Cardiac Cycle , EKG, and Fetal Circulation Flashcards
What are the phases of the cardiac cycle?
- Ventricular filling
- Isovolumetric contraction
- Ventricular ejection
- Isovolumetric relaxation
What is phase 1 of the cardiac cycle? Describe it?
Ventricular filling: (diastole)
During diastole, ventricles expand and their pressure drops below that of the atria, causing the AV valves to open allowing blood to flow into the ventricles, causing ventricular pressure to rise and atrial pressure to fall
What is phase 2 of the cardiac cycle? Describe it?
Isovolumetric contraction: (systole)
The atria repolarizes, relaxes, and remains in diastole for the rest of the cardiac cycle (all valves are closed), then the ventricles depolarize, generate the QRS complex, and begin to contract
What is phase 3 of the cardiac cycle? Describe it?
Ventricular ejection: (diastole)
The ejection of blood begins when ventricular pressure exceeds arterial pressure and forces the semilunar valves open
What is phase 4 of the cardiac cycle? Describe it?
Isovolumetric relaxation: (diastole)
This is early ventricular diastole, when the T wave ends and the ventricles begin to expand. (all valves are closed)
(Heart Sounds) Describe S1?
Sound: Lub, louder and longer
Valve: Closing AV valves
Cardiac Cycle: At isovolumetric contraction
(Heart Sounds) Describe S2?
Sound: Dup, little softer and sharper
Valve: Closing semilunar valves
Cardiac Cycle: At isovolumetric relaxation
(Heart Sounds) Describe S3?
In children and adolescents, it is normal to hear a 3rd heart sound.
This is rarely audible in people over 30
What is an EKG?
Electrocardiogram:
It provides a comprehensive image of the hearts electrical activity
Deviations from normal are invaluable for diagnosing abnormalities in conduction pathways
Does not measure action potential (all current from outside cell)
Flat line: no detective electrical change
Atrial repolarization: NOT recorded on EKG, does not happen with ventricular repolarization
What is an electrocardiograph?
It is typically attached to the wrists, ankles, and six locations on the chest
Describe P wave?
produced when a signal from the SA node spreads
PQ segment: SA node to AV node (0.1 sec between P & Q)
Describe QRS complex?
Is AV node to ventricular myocardium
ST segment: ventricular systole begins
Describe T wave?
Is generated immediately before diastole
The ventricles take longer to repolarize than to depolarize
(Electrical & Mechanical Reading) P Wave?
Electrical: Atrial depolarization
Mechanical: Contraction of atrium
(Electrical & Mechanical Reading) QRS Complex?
Electrical: Ventricular depolarization
Mechanical: Contraction of ventricle
