L1 Muscle Physiology: Membrane and Action Potentials
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Questions and Answers

What type of potential exactly balances the tendency of an ion to diffuse down its concentration gradient?

  • Membrane potential
  • Resting potential
  • Nernst potential (correct)
  • Equilibrium potential

    • What is the driving force behind the movement of uncharged molecules across a membrane?

  • Osmotic pressure
  • Hydrostatic pressure
  • Concentration gradient (correct)
  • Electrical charges

    • What is the typical value of the equilibrium potential for potassium ions (EK+)?

  • +65 mV
  • -90 mV
  • +120 mV
  • -85 mV (correct)

    • What is the primary factor that determines the diffusion potential across a membrane?

    <p>Concentration gradient</p> Signup and view all the answers

    What would happen if the membrane was not permeable to the ion in question?

    <p>No diffusion potential would be generated</p> Signup and view all the answers

    What type of cells undergo controlled changes in their membrane potential?

    <p>Neurons and muscle cells</p> Signup and view all the answers

    What is the term for the difference in electric potential between the interior and exterior of a biological cell?

    <p>Membrane potential</p> Signup and view all the answers

    What is the effect of a diffusion potential on the concentration of ions in bulk solution?

    <p>It has no effect on the concentration of ions</p> Signup and view all the answers

    What is the typical value of the equilibrium potential for sodium ions (ENa+)?

    <p>+65 mV</p> Signup and view all the answers

    What is the diffusion potential generated by?

    <p>The movement of a charged solute down its concentration gradient</p> Signup and view all the answers

    What is the relationship between the diffusion potential and the concentration gradient?

    <p>The diffusion potential is directly proportional to the concentration gradient</p> Signup and view all the answers

    What is the term for the membrane potential of a cell that remains relatively constant over time?

    <p>Resting potential</p> Signup and view all the answers

    What is the resting potential of nerve fibers when not transmitting nerve signals?

    <p>-70 millivolts</p> Signup and view all the answers

    What is the main contributor to the resting potential of nerve cells?

    <p>Potassium diffusion</p> Signup and view all the answers

    What is the selectivity of the potassium leak channels?

    <p>100x higher for K than for Na ions</p> Signup and view all the answers

    Why do potassium ions move into the cell?

    <p>Attracted to negative charges</p> Signup and view all the answers

    What is the role of the Na-K pump?

    <p>To maintain the resting potential of nerve cells</p> Signup and view all the answers

    Why is the membrane less permeable to sodium ions?

    <p>The membrane is more permeable to potassium ions</p> Signup and view all the answers

    What is the minimal membrane potential required to trigger an action potential?

    <p>-55 mV</p> Signup and view all the answers

    What happens to the membrane potential during depolarization?

    <p>It rises in the positive direction</p> Signup and view all the answers

    What causes the rapid diffusion of K ions out of the cell during repolarization?

    <p>Voltage-gated potassium channels</p> Signup and view all the answers

    What is the term for the state when neurons have a more negative membrane potential than normal?

    <p>Hyperpolarization</p> Signup and view all the answers

    What is the absolute refractory period?

    <p>The time needed for the voltage-gated sodium channels to revert from the inactivated state to the resting closed state</p> Signup and view all the answers

    What is the relative refractory period?

    <p>The time when the membrane is in a hyperpolarization state</p> Signup and view all the answers

    What is the primary function of the Na-K pump?

    <p>To transport Na+ out and K+ in</p> Signup and view all the answers

    What is the role of the ATPase function in the Na-K pump?

    <p>To activate the pump after binding of Na+ and K+ ions</p> Signup and view all the answers

    What is the significance of the resting potential in neurons?

    <p>It is necessary for the transmission of nerve signals</p> Signup and view all the answers

    What is the characteristics of an action potential?

    <p>A rapid change in the membrane potential that spreads rapidly along the nerve fiber</p> Signup and view all the answers

    What are the five stages of an action potential?

    <p>Resting, threshold, depolarization, repolarization, and hyperpolarization</p> Signup and view all the answers

    What is the significance of the Na-K pump in controlling the volume of a cell?

    <p>It helps to remove excess sodium ions from the cell</p> Signup and view all the answers

    What is the primary driving force behind the movement of charged molecules across a membrane?

    <p>Electrical charges</p> Signup and view all the answers

    What is necessary for a diffusion potential to be generated across a membrane?

    <p>A concentration gradient of charged molecules and membrane permeability</p> Signup and view all the answers

    What is the effect of a diffusion potential on the bulk solution?

    <p>No effect on the concentration of ions</p> Signup and view all the answers

    What determines the magnitude of the diffusion potential across a membrane?

    <p>Both the concentration gradient and permeability of the membrane</p> Signup and view all the answers

    What would happen if a membrane was not permeable to the ion in question?

    <p>No diffusion potential would be generated</p> Signup and view all the answers

    What is the relationship between the diffusion potential and the concentration gradient?

    <p>The diffusion potential increases with an increase in concentration gradient</p> Signup and view all the answers

    What is the main factor that determines the equilibrium potential of an ion?

    <p>Both the electrical charge and concentration inside and outside the membrane</p> Signup and view all the answers

    What is the characteristic of the membrane potential in most animal cells?

    <p>It does not vary with time</p> Signup and view all the answers

    What is the term for the membrane potential that remains relatively constant over time?

    <p>Resting potential</p> Signup and view all the answers

    What is the primary factor that determines the membrane potential of a cell?

    <p>The relative permeability of each ion</p> Signup and view all the answers

    What is the difference between the electric potential inside and outside a biological cell?

    <p>Membrane potential</p> Signup and view all the answers

    Which type of cells do not undergo controlled changes in their membrane potential?

    <p>Most animal cells</p> Signup and view all the answers

    What is the primary contributor to the resting potential of nerve cells?

    <p>Diffusion of potassium through the nerve cell membrane</p> Signup and view all the answers

    What determines the selectivity of potassium leak channels?

    <p>The protein structure of the channel</p> Signup and view all the answers

    What is the direction of potassium ion movement in the resting state?

    <p>Out of the cell</p> Signup and view all the answers

    What is the effect of the Na-K pump on the resting potential?

    <p>It maintains the resting potential</p> Signup and view all the answers

    Why are potassium ions attracted to the inside of the cell?

    <p>Because of the negative charges inside the cell</p> Signup and view all the answers

    What is the typical value of the resting potential of nerve fibers when not transmitting nerve signals?

    <p>-70 millivolts</p> Signup and view all the answers

    What is the primary function of the Na-K pump in neurons?

    <p>To control the volume of the cell and maintain the resting potential</p> Signup and view all the answers

    What is the characteristic of the action potential that allows it to spread rapidly along the nerve fiber membrane?

    <p>The sudden change from the resting negative membrane potential to a positive potential</p> Signup and view all the answers

    What is the consequence of the dynamic changes in the membrane potential in neurons and muscle cells?

    <p>The generation of action potentials</p> Signup and view all the answers

    What is the role of the ATPase function in the Na-K pump?

    <p>To activate the pump after binding of sodium and potassium ions</p> Signup and view all the answers

    What is the significance of the resting potential in nerve cells?

    <p>It is essential for the transmission of nerve signals</p> Signup and view all the answers

    How many stages are involved in the action potential?

    <p>5 stages</p> Signup and view all the answers

    What is the minimum membrane potential required to initiate an action potential?

    <p>-55 mV</p> Signup and view all the answers

    What type of channels are activated during depolarization?

    <p>Voltage-gated sodium channels</p> Signup and view all the answers

    What is the term for the state when neurons have a more negative membrane potential than normal after an action potential?

    <p>Hyperpolarization</p> Signup and view all the answers

    What is the primary function of the voltage-gated potassium channels during an action potential?

    <p>To slow down the depolarization process</p> Signup and view all the answers

    What is the period during which the voltage-gated sodium channels are closed and cannot be reopened?

    <p>Absolute refractory period</p> Signup and view all the answers

    What is the stage of the action potential during which the membrane potential becomes highly permeable to sodium ions?

    <p>Depolarization</p> Signup and view all the answers

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