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Quizzes > Science > Biology

Master the Nervous System: Take the Action Potential Quiz

Ready for neuron action potential questions? Ace this membrane potential quiz!

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

Calling all budding neuroscientists and biology buffs! Dive into our free action potential quiz to discover how neurons relay the messages that make us think, move, and feel. You'll tackle neuron action potential questions that probe your understanding of threshold dynamics, gauge your skills in a membrane potential quiz, and navigate tricky ion channel quiz scenarios. Ready for more context? Brush up with our quiz about the nervous system before testing your broader knowledge in the anatomy and physiology quiz . Challenge yourself, track your progress, and ace this nervous system quiz - start now!

What is the typical resting membrane potential of a neuron?
-70 mV
+30 mV
-55 mV
0 mV
Most neurons maintain a resting membrane potential around - 65 to - 75 mV due to selective permeability to K+ and the action of the Na+/K+ pump. This negative potential is essential for readiness to fire an action potential. Deviations from this range typically indicate altered ion channel function or pathological conditions. Khan Academy source
Which ion is primarily responsible for the depolarization phase of the action potential?
Ca²?
Na?
K?
Cl?
Depolarization is driven by the rapid opening of voltage-gated sodium channels, allowing Na? influx down its electrochemical gradient. This influx shifts the membrane potential toward Na?'s equilibrium potential. Without Na? entry, the rising phase of the action potential would not occur. NCBI source
During repolarization, which ion channel opens to return the membrane potential toward resting levels?
Voltage-gated Na? channels
Voltage-gated K? channels
Voltage-gated Ca²? channels
Chloride channels
Repolarization follows the peak of the action potential when voltage-gated K? channels open, allowing K? efflux. This outward current brings the membrane potential back down toward the K? equilibrium potential. Inactivation of Na? channels also contributes by stopping further inward current. Khan Academy source
What term describes the electrical state when the membrane potential becomes more positive than resting?
Repolarization
Hyperpolarization
Depolarization
Polarization
Depolarization refers to any shift in membrane potential toward a less negative (more positive) value relative to rest. This can lead to threshold crossing and the initiation of an action potential. Hyperpolarization is the opposite, making the inside more negative. NCBI source
The threshold potential for most neurons is approximately:
+30 mV
-55 mV
-90 mV
-30 mV
Threshold is typically around - 55 mV, the critical level to open enough voltage-gated Na? channels for regenerative depolarization. If this level isn't reached, the neuron will not fire an action potential. Slight variations occur between cell types. Khan Academy source
Which phase of the action potential corresponds to the absolute refractory period?
When Na? channels are inactivated
When K? channels remain closed
During hyperpolarization
During the resting potential
The absolute refractory period occurs while voltage-gated Na? channels are inactivated and no new action potential can be initiated, regardless of stimulus strength. This ensures one-way propagation. It spans from threshold until Na? channel reset. NCBI source
Saltatory conduction occurs in neurons that have which feature?
Myelinated axons
Dendrites
Nodes lacking Na? channels
Unmyelinated axons
Saltatory conduction describes action potentials jumping between nodes of Ranvier in myelinated axons, greatly increasing conduction velocity. Myelin insulates segments, forcing ionic exchange only at nodes. Unmyelinated fibers conduct continuously. Khan Academy source
The Goldman equation differs from the Nernst equation because it:
Calculates equilibrium potential for a single ion
Ignores membrane permeability
Is temperature-independent
Accounts for multiple ions and their permeability
The Goldman - Hodgkin - Katz equation calculates membrane potential by considering relative permeabilities and concentrations of multiple ions (Na?, K?, Cl?). In contrast, the Nernst equation applies to a single ion species. Temperature, charge, and concentration all factor into both formulas. Wikipedia source
During the relative refractory period, which statement is true?
Action potential amplitude is increased
No stimulus can generate an action potential
A stronger-than-normal stimulus can elicit another action potential
Na? channels are fully closed
The relative refractory period follows the absolute phase when some Na? channels have reset and K? channels remain open. A suprathreshold stimulus can produce a second action potential but with reduced amplitude. This period ensures controlled firing rates. NCBI source
In a voltage - clamp experiment, what is directly measured while holding the membrane potential constant?
Ionic currents across the membrane
Membrane capacitance only
Changes in membrane potential
Intracellular ion concentrations
Voltage clamp holds the membrane potential at a set level and records the current required to maintain that potential. This method isolates ionic currents through specific channels at defined voltages. It was fundamental to the Hodgkin - Huxley model. Wikipedia source
Which factor most directly influences conduction velocity in myelinated fibers?
Neurotransmitter type
Axon diameter
Synaptic input
Internode density
Conduction velocity in myelinated axons increases with axon diameter due to reduced internal resistance. Larger axons conduct signals faster. Internode length and myelin thickness also matter but are secondary. NCBI source
After-hyperpolarization (the undershoot) is primarily mediated by which channels?
Voltage-gated K? channels
Voltage-gated Na? channels
Ligand-gated Cl? channels
Voltage-gated Ca²? channels
After the action potential peak, prolonged opening of certain K? channels (e.g., delayed rectifier and 'M' channels) causes membrane to hyperpolarize below resting level. This undershoot aids in regulating firing frequency. Na? channels are inactivated during this phase. NCBI source
Which sodium channel mutation is most likely to cause neuronal hyperexcitability?
Mutation delaying channel inactivation
Mutation increasing inactivation rate
Mutation blocking activation gate
Mutation reducing peak conductance
Delays in sodium channel inactivation prolong Na? influx, lowering threshold and causing hyperexcitability (as in certain epilepsies). Reduced conductance or faster inactivation would have opposite effects. NCBI source
The safety factor for impulse conduction refers to:
Ratio of available current to threshold current
Duration of the refractory period
Peak amplitude of the action potential
Speed of propagation
The safety factor quantifies how much current exceeds the minimum needed to depolarize the next segment above threshold. A high safety factor ensures reliable conduction under varying conditions. It's altered in demyelinating diseases. NCBI source
Temperature increases conduction velocity primarily by:
Thickening myelin
Increasing axon diameter
Speeding kinetics of channel gating
Altering ion gradients
Higher temperatures accelerate the opening and closing rates of voltage-gated channels, thereby speeding action potential propagation. Structural features like diameter or myelin don't change with acute temperature shifts. NCBI source
The equilibrium potential for an ion depends on which factors?
Channel density
Absolute concentration values only
Membrane thickness
Ratio of extracellular to intracellular concentration and valence
According to the Nernst equation, an ion's equilibrium potential is determined by its concentration gradient and electrical charge (valence) across the membrane. Membrane thickness and channel density do not directly affect the equilibrium potential. Wikipedia source
Optimal internode length in myelinated axons is primarily determined by which relationship?
Axon diameter divided by myelin thickness
Product of conduction velocity and refractory period
Ratio of nodal ion channel density to internode number
Distance where passive current spread is just enough to reach threshold at the next node
Internode length is optimized so that the decremental spread of depolarization between nodes still reaches threshold; too long, and the signal decays below threshold. This maximizes conduction speed while ensuring reliability. NCBI source
The Hodgkin - Huxley model represents ionic currents as:
Constant current sources
Pure capacitors in parallel
Variable conductances dependent on gating variables and driving force
Fixed resistors in series
The Hodgkin - Huxley model uses time- and voltage-dependent conductances (gNa, gK) and the difference between membrane potential and equilibrium potential to describe ionic currents. This formalism accurately predicts action potential waveforms. Wikipedia source
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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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