Light Transduction + Receptive Field
(112).webp "Light Transduction + Receptive Field - Quiz")
p. 159-162
Questions and Answers
- 1.
What makes photoreceptors unique?
- A.
Only have membrane potential changes
- B.
Hyperpolarize when excited
- C.
Decrease NT release when excited
- D.
2 of the above
- E.
All of the above
Correct Answer
E. All of the aboveExplanation
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.Rate this question:
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- 2.
Rods follow the stimulus change closely, whereas cones have a latency in their response.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
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 closelyRate this question:
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- 3.
In the dark, Na channels are closed, preventing Na to enter the OS.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
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.Rate this question:
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- 4.
In the dark, photoreceptors release NTs continuously
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
In the dark, photoreceptors release neurotransmitters continuously. This is because in the absence of light, the photoreceptors are constantly depolarized, causing them to release neurotransmitters. This continuous release of neurotransmitters helps to maintain a baseline level of activity in the visual system, allowing for the detection of even very low levels of light.Rate this question:
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- 5.
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
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Opposite is true. Na pumped out of IS and then follows gradient to flow back into the PR through the OS.Rate this question:
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- 6.
What is the voltage potential inside a photoreceptor in the dark? What is it in presence of light?
- A.
-60mV; -20mV
- B.
-20mV; -50mV
- C.
-20mV; -60mV
- D.
-50mV; -20mV
Correct Answer
C. -20mV; -60mVExplanation
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.Rate this question:
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- 7.
When a photon of light strikes Rhodopsin, phosphodiesterase (PDE) becomes:
- A.
Active
- B.
Inactive
Correct Answer
A. ActiveExplanation
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".Rate this question:
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- 8.
Active PDE results DIRECTLY in conversion of:
- A.
GMP --> cGMP
- B.
Rho -->ospin + all trans retinal
- C.
CGMP --> GMP
- D.
Rho --> active Rho
Correct Answer
C. CGMP --> GMPExplanation
This results in a decrease in the cGMP concentration in the cytosol of the PR because it has been converted into GMPRate this question:
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- 9.
What is the purpose of cGMP in photorecptors?
- A.
Closes Na channels
- B.
Keeps Na channels open
- C.
Inhibits PDE
- D.
Regenerates Rho
Correct Answer
B. Keeps Na channels openExplanation
Decreasing the cGMP in the cytosol results in the CLOSURE of the Na channels when light is aroundRate this question:
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- 10.
Light needs to be present during the entire time that Rho is being transformed into opsin and all-trans retinal
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
(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.Rate this question:
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- 11.
What is Hartline's definition of a receptive field?
- 12.
The definition of a receptive field is only applied to ganglion cells.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
can be applied to any visual neuron: PR, BP, GC, H, ARate this question:
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Current Version
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Jan 24, 2024Quiz Edited by
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May 13, 2011Quiz Created by
Tseemore
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