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Questions and Answers
What type of recording is represented if the scale bar shows currents in pA or nA?
In an I-V plot for Na+, what happens when the membrane potential is at 80 mV?
When plotting the I-V relationship for a leak K+ channel, what feature characterizes its curve?
What is the behavior of Kv channels in relation to the membrane potential?
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What must be true about Eion when plotting the I-V relationship for ions?
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Study Notes
Current Clamp vs. Voltage Clamp Recordings
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Current clamp records the membrane potential (Vm) of a neuron while injecting a constant current.
- Traces in current clamp recordings show action potentials (APs), excitatory postsynaptic potentials (EPSPs), and inhibitory postsynaptic potentials (IPSPs).
- Scale bars for current clamp traces are in mV.
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Voltage clamp records the current flowing across the membrane while holding the Vm at a constant value.
- Traces show currents.
- Scale bars for voltage clamp traces are in pA or nA.
I-V Plot
- An I-V plot is a graph showing the relationship between current (y-axis) and voltage (x-axis).
- The reversal potential (Eion) of an ion is the voltage at which there is no net current flow for that ion. This is where the I-V curve crosses the x-axis.
- To determine the direction of current for a given voltage:
- Positive current: The ion moves out of the cell.
- Negative current: The ion moves into the cell.
Leak K+ Channels vs. Voltage-Gated K+ (Kv) Channels
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Leak K+ channels are always open and contribute to the resting membrane potential.
- I-V plot: Linear; inward current at voltages below -80 mV (EK).
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Voltage-gated K+ (Kv) channels open in response to membrane depolarization.
- I-V plot: Not linear; no inward current below -50 mV. The current gradually increases as Vm becomes more depolarized due to sequential activation of voltage sensors in the channel.
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Description
This quiz explores the differences between current clamp and voltage clamp techniques used in neuroscience. It covers how each method records neuronal activity and the significance of I-V plots in understanding ion behavior and reversal potentials. Test your knowledge on these fundamental concepts in electrophysiology!
