Peripheral Nervous System And Synaptic Pharmacology 2: Nervous Conduction
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Lecture 2
- 1.
Which of the following statements is correct?
- A.
The Em for a RBC isn't -20mV
- B.
The outside of a cell is always negative with respect to the outside
- C.
The inside of a cell is always negative with respect to the outside
- D.
The Em for a neuron isn't -70mV
Correct Answer
C. The inside of a cell is always negative with respect to the outsideExplanation
The correct answer is that the inside of a cell is always negative with respect to the outside. This is due to the presence of an electrical potential difference across the cell membrane, known as the membrane potential (Em). The inside of the cell has a higher concentration of negatively charged ions compared to the outside, creating a negative charge. This difference in charge is essential for various cellular processes, including the transmission of nerve impulses and the regulation of ion movement.Rate this question:
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- 2.
The resting membrane potential results from...
- A.
A high level of Cl- entering the cell
- B.
Active transport of ions across a membrane
- C.
An unequal distribution of ions across a selectively permeable membrane
- D.
Electrogenicity of NaK-ATP-ase
Correct Answer
C. An unequal distribution of ions across a selectively permeable membraneExplanation
The resting membrane potential is the electrical potential difference across the cell membrane when the cell is at rest. This potential is maintained by an unequal distribution of ions across the selectively permeable membrane. The cell membrane is more permeable to certain ions, such as potassium (K+) and less permeable to others, such as sodium (Na+). This creates a concentration gradient, with higher concentrations of K+ inside the cell and higher concentrations of Na+ outside the cell. This uneven distribution of ions generates an electrical potential difference across the membrane, resulting in the resting membrane potential.Rate this question:
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- 3.
Na+...
- A.
Diffuses into the cell
- B.
Diffuses out of the cell
Correct Answer
A. Diffuses into the cellExplanation
Na+ ions have a higher concentration outside the cell compared to inside. Due to the concentration gradient, Na+ ions will diffuse into the cell to equalize the concentration on both sides.Rate this question:
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- 4.
K+...
- A.
Diffuses into the cell
- B.
Diffuses out of the cell
Correct Answer
B. Diffuses out of the cellExplanation
K+ ions are positively charged and are typically found in higher concentrations inside the cell compared to outside. Due to this concentration gradient, K+ ions tend to diffuse out of the cell through the cell membrane. This process is facilitated by specific ion channels that allow the passage of K+ ions. As a result, K+ ions diffuse out of the cell, maintaining the electrochemical balance and playing a crucial role in various cellular processes such as nerve conduction and muscle contraction.Rate this question:
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- 5.
Cl-...
- A.
Diffuses into the cell
- B.
Diffuses out of the cell
Correct Answer
A. Diffuses into the cellExplanation
Chloride ions (Cl-) have a negative charge and are attracted to the positively charged interior of the cell. Therefore, they tend to diffuse into the cell through ion channels or transporters. This movement is driven by the concentration gradient, as Cl- ions are usually more concentrated outside the cell.Rate this question:
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- 6.
Ca2+...
- A.
Diffuses into the cell
- B.
Diffuses out of the cell
Correct Answer
A. Diffuses into the cellExplanation
Calcium ions (Ca2+) are positively charged and play a crucial role in various cellular processes. The movement of calcium ions into the cell is important for signaling pathways, muscle contraction, and neurotransmitter release. Calcium ions can diffuse into the cell through various channels or transporters present in the cell membrane. This influx of calcium ions is tightly regulated to maintain cellular homeostasis and ensure proper functioning of the cell. Therefore, the correct answer is that calcium ions diffuse into the cell.Rate this question:
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- 7.
In depolarization...
- A.
The Vm becomes more positive than the resting potential
- B.
The Vm becomes more negative than the resting potential
- C.
The Vm moves back to the resting potential following depolarisation
- D.
The Vm remains constant
Correct Answer
A. The Vm becomes more positive than the resting potentialExplanation
During depolarization, the Vm (membrane potential) becomes more positive than the resting potential. This occurs when there is an influx of positively charged ions, such as sodium ions, into the cell, causing the Vm to increase. This change in Vm is an essential step in the generation of an action potential, which allows for the transmission of electrical signals in neurons and muscle cells.Rate this question:
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- 8.
In repolarization...
- A.
The Vm becomes more positive than the resting potential
- B.
The Vm becomes more negative than the resting potential
- C.
The Vm moves back to the resting potential following depolarisation
- D.
The Vm remains constant
Correct Answer
C. The Vm moves back to the resting potential following depolarisationExplanation
During repolarization, the Vm (membrane potential) moves back to the resting potential following depolarization. Depolarization is the process where the Vm becomes more positive than the resting potential. After depolarization, the Vm gradually returns to its resting potential, which is a negative charge inside the cell compared to the outside. This movement back to the resting potential is known as repolarization.Rate this question:
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- 9.
In hyperpolarization...
- A.
The Vm becomes more positive than the resting potential
- B.
The Vm becomes more negative than the resting potential
- C.
The Vm moves back to the resting potential following depolarisation
- D.
The Vm remains constant
Correct Answer
B. The Vm becomes more negative than the resting potentialExplanation
In hyperpolarization, the Vm becomes more negative than the resting potential. This occurs when the membrane potential becomes even more negative than its normal resting level. It is usually caused by the efflux of potassium ions or the influx of chloride ions. Hyperpolarization makes the neuron less likely to generate an action potential as it increases the distance between the resting potential and the threshold potential required for depolarization.Rate this question:
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- 10.
Graded potentials...
- A.
Serve as short distance signals
- B.
Are 'all or nothing'
- C.
Serve as long distance signals
- D.
Do not act in muscles (end plate potentials)
Correct Answer
A. Serve as short distance signalsExplanation
Graded potentials serve as short-distance signals because they are localized changes in membrane potential that occur in response to stimuli. Unlike action potentials, which are all-or-nothing and propagate along the entire length of the neuron, graded potentials are variable in magnitude and decay over short distances. They are important for integrating and transmitting information over short distances within a neuron, such as in dendrites and cell bodies, before being converted into action potentials for long-distance signaling. Graded potentials do not directly act in muscles, as their role is primarily in neuronal communication.Rate this question:
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- 11.
Which of the following statements is untrue?
- A.
The change in voltage in a graded potential is greatest underneath a synapse
- B.
The signal of a graded potential is decromental
- C.
The larger the initial active area, the larger the decromental spread
- D.
The signal of a graded potential is undiminishing
Correct Answer
D. The signal of a graded potential is undiminishingExplanation
The statement "The signal of a graded potential is undiminishing" is untrue. Graded potentials are local changes in membrane potential that can be either depolarizing or hyperpolarizing. Unlike action potentials, which are all-or-nothing events, graded potentials can vary in magnitude and can decrease in strength as they spread away from the initial site of stimulation. Therefore, the signal of a graded potential is not undiminishing.Rate this question:
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- 12.
The first stage of generating an action potential is...
- A.
At peak of action potential voltage approaches Na+ equilibrium potential
- B.
Depolarization to the threshold potential activates voltage-gated Na+ channels. A positive feedback loop causes Na+ channels to further open.
- C.
Rapid depolarization occurs due to Na+ moving down its concentration and electrochemical gradient. Na+ channels rapidly inactivate.
- D.
Resting membrane potential; cell is permeable to K+
Correct Answer
D. Resting membrane potential; cell is permeable to K+Explanation
The correct answer is "Resting membrane potential; cell is permeable to K+". This is because the resting membrane potential is the initial stage of generating an action potential. At rest, the cell is permeable to potassium ions (K+), meaning that K+ ions can move across the cell membrane. This creates a negative charge inside the cell compared to the outside. This resting membrane potential needs to be reached before the depolarization and activation of voltage-gated sodium (Na+) channels can occur, leading to the generation of an action potential.Rate this question:
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- 13.
The second stage of generating an action potential is...
- A.
At peak of action potential voltage approaches Na+ equilibrium potential
- B.
Depolarization to the threshold potential activates voltage-gated Na+ channels. A positive feedback loop causes Na+ channels to further open.
- C.
Rapid depolarization occurs due to Na+ moving down its concentration and electrochemical gradient. Na+ channels rapidly inactivate.
- D.
Resting membrane potential; cell is permeable to K+
Correct Answer
B. Depolarization to the threshold potential activates voltage-gated Na+ channels. A positive feedback loop causes Na+ channels to further open.Explanation
The correct answer explains the second stage of generating an action potential. It states that depolarization to the threshold potential activates voltage-gated Na+ channels. This activation leads to a positive feedback loop, causing the Na+ channels to further open. This further opening of the channels results in rapid depolarization as Na+ moves down its concentration and electrochemical gradient. The answer correctly identifies the key events that occur during the second stage of generating an action potential.Rate this question:
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- 14.
The third stage of generating an action potential is...
- A.
At peak of action potential voltage approaches Na+ equilibrium potential
- B.
Depolarization to the threshold potential activates voltage-gated Na+ channels. A positive feedback loop causes Na+ channels to further open.
- C.
Rapid depolarization occurs due to Na+ moving down its concentration and electrochemical gradient. Na+ channels rapidly inactivate.
- D.
Resting membrane potential; cell is permeable to K+
Correct Answer
C. Rapid depolarization occurs due to Na+ moving down its concentration and electrochemical gradient. Na+ channels rapidly inactivate.Explanation
During the third stage of generating an action potential, rapid depolarization occurs as Na+ ions move down their concentration and electrochemical gradient. This happens because the depolarization to the threshold potential activates voltage-gated Na+ channels, causing a positive feedback loop that further opens these channels. As a result, Na+ ions rush into the cell, leading to rapid depolarization. However, shortly after, the Na+ channels rapidly inactivate, preventing further influx of Na+ ions. This process contributes to the generation of an action potential.Rate this question:
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- 15.
The fourth stage of generating an action potential is...
- A.
At peak of action potential voltage approaches Na+ equilibrium potential
- B.
Depolarization to the threshold potential activates voltage-gated Na+ channels. A positive feedback loop causes Na+ channels to further open.
- C.
Rapid depolarization occurs due to Na+ moving down its concentration and electrochemical gradient. Na+ channels rapidly inactivate.
- D.
Resting membrane potential; cell is permeable to K+
Correct Answer
A. At peak of action potential voltage approaches Na+ equilibrium potentialExplanation
During the fourth stage of generating an action potential, the voltage reaches its peak and approaches the equilibrium potential of Na+. This occurs due to the depolarization of the cell membrane, which is caused by the activation of voltage-gated Na+ channels. As these channels open, there is a positive feedback loop that further opens the Na+ channels, leading to rapid depolarization. This rapid depolarization is a result of Na+ ions moving down their concentration and electrochemical gradient. However, at this stage, the Na+ channels also rapidly inactivate. Therefore, the correct answer is that at the peak of the action potential, the voltage approaches Na+ equilibrium potential.Rate this question:
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- 16.
The fifth stage of generating an action potential is...
- A.
Voltage gated K+ channels inactivate
- B.
The NaK-ATP-ase gradually restores the ionic gradients
- C.
Voltage gated K+ channels open causing repolarization
- D.
Resting membrane potential is restored
Correct Answer
C. Voltage gated K+ channels open causing repolarizationExplanation
During the fifth stage of generating an action potential, voltage-gated K+ channels open causing repolarization. This means that the K+ channels in the membrane of the neuron become activated, allowing K+ ions to flow out of the cell. This movement of positive ions out of the cell helps to restore the negative charge inside the cell, bringing the membrane potential back to its resting state. This repolarization phase is crucial for the neuron to reset and prepare for the next action potential.Rate this question:
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- 17.
The sixth stage of generating an action potential is...
- A.
Voltage gated K+ channels inactivate
- B.
The NaK-ATP-ase gradually restores the ionic gradients
- C.
Voltage gated K+ channels open causing repolarization
- D.
Resting membrane potential is restored
Correct Answer
A. Voltage gated K+ channels inactivateExplanation
During the sixth stage of generating an action potential, the voltage gated K+ channels inactivate. This means that these channels close, preventing the flow of K+ ions out of the cell. This inactivation is an important step in the repolarization process, as it helps to restore the resting membrane potential by stopping the efflux of K+ ions. This allows for the gradual restoration of the ionic gradients by the NaK-ATP-ase, which helps to reset the cell for the next action potential.Rate this question:
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- 18.
The seventh stage of generating an action potential is...
- A.
Voltage gated K+ channels inactivate
- B.
The NaK-ATP-ase gradually restores the ionic gradients
- C.
Voltage gated K+ channels open causing repolarization
- D.
Resting membrane potential is restored
Correct Answer
D. Resting membrane potential is restoredExplanation
The correct answer is "Resting membrane potential is restored." After the depolarization and repolarization phases of an action potential, the resting membrane potential is eventually restored. This occurs when the voltage-gated potassium channels close and the sodium-potassium pump (NaK-ATPase) gradually restores the ionic gradients across the cell membrane. This process allows the cell to return to its resting state and be ready for the next action potential.Rate this question:
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- 19.
The eighth stage of generating an action potential is...
- A.
Voltage gated K+ channels inactivate
- B.
The NaK-ATP-ase gradually restores the ionic gradients
- C.
Voltage gated K+ channels open causing repolarization
- D.
Resting membrane potential is restored
Correct Answer
B. The NaK-ATP-ase gradually restores the ionic gradientsExplanation
In the eighth stage of generating an action potential, the NaK-ATP-ase gradually restores the ionic gradients. This is important because during an action potential, there is a rapid change in ion concentrations across the cell membrane. The NaK-ATP-ase is responsible for pumping sodium ions out of the cell and potassium ions back into the cell, which helps to restore the original ion concentrations and prepare the neuron for another action potential.Rate this question:
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- 20.
When a voltage-gated Na+ channel is closed...
- A.
Its activation and inactivation gates are open
- B.
Its activation and inactivation gates are closed
- C.
Its activation gate is open and its inactivation gate is closed
- D.
Its activation gate is closed and its inactivation gate is open
Correct Answer
D. Its activation gate is closed and its inactivation gate is openExplanation
When a voltage-gated Na+ channel is closed, it means that the channel is not allowing the flow of sodium ions. In this state, the activation gate is closed, preventing the ions from entering the channel. However, the inactivation gate is open, which means that it is allowing the ions to exit the channel. This combination of a closed activation gate and an open inactivation gate ensures that the channel remains closed and does not allow the passage of sodium ions.Rate this question:
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- 21.
When a voltage-gated Na+ channel is open...
- A.
Its activation and inactivation gates are open
- B.
Its activation and inactivation gates are closed
- C.
Its activation gate is open and its inactivation gate is closed
- D.
Its activation gate is closed and its inactivation gate is open
Correct Answer
A. Its activation and inactivation gates are openExplanation
When a voltage-gated Na+ channel is open, it means that both its activation and inactivation gates are open. This allows the flow of sodium ions through the channel, resulting in the depolarization of the cell membrane. The activation gate is responsible for opening the channel in response to a change in voltage, while the inactivation gate is responsible for closing the channel after a certain period of time or in response to a different voltage change. Therefore, the correct answer is that both the activation and inactivation gates are open when the channel is open.Rate this question:
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- 22.
When a voltage-gated Na+ channel is inactive...
- A.
Its activation and inactivation gates are open
- B.
Its activation and inactivation gates are closed
- C.
Its activation gate is open and its inactivation gate is closed
- D.
Its activation gate is closed and its inactivation gate is open
Correct Answer
C. Its activation gate is open and its inactivation gate is closedExplanation
When a voltage-gated Na+ channel is inactive, its activation gate is open and its inactivation gate is closed. This means that the channel is ready to be activated and allow the flow of sodium ions, but it is not currently allowing the ions to pass through. The closed inactivation gate prevents the ions from passing through even though the activation gate is open. This state of the channel allows for precise control of when the channel can be activated and when it is closed to prevent excessive sodium ion influx.Rate this question:
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- 23.
Which two of the following statements is true about absolute refractory periods?
- A.
The neuron cannot be restimulated
- B.
Na+ channels are inactivated
- C.
Greater stimulation required to trigger acion potential
- D.
K+ channels are still activated
Correct Answer(s)
A. The neuron cannot be restimulated
B. Na+ channels are inactivatedExplanation
During the absolute refractory period, the neuron cannot be restimulated because it is in a state of temporary insensitivity to further stimulation. This is due to the inactivation of Na+ channels, which are responsible for the depolarization phase of the action potential. The inactivation of these channels prevents the generation of another action potential until the neuron has repolarized and the channels have recovered from their inactivated state. Therefore, both statements are true about absolute refractory periods.Rate this question:
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- 24.
Which two of the following statements is true about relative refractory periods?
- A.
The neuron cannot be restimulated
- B.
Na+ channels are inactivated
- C.
Greater stimulation required to trigger acion potential
- D.
K+ channels are still activated
Correct Answer(s)
C. Greater stimulation required to trigger acion potential
D. K+ channels are still activatedExplanation
During the relative refractory period, the neuron can be restimulated, but it requires a greater stimulation compared to the normal threshold to trigger an action potential. Additionally, during this period, the K+ channels are still activated, which contributes to the repolarization of the neuron.Rate this question:
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- 25.
The conduction velocity of a neuron depends on which two of the following?
- A.
Neuron class
- B.
Axon diameter
- C.
Myelination
- D.
Concentration of Na+ within the cell
Correct Answer(s)
B. Axon diameter
C. MyelinationExplanation
The conduction velocity of a neuron depends on the axon diameter and myelination. Axon diameter affects conduction velocity because a larger diameter allows for faster transmission of electrical signals. Myelination, the presence of a fatty substance called myelin around the axon, also increases conduction velocity by allowing the electrical impulses to "jump" from one node of Ranvier to the next, instead of traveling along the entire length of the axon. The neuron class and concentration of Na+ within the cell do not directly influence conduction velocity.Rate this question:
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- 26.
The larger the axon diameter of a neuron...
- A.
The slower the speed of conduction
- B.
The faster the speed of conduction
Correct Answer
B. The faster the speed of conductionExplanation
The larger the axon diameter of a neuron, the faster the speed of conduction. This is because a larger axon diameter allows for a higher flow of ions, which are responsible for transmitting electrical signals. This increased flow of ions enables faster and more efficient conduction of the electrical impulses along the axon.Rate this question:
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