Cardiac Cycle And Regulation Flashcards
When does systole occur in relation to S1 and S2?
S1-lub
S2-dub
S1 at the beginning of systole-mitral and tricuspid valve closure
S2 at the end of systole
What happens in S2?
Aortic and pulmonary valve closure
What happens in S1?
Mitral and tricuspid valve closure
What is the cardiac cycle?
The cardiac events that occur from the beginning of one heartbeat to the beginning of the next are called the cardiac cycle. Each cycle is initiated by spontaneous generation of an action potential in the SINUS NODE.
Whaat are diastole and systole?
The cardiac cycle consists of a period of relaxation called diastole, during which the heart fills with blood, followed by a period of relaxation called systole
How much of the cardiac cycle is comprised by systole?
At a normal HR= 72 beats/minute systole comprises about 0.4 of the cardiac cycle
What is the total duration of the cardiac cycle?
Total duration of the cardiac cycle: including systole and diastole is the reciprocal of the heart rate. E.g. if HR= 75 beats/minute, cardiac cycle is about 0.8 second per beat
Describe diastole phase
Occurs right after systole: ventricular ejection
Diastole: Isovolumetric contraction-beginning: aortic valve closure
Diastole: ventricular fillling- beginning: mitral valve opening
Diastole: atrial systole- during late ventricular diastole
Describe systole phase
Happens after diastole: atrial systole
Systole-Isovolumetric contraction- beginning: mitral valve closure
Systole: volumetric ejection- beginning: aortic valve opening
What are the seven stages of the cardiac cycle in order?
- Atrial systole
- Isovolumetric contraction
- Rapid ventricular ejection
- Reduced ventricular ejection
S2 occurs after -aortic and pulmonary valve closure
- Isovolumetric ventricular relaxation
- Rapid ventricular filling
- Reduced ventricular filling
Where is the action potential generated?
The sinus node(SA node), and spread to the atria producing atrial contraction
What are the electrical events of the cardiac cycle?
Depolarization
Repolarization
What is the mechanical events of the cardiac cycle?
Contraction
Relaxation
What are the consequences of the cardiac cycle?
Pressure changes
Valve closure/opening
Blood volume changes
Blood flow
What are the useful parameters of the cardiac cycle?
- electrical activity= ECG
- Pressure changes (atrial, ventricular, arterial)(Cardiac Catheterization)
- blood volume changes (atrial, ventricular, arterial) echocardiography
- sounds- phonogram
What happens in the P wave?
Atrial depolarization at the beginning
At the peak, atrial contraction begins
What occurs in the QRS complex?
Ventricular depolarization
Top priority R wave- ventricular contraction begins
What occurs in T wave?
Ventricular repolarization
Then ventricular relaxation begins
What does AP stand for?
Aortic pressure
What does LVP stand for?
Left ventricular presssure
What does what does LAP stand for?
Left atrial pressure
What does LVEDV stand for?
Left ventricle end diastolic volume
What does LVESV stand for?
LEft ventricle end systolic volume
What are the waves of the electrocardiogram?
P wave: atrial depolarization
QRS complex: ventricular depolarization
T wave: ventricular repolarization
What are the events of atrial systole?
Completion of ventricular idling
After SA node fires an action potential the wave of depolarization spread through the atria (atria depolarization): P wave (ECG ), followed by Atrial contraction
Left atrial pressure increases
Left ventricle volume increases 20%
What are the events of the atrial systole?
SA node fires an action potential. The wave of depolarization spreads through the atria. This is the P wave seen on the ECG. Atrial muscle contracts (atrial systole) and atrial pressure arises (a wave). A little more blood (10-20%), sometimes called the “atrial kick” is pushed into the almost full ventricles. However, a small amount of blood is forced backwards into the great veins (because there are no one way valves between the veins and the atria) causing a similar a wave in the central veins (recorded as the central veinous pressure, CVP). This wave can actually be seen as a pulse in the jugular vein of a person who is lying with the head and chest elevated about 30 degrees.
