The Action Potential Flashcards

1
Q

What is the function of voltage-gated ion channels?

A

They facilitate the selective permeability of certain ions across the cell membrane.

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2
Q

Define selectivity filter.

A

A region in ion channels that allows specific ions to pass while excluding others.

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3
Q

What are permeant ions?

A

Ions that can pass through the selective filter of ion channels.

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4
Q

What are impermeant ions?

A

Ions that cannot pass through the selective filter of ion channels.

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5
Q

What does selective permeability refer to?

A

The ability of a membrane to allow certain ions to pass while blocking others.

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6
Q

List the main cations involved in action potentials.

A
  • K+
  • Na+
  • Ca2+
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7
Q

What is the primary anion involved in action potentials?

A

Cl-

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8
Q

What is the knock-on mechanism in ion channels?

A

A process that involves the movement of ions due to charge interactions.

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9
Q

True or False: Sodium channels open slowly and inactivate rapidly.

A

False

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10
Q

How quickly do sodium channels inactivate after opening?

A

After approximately 1 ms.

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11
Q

How do potassium channels behave compared to sodium channels?

A

Potassium channels open more slowly and can also inactivate.

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12
Q

What is an action potential?

A

A transient reversal of the membrane potential.

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13
Q

What is the duration range of action potentials?

A

From a few milliseconds (nerve, skeletal muscle) to a few hundred milliseconds (heart).

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14
Q

What is the threshold potential for action potential generation?

A

~ -55 mV.

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15
Q

What happens to action potentials with larger stimuli?

A

The size of the action potential remains fixed regardless of stimulus size.

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16
Q

How does the body code stimulus intensity?

A

By changes in frequency of action potentials, not size.

17
Q

Fill in the blank: The probability of _______ is greater than the probability of closing during depolarization.

18
Q

What are the phases of an action potential?

A
  • Resting potential
  • Rising phase
  • Peak
  • Falling phase
  • Undershoot (after hyperpolarization)
19
Q

Define absolute refractory period.

A

A period during which another action potential cannot be produced.

20
Q

What characterizes the relative refractory period?

A

The cell is less excitable and requires a larger stimulus to produce an action potential.

21
Q

What causes the refractory period?

A

Inactivation of Na current and activation of K current.

22
Q

What is the concentration of Na+ outside the cell before an action potential?

23
Q

What is the concentration of K+ inside the cell before an action potential?

24
Q

What is the concentration of Cl- outside the cell before an action potential?

25
Q

What happens to the permeability of Na+ and K+ during an action potential?

A
  • Na+ channels open
  • More Na+ channels open
  • Na+ channels close (inactivate)
  • K+ channels open
  • K+ channels close
26
Q

What is the peak action potential?

A

The maximum membrane potential reached during an action potential.

27
Q

What is the role of feedback loops in action potentials?

A

They help in self-terminating the depolarization process.