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CTR 2015 > CTR - 7 - AP > Flashcards

CTR - 7 - AP Flashcards

1
Q

What is depolarisation?

A

A decrease in potential difference between the inside and outside of the cell. (inside less negative than RMP)

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2
Q

What is hyperpolarisation?

A

An increase in potential difference between the inside and outside of the cell. (inside more negative than RMP)

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3
Q

What is repolarisation?

A

Return to RMP from either direction

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4
Q

What is overshoot

A

When the inside of the cell becomes positive due to reversal of membrane potential polarity

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5
Q

What is this? A decrease in potential difference between the inside and outside of the cell.

A

Depolarisation

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6
Q

What is this? An increase in potential difference between the inside and outside of the cell.

A

Hyperpolarisation

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7
Q

What is this? Return to RMP from either direction

A

Repolarisation

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8
Q

What is this? When the inside of the cell becomes positive due to reversal of membrane potential polarity

A

Overshoot

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9
Q

What cells are excitable cells?

A

Muscle and nerve cells

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10
Q

What are excitable cells?

A

Allow an action potential to propagate along it

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11
Q

What are the two ways a change in membrane potential can be achieved?

A

1 - altered membrane ion permeability

2 - anything that alters ion concentrations on either side

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12
Q

What are the two types of potentials?

A

Graded potentials (sub threshold potentials)

Action potentials

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13
Q

How is a GP/AP generated (in broad terms)?

A

Increase in Na+ permeability –> sodium moves into cell –> if this reaches the threshold potential –> depolarise the cell

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14
Q

A _________ stimuli causes _________ potentials.

A

subthreshold stimuli –> sub threshold/graded potentials

suprathreshold stimuli –> APs

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15
Q

What is the threshold which must be reached?

A

-50 mV

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16
Q

The strength of a GP is proportional to the ________.

A

strength of the stimulus

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17
Q

The_________ is proportional to the stimulus strength.

A

GP strength

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18
Q

What happens to GP strength? Why?

A

Loses strength moving through the cell

Due to leakage of charge across membrane

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19
Q

What happens to GP strength in dendrites?

A

As there are NO voltage gated channels –> current leaks –> decreases GP strength

20
Q

Do dendrites have voltage gated channels? Consequence of this?

A

NO! Current leaks –> decreases GP strength

21
Q

The GP must _____________ at the trigger zone!

A

be above threshold (-50 mV)

22
Q

What is another name for the trigger zone?

A

Axon hillock

23
Q

What does a suprathreshold GP do at the trigger zone?

A

Triggers an AP

24
Q

What does a subthreshold GP do at the trigger zone?

A

Does not trigger an AP

25
Q

Do subthrehsold stimuli result in APs?

A

No (subhreshold stimulus –> sub threshold GP –> no AP)

26
Q

Do suprathrehsold stimuli result in APs?

A

Yes (supra threshold stimulus –> suprathreshold GP –> AP)

27
Q

What happens to the strength of a supra threshold GP in the ______?

A

Dendrite.

It decreases, but not enough to fall below threshold (-50mV) –> AP!

28
Q

What happens to the strength of a subthreshold GP in the ______?

A

Dendrite.

It decreases, below threshold (-50mV) –> no AP!

29
Q

The movement of K+ out of a cell results in

A

hyperpolarisation

30
Q

The movement of Na+ into a cell results in

A

depolarisation

31
Q

Chemically-Gated channels are also known as ______.

A

receptor-mediated

32
Q

Voltage-gated channels are also known as _________.

A

Electrically stimulated

33
Q

Duration of AP

A

4 milliseconds

34
Q

What are the three states of the sodium channel? What happens to the gates?

A

Resting - activation gate closed
Activated - activation gate open
Inactivated - inactivation gate closed

35
Q

What is the function of the absolute refractory period? Why does it exist?

A

Gates on Na+ channel have not reset

Assures one way propagation - so that the AP reaches the effector organ

36
Q

Refractory periods limit ____________.

A

the rate of propagation

37
Q

How do APs code behaviour

A

frequency

38
Q

How does increased stimulus frequency affect APs?

A

Increased frequency (not size!)

39
Q

What is the structural difference between the axon and dendrite

A

Axon has voltage gated sodium channels

Dendrite does not

40
Q

What factors affect the rate of propagation?

A

Diameter of axon

  • smaller diameter (greater resistance –> slower speed)
  • larger diameter (less resistance –> higher speed)

Degree of myelination
- presence of myelin sheath (acts as an insulator –> prevents charge from leaking from axon)

41
Q

What is the difference between continuous conduction and saltatory conduction. How much faster is one of these?

A

Continous = non-myelinated axons

  • channels are immediately adjacent
  • to ensure voltage does not decay - must regenerated AP at every voltage gated ion channels - SLOW

Saltatory conduction = myelinated axons (acts as insulator)
-channels separated by myelin sheaths (channels in nodes of ranvier)
-APs only generated in nodes of ranvier (decreased number of regeneration points)
FAST

42
Q

What are the two types of conduction?

A

Saltatory (fast) and continuous (slow)

43
Q

What is multiple sclerosis caused by? What cells does it affect?

A

Demyelination of nerves in CNS (not PNS) due to auto-immune disease

Affects oligodendrocytes

44
Q

What are some symptoms of MS?

A

muscle, weakness, fatigue, difficulty walking, loss of vision

45
Q

How is MS treated?

A

Anti-inflammatory drugs (prevent immune cells destroying myelin)

46
Q

How do local anaesthetics works?

A

Blocking voltage gated Na+ channels (no Na+ entry) –> no AP.

CTR 2015 (6 decks)

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