Neurophysiology: Hodgkin and Huxley Experiments
40 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What organism was primarily utilized by Hodgkin and Huxley in their Nobel Prize-winning action potential experiments?

  • Human neuron
  • Mouse neuron
  • Frog muscle fiber
  • Squid giant axon (correct)
  • What was the primary technique employed by Hodgkin and Huxley to measure the action potential in the squid giant axon?

  • Voltage-clamp technique (correct)
  • Patch-clamp recording
  • Immunofluorescence microscopy
  • Electron microscopy
  • Before stimulation, what electrical characteristic did Hodgkin and Huxley observe in the squid giant axon?

  • Negative membrane potential (correct)
  • Positive membrane potential
  • Neutral membrane potential
  • Fluctuating membrane potential
  • What type of stimulus is required to initiate an action potential in the squid giant axon, according to the text?

    <p>Depolarization (B)</p> Signup and view all the answers

    Which of the following is a characteristic of the action potential waveform, as described in the content?

    <p>It overshoots 0 mV and undershoots resting VM. (D)</p> Signup and view all the answers

    How does altering the extracellular potassium concentration ([K+]OUT) affect the membrane potential (VM), based on the experiments described?

    <p>VM follows the changes in the equilibrium potential for potassium (EK). (D)</p> Signup and view all the answers

    What is the effect of altering the extracellular sodium concentration ([Na+]OUT) on the resting membrane potential?

    <p>Resting membrane potential remains unchanged. (A)</p> Signup and view all the answers

    What was Hodgkin and Huxley's 'sodium hypothesis' regarding the rising phase of the action potential?

    <p>The rising phase is attributed to voltage-dependent sodium influx. (A)</p> Signup and view all the answers

    What is the primary trigger for the opening of the M gate in a nerve cell membrane?

    <p>Depolarization of the membrane (B)</p> Signup and view all the answers

    Which gate is responsible for the active repolarization phase by decreasing sodium conductance?

    <p>H gate (B)</p> Signup and view all the answers

    Which ion channel is associated with the N gate?

    <p>Potassium channel (C)</p> Signup and view all the answers

    Which segment is identified as the voltage sensor in ion channels like Na, K, and Ca channels?

    <p>S4 segment (A)</p> Signup and view all the answers

    What is the primary function of the 'm' gate in the sodium channel?

    <p>Sodium activation (A)</p> Signup and view all the answers

    What prevents Sodium (Na+) and Potassium (K+) ions from canceling each other out during an action potential?

    <p>The gates have different kinetics/timing (D)</p> Signup and view all the answers

    Which structural element constitutes the pore region in ion channels?

    <p>6 segment domains (B)</p> Signup and view all the answers

    What technique is employed to measure currents flowing through individual ion channels?

    <p>All of the above (D)</p> Signup and view all the answers

    What structures fold into the ion channel pore and contribute to ion selectivity?

    <p>S5-S6 linkers (P loops) (A)</p> Signup and view all the answers

    Which segment acts as the voltage sensor in ion channels?

    <p>S4 (B)</p> Signup and view all the answers

    What is the role of the inactivation particle in an ion channel?

    <p>Acts as a cytoplasmic &quot;cork&quot; to block the pore (A)</p> Signup and view all the answers

    Which charges stabilize the S4 segment in its resting state?

    <p>Negative charges on S1-S3 (C)</p> Signup and view all the answers

    What ion is shown passing through the ion channel in the provided diagram?

    <p>Na+ (A)</p> Signup and view all the answers

    What does the length constant (λ) represent in electrotonic membrane properties?

    <p>Distance for voltage change to decay to 37% (B)</p> Signup and view all the answers

    What does the time constant (τ) represent in electrotonic membrane properties?

    <p>Time for voltage change to decay to 37% (D)</p> Signup and view all the answers

    Which of the following is crucial for action potential propagation?

    <p>Passive membrane properties (B)</p> Signup and view all the answers

    What is the primary purpose of action potentials in neurons and muscle cells?

    <p>To transmit information quickly across long distances. (A)</p> Signup and view all the answers

    Which of the following best describes "frequency coding" in the context of action potentials?

    <p>The rate of action potential firing corresponds to the intensity of the information being transmitted. (C)</p> Signup and view all the answers

    What distinguishes electrically excitable neurons from electrically inexcitable neurons?

    <p>Electrically excitable neurons utilize action potentials for long-distance communication. (C)</p> Signup and view all the answers

    Which ions play a critical role in the generation of action potentials through voltage-gated channels?

    <p>Na+, K+, Ca++ (D)</p> Signup and view all the answers

    What occurs during the rising phase of an action potential?

    <p>The membrane potential rapidly depolarizes, approaching the equilibrium potential of sodium (ENa+). (C)</p> Signup and view all the answers

    What characterizes the absolute refractory period of an action potential?

    <p>No second action potential can be initiated due to sodium channel inactivation. (D)</p> Signup and view all the answers

    Which equation represents the membrane potential (VM)?

    <p>VM = ∑ {PION x EION} (D)</p> Signup and view all the answers

    What makes the squid axon a suitable model for studying action potentials?

    <p>Squid axons are large enough to allow for detailed electrophysiological measurements. (B)</p> Signup and view all the answers

    What biophysical property limits the frequency of action potentials?

    <p>Inactivation of voltage-dependent channels (D)</p> Signup and view all the answers

    How does an action potential propagate along an axon?

    <p>Passive decay of membrane potential followed by triggering of voltage-gated channels in the next area of the axon (A)</p> Signup and view all the answers

    What is saltatory conduction?

    <p>Rapid propagation of action potentials in myelinated axons (D)</p> Signup and view all the answers

    How does myelin increase action potential conduction velocity?

    <p>Increases length constant (A)</p> Signup and view all the answers

    Which channels are concentrated at the Nodes of Ranvier?

    <p>Voltage-gated sodium and potassium channels (B)</p> Signup and view all the answers

    What impact does increasing axonal diameter have on conduction velocity?

    <p>Increases velocity (C)</p> Signup and view all the answers

    What role does the length constant (l) play in action potential propagation?

    <p>Determines the distance over which passive current flow effectively depolarizes the membrane (A)</p> Signup and view all the answers

    What is Multiple Sclerosis?

    <p>A disease where myelin degrades impairing action potential propagation. (B)</p> Signup and view all the answers

    Study Notes

    Action Potential Overview

    • Action potentials are crucial for rapid information transport in axons and muscles.
    • They are generated by the opening and closing of voltage-gated ion channels, leading to a rapid change in membrane potential.
    • Action potentials are all-or-none events, meaning they either occur completely or not at all, once triggered.

    Mechanisms of Action Potential

    • Frequency coding: The intensity of a signal is represented by the frequency of action potentials.
    • Recruitment: The number of axons firing action potentials represents a stronger signal.
    • Place code: The identity of the axon carrying the action potential indicates the origin of the signal.
    • Voltage-gated Na+, K+, and Ca++ channels generate the action potential's rapid and faithful propagation.

    Types of Neurons

    • Some neurons utilize graded potentials for short-distance signaling. These graded potentials are passive and do not propagate long distances.
    • Example: retinal bipolar neurons
    • Most neurons use action potentials (nerve impulses), which regenerate and propagate over long distances. These potentials are electrically excitable.
    • Example: lower motor neurons in the spinal cord

    Action Potential Phases

    • Resting phase: The membrane potential is negative (approximately -70 mV). Specific ion channels are open at this point in time.
    • Rising phase: The membrane potential rapidly increases toward a positive value. This is driven by the influx of Na+ ions across the membrane.
    • Overshoot: The membrane potential briefly becomes positive.
    • Falling phase: The membrane potential rapidly returns to a negative value. This is due to the outward movement of K+ ions.
    • Undershoot (after-hyperpolarization): The membrane potential dips below the resting potential before gradually returning.

    Action Potential Characteristics

    • Threshold: The minimum voltage necessary to initiate an action potential.
    • Refractory periods: A period during and after an action potential firing where it's difficult or impossible to fire another action potential. This includes the absolute and relative refractory periods.

    Investigating the Action Potential

    • Factors affecting membrane potential (VM) - P(ION), E(ION)
    • Role of squid giant axon in studying action potentials - Easy preparation of the large axon allowed detailed studies of ion currents during the action potential.
    • Hodgkin and Huxley - Proposed the voltage-gated ion channels as the basis for generating and propagating action potentials.

    Ionic Basis of Action Potential

    • Sodium hypothesis: The change in membrane potential(VM) during an action potential is primarily due to changes in Na+ permeability.
    • Voltage-gated Na+ channels open and close rapidly in response to depolarization.
    • Voltage-gated K+ channels open and close more slowly than Na+ channels as the membrane potential rises and falls.
    • Voltage-dependent ion channel gates-m, h, n states represent the different conformational states of the ion channels.
    • Structure and function of ion channels: Pore, voltage sensing module, inactivation particle

    Passive and Active Membrane Properties

    • Passive decay or electrotonic spread occurs in the absence of voltage-dependent ion channel opening.
    • Length constant (λ): distance over which an initial voltage change decays to about 37% of its original value, depending on the resistance along and across the membrane.
    • Time constant (τ): time (in milliseconds) it takes for a change in membrane potential to decay to about 37% of its original value.

    Action Potential Propagation

    • Propagation occurs due to passive spread of depolarization and the opening of voltage-gated channels.
    • Myelin significantly increases conduction velocity.
    • Saltatory conduction: action potential "jumps" between gaps in the myelin sheath (nodes of Ranvier)

    Action Potential Velocity Improvement

    • Decrease RA (axon resistance): Larger diameter axons have lower resistance, leading to faster conduction.
    • Increase RM (membrane resistance): Myelin sheaths increase membrane resistance, increasing length constant, facilitating saltatory conduction.

    Synaptic Summation

    • The summation of EPSPs (excitatory postsynaptic potentials) and IPSPs (inhibitory postsynaptic potentials) results in a total postsynaptic potential.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Neuro Lecture #3 PDF

    Description

    Test your knowledge on the groundbreaking action potential experiments conducted by Hodgkin and Huxley. Explore key concepts such as the organism used, measurement techniques, and the effects of ion concentrations on membrane potentials. This quiz delves into the fundamental aspects of neurophysiology and action potentials in the squid giant axon.

    More Like This

    Action Potential Graph Labeling
    5 questions

    Action Potential Graph Labeling

    EffortlessGyrolite7402 avatar
    EffortlessGyrolite7402
    Neurons: Steps of Action Potential
    6 questions

    Neurons: Steps of Action Potential

    WellConnectedComputerArt avatar
    WellConnectedComputerArt
    Hodgkin-Huxley Modell Notizen
    8 questions
    Hodgkin-Huxley Model Quiz
    10 questions

    Hodgkin-Huxley Model Quiz

    ReverentCosine1859 avatar
    ReverentCosine1859
    Use Quizgecko on...
    Browser
    Browser