Physiology & Anatomy of Systems: Electrochemical Potentials
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Questions and Answers

What is the result of sodium channels opening in a cell?

  • No change in membrane potential
  • Stabilization of the resting membrane potential
  • Hyperpolarization (more negative)
  • Depolarization (more positive) (correct)

    • What is the primary force responsible for the movement of potassium ions out of the cell through potassium channels?

  • Electromagnetic force
  • Force of diffusion (correct)
  • Gravity
  • Electrostatic force

    • What is the primary function of the sodium pump in generating the membrane potential?

  • To maintain a constant membrane potential
  • To pump sodium ions out of the cell (correct)
  • To generate an action potential
  • To pump potassium ions into the cell

    • What is the approximate value of the resting membrane potential?

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

    What is the term for the period of time during which an excitable cell is unable to generate another action potential?

    <p>Refractory period</p> Signup and view all the answers

    What is the primary advantage of patch clamping over extracellular and intracellular recording techniques?

    <p>Ability to record from single ion channels</p> Signup and view all the answers

    Which ion is most responsible for the resting membrane potential?

    <p>Potassium (K+)</p> Signup and view all the answers

    What is the purpose of the Nernst equation in physiology?

    <p>To calculate the resting membrane potential</p> Signup and view all the answers

    What is the primary reason for the differential permeability of the cell membrane to sodium and potassium ions?

    <p>The properties of the ion channels</p> Signup and view all the answers

    What happens to the membrane potential when potassium channels are opened?

    <p>Hyperpolarization (more negative)</p> Signup and view all the answers

    What is the term for the difference in electric potential between two points?

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

    Which of the following is NOT a force that affects ion movement across the membrane?

    <p>Thermal energy</p> Signup and view all the answers

    What is the primary function of voltage-dependent ion channels in generating the action potential?

    <p>To allow sodium ions to enter the cell</p> Signup and view all the answers

    What is the term for the ability of a cell membrane to store electric charge?

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

    What is the primary function of sodium channels in a cell?

    <p>To facilitate the rapid influx of sodium into the cell</p> Signup and view all the answers

    What is the term for the point at which an excitable cell generates an action potential?

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

    What is the resting membrane potential (RMP) of a cell driven towards?

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

    What would happen to Vm if a cell becomes permeable to sodium ions?

    <p>Vm would increase towards ENa</p> Signup and view all the answers

    What is the driving force on potassium ions when Vm is -70mV?

    <p>+20 mV</p> Signup and view all the answers

    What would happen to the net flow of ions at a constant Vm?

    <p>Net flow of ions is zero</p> Signup and view all the answers

    Why is the membrane more permeable to potassium ions?

    <p>Because there are more K+ channels</p> Signup and view all the answers

    What is the equilibrium potential for sodium ions?

    <p>+50mV</p> Signup and view all the answers

    What is the driving force on sodium ions when Vm is -70mV?

    <p>-120 mV</p> Signup and view all the answers

    What is the relationship between permeability and conductance?

    <p>High permeability means high conductance</p> Signup and view all the answers

    What is the limitation of the Nernst equation?

    <p>It only deals with one ion at a time</p> Signup and view all the answers

    What would happen to Vm if the cell becomes impermeable to potassium ions?

    <p>Vm would increase towards ENa</p> Signup and view all the answers

    What is the primary reason for the rapid depolarization of the neuron beyond the threshold?

    <p>The rapid entry of sodium ions into the neuron</p> Signup and view all the answers

    What is the effect of the inactivation of voltage-gated sodium channels on the neuron?

    <p>It prevents the neuron from generating another action potential</p> Signup and view all the answers

    During which phase of the action potential is the neuron most susceptible to further stimulation?

    <p>The resting membrane potential phase</p> Signup and view all the answers

    What is the primary function of the potassium ion channels that open during the repolarization phase?

    <p>To repolarize the neuron and return it to its resting membrane potential</p> Signup and view all the answers

    What is the effect of the hyperpolarization phase on the neuron's ability to generate an action potential?

    <p>It decreases the neuron's ability to generate an action potential</p> Signup and view all the answers

    What is the primary difference between the absolute and relative refractory periods?

    <p>The underlying mechanisms that cause the refractory period</p> Signup and view all the answers

    What is the effect of the closure of potassium ion channels on the neuron's membrane potential?

    <p>It causes the neuron to return to its resting membrane potential</p> Signup and view all the answers

    What is the primary function of the leak channels in the neuron?

    <p>To regulate the resting membrane potential of the neuron</p> Signup and view all the answers

    What is the primary function of the transient Na+ channels in the action potential?

    <p>To generate a rapid depolarization of the membrane potential</p> Signup and view all the answers

    What is the significance of the -55mV threshold in V-gated Na channels?

    <p>It is the point at which the Na+ channels open</p> Signup and view all the answers

    What is the primary difference between V-gated Na and K channels?

    <p>V-gated Na channels are responsible for depolarization, while V-gated K channels are responsible for repolarization</p> Signup and view all the answers

    What is the significance of the after-hyperpolarization phase of the action potential?

    <p>It is the point at which the membrane potential returns to its resting state</p> Signup and view all the answers

    What is the primary function of the delayed, persistent K+ channels in the action potential?

    <p>To generate a rapid repolarization of the membrane potential</p> Signup and view all the answers

    What is the significance of the -90mV threshold in the action potential?

    <p>It is the point at which the threshold potential is reached</p> Signup and view all the answers

    What is the primary difference between non-myelinated and myelinated axons?

    <p>Myelinated axons have a faster conduction velocity than non-myelinated axons</p> Signup and view all the answers

    What is the significance of the inactivation state of V-gated Na channels?

    <p>It is the point at which the Na+ channels are inactivated</p> Signup and view all the answers

    What is the primary function of the voltage-dependent ion channels in the action potential?

    <p>To generate a rapid depolarization of the membrane potential</p> Signup and view all the answers

    What is the significance of the capacitance of the cell membrane?

    <p>It is responsible for the storage of electric charge</p> Signup and view all the answers

    Study Notes

    Electrochemical Potentials and Axon Potentials

    • The inside of a cell is more negatively charged than the outside, with a resting membrane potential of -70mV.
    • Sodium (Na+) channels permit rapid influx of sodium into the cell, resulting in depolarization (more positive).
    • Potassium (K+) channels permit rapid efflux of potassium out of the cell, resulting in hyperpolarization (more negative).

    Measuring Electrical Events

    • Extracellular recording: electrode outside the cell.
    • Intracellular recording: electrode inside the cell.
    • Patch clamping: electrode sealed to the cell surface.

    The Membrane Potential

    • The specific ionic distribution across the membrane sets the resting membrane potential.
    • The membrane has a higher permeability to K+ than Na+ ions.
    • The Nernst equation is used to calculate the equilibrium potential for an ion.

    The Resting Membrane Potential

    • The membrane potential is determined by the balance of electrostatic force and the force of diffusion.
    • The resting membrane potential is closer to the equilibrium potential for K+ (-90mV) than Na+ (+50mV).
    • The net flow of ions is zero at a constant membrane potential.

    Action Potential and Propagation

    • The action potential is generated by the rapid influx of sodium ions, followed by the rapid efflux of potassium ions.
    • The action potential has a threshold, at which the voltage-gated sodium channels open, and a refractory period, during which the channels are inactivated.
    • The action potential is conducted through the neuron, with the myelinated axon allowing for faster conduction.

    Refractory Periods

    • The absolute refractory period results from the inactivation of Na+ channels and lasts until the resting membrane potential is restored.
    • The relative refractory period results from the hyperpolarization phase, during which a greater stimulus is needed to reach threshold.

    Ion Channels

    • Voltage-gated sodium channels have three states: closed, open, and inactive.
    • Voltage-gated potassium channels have two states: open and closed.
    • The functional states of ion channels determine the action potential.

    Action Potential Conduction

    • Non-myelinated axons: action potential conduction occurs through the entire length of the axon.
    • Myelinated axons: action potential conduction occurs through the nodes of Ranvier, allowing for faster conduction.
    • The speed of action potential conduction is increased in myelinated axons.

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    Description

    This quiz covers the physiology and anatomy of systems, focusing on establishing electrochemical potentials and axon potentials. It tests your knowledge of ion concentrations and electrical events in excitable cells.

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