Cardio Electrophysiology 1 Flashcards
(52 cards)
What determines the Magnitude (strength) of a cell’s electrical potential?
1) Pump mechanisms
2) Membrane Permeability of ions
3) The Electro-chemical gradient
What is the Ionic concentration of a Cardiac Cell?
It has a lot of K+ inside the cell
It has a lot of Na+ and Ca2+ outside the cell
Cardiac Cells are extremely permeable to what ion?
K+
What are the 2 opposing forces that move K+ across the resting cell?
1) Chemical Force (outward)= concentration gradient
2) Electrostatic Force (inward) = K+ ions are attracted to the highly negative charge inside the cell
List the concentrations and equilibriums of Na+:
Extracellular Concentration
Intercellular Concentration
Equilibrium Potential
Extracellular: 145 mV
Intracellular: 10 mV
Equilibrium Potential: 70 mV
List the concentrations and equilibriums of K+:
Extracellular Concentration
Intercellular Concentration
Equilibrium Potential
Extracellular Concentration: 4 mV
Intercellular Concentration: 135 mV
Equilibrium Potential: -94 mV
List the concentrations and equilibriums of Ca2+:
Extracellular Concentration
Intercellular Concentration
Equilibrium Potential
Extracellular Concentration: 2 mV
Intercellular Concentration: 10^-4 mV
Equilibrium Potential: 132 mV
If a cardiac cell has a high concentration of K+, which has a equilibrium potential of -94 mV, how do you explain the resting membrane potential of the cell being -90 mV?
Well, there is a Na+ leak, which increases the resting membrane potential from -94 to -90 mV. If the Na+/K+ pump was partially inhibited (Digitalis), the cell will still be able to depolarize, just at a much slower rate.
The ventricular muscle action potential has how many phases?
5
Phase 0 Phase 1 Phase 2 Phase 3 Phase 4
How long does the ventricular muscle action potential las?
200-300 msec
The duration of the ventricular muscle action potential depends on what?
The Interbeat Interval
If the heart rate is 40 beats/min, how long would the Ventricular Muscle action potential be?
500 msec
If the heart rate is 150 beats/min, how long would the ventricular muscle action potential be?
Less than 200 msec
Draw the ventricular muscle action potential graph. Label the axis and phases. Describe the events occurring in each phase.
Really, like draw the freaking graph. :(
When the Fast Na+ channels open, the cell is how much more permeable to Na+ versus K+?
The cell is 500x more permeable to Na+ than K+ at the time the Fast Channels open
What causes the end of Phase 0?
The closing of the h gate.
What happens to the conductance of K+ during Phase 0?
K+ conductance goes down to help keep the cell depolarized.
What is the range of membrane potentials in most mammalian cells?
-10 to -100 mV
What are T Type Ca2+ Channels?
They are small Ca2+ currents and found mostly in nodal tissue
What are L Type Ca2+ channels?
They are long lasting Ca2+ currents that are found mostly in cardiac muscle.
Where are T type channels found? Where are L type channels found?
T types: SA nodes and AV nodes
L types: Cardiac Muscle Cells
Give an example of a drug that blocks T and L Type Ca2+ channels?
Diltiazem, it blocks Ca2+ channels
Describe Phases 0 -4.
Phase 0: Influx of Na+ thru fast channels generates upstroke
Phase 1: Efflux of K+ generates early partial repolarization
Phase 2: Plateau, Influx of Ca2+ = to Efflux of K+
Phase 3: Efflux of K+
Phase 4: Efflux of K+ > Influx of K+
What are the states of the gated channels During Phase 0?
The M and H gates are both open.
