resting potential

Examples of resting potential in the following topics:

• Nerve Impulse Transmission within a Neuron: Resting Potential

  • The resting potential of a neuron is controlled by the difference in total charge between the inside and outside of the cell.
  • For quiescent cells, the relatively-static membrane potential is known as the resting membrane potential.
  • As potassium is also the ion with the most-negative equilibrium potential, usually the resting potential can be no more negative than the potassium equilibrium potential.
  • The actions of the sodium-potassium pump help to maintain the resting potential, once it is established.
  • Voltage-gated ion channels are closed at the resting potential and open in response to changes in membrane voltage.

• Nerve Impulse Transmission within a Neuron: Action Potential

  • As soon as depolarization is complete, the cell "resets" its membrane voltage back to the resting potential.
  • The diffusion of K+ out of the cell hyperpolarizes the cell, making the membrane potential more negative than the cell's normal resting potential.
  • At this point, the sodium channels return to their resting state, ready to open again if the membrane potential again exceeds the threshold potential.
  • Eventually, the extra K+ ions diffuse out of the cell through the potassium leakage channels, bringing the cell from its hyperpolarized state back to its resting membrane potential.
  • The hyperpolarized membrane is in a refractory period and cannot fire. (5) The K+ channels close and the Na+/K+ transporter restores the resting potential.

• Control of Muscle Tension

  • If a sarcomere at rest is stretched past an ideal resting length, thick and thin filaments do not overlap to the greatest degree so fewer cross-bridges can form.
  • The primary variable determining force production is the number of myofibers (long muscle cells) within the muscle that receive an action potential from the neuron that controls that fiber.
  • As mentioned above, increasing the frequency of action potentials (the number of signals per second) can increase the force a bit more because the tropomyosin is flooded with calcium.
  • Muscle tone is residual muscle tension that resists passive stretching during the resting phase.

• Regulatory Proteins

  • Tropomyosin and troponin prevent myosin from binding to actin while the muscle is in a resting state.
  • When a muscle is in a resting state, actin and myosin are separated.
  • A change in the receptor conformation causes an action potential, activating voltage-gated L-type calcium channels, which are present in the plasma membrane.

• Autonomic Nervous System

  • Examples of functions controlled by the sympathetic nervous system include an accelerated heart rate and inhibited digestion, both of which help prepare an organism's body for the physical strain required to escape a potentially dangerous situation or to fend off a predator.
  • Scientists have found evidence that it may also increase long term potentiation in neurons, allowing the animal to remember the dangerous situation and avoid it in the future.
  • While the sympathetic nervous system is activated in stressful situations, the parasympathetic nervous system allows an animal to "rest and digest."
  • One way to remember this is to think that during a restful situation like a picnic, the parasympathetic nervous system is in control ("picnic" and "parasympathetic" both start with "p").
  • The sympathetic system activates the "fight or flight" response, while the parasympathetic system activates the "rest and digest" response.

• Water and Solute Potential

  • Water potential is the measure of potential energy in water and drives the movement of water through plants.
  • Water potential is a measure of the potential energy in water, or the difference in potential energy between a given water sample and pure water (at atmospheric pressure and ambient temperature).
  • Solute potential (Ψs), also called osmotic potential, is negative in a plant cell and zero in distilled water.
  • Solutes reduce water potential (resulting in a negative Ψw) by consuming some of the potential energy available in the water.
  • This is why solute potential is sometimes called osmotic potential.

• Pressure, Gravity, and Matric Potential

  • Water potential is affected by factors such as pressure, gravity, and matric potentials.
  • Pressure potential is also called turgor potential or turgor pressure and is represented by Ψp.
  • Pressure potential may be positive or negative; the higher the pressure, the greater potential energy in a system, and vice versa.
  • Plants must overcome the negative forces of gravity potential (Ψg) and matric potential (Ψm) to maintain a positive pressure potential.
  • Without height, there is no potential energy in the system.

• Types of Energy

  • The various types of energy include kinetic, potential, and chemical energy.
  • Objects transfer their energy between potential and kinetic states.
  • At the same time, the ball loses potential energy as it nears the ground.
  • This type of potential energy is called chemical energy, and like all potential energy, it can be used to do work.
  • Water behind a dam has potential energy.

• The Role of Species within Communities

  • Another keystone species is the banded tetra, a fish in tropical streams, which supplies nearly all of the phosphorus, a necessary inorganic nutrient, to the rest of the community.
  • Voracious eaters and rapid reproducers, Asian carp may outcompete native species for food, potentially leading to native species extinctions.

• DNA and RNA

  • In eukaryotes, the DNA molecules never leave the nucleus but instead use an intermediary to communicate with the rest of the cell.
  • They are bases because they contain an amino group that has the potential of binding an extra hydrogen, and thus, decreasing the hydrogen ion concentration in its environment, making it more basic.