Action Potential Flashcards

1
Q

What is an Action Potential?

A
  • large, rapid, reversible change in membrane potential
  • once initiated, propagates across entire excitable membrane in nerves
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2
Q

Where does an Action Potential occur?

A
  • starts at axon hillock
  • propagates along axon
  • terminates at synaptic knobs
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3
Q

What does the production of an AP require?

A
  • depolarising threshold stimulus (i.e. strong enough graded potential)
  • presence of voltage-gated Na+ and K+ channels
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4
Q

What is the relationship of the AP and depolarising stimulus?

A

Size of AP is independent of the depolarising stimulus

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5
Q

Why does the membrane become depolarized after the channels open?

A

Rapid influx of Na+ ions

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6
Q

What is the Action Potential sequence?

A
  • neuron in resting state (-70mV)
  • depolarization to threshold (-60mV)
  • activation of Na+ channels, rapid depolarization (+10mV)
  • inactivation of Na channels & activation of K channels (+30mV)
  • return to normal permeability (-90mV)
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7
Q

What is the (Absolute) Refractory Period?

A

No stimulus is capable of generating an AP (AP is unresponsive to second stimulus).
- Na+ channels are open/closed and inactivatable

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8
Q

What is the Relative Refractory Period?

A

stronger than normal stimulus (>10mV) is required to generate an AP
(AP can respond to second stimulus before it has fully recovered from first)

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9
Q

What happens in the 2 phases of the Relative Refractory Period?

A

A: not all Na+ channels are activatable
B: membrane is hypolarised (membrane potential < resting membrane potential)

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10
Q

What does an AP result in?

A
  • increased Na+
  • decreased K+
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11
Q

What does the Na+/K+ pump do to restore the RMP?

A

rapidly restores ionic balance by:
- pumps Na+ out
- pumps K+ in

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