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Quizzes > Health & Medicine

Action potential quiz: Test your neuron signaling basics

Quick, free action potential practice test. Instant results.

Editorial: Review CompletedCreated By: Salma BasionyUpdated Aug 24, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art style neuron with ion channels and membrane potential waves on golden yellow background for action potential quiz

This action potential quiz helps you practice how neurons fire, from threshold to depolarization and the refractory period. Use it to check your understanding before class or lab, then build related skills with the eeg quiz and the spinal cord anatomy quiz. Get instant feedback to see what to review next.

Which ion has the greatest permeability at a neuron's resting membrane potential in most central neurons?
Chloride (Cl-)
Sodium (Na+)
Calcium (Ca2+)
Potassium (K+)
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During the rising phase of a typical neuronal action potential, which event is dominant?
Rapid opening of voltage-gated Na+ channels increases Na+ influx
Opening of voltage-gated K+ channels increases K+ influx
Closing of leak K+ channels halts K+ efflux
Activation of Na+/K+ pump depolarizes the membrane
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Absolute refractory period is primarily due to what channel state?
Closed leak K+ channels
Inactivated voltage-gated Na+ channels
Open voltage-gated K+ channels
Activated Na+/K+ ATPase
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Which toxin selectively blocks voltage-gated Na+ channels on the extracellular side, preventing action potentials?
Tetraethylammonium (TEA)
Tetrodotoxin (TTX)
Botulinum toxin
Ouabain
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Saltatory conduction depends on which structural feature of myelinated axons?
Nodes of Ranvier with high Na+ channel density
Uniform myelin thickness along dendrites
Continuous distribution of Ca2+ channels along the axon
Large numbers of Cl- channels at internodes
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The threshold for triggering an action potential is best described as the membrane potential at which what occurs?
All ion channels open simultaneously
Voltage-gated Na+ channel activation outpaces K+ currents, causing net inward current
The membrane potential equals the Na+ equilibrium potential
The refractory period ends
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Relative refractory period occurs because of which main factor?
Complete inactivation of Na+ channels
Elevated K+ conductance hyperpolarizes the membrane
Closure of all Ca2+ channels
Depletion of extracellular Na+
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Local anesthetics like lidocaine reduce pain sensation mainly by what mechanism?
Enhancing Na+/K+ pump activity
Blocking voltage-gated K+ channels
Stabilizing the inactivated state of voltage-gated Na+ channels
Antagonizing GABA receptors
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Which equation best predicts resting membrane potential considering multiple ions and their permeabilities?
Nernst equation
Ohm's law
Michaelis-Menten equation
Goldman-Hodgkin-Katz equation
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At the peak of a standard neuronal action potential, the membrane potential approaches which value relative to ionic equilibrium potentials?
Near the Cl- equilibrium potential (ECl)
Near the Na+ equilibrium potential (ENa)
Near the K+ equilibrium potential (EK)
Exactly 0 mV regardless of ion gradients
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Which component of a voltage-gated Na+ channel mediates fast inactivation in many neurons?
Intracellular loop acting as a ball-and-chain gate
Beta subunit transmembrane helix
S4 voltage sensor extracellular loop
Selectivity filter within the pore helix
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Temporal summation of EPSPs is most effective when which condition is met?
Long membrane time constant prolongs EPSP decay
Low input resistance shunts currents
Short membrane time constant limits decay between inputs
Strong inhibition at the axon initial segment
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The length constant (lambda) of a dendrite increases most when which change occurs?
Membrane resistance increases and axial resistance decreases
Membrane resistance decreases and axial resistance increases
Both resistances decrease
Both resistances increase
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Which best describes accommodation in neurons?
Axonal failure due to demyelination
Increased transmitter release after repetitive firing
Enhanced excitability during rapid hyperpolarization
Reduced excitability during slow depolarization due to Na+ channel inactivation and K+ activation
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In hypokalemia (reduced extracellular K+), what happens to resting membrane potential and excitability?
No change in potential; marked increased excitability
Membrane hyperpolarizes; massive spontaneous firing
Membrane hyperpolarizes; initial decreased excitability
Membrane depolarizes; increased excitability
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Which best characterizes the safety factor for conduction in axons?
Difference between ENa and resting potential
Ratio of available depolarizing current to that required to bring adjacent membrane to threshold
Time between spikes during high-frequency firing
Number of Na+ channels per micron of axon
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What property of the S4 segment in voltage-gated channels enables voltage sensing?
Hydrophobic residues create a water-filled pore
Phosphorylation sites directly conduct ions
Positively charged residues at every third position move in the electric field
Calcium-binding motifs alter gating
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Which best explains why Cl- currents can be depolarizing yet inhibitory in some neurons?
Cl- influx always triggers action potentials
Depolarization toward ECl reduces input resistance and shunts EPSPs
Cl- channels only open during hyperpolarization
Cl- channels reverse Na+ currents
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What change would most increase the likelihood of ectopic spike initiation along an axon?
Upregulation of Na+ channels at a demyelinated internode
Shorter nodes of Ranvier with fewer channels
Higher membrane capacitance at the initial segment
Decreased extracellular K+ around the axon
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Voltage-gated Na+ channel selectivity for Na+ over K+ is mainly due to what feature?
Extracellular Mg2+ block at rest
A large pore that fits only hydrated Na+
A narrow, negatively charged selectivity filter that stabilizes partially dehydrated Na+
Direct ATP binding opens the channel
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Study Outcomes

  1. Understand Action Potential Phases -

    Recognize and describe the sequential stages of resting potential, depolarization, repolarization, and hyperpolarization in a neuron's action potential.

  2. Analyze Ion Channel Function -

    Examine how voltage”gated sodium and potassium channels open and close to drive changes in membrane potential during nerve impulses.

  3. Apply Membrane Potential Concepts -

    Solve scenario”based questions to calculate and predict resting and equilibrium potentials using fundamental electrophysiology principles.

  4. Evaluate Neuronal Excitability -

    Assess how alterations in ion gradients, channel densities, or stimulus strength affect the threshold and firing rate of neurons.

  5. Differentiate Neuron Response Patterns -

    Compare single”unit action potential recordings under varying conditions to identify factors that influence spike amplitude and frequency.

  6. Interpret Action Potential Data -

    Read and interpret voltage”time graphs to determine key metrics such as peak voltage, duration, and refractory periods.

Cheat Sheet

  1. Resting Membrane Potential Basics -

    The resting membrane potential (~ - 70 mV) arises from differential ion distributions maintained by the Na❺/K❺-ATPase pump and leak channels. Remember the mnemonic "Pump In 2, Push Out 3" to recall that three Na❺ ions exit for every two K❺ ions entering (source: university physiology texts).

  2. Phases of an Action Potential -

    Depolarization, repolarization, and hyperpolarization mark the classic phases of neuron firing in your action potential quiz. Think "D-R-H" in order: Na❺ influx opens rapidly to depolarize, K❺ efflux repolarizes, then channels briefly overshoot before resting potential restores (as outlined in neuroscience journals).

  3. Nernst and Goldman Equations -

    The Nernst equation (E_ion = 61.5 mV log([ion]_out/[ion]_in)) predicts equilibrium potentials for individual ions, while the Goldman equation integrates multiple ions to calculate membrane potential. Practice plug-and-chug problems in your membrane potential quiz to master these formulas (recommended by physiology course materials).

  4. Ion Channel Types and Kinetics -

    Voltage-gated Na❺ channels open within microseconds to drive depolarization, whereas voltage-gated K❺ channels open more slowly to repolarize the membrane. In your ion channel quiz, focus on differences in activation/inactivation gates - labeled m, h, and n in the Hodgkin-Huxley model - to solidify kinetics understanding (per peer-reviewed research).

  5. Saltatory Conduction & Myelin -

    Myelinated axons jump depolarization events between nodes of Ranvier, dramatically increasing conduction speed and energy efficiency. When you tackle neuron action potential questions, visualize the "spark hops" and recall that thicker myelin yields faster transmission (supported by neurophysiology publications).

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