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Flashcards in 2 - Membrane Potential Deck (46):
1

Is the intracellular or extracellular concentration higher for K+?

Intracellular

2

Is the intracellular or extracellular concentration higher for Na+?

Extracellular

3

Is the intracellular or extracellular concentration higher for Cl-?

Extracellular

4

Is the intracellular or extracellular concentration higher for Ca++

Extracellular (or intracellular if it is sequestered in the SER)

5

What does the strength of the chemical concentration gradient depend on?

The chemical that is diffusing and the membrane it is diffusing through

6

If an ion was responding to just a chemical force, how would it respond?

It would move down its concentration gradient

7

If an ion was responding to just the electrical potential, how would it move?

It would move its electrical gradient

8

What is the net effect of the electrical and chemical forces?

You can have equilibrium, slight diffusion or rapid diffusion

9

What happens to EK+ when the extracellular concentration of K+ is raised?

Remember that the intracellular concentration of K+ is typically higher than the extra cellular concentration

When the extracellular concentration of K+ is raised, the EK+ value is decreased

10

What happens to EK+ when the extracellular concentration of K+ is lowered?

Remember that the intracellular concentration of K+ is typically higher than the extra cellular concentration

When the extracellular concentration of K+ is lowered (lower than it already is), the EK+ value is increased

11

What happens to ENa+ when the extracellular concentration of Na+ is raised?

Remember that the extracellular concentration of Na+ is typically higher than the intracellular concentration

When the extracellular concentration of Na+ is raised, the ENa+ is increased

12

What happens to ENa+ when the extracellular concentration of Na+ is lowered?

Remember that the extracellular concentration of Na+ is typically higher than the intracellular concentration

When the extracellular concentration of Na+ is lowered, the ENa+ is decreased

13

What happens to the membrane potential if the extracellular K+ is raised?

The membrane potential is decreased

The cell is depolarized

14

What happens to the membrane potential if the extracellular K+ is lowered (more than it already is)?

The membrane potential is increased

The cell is hyperpolarized

15

What happens to the membrane potential if the extracellular Na+ is raised (more than it already is)?

The membrane potential is decreased (small effect)

The cell is depolarized (slightly)

16

What happens to the membrane potential if the extracellular Na+ is lowered?

The membrane potential is increased (small effect)

The cell is hyperpolarized

17

How does the membrane potential change when it becomes more permeable to K+?

Remember that as the relative permeability of the membrane to an ion increases, the membrane potential of the cell moves closer to the equilibrium potential of that ion

Depolarization of the cell

18

How does the membrane potential change when it becomes more permeable to Na+

Hyperpolarizes the cell

19

How does the membrane potential change when it becomes more permeable to Cl-?

Hyperpolarizes the cell

20

As the EK+ value decreases, the membrane potential __________.

Also decreases

21

As the ENa+ value decreases, the membrane potential __________.

Also decreases

22

The actual membrane potential is balanced between two values, what are they?

EK+ and ENa+

23

In the resting state, the cell is much more permeable to ____ than it is to _____.

More permeable to K+
Less permeable to Na+

24

What does this mean about the actual membrane potential?

It is closer to EK+ than it is to ENa+

25

During an action potential, the membrane becomes more permeable to ____.

Na+

26

The increased permeability to Na+ makes the actual membrane potential move closer to _____.

ENa+

27

So, in general, how is the membrane potential affected by its permeability?

If the membrane becomes more permeable to either sodium or potassium, the membrane potential of the cell becomes closer to the equilibrium potential for that particular ion

28

The well known sodium-potassium pump is "electrogenic" - what does that mean?

It changes the electric potential of the membrane

29

How does the Na+-K+ pump change the electric potential of the membrane?

It pumps 3 Na+ OUT of the cell for every 2 K+ is pumps INTO the cell

30

What is the net effect of the Na+-K+ proton pump on the membrane potential?

Over time, the membrane potential will become more negative or more hyperpolarized because more Na+ is going out than the K+ coming in (there is a net eflux of positive ions)

31

What is the MAIN role of the sodium-potassium pump?

***Important***

The role of the sodium-potassium pump is to maintain the membrane potential in an INDIRECT way - it is able to do this simply by maintaining the Na+ and K+ concentration gradients

32

What does it mean when a cell is at its resting membrane potential?

The cell is NOT at equilibrium but at a STEADY state

33

Describe the "steady state" of a resting membrane potential

The cell is "leaky"
- K+ is leaking out
- Na+ is leaking in

34

What balances the "leakiness" of the cell in order for it to maintain its resting membrane potential?

This "leakage" is EXACTLY balanced by the actions of the sodium-potassium pump that is pumping Na+ out and K+ in

35

This process of maintaining the membrane potential requires _________________.

Metabolic energy

36

What else does the sodium-potassium pump maintain?

Cell volume

37

How does the sodium-potassium pump also maintain cell volume?

By pumping sodium out of the cell, it decreases the osmotic pressure in the cytoplasm, which increases the osmotic pressure in the extracellular fluid

38

What is hyperkalemia?

High potassium

39

What is hypokalemia?

Low potassium

40

What is hypernatremia?

High sodium

41

What is hyponatremia?

Low sodium

42

What is hypercalcemia?

High calcium

43

What is hypocalcemia?

Low calcium

44

What does membrane polarization mean?

At rest, a cell has negative charges on the inside of the membrane and positive charges on the outside of the membrane

This makes the cell membrane POLARIZED

45

What does membrane depolarization mean?

Depolarization is when the membrane becomes less negative inside the cell (or more positive)

Example: the membrane potential would change from -80 mV to -50 mV due to an influx of positive ions into the cell

46

What does membrane hyperpolarization mean?

Hyperpolarization is when the membrane becomes more negative inside the cell

Example: the membrane potential changes from -80 mV to -90 mV