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Questions and Answers
Which of the following best describes the role of the Na+/K+ pump in maintaining the resting membrane potential (RMP) in human cells?
Which of the following best describes the role of the Na+/K+ pump in maintaining the resting membrane potential (RMP) in human cells?
- It solely determines the permeability of the cell membrane to chloride ions.
- It primarily establishes the diffusion potential for sodium ions.
- It directly sets the Nernst potential for potassium ions.
- It actively transports ions to counteract leakage, helping to maintain ionic gradients. (correct)
According to the Goldman-Hodgkin-Katz equation, what would be the effect on the resting membrane potential (RMP) if the permeability of the cell membrane to potassium ions (K+) significantly increased?
According to the Goldman-Hodgkin-Katz equation, what would be the effect on the resting membrane potential (RMP) if the permeability of the cell membrane to potassium ions (K+) significantly increased?
- The RMP would become more positive, approaching the Nernst potential for sodium (Na+).
- The RMP would remain unchanged, as permeability changes do not affect the overall RMP.
- The RMP would depolarize due to an influx of sodium ions.
- The RMP would become more negative, approaching the Nernst potential for potassium (K+). (correct)
During an action potential, what is the significance of the 'all-or-none' phenomenon?
During an action potential, what is the significance of the 'all-or-none' phenomenon?
- The duration of the action potential is directly related to the duration of the stimulus.
- The action potential either occurs fully or does not occur at all, regardless of stimulus strength above threshold. (correct)
- A stimulus below a certain threshold will trigger a partial action potential.
- The magnitude of the action potential is proportional to the strength of the stimulus.
How does the frequency of action potentials encode sensory information and control motor output?
How does the frequency of action potentials encode sensory information and control motor output?
In the context of electrophysiology, what is the purpose of the voltage clamp technique?
In the context of electrophysiology, what is the purpose of the voltage clamp technique?
During the application of the voltage clamp technique, what is the role of the current electrode?
During the application of the voltage clamp technique, what is the role of the current electrode?
What would be the impact on the sodium/potassium pump activity if there were an increase in intracellular sodium concentration?
What would be the impact on the sodium/potassium pump activity if there were an increase in intracellular sodium concentration?
Which of the following is a critical difference between action potentials and local currents?
Which of the following is a critical difference between action potentials and local currents?
A researcher is using the voltage clamp technique and applies TTX (tetrodotoxin) to a neuron. What specific effect would this have on the recorded ionic currents?
A researcher is using the voltage clamp technique and applies TTX (tetrodotoxin) to a neuron. What specific effect would this have on the recorded ionic currents?
The diffusion potential across a cell membrane directly arises from what?
The diffusion potential across a cell membrane directly arises from what?
Flashcards
Membrane Potential
Membrane Potential
The voltage difference across a cell membrane due to unequal distribution of ions.
Diffusion Potential
Diffusion Potential
Potential difference across a cell membrane resulting from differing ion concentrations.
Nernst Potential
Nernst Potential
The membrane potential at which there is no net (overall) flow of a particular ion from one side of the membrane to the other.
Goldman-Hodgkin-Katz Equation
Goldman-Hodgkin-Katz Equation
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Action Potential Definition
Action Potential Definition
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Voltage Clamp Technique
Voltage Clamp Technique
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All-or-None Phenomenon
All-or-None Phenomenon
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Study Notes
- Cell membranes maintain voltage gradients.
- Diffusion potential exists because of ionic differences across the phospholipid bilayer.
- If the permeability across the cell membrane for a given ion is increased, ion flux occurs until the Nernst potential for the given ion is achieved.
- ENa+ = +70 millivolts
- EK+ = -94 millivolts
Goldman-Hodgkin-Katz Equation
- Determines the resting membrane potential (rmp) of a cell that is permeable to more than one ion
- EM = -61 x log [[Na+]i x PNa+ + [K+]i x PK+ + [Cl-]o x PCl-]/[[Na+]o x PNa+ + [K+]o x PK+ + [Cl-]i x PCl-
- Key figures associated: Alan Hodgkin and Bernard Katz
Key Determinants of Resting Membrane Potential in Human Cells
- K+ leak channels
- Na+/K+ pump
Action Potentials
- Includes periods of depolarization, repolarization, and hyperpolarization
- Travels without decrement and exemplifies positive feedback
- It is different from local current
- Vary across different types of electrically excitable cells
Voltage Clamp Technique
- Used to measure ionic flux via different channels
- The researcher selects a voltage, which is applied at the current electrode
- The current electrode automatically injects positive or negative electricity to "clamp" the voltage
- Ion channels respond and induce ion flux, which is recorded at the recording electrode
- Experimental variables include: intra- and extracellular concentrations, TTX, and TEA
Additional Action Potential Characteristics
- All-or-none phenomenon
- Frequency codes sensory information and controls the magnitude of motor output
- Relevant electrolyte concentrations barely change
- An increase in intracellular Na+ stimulates the sodium/potassium pump
- Ions of membrane potential represent 1/200,000th of the total charges in the cell’s cytoplasm
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