Physiology Chapter: Electrochemical Potentials and Axon Potentials
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Questions and Answers

What is the typical resting membrane potential of a cell?

  • -90 mV
  • -70 mV (correct)
  • 0 mV
  • -50 mV

    • What determines the equilibrium potential of an ion?

  • Size of the ion
  • Concentration gradient of the ion
  • Membrane voltage required to prevent movement of the ion (correct)
  • Charge of the ion

    • What is the primary function of the Na+/K+-ATPase pump?

  • To create a voltage gradient across the membrane
  • To facilitate ion movement down concentration gradients
  • To maintain a stable resting membrane potential (correct)
  • To generate action potentials

    • What type of recording is used to measure electrical potentials from inside a cell?

    <p>Intracellular recording</p> Signup and view all the answers

    What is the primary component of the membrane that provides a hydrophobic barrier?

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

    What is the result of the inside of the cell becoming very negative?

    <p>K+ ions are prevented from leaving</p> Signup and view all the answers

    What is the purpose of the ion channels in the membrane?

    <p>To facilitate ion movement</p> Signup and view all the answers

    What is the result of depolarization of the cell membrane?

    <p>The inside of the membrane becomes more positively charged</p> Signup and view all the answers

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

    <p>To maintain the electrochemical gradient of sodium ions</p> Signup and view all the answers

    What is the term for the period of time during which an action potential cannot be generated?

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

    What is the purpose of patch clamping in measuring electrical potentials?

    <p>To record the electrical activity of a single ion channel</p> Signup and view all the answers

    What is the property of the cell membrane that allows it to store charges?

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

    What is the term for the difference in electrical potential between the inside and outside of a cell?

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

    What is the role of voltage-dependent ion channels in generating the membrane potential?

    <p>To contribute to the establishment of the membrane potential</p> Signup and view all the answers

    What is the term for the minimum amount of electrical potential required to generate an action potential?

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

    What is the purpose of extracellular recording in measuring electrical potentials?

    <p>To record the electrical activity of a neuron or group of neurons</p> Signup and view all the answers

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

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

    What is the result of the rapid influx of sodium into the cell through sodium channels?

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

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

    <p>To permit the rapid efflux of potassium out of the cell</p> Signup and view all the answers

    What is the result of the rapid efflux of potassium out of the cell through potassium channels?

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

    What determines the resting membrane potential?

    <p>The specific ionic distribution across the membrane</p> Signup and view all the answers

    What are the two specific forces that ions are under?

    <p>The electrostatic force and the force of diffusion</p> Signup and view all the answers

    What is the equation used to calculate the resting membrane potential?

    <p>The Nernst equation</p> Signup and view all the answers

    What is the value of the resting membrane potential under physiological conditions?

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

    What is the primary cause of the 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 sodium channels?

    <p>The neuron cannot reach the threshold again</p> Signup and view all the answers

    What is the purpose of the relative refractory period?

    <p>To allow the neuron to recover and respond to stronger stimuli</p> Signup and view all the answers

    What is the typical resting membrane potential of a neuron?

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

    What happens to the potassium channels during the hyperpolarization phase?

    <p>They open and allow more potassium ions to leave the neuron</p> Signup and view all the answers

    What is the primary function of the leak channels?

    <p>To regulate the membrane potential during the resting state</p> Signup and view all the answers

    What is the result of the rapid entry of sodium ions into the neuron?

    <p>The neuron becomes depolarized</p> Signup and view all the answers

    What is the purpose of the voltage-gated sodium channels?

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

    What is the typical voltage at which the voltage-dependent, transient Na+ channels open?

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

    What is the primary function of the V-gated K channels?

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

    What is the term for the period of time during which the V-gated Na channels are inactivated?

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

    What is the primary difference between the conduction of action potentials in non-myelinated and myelinated axons?

    <p>Speed of conduction</p> Signup and view all the answers

    What is the term for the ability of an excitable cell to generate an action potential?

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

    What is the typical concentration of Na+ ions inside a cell?

    <p>10mM</p> Signup and view all the answers

    What is the term for the movement of ions across the cell membrane?

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

    What is the term for the ability of a cell membrane to store electrical energy?

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

    What is the term for the flow of electrical charge across the cell membrane?

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

    What is the term for the difference in electrical potential between the inside and outside of a cell?

    <p>Potential difference</p> Signup and view all the answers

    Study Notes

    Establishing Electrochemical Potentials and Axon Potentials

    • Electrochemical equilibria and membrane potential:
      • The membrane separates and stores charges
      • Na+ and K+ ion channels contribute to generating the membrane potential (MP)
      • The differential permeability of the membrane to Na+ and K+ ions is significant
      • Electrochemical gradients are established through the sodium pump, voltage-dependent ion channels, and membrane capacitance
    • Action potential, propagation, and nerve conduction:
      • Properties of the action potential (AP):
        • Voltage and conductance changes during the AP
        • Capacitance
      • Threshold and refractory periods:
        • What is meant by 'threshold' and 'refractory periods'
        • Importance of myelin in nerve conduction

    Measuring Electrical Potentials

    • Methods of measuring electrical potentials:
      • Extracellular recording (electrode outside the cell)
      • Intracellular recording (electrode inside the cell)
      • Patch clamping (electrode sealed to the cell surface)
    • Measurement units:
      • 100 mV (intracellular recording)
      • 0.1 mV (extracellular recording)

    Basic Principles

    • At rest, the inside of the membrane is more negatively charged than the outside (hyperpolarized)
    • When cells become activated, the inside of the membrane becomes more positively charged (depolarized)

    The Resting Membrane Potential

    • The resting membrane potential (Vm) is typically around -70 mV
    • It is determined by Na+ and K+ ions (and Ca2+ ions)
    • Equilibrium potential of an ion is the membrane voltage required to prevent movement of an ion down its concentration gradient
    • If the inside of the cell is very negative, K+ will be prevented from leaving; if the inside of the cell is very positive, Na+ will be prevented from entering

    The Membrane

    • The membrane surrounds the entire neuron, providing a hydrophobic, relatively impermeable barrier
    • Composed of lipids and proteins, with ion channels and pumps providing entry and exit routes for ions
    • Na+/K+-ATPase pump:
      • Uses energy (ATP) to actively pump three sodium (Na+) and two potassium (K+) ions out and into the cell, respectively
      • Maintains a more depolarized internal environment
    • Sodium channels:
      • Permit the rapid influx of sodium into the cell upon opening, resulting in depolarization
    • Potassium channels:
      • Permit the rapid efflux of potassium out of the cell upon opening, resulting in hyperpolarization

    The Action Potential

    • The action potential is generated by the rapid influx of sodium ions and the rapid efflux of potassium ions
    • The Nernst equation is used to calculate the equilibrium potential of an ion
    • The action potential has five stages:
      1. Depolarization reaches threshold
      2. Voltage-gated sodium channels (NaV) open, and sodium ions (Na+) enter the neuron
      3. Rapid Na+ entry depolarizes the neuron further
      4. NaV channels inactivate, and slower (0.5 mS) potassium channels (Kv) open
      5. Potassium ions (K+) move out of the neuron, repolarizing it

    Refractory Periods

    • Absolute refractory period:
      • Results from the inactivation of Na+ channels
      • Lasts until the resting membrane potential is restored
    • Relative refractory period:
      • Results from the hyperpolarization phase
      • During which a greater stimulus is needed to reach threshold

    Functional States of Ion Channels

    • Ion channels have three states:
      • Closed (resting)
      • Open (active)
      • Inactive (refractory)
    • V-gated Na channels have all three states, while V-gated K channels have no inactivation state

    Action Potential Conduction

    • Action potential conduction in non-myelinated axons:
      • Involves the continuous generation of action potentials along the length of the axon
    • Action potential conduction in myelinated axons:
      • Involves the saltatory conduction of action potentials between nodes of Ranvier
      • The myelin sheath insulates the axon, increasing the speed of transmission

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    Related Documents

    Establishing Electrochemical Potentials and Action Potentials PDF

    Description

    This quiz covers the physiology of electrochemical potentials and axon potentials, including the concentrations of Na+ and K+ ions inside and outside of cells and how electrical events are measured.

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