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The Refractory Period quiz #1

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  • What are the two phases of the refractory period during an action potential, and how do they differ in terms of neuronal responsiveness to stimuli?
    The two phases are the absolute refractory period, during which no additional action potentials can be generated regardless of stimulus strength, and the relative refractory period, during which only a stronger-than-normal stimulus can evoke another action potential.
  • What is the physiological basis for the absolute refractory period, and how long does it typically last?
    The absolute refractory period is caused by the opening and subsequent inactivation of voltage-gated sodium channels, preventing any new action potentials until these channels return to their resting state. It typically lasts between 0.4 to 2 milliseconds.
  • Why does the relative refractory period require a stronger-than-normal stimulus to generate an action potential?
    During the relative refractory period, some potassium channels remain open, causing hyperpolarization of the membrane. This means a larger depolarization is needed to reach threshold, so only a stronger-than-normal stimulus can trigger another action potential.
  • How do the refractory periods contribute to the unidirectional propagation of action potentials along an axon?
    The refractory periods prevent the action potential from traveling backward by making recently activated regions temporarily unresponsive or less responsive to new stimuli, ensuring the action potential only moves forward along the axon.
  • What role do the refractory periods play in regulating the maximum rate of neuronal firing and preventing overexcitation?
    The absolute refractory period sets a minimum time between action potentials, establishing the maximum firing rate, while the relative refractory period ensures neurons do not fire too rapidly, preventing overexcitation and maintaining neuronal health.
  • What are the two phases of the refractory period during an action potential, and how do they differ in terms of neuronal responsiveness to stimuli?
    The two phases are the absolute refractory period, when no additional action potentials can be generated, and the relative refractory period, when only a stronger-than-normal stimulus can evoke another action potential.
  • What is the physiological basis for the absolute refractory period, and how long does it typically last?
    The absolute refractory period is caused by the opening and inactivation of voltage-gated sodium channels, preventing new action potentials until these channels reset. It typically lasts between 0.4 to 2 milliseconds.
  • Why does the relative refractory period require a stronger-than-normal stimulus to generate an action potential?
    During the relative refractory period, some potassium channels remain open, causing hyperpolarization of the membrane. This means a larger depolarization is needed to reach threshold, so only a stronger-than-normal stimulus can trigger another action potential.
  • How do the refractory periods contribute to the unidirectional propagation of action potentials along an axon?
    The refractory periods make recently activated regions of the membrane temporarily unresponsive or less responsive to new stimuli, preventing the action potential from traveling backward and ensuring it only moves forward along the axon.
  • What role do the refractory periods play in regulating the maximum rate of neuronal firing and preventing overexcitation?
    The absolute refractory period sets a minimum time between action potentials, establishing the maximum firing rate, while the relative refractory period ensures neurons do not fire too rapidly, preventing overexcitation and maintaining neuronal health.