Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
35 Cards in this Set
- Front
- Back
|
Define resting potential. What is its range?
|
Charge of inside of cell relative to charge of outside of cell, e.g., if Vrest = -70 mV, inside of cell is 70 mV more negative than outside.
Range is -40 to -90 mV |
|
|
What occurs during depolarization?
|
Inside of cell becomes more positive
|
|
|
What occurs during hyperpolarization?
|
Inside of cell becomes more negative
|
|
|
What does current describe?
|
The direction of flow of POSITIVE charges
|
|
|
What is Ohm's law?
|
V = IR
|
|
|
What is inward current? Outward current?
|
Inward current: flow of POSITIVE charges into a cell
Outward current: flow of POSITIVE charges out of a cell |
|
|
How does intracellular charge compare to extracellular charge?
|
The cell is more negative on the inside
|
|
|
What are the effect of concentration and electrochemical gradients on sodium and potassium?
|
Sodium wants to enter cell because cell interior is more negative, and because there is a lower [Na] within the cell.
There is a net leakage of K out of the cell, this is due to a concentration gradient pushing K+ outward (there is a lower [K+] outside of the cell), and an electrochemical gradient pushing K+ back into the cell (the cell is more negative on the inside). |
|
|
Why is the cell membrane considered a capacitor? What is a capacitor?
|
A capacitor is an insulator (lipid bilayer) separating two conductors (intracellular and extracellular solutions). Much like an electrical capacitor, charges are stored along the intra- and extracellular sides of the cell membrane. This is where resting potential is derived from.
|
|
|
A container is divided in two by a membrane permeable to K+ only.
The left half of the container contains a much greater concentration of KCl than the right half. What will happen? |
K+ ions will migrate to solution of lower concentration. This will allow for negative charges (Cl-) to collect along membrane in the left-hand container.
As K+ travels to the right, positive charges (K+) will collect along the membrane of the right container. When charge buildup prevents anymore K+ from passing, there'll be no netflux of K+, regardless of its concentration. This is known as the NERNST EQUILIBRIUM |
|
|
What is a logarithm?
|
In mathematics, the logarithm of a number to a given base is the power or exponent to which the base must be raised in order to produce that number.
|
|
|
log 1 = ?
|
0
|
|
|
log 100 = ?
|
2
|
|
|
log 1000 = ?
|
3
|
|
|
log 10 = ?
|
1
|
|
|
Provide the general equation for Nernst Equilibrium. Describe each constant.
|
Eion = (-RT)/(ZF) * ln [ion]i/[ion]o
Z is valence of ion (CHARGE!!!) F = Faraday constant |
|
|
Provide the equation for Nernst Equilibrium potential at body temperature.
|
At 37 degrees C:
Eion = -61/Z * log Ci/Co C = [ion] |
|
|
Assume:
[Na]i = 10 mM [Na]o= 100 mM Vrest = -70 mV What is the Nernst Equil Potential of Na? |
E of Na = -61/(+1) * log 10/100
=-61*log.1 =-61*-1 =+61 mV |
|
|
What is the equation for determining the net driving force of an ion?
|
Vmembrane - Eion
|
|
|
Assume:
Vm = -70 mV E Na+ = +60 mV E K+ = -90 mV What would be the driving force of each ion? In which direction would each travel? Which would travel more forcefully? |
Driving Force = Vm - Eion
DF Na = -70 - +60 = -130 mV DF K= -70 - -90= +20 mV Na+ would enter cell, K+ would leave cell. Na+ would travel much more quickly! |
|
|
What is E of Na+?
|
+60 mV
|
|
|
What is E of Cl-?
|
-70 mV
|
|
|
What is E of K+?
|
-90 mV
|
|
|
Would you need a negative or positive internal voltage (compared to outside of cell) to prevent Na+ from entering a cell? What would this say about the Nernst Equilibrium Potential necessary?
|
Positive, and positve
|
|
|
Would you need a negative or positive internal voltage (compared to outside of cell) to prevent K+ from leaving a cell? What would this say about the Nernst Equilibrium Potential necessary?
|
Negative, and negative
|
|
|
What is the flow of Cl- like at Vrest? Why?
|
Not much flux, because Vrest ~ E of Cl- (-70)
|
|
|
What is the E of Ca++? Why is this significant?
|
+120 mV, this is really high, cells normally never get this positive, so cells can never have NO net flow of Ca++ when Ca++ channels open.
|
|
|
Describe the relative number of Ca++ channels. Describe their transport.
|
Not very many, very slow transport.
|
|
|
What is the function of the GOLDMAN-HODGKIN-KATZ EQUATION? What does it demonstrate?
|
Vm = -RT/F * ln [P(Na)*[Na inside]*P(K)*[K inside]*P(Cl)*[Cl OUTSIDE]/[P(Na)*[Na outside]*P(K)*[K outside]*P(Cl)*[Cl INSIDE]
At body temp: = -61 log (" ") Tells you Vm; demonstrates that the contribution of various ions to Vm depends on their relative permeabilities and concentration gradients. |
|
|
Why are Vmembranes so close to E of K?
|
Potassium is much more permeable to the membrane than any other cation. As such, Vrest is near E of K.
In short, ions with greatest cell permeability influence the membrane most |
|
|
How are cells in a dynamic steady state?
|
Ionic concentrations within cell remain the same in spite of a lack of equilibrium. Due to pumps/carriers fighting [ ] grads.
|
|
|
What is reversal potential?
|
The voltage at which there is no net flux of ions through an ion channel
|
|
|
What is the reversal potential of a non-selective cation channel? What determines the potential?
What about for an ion channel selective for one ion? Two ions? |
0; determined by concentration gradient and permeability of ions passing through.
Would equal E of ion. Would be somewhere between the E of those two ions. |
|
|
What's the main ion traveling through non-selective cation channels?
|
Na+
|
|
|
If P of Na were increased and the P value for all other ions were held constant, what would happen to the cell?
|
Become depolarized
|
