Additionally, they hyperpolarize when excited, which means that their membrane potential becomes more negative. Lastly, they decrease neurotransmitter (NT) release when excited, indicating that their response to light leads to a reduction in the release of neurotransmitters. Therefore, all of the above statements accurately describe the unique features of photoreceptors.

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10.

Active PDE results DIRECTLY in conversion of:

GMP --> cGMP
Rho -->ospin + all trans retinal
CGMP --> GMP
Rho --> active Rho

Correct Answer

A. CGMP --> GMP

Explanation

This results in a decrease in the cGMP concentration in the cytosol of the PR because it has been converted into GMP

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11.

Light needs to be present during the entire time that Rho is being transformed into opsin and all-trans retinal

True
False

Correct Answer

A. False

Explanation

(I'm not sure that I've articulated this question very well...but check out pg. 161 picture for more clarification)

The only thing that the absorption of light does to Rho is convert it to Beta-Rho. All other changes occur at normal body temperature.

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12.

Light Transduction + Receptive Field

In the dark, photoreceptors release NTs continuously

Quiz Preview

Rods follow the stimulus change closely, whereas cones have a latency in their response.

When a photon of light strikes Rhodopsin, phosphodiesterase (PDE) becomes:

The definition of a receptive field is only applied to ganglion cells.

What is the purpose of cGMP in photorecptors?

What is the voltage potential inside a photoreceptor in the dark? What is it in presence of light?

In the dark, Na channels are closed, preventing Na to enter the OS.

As part of the dark current, Na is continuously pumped out of the OS and follows it's concentration gradient and enters the photoreceptor in the IS

What makes photoreceptors unique?

Active PDE results DIRECTLY in conversion of:

Light needs to be present during the entire time that Rho is being transformed into opsin and all-trans retinal

What is Hartline's definition of a receptive field?