Biological Systems MCAT Practice Exam

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Prepare for the Biological Systems section of the MCAT. Review detailed explanations and interactive questions to understand complex systems. Enhance your exam readiness and aim for a high score!

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What is the typical resting membrane potential of a neuron?

-50 mV
-70 mV
-90 mV
0 mV

The correct answer is: -70 mV

The typical resting membrane potential of a neuron is around -70 mV. This value indicates that the inside of the neuron is more negatively charged compared to the outside, which is primarily due to the distribution of ions across the cell membrane. At rest, neurons have a higher concentration of potassium ions (K+) inside the cell and a higher concentration of sodium ions (Na+) outside the cell. The uneven distribution of these ions, maintained by the sodium-potassium pump, contributes significantly to the negative charge inside the neuron. Additionally, the membrane is more permeable to K+ than Na+ at rest, allowing K+ to flow out of the cell, which further contributes to the negative membrane potential. As a result, -70 mV is considered the standard resting state for most neurons, providing a baseline from which action potentials can occur when the neuron is stimulated. This value is crucial for the proper functioning of neuronal communication and transmission of signals throughout the nervous system.