Dr Gawad Physiology Course Online Exam - Excitable - Lec 1 (Introduction, Resting Membrane Potential, Action Potential)
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Regarding the physiology of active (Na-K) pump:
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It is a Trans membrane protein showing large number of binding sites on its interior aspect
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Inner ATPase activity is concerned to produce conformational change followed by 2 K+ pumped inside
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Ions migrate uphill against both (concentration + electrical) gradient
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Binding of (Na – K) to their respective binding sites is followed by activation of the inner ATPase
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All is true
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8 MCQs (Only one correct answer)
Each MCQ: 1 mark, Total mark: 8 (you will get the results immediately with correction by the web)
Allowed time: 10 minGood Luck
- 2.
The main cause of depolarization of nerve is:
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K outflux
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Na influx
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Cl outflux
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None of the above
Correct Answer
A. Na influxExplanation
The main cause of depolarization of a nerve is the influx of sodium ions (Na+). When a nerve is at rest, there is a higher concentration of sodium ions outside the cell compared to inside. However, when a nerve is stimulated, sodium channels open, allowing sodium ions to enter the cell. This influx of positive ions leads to a change in the electrical charge of the cell membrane, causing depolarization and the generation of an action potential.Rate this question:
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- 3.
At stage of complete depolarization of action potential of the curve
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K out flux is the major change
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Na out flux is the major change
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The potential difference between outer and inner surface is Zero
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Na-K pump is acting with full capacity
Correct Answer
A. The potential difference between outer and inner surface is ZeroExplanation
At the stage of complete depolarization of the action potential curve, the potential difference between the outer and inner surface is zero. This means that the electrical charge inside and outside the cell membrane is equal, resulting in no potential difference. This occurs when the cell membrane is fully depolarized and the action potential has reached its peak.Rate this question:
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- 4.
RMP is due to which of the following:
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Passive movements of ions along the membrane
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Selective permeability of the membrane
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Active Na and K transport
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Impermeability of the membrane to protein
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All of the above
Correct Answer
A. All of the aboveExplanation
The resting membrane potential (RMP) is due to a combination of factors. Passive movements of ions along the membrane contribute to the establishment of RMP. The selective permeability of the membrane allows certain ions to pass through more easily, influencing the RMP. Active transport of sodium (Na) and potassium (K) ions also plays a role in maintaining RMP. Additionally, the impermeability of the membrane to proteins helps maintain the electrical balance required for RMP. Therefore, all of the given options contribute to the establishment of RMP.Rate this question:
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- 5.
Point of rapid complete depolarization is the point at which:
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Outer membrane is more negative than inner membrane
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Inner membrane is more negative than outer membrane
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Potential difference between two membranes is zero
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None of the above.
Correct Answer
A. Potential difference between two membranes is zeroExplanation
The point of rapid complete depolarization occurs when the potential difference between the outer and inner membranes is zero. This means that there is no electrical charge difference between the two membranes, indicating a state of equilibrium.Rate this question:
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- 6.
Reversal of polarity, which is true:
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Outer membrane is more negative than inner membrane.
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Action potenial is – 50 mv
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Potential magnitude is + 35 mv
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None of the above
Correct Answer
A. Outer membrane is more negative than inner membrane.Explanation
The correct answer is that the outer membrane is more negative than the inner membrane. This is because the outer membrane of a cell typically has a higher concentration of negatively charged ions compared to the inner membrane. This difference in charge creates a polarity across the cell membrane, with the outer membrane being more negative and the inner membrane being more positive. This polarity is important for various cellular processes, including the movement of ions and the generation of electrical signals.Rate this question:
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- 7.
Repolarization of nerve coincides with:
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Influx of Na
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Out flux of K
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Out flux of Cl
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Impermeability of the membrane to protein
Correct Answer
A. Out flux of KExplanation
During repolarization of a nerve, the cell membrane returns to its resting state after depolarization. This is achieved by the out flux of potassium ions (K+) from the cell. As the K+ ions move out of the cell, the positive charge inside the cell decreases, leading to the restoration of the negative resting membrane potential. Therefore, the out flux of K+ is responsible for repolarization in nerve cells.Rate this question:
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- 8.
Ascending limb of nerve action potential is due to Na movement through:
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Leak channels
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Ligand gated channels
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Voltage gated channels
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None of the above
Correct Answer
A. Voltage gated channelsExplanation
The ascending limb of nerve action potential is due to the movement of Na+ ions through voltage-gated channels. These channels open in response to a change in the membrane potential, allowing Na+ ions to flow into the cell and depolarize it. This depolarization is responsible for the propagation of the nerve impulse along the axon. Leak channels allow for the passive movement of ions down their concentration gradient, while ligand-gated channels open in response to the binding of a specific molecule. Therefore, neither leak channels nor ligand-gated channels are responsible for the ascending limb of the nerve action potential.Rate this question:
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