membrane potential

Examples of membrane potential in the following topics:

• Resting Membrane Potentials

  • The potential difference in a resting neuron is called the resting membrane potential.
  • The potential difference in a resting neuron is called the resting membrane potential.
  • The value of the resting membrane potential varies from -40mV to -90mV in a different types of neurons.
  • The resting membrane potential exists only across the membrane.
  • The Goldman formula essentially expresses the membrane potential as an average of the reversal potentials for the individual ion types, weighted by permeability.

• Membrane Potentials as Signals

  • In neurons, a sufficiently large depolarization can evoke an action potential in which the membrane potential changes rapidly.
  • Membrane potential (also transmembrane potential or membrane voltage) is the difference in electrical potential between the interior and the exterior of a biological cell.
  • The membrane potential has two basic functions.
  • The changes in membrane potential can be small or larger (graded potentials) depending on how many ion channels are activated and what type they are.
  • The action potential is a clear example of how changes in membrane potential can act as a signal.

• The Action Potential and Propagation

  • Action potential is a brief reversal of membrane potential where the membrane potential changes from -70mV to +30mV.
  • When the membrane potential of the axon hillock of a neuron reaches threshold, a rapid change in membrane potential occurs in the form of an action potential.
  • This moving change in membrane potential has three phases.
  • As additional sodium rushes in, the membrane potential actually reverses its polarity.  
  • The action potential is a clear example of how changes in membrane potential can act as a signal.

• Postsynaptic Potentials and Their Integration at the Synapse

  • Postsynaptic potentials are excitatory or inhibitory changes in the graded membrane potential in the postsynaptic terminal of a chemical synapse.
  • Postsynaptic potentials are changes in the membrane potential of the postsynaptic terminal of a chemical synapse.
  • Chemical synapses are either excitatory or inhibitory depending on how they affect the membrane potential of the postsynaptic neuron.
  • Unlike the action potential in axonal membranes, chemically-gated ion channels open on postsynaptic membranes.
  • EPSPs and IPSPs are transient changes in the membrane potential.

• Nerve Impulse Transmission within a Neuron: Resting Potential

  • The difference in total charge between the inside and outside of the cell is called the membrane potential.
  • For quiescent cells, the relatively-static membrane potential is known as the resting membrane potential.
  • The resting membrane potential is at equilibrium since it relies on the constant expenditure of energy for its maintenance.
  • Voltage-gated ion channels are closed at the resting potential and open in response to changes in membrane voltage.
  • The (a) resting membrane potential is a result of different concentrations of Na+ and K+ ions inside and outside the cell.

• Nerve Impulse Transmission within a Neuron: Action Potential

  • As an action potential travels down the axon, the polarity changes across the membrane.
  • Once the sodium channels open, the neuron completely depolarizes to a membrane potential of about +40 mV.
  • As K+ ions leave the cell, the membrane potential once again becomes negative.
  • The diffusion of K+ out of the cell hyperpolarizes the cell, making the membrane potential more negative than the cell's normal resting potential.
  • The action potential is conducted down the axon as the axon membrane depolarizes, then repolarizes.

• Principles of Electricity

  • Since there is a slight difference in the number of positive and negative ions on the two sides of the cellular plasma membrane, there is a potential difference across the membranes.
  • The difference in potential established between the outside of a cell and the inside of the cell can affect the flow of current across the cell membrane.
  • Differences in concentration of ions on opposite sides of a cellular membrane lead to a voltage called the membrane potential.
  • Many ions have a concentration gradient across the membrane, including potassium (K+), which is at a high inside and a low concentration outside the membrane.
  • These concentration gradients provide the potential energy to drive the formation of the membrane potential.

• Electric Potential in Human

  • Electric potentials are commonly found in the body, across cell membranes and in the firing of neurons.
  • Thus, a potential, called the resting potential, is created on either side of the membrane.
  • Resting membrane potential is approximately -95 mV in skeletal muscle cells, -60 mV in smooth muscle cells, -80 to -90 mV in astroglia, and -60 to -70 mV in neurons.
  • Potentials can change as ions move across the cell membrane.
  • This impulse is passed through the axon, a long extension of the cell, in the form of an electrical potential created by differing concentrations of sodium and potassium ions on either side of a membrane in the axon.

• Injuring the Plasma Membrane

  • The plasma membrane or cell membrane is a biological membrane that separates the interior of all cells from the outside environment.
  • The plasma membrane is selectively permeable to ions and organic molecules.
  • The membrane basically protects the cell from outside forces.
  • It appears to bind to the membrane causes rapid depolarization, resulting in a loss of membrane potential leading to inhibition of protein, DNA and RNA synthesis, which results in bacterial cell death.
  • Diagram of a typical gram-negative bacterium, with the thin cell wall sandwiched between the red outer membrane and the thin green plasma membrane.

• Components of Plasma Membranes

  • The plasma membrane protects the cell from its external environment, mediates cellular transport, and transmits cellular signals.
  • The plasma membrane (also known as the cell membrane or cytoplasmic membrane) is a biological membrane that separates the interior of a cell from its outside environment.
  • The primary function of the plasma membrane is to protect the cell from its surroundings.
  • The membrane also maintains the cell potential.
  • The cell employs a number of transport mechanisms that involve biological membranes: