Resting Membrane Potential
Which Anion has the highest concentration in the ECF?
Cl-
Describe the role of the Na+/K+ ATP pump and its functional role in the maintenance of resting membrane potential.
It pumps 3 Na+ out of the cell and 2 K+ into the cell. By pumping more positive changes out of the cell than into the cell, the pump activity creates a negative potential within the cell. REMEMBER Na+/K+ pump is not directly responsible for the generation of the resting membrane potential.
In the resting cell, describe what leak channels and gated channels are doing?
Leak channels = opened Gated channels = closed. Na+ moves into the cell and K+ moves out
Why is the concentration of K+ inside the plasma membrane is higher than that outside the plasma membrane?
More K+ leak channels than Na+ leak channels (Na+ leak channels are present at a ratio 100:1 K+ to Na+) K+ ions leave the cell at a greater rate than the Na ions enter the cell.
What is the Equilibrium Potential of Na+ and K+ when the electrochemical gradient has been equilibrated?
Na+ = +60 mV K+ = -90 MV
In a resting cell, describe the flow of Na+ and K+?
Na+ moves into the cell and K+ moves out by moving down its ion concentration gradient
Diffusion forces move K+ ______ the cell and electrostatic forces push K+ ______ the cell.
Out of; into
If inside of the cell is more positive than outside then the voltage potential is _________. If inside of the cell is more negative than the outside then the voltage potential is ___________.
POSITIVE; NEGATIVE
How do you calculate net driving force? What does it mean if it is positive or negative?
Resting Potential - Equilibrium Potential = Net driving Force Positive = passive leak out of the cell (net efflux) Negative = passive leak into the cell (net influx)
What is the concentration of sodium and Potassium, inside and out of the cell?
Sodium... Inside: 12 MEq/l Outside: 145 MEq/l Potassium Inside: 150 MEq/l Outside: 4 MEq/l
Describe the slight imbalance in electrical charge across the plasma membrane?
The cell is slightly negative on the inside and slightly positive on the outside.
List which ions make up resting membrane potential, and describe the differences in plasma membrane permeability of these ions and how this contributes to resting membrane potential.
The resting membrane potential is the result of three factors: 1. The concentration of K+ inside the plasma membrane is higher than that outside the plasma membrane. 2. The concentration of Na+ outside the plasma membrane is higher than that inside the plasma membrane. 3. The plasma membrane is more permeable to K+ than to Na+ .
What is the Electrochemical Gradient?
a concentration (chemical) difference plus an electrical difference When ion channels are open, they allow specific ions to move across the plasma membrane, down their electrochemical gradient
Due to the K+ leak channels, the plasma membrane is ________ times more permeable to K+ than to other positively charged ions, such as Na+.
50-100
With regards to the Nernst Equation: Whenever IONin is greater than IONout, the log will be _________. Whenever IONout is greater than IONin, the log will be _________. If IONout = IONin, the log will be ______ and so will the Nernst potential.
negative, positive, 0
What is resting Membrane Potential for neurons?
-70 m V.
What is resting membrane potential for cardiac muscle?
-90mV
Which two main forces control the movement of ions?
Electrostatic force = positively charged ions are attracted to negatively charged areas Diffusion Force = Ions flow from area of high concentrations to areas of low concentration
What does the Nernst equation give us?
Equilibrium potential
