Exam #1: Membrane Potential Flashcards
Is the intracellular concentration or extracellular concentration higher for K+?
Intracellular
Is the intracellular concentration or extracellular concentration higher for Na+?
Extracellular
Is the intracellular concentration or extracellular concentration higher for Cl-?
Extracellular
Is the intracellular concentration or extracellular concentration higher for Ca++?
Extracellular
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.
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.
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.
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.
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
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
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.
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
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.
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
Hyperkalemia
Higher than normal ECF concentration of K+
Hypokalemia
Lower than normal ECF concentration of K+
Hypernatermia
Higher than normal ECF concentration of Na+
Hyponatremia
Lower than normal ECF concentration of Na+
Hypercalcemia
Higher than normal ECF concentration of Ca++
Hypocalcemia
Lower than normal ECF concentration of Ca++
What is depolarization?
Membrane becomes more negative outside
What is hyperpolarization?
Membrane becomes more negative inside
What is membrane potential due to?
Separation of electrical charges across the membrane
How did the charges get separated?
1) Active transport of ions through the cell membrane
2) Diffusion of ions through selectively permeable membrane
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
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
If a positive ion moves out of a cell, what happens to the membrane potential?
More negative
If a positive ion moves into a cell, what happens to the membrane potential?
More positive
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
What is the principle of electroneutrality?
Any macroscopic region of a solution must have equal numbers of positive & negative charges.
Write the Goldman-Hodgkin-Katz equation.
N/A
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
What is Quabain?
- Sodium-potassium pump inhibitor
- Causes the cell to lose its membrane potential
At rest, does Ca++ contribute to resting membrane potential?
No, the membrane is impermeable to Ca++
