Exam #1: Membrane Potential Flashcards Preview

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

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

A

Intracellular

2
Q

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

A

Extracellular

3
Q

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

A

Extracellular

4
Q

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

A

Extracellular

5
Q

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

A

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
Q

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

A

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
Q

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

A

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
Q

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

A

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
Q

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

A

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
Q

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

A

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
Q

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

A
  • 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
Q

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

A
  • 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
Q

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

A

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
Q

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

A
  • The Na+/K+ Pump is electrogenic
  • 3x Na+ Out
  • 2x K+ In
  • Thus, the sodium-potassium pump maintains the membrane potential & cell volume
15
Q

Hyperkalemia

A

Higher than normal ECF concentration of K+

16
Q

Hypokalemia

A

Lower than normal ECF concentration of K+

17
Q

Hypernatermia

A

Higher than normal ECF concentration of Na+

18
Q

Hyponatremia

A

Lower than normal ECF concentration of Na+

19
Q

Hypercalcemia

A

Higher than normal ECF concentration of Ca++

20
Q

Hypocalcemia

A

Lower than normal ECF concentration of Ca++

21
Q

What is depolarization?

A

Membrane becomes more negative outside

22
Q

What is hyperpolarization?

A

Membrane becomes more negative inside

23
Q

What is membrane potential due to?

A

Separation of electrical charges across the membrane

24
Q

How did the charges get separated?

A

1) Active transport of ions through the cell membrane

2) Diffusion of ions through selectively permeable membrane

25
Q

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?

A
  • 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
Q

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

A
  • Cations drawn IN

- Anions pushed OUT

27
Q

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

A

More negative

28
Q

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

A

More positive

29
Q

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

A
  • Value of membrane potential that would prevent any net diffusion of the ion
  • Thus, strength of the chemical force on the ion
30
Q

What is the principle of electroneutrality?

A

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

31
Q

Write the Goldman-Hodgkin-Katz equation.

A

N/A

32
Q

What are the differences between the Nernst & Goldman equations?

A

Nernst=

  • Equilibrium potential
  • Single ion
  • Permeability is NOT a factor

Goldman=

  • Multiple ions
  • Permeability is a factor
33
Q

What is Quabain?

A
  • Sodium-potassium pump inhibitor

- Causes the cell to lose its membrane potential

34
Q

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

A

No, the membrane is impermeable to Ca++

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