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Measuring the Resting Membrane Potential

  • In a resting axon, the distribution of cations and anions polarizes the plasma membrane. The intracellular fluid (ICF) becomes relatively negative to the extracellular fluid (ECF).
  • A image descriptionvoltmeter is used to measure the charge difference (voltage or elec-trical potential) between the ECF and ICF. The greater the difference, the greater the voltage.
An image showing how to measure the resting membrane potential using voltmeter with 2 electrods
An image showing how to measure the resting membrane potential using voltmeter (which is labeled) with 2 electrods
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An image showing how to measure the resting membrane potential using voltmeter (which is labeled) with 2 electrods
An image showing a ground electrod of voltmeter placed on the surface of a neuron cell membrane
An image showing a ground and recording electrods of voltmeter placed on the surface of a neuron cell membrane
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  • The recording electrode typically consists of a glass tube filled with KCl solution and a silver wire coated with Ag/AgCl. The electrode is able to convert ionic current to electrical current, which is sent to the voltmeter.
  • The ground electrode is image descriptionplaced outside the membrane and the recording electrode is inserted image descriptionrecording electrode into the axon.
  • Charge differences between the ECF and ICF (resting membrane potential or RMP) are image descriptiondisplayed in millivolts (mV) on the voltmeter.