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Resting Membrane Potential
Cells of multicellular organisms such as animals and plants, as well as those of unicellular organisms such as yeast exhibit a potential difference across the cell plasma membrane. That is to say that there is an electrical potential difference between the inside of the cell and the surrounding bathing medium of the cell. This potential difference is referred to as the membrane potential (Vm). The numerical value of the membrane potential is generally negative, meaning that the inside of the cell is negative with respect to the outside solution, which is taken as the reference or zero value. In this lecture, we will learn how the membrane potential is established and how it can be measured experimentally. We will also learn about the factors that govern the value of the membrane potential. Finally, we will learn about the significance of the membrane potential in enabling a myriad of physiological processes. Throughout the lecture, we will encounter additional fundamental principles that govern physiological processes.
Measuring the membrane potential - basic method

Lecture Outline

Lecture Objectives  
After studying this lecture, you will be able to:
  • Understand the basic principles as well as experimental methods used to measure the potential difference across the plasma membrane.
  • Describe the minimum essential factors required to establish a potential difference (i.e., membrane potential) across biological membranes.
  • Describe in detail how selective ion channels as well as ionic concentration differences across the plasma membrane lead to the establishment of a membrane potential.
  • Describe the ions that play a major role in most cells in establishing a potential difference across the plasma membrane.
  • Describe Nernst potentials and equilibrium potentials and their significance.
  • Describe the Goldman-Hodgkin-Katz (GHK) equation and its significance in calculating the membrane potential.
  • Explain how the resting membrane potential is maintained in cells.
  • Name a few pharmacological agents that inhibit the Na+/K+ ATPase (i.e., sodium pump), and how inhibition of the Na+ pump influences the value of the membrane potential.
  • Provide examples that highlight the physiological significance of the membrane potential.
  • Understand and properly use the membrane ionic current equations.
  • Describe the usefulness of the Chord Conductance equation and how it differs from the Goldman-Hodgkin-Katz (GHK) equation.
  • Describe the Gibbs-Donnan equilibrium.

Required Mastery of Previous Materials  
In order to fully understand this lecture, you need to have already mastered the following topics:
  • Physiological values for the extracellular and cytoplasmic concentration of ions, particularly those for Na+, K+, and Cl
  • Structure, function, and molecular composition of phospholipid bilayers as well as biological membranes.
  • Pathways and mechanisms of transport across biological membranes.

Key Terms  
After studying this lecture, you should be able to define all of the following terms:

Go to Glossary of Key Terms for this lecture.

Posted: Saturday, February 15, 2014
Last updated: Saturday, November 21, 2015