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  • Action potential generation

  • the plasma membrane of a neuron

  • separates the extracellular space from the intracellular space

  • sodium ions are found in high concentration

  • outside of the cell whereas potassium ions are found in high concentration

  • inside of the cell. Voltage-gated

  • sodium channels, sodium potassium ATP-ase pumps

  • and voltage-gated potassium channels

  • are found embedded in the plasma membrane of the neuron.

  • To initiate an action potential

  • a stimulus causes the wave a positive charge to reach

  • voltage-gated sodium channels on the neuron membrane. The increase in positive

  • charge

  • causes the voltage-gated sodium channels to open. Positively charged sodium ions

  • flood into the neuron following their concentration gradient

  • this causes the inside a membrane near to the open sodium channel to become

  • more positively charged

  • this process is the deep polarization of the cell membrane

  • The build up a positive charge on the inside of the membrane eventually causes

  • the voltage-gated

  • sodium channels to close. At the same time

  • voltage-gated potassium channels open since open only when the inside

  • remember is that maximum positive charge. Positively charged

  • potassium ions flow rapidly out of the neuron following their concentration

  • gradient this decreases the level of positive charge

  • on the inside surface of the neuron. This return of the membrane to resting

  • levels of negative

  • charge is called repolarization. Once

  • the region and the membrane has been fully repolarized, potassium

  • channels close

  • a sodium/potassium pump

  • uses ATP energy to restore the concentration gradient

  • and put potassium and sodium to the resting values

  • Let's summarize the processes of generating an action potential

  • resting potential is the membrane

  • potential of a neuron when it is at rest. The resting potential is well below

  • zero

  • to initiate an action potential the stimulus causes a slight depolarization

  • or increase in positive charge. If the stimulus is strong enough to cause the

  • membrane potential to reach a certain threshold

  • action potential will begin. In the rising phase of an action potential

  • wilted kid sodium channels open and sodium ions flow into the cell

  • this causes voltage to increase inside the cell

  • During the following phase of the action potential

  • voltage-gated sodium channels close, voltage-gate potassium channels open

  • the opening of the potassium channels causes potassium ions to diffuse out of the cell

  • rapidly

  • causing a sharp decrease in voltage. During the recovery phase

  • sodium potassium ATP-ase pump restores the resting potential

  • sodium potassium ATP-ase pumps

  • pump 2 sodium ions in and 3 potassium ions out

  • of the neuron. Sodium potassium ATP-ase pumps require ATP to function

Action potential generation

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B2 中上級

アクション ポテンシャルジェネレーション (Action Potential Generation)

  • 96 9
    Cheng-Hong Liu に公開 2021 年 01 月 14 日
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