Cardio Basics Flashcards
What is the action potential?
Contractions triggered by an electrical impulse that causes a changes in voltage of the membrane potential that cause la a cell to go from its negative resting state to a positive state
What are the two main types of cardiac cells?
Pacemaker and contractile
Where are pacemakers cells located
In the atria
Where are contractile cells located
Ventricles
What happens in phase 4 of contractile cells?
Inward movement of potassium and increased sodium permeability. It is during ventricular diastole and is the period of rest before the next depolarization
What happens in phase 0 of contractile cells
Sodium moves into the cells and has fast depolarization.
What happens when you give a sodium channel blocker in contractile cells?
QRS will widen
What happens in phase 1 of contractile cells
Initial repolarization. Sodium channels are inactivated and potassium channels open and close.
What happens in phase 2 ?
Plateau phase. Slow influx of calcium and potassium leaks out.
What charge does the threshold reach in phase 2 to cause the calcium channels to open up
-40mV
What happens in phase 3 of contractile cells
Repolarization, calcium channels close, potassium opens.
What happens in phase 3 when you give a potassium channel blocker on a ECG
The T wave will be delayed and the QT and ST will be longer
What are the three important ions in cardiac cell membrane
Potassium, sodium, and calcium
How do pacemaker cells start action potentials?
They generate regular spontaneous action potentials
Why are action potentials slower in SA node?
They are no fast sodium channels or current in the pacer cells there
In which phase is there a rapid influx of sodium ions and rapid depolarization?
Phase 0
What is the preload in cardiac output
Blood in the ventricle at the end of diastole
What is afterload
Force against which the heart must beat to eject blood
What do vasodilators reduce
After load and improve stroke volume
How does acetylcholine affect the heart
Decrease heart rate, contractility, and conductance. They also relax vascular smooth muscle.
How do you solve the arterial blood pressure
cardiac output x peripheral vascular resistance
How is stroke volume found
Pre load or (degree of stretch of cardiac fibers )
The contractility cardiac fibers
And afterload ( pressure ventricles must overcome)
What three mechanisms regulate homeostatic cardiac output
Neural, chemical, and physical
What system provides short term control of cardiac output
Baroreceptor reflex
