What is membrane potential: Definition and 17 Discussions

Membrane potential (also transmembrane potential or membrane voltage) is the difference in electric potential between the interior and the exterior of a biological cell. That is, there is a difference in the energy required for electric charges to move from the internal to exterior cellular environments and vice versa, as long as there is no acquisition of kinetic energy or the production of radiation. The concentration gradients of the charges directly determine this energy requirement. For the exterior of the cell, typical values of membrane potential, normally given in units of milli volts and denoted as mV, range from –80 mV to –40 mV.
All animal cells are surrounded by a membrane composed of a lipid bilayer with proteins embedded in it. The membrane serves as both an insulator and a diffusion barrier to the movement of ions. Transmembrane proteins, also known as ion transporter or ion pump proteins, actively push ions across the membrane and establish concentration gradients across the membrane, and ion channels allow ions to move across the membrane down those concentration gradients. Ion pumps and ion channels are electrically equivalent to a set of batteries and resistors inserted in the membrane, and therefore create a voltage between the two sides of the membrane.
Almost all plasma membranes have an electrical potential across them, with the inside usually negative with respect to the outside. The membrane potential has two basic functions. First, it allows a cell to function as a battery, providing power to operate a variety of "molecular devices" embedded in the membrane. Second, in electrically excitable cells such as neurons and muscle cells, it is used for transmitting signals between different parts of a cell. Signals are generated by opening or closing of ion channels at one point in the membrane, producing a local change in the membrane potential. This change in the electric field can be quickly sensed by either adjacent or more distant ion channels in the membrane. Those ion channels can then open or close as a result of the potential change, reproducing the signal.
In non-excitable cells, and in excitable cells in their baseline states, the membrane potential is held at a relatively stable value, called the resting potential. For neurons, resting potential is defined as ranging from –80 to –70 millivolts; that is, the interior of a cell has a negative baseline voltage of a bit less than one-tenth of a volt. The opening and closing of ion channels can induce a departure from the resting potential. This is called a depolarization if the interior voltage becomes less negative (say from –70 mV to –60 mV), or a hyperpolarization if the interior voltage becomes more negative (say from –70 mV to –80 mV). In excitable cells, a sufficiently large depolarization can evoke an action potential, in which the membrane potential changes rapidly and significantly for a short time (on the order of 1 to 100 milliseconds), often reversing its polarity. Action potentials are generated by the activation of certain voltage-gated ion channels.
In neurons, the factors that influence the membrane potential are diverse. They include numerous types of ion channels, some of which are chemically gated and some of which are voltage-gated. Because voltage-gated ion channels are controlled by the membrane potential, while the membrane potential itself is influenced by these same ion channels, feedback loops that allow for complex temporal dynamics arise, including oscillations and regenerative events such as action potentials.

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  1. somasimple

    Medical Growth and membrane potential

    Hello everyone, All living things have a growth cycle in which they gain mass and volume. These elements are obviously and undoubtedly taken from the environment in which these creatures live. Therefore, it is undeniable that the amount of potassium, for example, in the body increases during...
  2. J

    Membrane potential explained: Nernst potential

    Good evening, I got a seriously problem at understanding the membrane potential for ions in a cell. Particulary, i don't understand the case for example for ions with a charge of 2 or higher. I take a look on two scenarios: If you got an ion like calium and got a concentration ratio of 1:10...
  3. F

    3d printing neuron with membrane potential

    Is it possible to 3d print a neuronal structure with a different material than neurons that would work just like a neuron with membrane potential?
  4. W

    Extracellular ion concentrations and neural membrane potential

    I'm learning about a very basic model neuron, in which only potassium and chloride is permeable. Why is it that when the extracellular concentration of potassium is increased, the neuron become depolarized, whereas when extracellular concentration of chloride is reduced, the neural membrane...
  5. S

    Membrane Potential: Zero Permeability Contribution | Goldman-Hodgkin-Katz

    In membrane potential determination of a cell, the Goldman Hodgkin Katz equation says the contribution of an ion to diffusion potential is dependent on its membrane permeability. So in case an ion, one that has a zero permeability, is present outside the cell, using the equation , one will get...
  6. M

    Confused with resting membrane potential

    hello world long time no see..actually I've been very confused with this resting membrane potential I've sooo many questions but i'll only ask one question for now .at rest the membrane of nerve cell is permeable to potassium , potassium goes outside the cell along its concentration gradient...
  7. T

    Resting membrane potential

    Is there any reason,resting membrane potential is cca -70mV?because teacher asked us today,and it was not enough for him to say,that it is due concentrations of ions...What is the reason of this value? Thanks
  8. A

    Membrane Potential and Permittivity

    Hi, Was wondering if I could get some help with part b of this question? I've attached the question and my attempt in the pictures as there was a lot of data and writing, so thought this would be the easiest way. With my attempt I think I'm missing something pretty obvious, but I'm drawing...
  9. H

    Medical Why Does Permeability Alter Membrane Potential?

    I've just finished reading through the generally well-written Wikipedia article on membrane potential: http://en.wikipedia.org/wiki/Membrane_potential I found almost everything to be clear, but one question is nagging at me. Why do changes in membrane permeability directly affect membrane...
  10. N

    Calculating membrane potential (Vm) given resistance and equilibrium potentials

    Homework Statement Calculate the membrane potential (Vm) of a cell, given the following resistances and equilibrium potentials (10 marks) E(K) = -80mV, R(K) = 0.2*10^6 ohms, E(Na) = 60mV, R(Na) = 0.2*10^6 ohmsHomework Equations Not sure The Attempt at a Solution In my texts I have read...
  11. S

    Resting membrane potential and some neurophysio questions?

    Hello everyone, These are true,false questions. I'm on holiday so can't get help yet and this is not homework. 1.Increased permeability of the cell membraneto K+ than Na+ is important for maintaining resting membrane potential of cell? Ok I know this is true but I don't understand...
  12. L

    HelpResting membrane potential, hyperpolrization ?

    hi i was wondering if you could help me answering this question please .. "compare between forces that involved in the K+ channel during resting membrane potential and hyperpolrization" ? I'm sorry but i need to know the answer ASAP .. :biggrin:
  13. B

    Medical Physiology: Effect on Membrane Potential

    Hello all. I just had a few conceptual problems if someone wouldn't mind explaining to me. When looking at a simple cell membrane, potassium ions tend to move out of the cell along their concentration gradient until its electrical gradient is strong enough to counterbalance it, thus...
  14. M

    Membrane Potential question: neuron function or location?

    Homework Statement Which of the following is NOT important in determining a neurons membrane potential: The function of the neuron or the location of the neuron? Homework Equations N/a The Attempt at a Solution The function of a neuron is obviously the integration, summation, and...
  15. H

    Membrane Potential Homework: Calculating [Na+] Inside Cell

    Homework Statement a biological cell is immersed in a 50mM solution of NaCl at 37C. the cell's membrane is permeable only to Na+ ions. When the system reaches equilibrium, a potential diff of 54.9mV is measured between the inside and the outside of the cell where the inside has the higher(...
  16. S

    Question about membrane potential

    This question is the last thing that is bugging me about my basic understanding of a nerve impulse: How can the there be a non-zero voltage across a membrane if the solutions on either side are electrically neutral? It seems like the existence of a gradient should necessitate at least one...
  17. J

    [Chemistry] Membrane Potential

    [Chemistry] Another electrochemistry question Homework Statement Given the following half-reactions: Ce4+ + e− → Ce3+ E° = 1.72 V Fe3+ + e− → Fe2+ E° = 0.771 V A solution is prepared by mixing 7.0 mL of 0.30 M Fe2+ with 8.0 mL of 0.12 M Ce4+. Calculate [Ce4+] in the...
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