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A&P Test 1 > 9/04 Class 5 > Flashcards

9/04 Class 5 Flashcards

1
Q

Where is one place that we have a lot of Chloride permeability?

A

In neurons

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2
Q

The membrane potential permeable to multiple ions will reflect which ion?

A

The ion with the most permeability

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3
Q

If the Nernst potential for K+ is -91, and a cell is ONLY permeable to K+, then what is the lowest limit for cell membrane potential?

A

-91

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4
Q

If the Nernst Potential for K+ is -91, the Nernst potential for Na+ is 61, and the cell is permeable to both ions, what will the membrane potential be of the cell?

A

Somewhere between -91 and +61, depending on how permeable each of those ions are

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5
Q

When an action potential happens, the cell becomes more positive than 0. What is the mechanism behind this?

A

The cell becomes more permeable to sodium than it does to potassium

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6
Q

What are the channels called that are open all the time to it’s specific ion?

A

leak channels

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7
Q

If you have bad hyperkalemia, and your potassium is 8 in the ECF (ICF is still 120), what would potassium want to do? What does that do to the overall cell membrane potential?

A

It will want to move out at a slower rate than it would in it’s normal concentrations of 4/120
It shifts it more positively because less potassium is leaving the cell, making the cell more positive.

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8
Q

Why is it important for cells to get back to their resting state?

A

So that they are reset and ready to be fired again.

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9
Q

What does Vrm mean?

A

resting membrane potential

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10
Q

Why does a patient with a K+ of 12 have VFib?

A

Because K+’s concentration gradient has increased trifold, making K+ less likely to leave the cell, which makes the cell more positive. Since the cell is so positive, it can never get back to the resting state, making it overreact.

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11
Q

What is depolarization?

A

To become less polar (or more + charged) usually means stimulated or turned on

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12
Q

Define cell polarization

A

A difference in electrical charge between inside and outside of the cell. (negative inside, positive outside)

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13
Q

Define hyperpolarized?

A

To become more polar (or more - charged) usually means inhibited (or more - charged and more difficult to excite)

circled part of image

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14
Q

Define repolarize

A

to return to Vrm from a depolarized state.

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15
Q

What is another way to describe a “polarized cell”?

A

a normal cell polarity

So resting cells are said to be polarized. And by convention, because they’re usually negatively charged, we just say that that’s normal cell polarity at rest.

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16
Q

If a cell becomes more positively charged, we say that it is

A

depolarized

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17
Q

What does a plateau period on an action potential graph drawing of a heart cell tell us?

A

The plateau usually defines how well the heart muscles are going to pump (squeeze). A longer plateau=a stronger pump.

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18
Q

Do all action potential graphs look the same?

A

No, they look different for different areas in the body. Action potentials are usually specialized for specific organs.

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19
Q

What does conductance mean?

A

It’s the relative ease in which an ion can get across the cell wall.

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20
Q

How long are sodium channels open in an action potential?

A

a very short amount of time

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21
Q

What is repolarization dependent on?

A

specialized potassium channels that open up after the cell has been depolarized

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22
Q

What are the special potassium channels called in an action potential?

A

Voltage Gated K+ channels

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23
Q

What speeds up action potential repolarization?

A

V-G K+ channels

24
Q

What generates an action potential?

A

Sodium entering the cell

25
Q

Where in the body is it really important that the action potential goes back to rest very quickly?

A

In neurons

26
Q

What causes a voltage gated sodium channel to open?

A

some initial change in voltage

27
Q

Describe what’s happening in this photo

A

At -80mV, the cell is at rest. When it starts repolarizing, voltage gated Na+ and K+ channels are being opened and allowing Na+ to flood into the cell. When it reaches the peak is when Na+ channels close. Now VG K+ channels are all the way open, allowing Potassium back out of the cell. VG K+ channels close slower than Na+ and overshoot a little bit, leaving the cell closer to -90mV, but they then close and the cell is back at -80mV or resting potential.

28
Q

What does the driving force for an ion depend on?

A
  • the charge
  • the concentration gradient
  • the charge of the inside of the cell.
28
Q

What is another name for voltage gated Na+ channels?

A

“fast” Na+ channels

29
Q

At what point would the membrane potential be positive or negative enough that an ion will no longer attempt to cross into the cell?

A

When the membrane potential is equal to the ion’s Nernst or equilibrium potential

30
Q

What would happen if the membrane potential has a much more positive, or much more negative charge the same charged ions?

A

That ion would not only refuse to come into the cell, but the ions that are already in the cell will start to leave

31
Q

How many more potassium channels are there than sodium channels?

A

10:1

32
Q

Which way does K+ want to go in a normal resting cell? in or out

A

wants to go outside of the cell

33
Q

which way does Na+ want to go in a normal resting cell? in or out?

A

wants to go inside the cell

34
Q

What effect does a resting cell at -80mV have on the movement of K+?

A

K+ loss out of the cell is blunted. -80mV works to hold the positive charge of K+ inside the cell.

35
Q

If potassium loss is blunted because it is positive and the -80mV holds onto it, what is limiting massive amounts of sodium from entering the cell?

A

There aren’t that many sodium channels. Only 1 for every 10 K+ channels

36
Q

What is driving the membrane potential to such a low number?

A

The cell doesn’t always have to have movement across it, it just has to have the potential to have current

37
Q
  1. Ion X- has an equilibrium potential of -50. What is the electrolyte concentration set up for this ion?
  2. What would happen if the cells membrane was -80mV?
A
  1. Ion X- has a higher concentration outside of the cell, making it want to go inside of the cell.
  2. This would not only prevent X- from entering the cell, but the interior of the cell would be so negative that it would repel X- and move it back out of the cell.
38
Q

What drugs affect “Fast” sodium channels?

A

Any drug that ends in -Cain

39
Q

Voltage gated sodium channels are part of the process of taking a localized depolarization and turning into _________

A

a full fledged action potential.

40
Q

What type of ions can move through a voltage gated Na+ channel?

A

ONLY sodium. There is a selectivity filter in there that only allows Na+ through.

41
Q

How many gates does a Fast Na+ channel have?

A

2

42
Q

What is the gate on the inside of the cell called on a fast Na+ channel?

A

H gate or inactivation gate

43
Q

What is the gate on the outside of the cell called on a fast Na+ channel?

A

M gate or activation gate

44
Q

In the resting state of a fast Na+ channel, how are the gates positioned?

A

M gate is closed and H gate is open.

45
Q

In the activated state of a fast Na+ channel, how are the gates positioned?

A

M (activation) gate is open and H(inactivation) gate is open.

46
Q

What is the cycle of a Fast Na+ gates?

A
  1. M (activation) gate is closed and H (inactivation) gate is open. This is called closed, or resting
  2. Stimulus comes through and tells the M (activation) gate to open. Both are open now and this is called activated.
  3. The H(inactivation) gate swings shut a milisecond after the M(activation) gate is open. This is called inactivated
  4. The M(activation) gate closes and the H (inactivation) gate opens back up. This process is called repolarization. The cell is now back at rest and ready to be fired again. Dr. Schmidt says this process can also be labeled inactivated
47
Q

How do -cain drugs effect the fast Na+ channels?

A

They interefere with the repolarization stage.

48
Q

Where are the gates on a voltage gated potassium channel found?

A

On the inside of the cell

49
Q

How many gates are on a voltage gated potassium channel?

A

1

50
Q

Which is faster, a voltage gated sodium channel or a voltage gated potassium channel?

A

voltage gated sodium channel

51
Q

Why do you want the voltage gated potassium channel to be delayed in opening?

A

because if it opened to pump K+ out of the cell at the same time that the Na+ opened to pump Na+ in the cell, they would cancel each other out and you wouldn’t achieve as fast of an action potential.

52
Q

What does the slow closing of the voltage gated potassium channel cause?

A

Momentary Hyperpolarization

53
Q

Fill in this graph

A
54
Q

At what charge is a voltage gated sodium or potassium channel resting?

A

-90mV or -80 for this class

55
Q

At what charge is a voltage gated sodium or potassium channel activated?

A

-79mV to +35mV

56
Q

At what charge is a voltage gated sodium channel deactivated?

A

+35mV to -80mV

A&P Test 1 (5 decks)

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