Exam #1: Membrane Potential Flashcards Preview

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Flashcards in Exam #1: Membrane Potential Deck (34):
1

Is the intracellular concentration or extracellular concentration higher for K+?

Intracellular

2

Is the intracellular concentration or extracellular concentration higher for Na+?

Extracellular

3

Is the intracellular concentration or extracellular concentration higher for Cl-?

Extracellular

4

Is the intracellular concentration or extracellular concentration higher for Ca++?

Extracellular

5

Will the chemical driving force for K+ tend to push the ion into the cell or out of the cell?

Out

*Note that chemical force on an ion is only due to the chemical concentration gradient; charge nor membrane potential affect the direction of the chemical force.

6

Will the chemical driving force for Na+ tend to push the ion into the cell or out of the cell?

In

*Note that chemical force on an ion is only due to the chemical concentration gradient; charge nor membrane potential affect the direction of the chemical force.

7

Will the chemical driving force for Cl- tend to push the ion into the cell or out of the cell?

In

*Note that chemical force on an ion is only due to the chemical concentration gradient; charge nor membrane potential affect the direction of the chemical force.

8

Will the chemical driving force for Ca++ tend to push the ion into the cell or out of the cell?

In

*Note that chemical force on an ion is only due to the chemical concentration gradient; charge nor membrane potential affect the direction of the chemical force.

9

How does Ek+ change if the extracellular concentration of K+ is raised? What if it is lowered?

Remember that Ek+, or the electrochemical equilibrium, is the voltage where the chemical & electrical driving forces balance each other with no net movement of ions.
- Normal= -95mV
- Increase ECF K+ & Ek+ will be less negative
- Decrease ECF K+ & Ek+ will be more negative

10

How does ENa+ change if the extracellular concentration of Na+ is raised? What if it is lowered?

Remember that ENa+, or the electrochemical equilibrium, is the voltage where the chemical & electrical driving forces balance each other with no net movement of ions.
- Normal= +70mV
- Increase ECF Na= ENa+ will be more positive
- Decrease ECF Na= ENa+ will be less positive

11

How does the membrane potential change if the extracellular concentration of K+ is raised? What if it is lowered?

- Resting membrane potential is primarily determined by K+. - Thus, raising the ECF concentration of K+ will make the resting membrane potential less negative.
- Decreasing ECF concentration of K+ will make resting membrane potential more negative.

12

How does the membrane potential change if the extracellular concentration of Na+ is raised? What if it is lowered?

- Elevated ECF Na+ would make the resting membrane potential more positive, but remember that Na+ contributes less than K+
- Diminished ECF Na+ would make the resting membrane potential less positive

13

How does membrane potential change if the membrane permeability is changed?

The greater an ion's permeability, the greater the "presence" it holds in determining Vm; i.e. more permeability= Vm close to the Ex of that ion.

14

What is the role of the Na+-K+ Pump in maintaining cell membrane potential?

- The Na+/K+ Pump is electrogenic
- 3x Na+ Out
- 2x K+ In
- Thus, the sodium-potassium pump maintains the membrane potential & cell volume

15

Hyperkalemia

Higher than normal ECF concentration of K+

16

Hypokalemia

Lower than normal ECF concentration of K+

17

Hypernatermia

Higher than normal ECF concentration of Na+

18

Hyponatremia

Lower than normal ECF concentration of Na+

19

Hypercalcemia

Higher than normal ECF concentration of Ca++

20

Hypocalcemia

Lower than normal ECF concentration of Ca++

21

What is depolarization?

Membrane becomes more negative outside

22

What is hyperpolarization?

Membrane becomes more negative inside

23

What is membrane potential due to?

Separation of electrical charges across the membrane

24

How did the charges get separated?

1) Active transport of ions through the cell membrane
2) Diffusion of ions through selectively permeable membrane

25

How is membrane potential measured? By convention what is the outside of the cell considered to be? What does that mean for the inside of the cell?

- Membrane potential is measured by placing electrodes in & outside the cell, then measure potential with a voltmeter
- Outside of the cell is 0 volts by convention
- Thus, inside of the cell is always negative relative to the outside of the cell

26

If the membrane potential is negative, which direction will the electrical force draw positive ions? What about negative ions?

- Cations drawn IN
- Anions pushed OUT

27

If a positive ion moves out of a cell, what happens to the membrane potential?

More negative

28

If a positive ion moves into a cell, what happens to the membrane potential?

More positive

29

Write the Nernst Equation. What does the Nernst Equation tell us?

- Value of membrane potential that would prevent any net diffusion of the ion
- Thus, strength of the chemical force on the ion

30

What is the principle of electroneutrality?

Any macroscopic region of a solution must have equal numbers of positive & negative charges.

31

Write the Goldman-Hodgkin-Katz equation.

N/A

32

What are the differences between the Nernst & Goldman equations?

Nernst=
- Equilibrium potential
- Single ion
- Permeability is NOT a factor

Goldman=
- Multiple ions
- Permeability is a factor

33

What is Quabain?

- Sodium-potassium pump inhibitor
- Causes the cell to lose its membrane potential

34

At rest, does Ca++ contribute to resting membrane potential?

No, the membrane is impermeable to Ca++

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