Skip to main content
Sign in Create a free account
Varsity Tutors
Sign in Sign up

Membrane Potential Basics and Ion Gradients - Anatomy and Physiology

  1. A neuron's membrane potential changes from -70 mV to -80 mV. What is this change called?
    Hyperpolarization, a change to a more negative membrane potential than rest.
  2. Which ion is more concentrated inside a resting cell, and which is more concentrated outside?
    K+ is more concentrated inside; Na+ (and Cl-) is more concentrated outside.
  3. What is an ion's equilibrium potential?
    The membrane potential at which the electrical force exactly balances the concentration gradient for that ion, so there is no net movement.
  4. Using E=61log⁡[C]o[C]iE = 61\log\frac{[C]_o}{[C]_i} mV, find the equilibrium potential of a monovalent cation 10 times more concentrated outside.
    About +61 mV. The log of 10 is 1, so E=61×1=61E = 61 \times 1 = 61 mV.
  5. What is the approximate equilibrium potential for K+ in a typical neuron?
    About -90 mV. The resting potential (about -70 mV) is slightly less negative because of a small Na+ leak.
  6. What is the typical resting membrane potential of a neuron?
    About -70 mV, meaning the inside of the cell is negative relative to the outside.
  7. What is the approximate equilibrium potential for Na+ in a typical neuron?
    About +60 mV, positive because Na+ is much more concentrated outside the cell.
  8. What is an electrochemical gradient?
    The combined driving force on an ion from its concentration gradient and the electrical gradient across the membrane.
  9. Why is the resting membrane potential much closer to the K+ equilibrium potential than to that of Na+?
    At rest the membrane is far more permeable to K+ than to Na+ because it has many more K+ leak channels.
  10. Extracellular K+ concentration rises well above normal. How does the resting membrane potential change?
    It depolarizes (becomes less negative), because the smaller K+ gradient drives less K+ out of the cell.
  11. How many Na+ and K+ ions does the Na+/K+ ATPase move for each ATP used?
    It pumps 3 Na+ out of the cell and 2 K+ into the cell.
  12. What is the main role of the Na+/K+ pump in maintaining the resting membrane potential?
    It maintains the Na+ and K+ concentration gradients that the leak channels depend on; its direct electrical contribution is only a few mV.

Study these flashcards