Neuroscience: Action Potentials and Ionic Mechanisms Quiz
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Questions and Answers

What initiates the action potential (AP) in a neuron?

  • Membrane hyperpolarization
  • Propagation of APs
  • Threshold depolarization (correct)
  • Neurotransmitter-induced depolarization

    • What type of stimuli will not evoke an AP in a neuron?

  • Sensory potential in response to some stimulus
  • Stimuli greater than threshold strength (correct)
  • Neurotransmitter-induced depolarization
  • Depolarizing stimuli

    • What is the regenerating portion of the action potential (AP) called?

  • Propagation of APs (correct)
  • Threshold depolarization
  • Hyperpolarization
  • Transient period after the AP

    • What does the 'all or none' phenomenon refer to in relation to the action potential (AP)?

    <p>No additional increases in AP amplitude with stimuli greater than threshold strength</p> Signup and view all the answers

    What brings the membrane potential to a special value referred to as threshold?

    <p>Depolarizing stimuli</p> Signup and view all the answers

    Which of the following does not contribute to the initiation of an action potential (AP)?

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

    What type of depolarizing stimulus will not evoke an action potential (AP)?

    <p>(an inhibitory post-synaptic potential)</p> Signup and view all the answers

    What characterizes the regenerating portion of the action potential (AP)?

    <p>#4 in 2-3</p> Signup and view all the answers

    'All or none' phenomenon refers to which aspect of the action potential (AP)?

    <p>(no additional increases in AP amplitude with stimuli greater than threshold strength)</p> Signup and view all the answers

    'Equivalent circuit' refers to the membrane as a representation of:

    <p>#3 in PPT 2-3</p> Signup and view all the answers

    'Refractory period' refers to the period after the action potential during which:

    <p>#4 in 2-3</p> Signup and view all the answers

    What type of stimuli do not produce additional increases in action potential amplitude?

    <p>Depolarizing stimuli greater than threshold strength</p> Signup and view all the answers

    What is the duration of the depolarization phase in the action potential (AP) of neurons?

    <p>Less than 1 ms</p> Signup and view all the answers

    What occurs when Na+ ions enter the cell unbalanced by K+ ions during the action potential (AP)?

    <p>Net positive charge is deposited and more Na+ channels open in a regenerative cycle</p> Signup and view all the answers

    What is the membrane potential at which inward Na+ current equals outward K+ current called?

    <p>Threshold (Vth)</p> Signup and view all the answers

    What is the effect of depolarizing stimuli on voltage-sensitive Na+ channels?

    <p>Lead to opening of voltage-sensitive Na+ channels and Na+ influx, initiating the depolarization phase</p> Signup and view all the answers

    What is the influence of sodium (ENa+) during the action potential (AP)?

    <p>The influence of sodium (ENa+) is short-lived as membrane permeability to potassium (EK+) increases</p> Signup and view all the answers

    What is the effect of Cl- ions on the action potential (AP)?

    <p>Cl- ions may have an effect on the AP since Cl- channels are open at the resting potential and during the AP</p> Signup and view all the answers

    What is the ionic basis of the threshold and accommodation, and what role do they play in excitability?

    <p>Threshold and accommodation involve the influx of Na+ ions, leading to depolarization and increased excitability.</p> Signup and view all the answers

    How do the characteristics of voltage-gated Na+ channels influence the shape of the action potential (AP)?

    <p>Voltage-gated Na+ channels contribute to the rising phase of the AP.</p> Signup and view all the answers

    What is the transient period of hyperpolarization after the action potential (AP) known as?

    <p>After-hyperpolarization</p> Signup and view all the answers

    What does the membrane potential need to reach for an action potential (AP) to be initiated?

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

    What role do passive membrane properties EMF, R, and C play in action potential (AP) production and characteristics?

    <p>They contribute to the ability of the neuron to generate APs.</p> Signup and view all the answers

    What is the effect of depolarizing stimuli that do not reach threshold strength on action potential (AP) amplitude?

    <p>They do not affect AP amplitude.</p> Signup and view all the answers

    'Equivalent circuit' refers to the membrane viewed as an:

    <p>Active conductor</p> Signup and view all the answers

    'All or none' phenomenon refers to which aspect of the action potential (AP)?

    <p>The ability of any stimulus above threshold strength to evoke an AP of consistent amplitude.</p> Signup and view all the answers

    'Refractory period' refers to the period after the action potential (AP) during which:

    <p>The neuron is unable to generate another AP, regardless of stimulus strength.</p> Signup and view all the answers

    During the action potential, what causes the depolarization phase to initiate?

    <p>Opening of voltage-sensitive Na+ channels and Na+ influx</p> Signup and view all the answers

    What is the significance of the slight hyperpolarization beyond the resting membrane potential in many neurons?

    <p>It prepares the neuron for the next action potential</p> Signup and view all the answers

    What happens when Na+ ions enter the cell unbalanced by K+ ions during the action potential?

    <p>Net positive charge is deposited, leading to more Na+ channel opening</p> Signup and view all the answers

    What characterizes the regenerating portion of the action potential?

    <p>Simultaneous activation of Na+ and K+ channels</p> Signup and view all the answers

    What is the primary cause of the decrease in Na+ current during the action potential?

    <p>Inactivation gate of Na+ channels shifting into an occluding position</p> Signup and view all the answers

    What is the membrane potential at which inward Na+ current equals outward K+ current called?

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

    'Equivalent circuit' refers to the membrane as a representation of:

    <p>An electrical circuit with EMF, resistances, and capacitance</p> Signup and view all the answers

    'All or none' phenomenon refers to which aspect of the action potential?

    <p>'All or none' response of ion channels to depolarizing stimuli</p> Signup and view all the answers

    'Refractory period' refers to the period after the action potential during which:

    <p>The neuron exhibits decreased sensitivity to depolarizing stimuli</p> Signup and view all the answers

    Study Notes

    • The repolarization phase follows the depolarization phase in the action potential (AP) of neurons.

    • The depolarization phase typically lasts less than 1 ms, while the repolarization phase lasts 1-2 ms.

    • A slight hyperpolarization beyond the resting membrane potential is common in many neurons.

    • A sudden increase in membrane permeability to Na+ and K+ ions causes the AP.

    • Depolarizing stimuli lead to opening of voltage-sensitive Na+ channels and Na+ influx, initiating the depolarization phase.

    • The influence of sodium (ENa+) is short-lived as membrane permeability to potassium (EK+) increases, allowing potassium to leave and restoring dominance of EK+.

    • The membrane potential at which inward Na+ current equals outward K+ current is called threshold (Vth).

    • When Na+ ions enter the cell unbalanced by K+ ions, net positive charge is deposited and more Na+ channels open in a regenerative cycle.

    • The decrease in Na+ current during the AP is due to the inactivation gate of Na+ channels shifting into an occluding position after the channel opens.

    • Cl- ions may have an effect on the AP since Cl- channels are open at the resting potential and during the AP, and ECl is at the resting membrane potential in many neurons.

    • The membrane can be modeled as an equivalent circuit with electromotive forces (EMF), resistances (R), and capacitance (C), illustrating passive membrane properties.

    • An action potential can be described as a transient decrease in resistance in the Na+ arm followed by a transient decrease in resistance of the K+ arm.

    • Threshold potential is not a fixed value and can be affected by factors such as changes in the magnitudes of inward Na+ and outward K+ currents.

    • Accommodation is a process where significant numbers of Na+ channels become inactivated, decreasing the neuron's sensitivity to depolarization and affecting the threshold potential.

    • The repolarization phase follows the depolarization phase in the action potential (AP) of neurons.

    • The depolarization phase typically lasts less than 1 ms, while the repolarization phase lasts 1-2 ms.

    • A slight hyperpolarization beyond the resting membrane potential is common in many neurons.

    • A sudden increase in membrane permeability to Na+ and K+ ions causes the AP.

    • Depolarizing stimuli lead to opening of voltage-sensitive Na+ channels and Na+ influx, initiating the depolarization phase.

    • The influence of sodium (ENa+) is short-lived as membrane permeability to potassium (EK+) increases, allowing potassium to leave and restoring dominance of EK+.

    • The membrane potential at which inward Na+ current equals outward K+ current is called threshold (Vth).

    • When Na+ ions enter the cell unbalanced by K+ ions, net positive charge is deposited and more Na+ channels open in a regenerative cycle.

    • The decrease in Na+ current during the AP is due to the inactivation gate of Na+ channels shifting into an occluding position after the channel opens.

    • Cl- ions may have an effect on the AP since Cl- channels are open at the resting potential and during the AP, and ECl is at the resting membrane potential in many neurons.

    • The membrane can be modeled as an equivalent circuit with electromotive forces (EMF), resistances (R), and capacitance (C), illustrating passive membrane properties.

    • An action potential can be described as a transient decrease in resistance in the Na+ arm followed by a transient decrease in resistance of the K+ arm.

    • Threshold potential is not a fixed value and can be affected by factors such as changes in the magnitudes of inward Na+ and outward K+ currents.

    • Accommodation is a process where significant numbers of Na+ channels become inactivated, decreasing the neuron's sensitivity to depolarization and affecting the threshold potential.

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    Action Potentials PDF

    Description

    Test your understanding of action potentials (AP) in medical neurosciences with this quiz. Explore the ionic mechanisms involved, the contribution of Na+ and K+ to the AP, the membrane as an 'equivalent circuit', passive membrane properties, voltage-gated channels, and the significance of threshold and accommodation.

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