Action Potential Essay

Good Essays
RESTING POTENTIAL
Resting potential is the membrane potential when a neuron is not conducting any electrical impulse or signal. The resting potential is around -75 mV. During resting potential, the inside of the axon is negative

GRADED POTENTIAL

ACTION POTENTIAL
Action potential is a fleeting reversal of the membrane potential, caused by changes in permeability of the plasma membrane of neuron to potassium and sodium ions causing an electrical impulse to be transmitted along the axon.

When a stimulus depolarizes the membrane, a few of the voltage-gated sodium channels that are found in the neuronal plasma membrane open permitting sodium ions to pass through. Since there is much greater concentration of sodium ions outside the axon than inside, they diffuse in through the open sodium channels down their concentration gradient. This result in the relatively high concentrations of positively charged sodium ions inside the axon and makes it less negative inside that it was before. The continue diffusion of sodium ions into the axon depolarizes the membrane more and brings it closer to the threshold. When the potential across the membrane reach the threshold (about –55 mV), additional voltage-gated sodium channel open. When this happens, there is rapid and intense influx of sodium ions into the axon causing the inside of the axon swiftly continues to build up more positive charges, until the membrane potential reaches a potential of about +40 mV compared with the outside. At this point, the sodium channels are temporary close and are inactivated, so the sodium ions stop diffusing into the axon. At the same time, the voltage-gated potassium channels open. Potassium ions therefore diffuse out of the axon, down their concentration gradient. The outward movement of potassium ions removes positive charge from inside the axon to the outside, thus beginning to return the potential difference to normal. This is called repolarisation or refractory period.

You May Also Find These Documents Helpful

  • Good Essays

    Action Potentials

    • 408 Words
    • 2 Pages

    Action Potentials An action potential is the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell. An action potential occurs when a neuron sends information down an axon, away from the cell body. A threshold is the minimum amount of stimulation needed to start a neural impulse (you know, the electrical impulses that travel throughout your body carrying important information). Action potentials generated by neural impulses are…

    • 408 Words
    • 2 Pages
    Good Essays
  • Better Essays

    action potential

    • 1527 Words
    • 7 Pages

    The formation of an action potential can be divided into five steps. (1) A stimulus from a sensory cell or another neuron causes the target cell to depolarize toward the threshold potential. (2) If the threshold of excitation is reached, all Na+ channels open and the membrane depolarizes. (3) At the peak action potential, K+ channels open and K+ begins to leave the cell. At the same time, Na+ channels close. (4) The membrane becomes hyperpolarized as K+ ions continue to leave the cell. The…

    • 1527 Words
    • 7 Pages
    Better Essays
  • Good Essays

    What is an action potential? To put it simply, it is a message that is sent down the nervous line. The message is written and is sent from the central nervous system. That message is addressed to muscles or glands. This essay will explain what happens before, during, and after an interneuron action potential. To accurately define an action potential, it is part of the incredible course of events that occur during the firing of a neuron. When a neuron is not firing signals, the interior of the…

    • 626 Words
    • 3 Pages
    Good Essays
  • Better Essays

    This essay will describe the electrochemical processes that allow an Action potential to occur in a neuron. This will be achieved by firstly, defining the purpose of neurons in the body along with a description of the components within a neuron and how they enable information to be passed through the cell membrane and on to other neurons. Secondly, the resting potential of a neuron will be explored with relation to the concept of selective permeability and the purpose of the Sodium - Potassium…

    • 2501 Words
    • 11 Pages
    Better Essays
  • Better Essays

    Compound Action Potentials

    • 1907 Words
    • 8 Pages

    Smith BIOL 3810-504 Compound Action Potentials Date Performed: 15FEB2011 Date Due: 01MAR2011 Introduction Neurons are the cells that receive and transmit electrical signals (University of North Texas, 2010). The ability of the neuron to conduct these impulses is because of an electrochemical voltage across the plasma membrane of that neuron. An action potential is an all or nothing response to a stimulus along a single axon. A compound action potential is a graded response that results…

    • 1907 Words
    • 8 Pages
    Better Essays
  • Powerful Essays

    Neuro Action Potential

    • 2553 Words
    • 11 Pages

    membrane Na cl ,K and Ca ions and they just flow back and fourth without any gate keeper or obstruction, When the neuron is at rest its cytoplasm is Negatively charged. That means that it is not going under depolarization, we use the term resting potential. Modality gated channels- specific to sensory neurons, open in response to mechanical forces (i.e. stretch, touch, pressure, temperature changes or chemicals) Ligand- is a particular molecule that causes a receptor to open. The ligand gated…

    • 2553 Words
    • 11 Pages
    Powerful Essays
  • Powerful Essays

    Cardiac Action Potential

    • 628 Words
    • 3 Pages

    which of the following? You correctly answered: c. autorhythmicity 2. Phase 2 of the cardiac action potential, when the calcium channels remain open and potassium channels are closed, is called the You correctly answered: a. plateau phase. 3. Which of the following is true of the cardiac action potential? You correctly answered: b. The cardiac action potential is longer than the skeletal muscle action potential. 4. The main anatomical difference between the frog heart and the human heart is that the…

    • 628 Words
    • 3 Pages
    Powerful Essays
  • Good Essays

    A graded potential in physiology, is described as local changes in membrane potential that occur in varying grades or degrees of magnitude or strength. When compared to graded potential, an action potential is described as brief, rapid, large (100mV) changes in membrane potential during which the potential actually reverses so that the inside of the excitable cell transiently becomes more positive than the outside. As with a graded potential, an action potential involves only a small portion of…

    • 911 Words
    • 4 Pages
    Good Essays
  • Satisfactory Essays

    the channel on the axon membrane, the membrane potential increases. Eventually, it reaches the action potential. The sodium channels will close and the potassium channels will open. Once the potassium ions enter the channels on the axon membrane, the membrane potential decreases. When the sodium ions go into the intracellular fluid, the membrane voltage increases from -70 and continues to +40. It will then reach the peak known as the action potential. When the potassium ions go into the extracellular…

    • 142 Words
    • 1 Page
    Satisfactory Essays
  • Powerful Essays

    Activity: Action Potentials Name: Caitlin Magnacca Instructor: Date: 03.19.2015 Predictions Exceeding threshold depolarization at the trigger zone______the likelihood of generation of an action potential. increases Action potential amplitude decreases with distance Increasing frequency of stimulation to the trigger zone increases number of action potentials Materials and Methods Experiment 1: Effect of Stimulus Strength on Action Potential Generation Dependent Variable membrane potential Independent…

    • 772 Words
    • 8 Pages
    Powerful Essays