2025-02-19T02:15:19+03:00[Europe/Moscow] en true <p>What is an Action potential?</p>, <p>Where is the trigger zone that APs initiate?</p>, <p>What are the events that take place for/in an action potential?</p>, <p>What happens in the depolarization phase of an AP?</p>, <p>What happens in the repolarization phase of AP?</p>, <p>What increases and decreases permeability of an ion in a cell?</p>, <p>What happens during the after-hyperpolarization phase in AP?</p>, <p>When does the MP return to RMP after AP?</p>, <p>How many APs does it take to cause measurable change in charge in the cell?</p>, <p>What is the all-or-none principle of APs?</p>, <p>What are the refractory periods of an AP?</p>, <p>When is the absolute refractory period?</p>, <p>When is the relative refractory period?</p> flashcards

3. Nervous System I (pt. 2)

Action potentials,

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  • What is an Action potential?

    - large change in membrane potential that propagates along an axon with no change in intensity and initiates at trigger zone

  • Where is the trigger zone that APs initiate?

    - axon hillock of multipolar and bipolar neurons

    - just past dendrites of unipolar neurons

  • What are the events that take place for/in an action potential?

    - GP reaches threshold

    - Action potential phases (depolarization, repolarization, after-hyperpolarization)

    - repolarization

  • What happens in the depolarization phase of an AP?

    - voltage-gated Na+ channels respond to MP change (GP) and open, increasing Na+ permeability

    - increased Na+(pos MP change) in cell stimulates more Na+ channels to open (positive feedback mechanism) until +30mV

  • A. GP to threshold

    B. depolarization

    C. Repolarization

    D. After-hyperpolarization

    E. return to rest

  • What happens in the repolarization phase of AP?

    - Na+ channels close/inactivate, Na+ movement returns to resting levels

    - voltage-gated K+ channels open so K+ diffuses out  (positive charges (K+) move out – decreases MP)

  • What increases and decreases permeability of an ion in a cell?

    - channels of that ion type opening (increasing permeability) or closing (decreasing)

  • What happens during the after-hyperpolarization phase in AP?

    - K+ channels are slow to close and remain open longer than necessary

    - Na+ channels are reactivated – can respond to stimuli at this point

  • When does the MP return to RMP after AP?

    When K+ channels close

  • How many APs does it take to cause measurable change in charge in the cell?

    10 000 *

  • What is the all-or-none principle of APs?

    - if threshold is reached, AP is produced (one level of intensity, same every time)

    - if not reached, then no action potential

    - means no change in size really, AP or no AP

  • What are the refractory periods of an AP?

    - absolute refractory periods (prevents AP summation) and relative refractory period (can only be generated by greater than normal stimulus)

  • When is the absolute refractory period?

    - when all Na+ channels are open (i.e. depolarization)

    - all Na+ channels being inactivated (i.e. repolarization), cant open until MP reaches RMP

  • When is the relative refractory period?

    - after-hyperpolarization phase

    - larger stimulus needed because it is further reach threshold

    - Na+ channels are closed but can be reopened if threshold is reached

    - K+ channels are open and membrane hyperpolarized