Apex Cardiac WB KEY Flashcards
How is cardiac muscle like skeletal muscle and neural tissue?
- have myosin and actin, can contract
- T-tubule system and SR maintain Ca2+ homeostasis for contraction and relaxation
How is cardiac muscle DIFFERENT from skeletal muscle and neural tissue?
They have tight Junctions and they contain more mitochondria and skeletal muscle cells.
Neural tissue is similar to cardiac in the sense that they can
propagate an action potential.
Ability to spontaneously generate an AP is known as
Automaticity
Conductance : open channels, closed channels
Increase conductance; decrease conductance.
What is the RMP? Which is more negative inside or outside?
The difference in electrical potential between the inside and the outside of the cell.
Inside is NEGATIVE relative to the outside
RMP is established by what 3 mechanisms?
- Chemical force
- Electrostatic counter force
- Na/K ATPase
What predicts an ion’s equilibrium potential?
NERNST Equation.
When is equilibrium established?
When there is no concentration gradient and NO net flow of ions. Charge inside balanced with charge outside.
How much K+ INSIDE the Myocyte?
135 mM
How much Na+ INSIDE the Myocyte?
10 mM
How much Cl- INSIDE the myocyte
4 mM
How much Ca2+ INSIDE the myocyte
10mM (-4)
How much K+ OUTSIDE the Myocyte, meaning in ECF?
4 mM
How much Na+ OUTSIDE the Myocyte, meaning in ECF?
145 mM
How much Cl- OUTSIDE the Myocyte, meaning in ECF?
114 mM
How much Ca2+ OUTSIDE the Myocyte, meaning in ECF?
2mM
When is the cell easier to depolarize
When RMP is closer to TP
When is the cell harder to depolarize
RMP is further from TP
When there is a decrease in polarity across a membrane / less charge difference between inside and outside of the cell is known as
Depolarization, and results in AP.
Restoration of RMP following a depolarization known as
Repolarization
Increase in polarity across a membrane , where there is a larger charge difference between inside and outside of the cell Is known as
Hyperpolarization
Why is the inside of the cells more negative than outside of the cell?
Because the myocyte is permeable to K+ but not other ions or proteins and CONTINUOUSLY LEAK K+ causing them to lose their POSITIVE CHARGE.
When serum K+ decreases, RMP become more ________and the myocyte becomes more ________
Negative , Hyperpolarized
When serum K+ increases, RMP become more ________and the myocyte becomes more ________
more positive, depolarize more easily
What is the primary determinant of RMP?
K+
When the cell is at rest, Na+ permeability is____compared to K+ permeability (high or low)
Low
When RMP approaches TP voltage gated Na+ Channels _______ and _______ conductance cell
Open and increase Na+ conductance –> cell depolarization
Sodium-Potassium ATPase: ions movement
3 Na+ out
2 K+ in
For the VENTRICULAR ACTION potential, The RMP is ______mV and the TP is ____mV
- 90 mV
- 70 mV
What happens during Phase O of the Ventricular action potential? how?
SODIUM rushes IN
How: The cells reaches the threshold potential of -70mV and Depolarizes
Fast voltage-gated Na+ channels is activated.
What happens during Phase 1 of the Ventricular action potential? how?
Initial repolarization
Na+ channels become inactivated so cell becomes less positive
K+ channels open and Cl- channels open
What is ion movement during phase 1 of the Ventricular action potential?
K+ out
Cl - in
What happens during Phase 2 of the Ventricular action potential? how?
Slow Ca2+ channels counters loss of K+ ions = Maintains depolarization
Delays repolarization
Na+ channels stay in the inactivated state
What is ion movement during phase 2 of the Ventricular action potential?
K+ Out
Ca2+ IN
Absolute refractory period and Phase II
Phase II prolongs the absolute Refractory period
In which phase is the fast Na+ Channel maintained in the inactivated state?
Phase II
What is ion movement during phase III of the Ventricular action potential?
Final Repolarization
K+ Out
Ca2+ IN (briefly)
What is ion movement during phase IV of the Ventricular action potential?
Resting phase
