Electrophysiological Principles Flashcards
How does increasing stimulus intensity affect action potentials?
increase intensity = increase frequency of APs
What is the restinge membrane potential?
-60 mV
What is voltage? What is another name?
- work done required to move a unit of positive charge from a more negative point (lower potential) to the more positive point (higher potential)
- potential difference
What is current?
rate of flow of electric charge past a point
What is capacitance? What is capacitance for for all cells per unit area?
- ability to store charge with ease
- 1 uF/cm^2
How is capacitance related to surface area (SA) and distance (L)?
- directly proportional to SA
- inversely proportional to L
Between the cell membrane and the lipid bilayer, which would be the capacitor and insulator?
- cell membrane = capacitor
- lipid bilayer = insulator
Larger cells can store more charge. Which 2 equations can explain this?
- Q = CV
- C proportional to SA/L
Which factors allow for charge separation across the cell membrane?
- cell membrane is semi-permeable to K+
- cell membrane is not permeable to many ions (Na+ and Ca2+)
- ATP-dependent transporters pump ions (Na+ and K+) across the membrane in order to redistribute and maintain charge separation
TRUE or FALSE: the cell membrane is permeable to Cl-
FALSE: impermeable to Cl-
TRUE or FALSE: the electrical gradient opposes the concentration gradient
TRUE
Requirements for the model cell?
- intracellular and extracellular solution must each be electrically neutral
- cell must be in osmotic balance
- there must be no net movement of any ion into or out of the cell
TRUE or FALSE: the cell membrane potential is maintained by many ions.
FALSE: maintained by RELATIVELY FEW ions
note: 1/100,000 ions are required to maintain Vm, or else too much work is required
What does the Nernst equation tell us?
potential at which there will be no net flux of an ion across the membrane (i.e. at equilibrium)
Does depolarization or hyperpolarization of the cell occur when you increase extracellular K+? Explain.
- depolarization
- positive K+ ions flow into the cell
Adjusting the extracellular concentration of which ion will change membrane potential? which will NOT change Vm?
- change: K+
- NOT change: Cl-
What is the approximate equilibrium potentials for the following ions:
- K+
- Na+
- Cl-
- Ca2+
- K+ = -90 mV
- Na+ = +60 mV
- Cl- = -85 mV
- Ca2+ = +150 mV
Which ion has the greatest effect at rest?
- K+ because it is quite negative
To which ion’s equilibrium potential is the membrane potential closest to?
K+
Why does the membrane potential deviate from Ek at more negative potentials?
Na+ flow into the cell and pulls up the curve more at negative potentials because Na+ equilibrium potential is very positive (+60 mV)
(note: if Na+ CAN flow in, it WILL flow in)
Which equation is used to calculate the REAL resting membrane potential? Which ions does it take into account?
Goldman-Hodgkin-Katz equation; Na+, K+, Cl-
What is the relative permeability of K+? Na+? Cl-?
- Pk = 1
- Pna = 0.04
- Pcl = 0.45
What are ion equilibrium potentials and membrane potential maintained by?
active transport (pumps) ensure that ions do not run down their concentration gradient
Describe the Na-K-ATPase.
- 3 Na out
- 2 K in
What would the resting membrane potential be without Na-K-ATPase? Explain.
- 0 mV
- without the pump, ions would run down their concentration gradients until equilibrium is reached; both charge and concentration will be balanced, leaving no difference inside and outside the cell
Which drug can inhibit ATPases?
ouabain
What do pumps require to work?
- Na+ inside
- ATP/energy
- K+ outside
TRUE or FALSE: pumps only work during action potentials
FALSE: pumps work all the time, but harder during APs
