Cardiac Cycle And Regulation

Question 1

When does systole occur in relation to S1 and S2?

Answer 1

S1-lub

S2-dub

S1 at the beginning of systole-mitral and tricuspid valve closure

S2 at the end of systole

Question 2

What happens in S2?

Answer 2

Aortic and pulmonary valve closure

Question 3

What happens in S1?

Answer 3

Mitral and tricuspid valve closure

Question 4

What is the cardiac cycle?

Answer 4

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.

Question 5

Whaat are diastole and systole?

Answer 5

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

Question 6

How much of the cardiac cycle is comprised by systole?

Answer 6

At a normal HR= 72 beats/minute systole comprises about 0.4 of the cardiac cycle

Question 7

What is the total duration of the cardiac cycle?

Answer 7

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

Question 8

Describe diastole phase

Answer 8

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

Question 9

Describe systole phase

Answer 9

Happens after diastole: atrial systole

Systole-Isovolumetric contraction- beginning: mitral valve closure

Systole: volumetric ejection- beginning: aortic valve opening

Question 10

What are the seven stages of the cardiac cycle in order?

Answer 10

1. Atrial systole
2. Isovolumetric contraction
3. Rapid ventricular ejection
4. Reduced ventricular ejection

S2 occurs after -aortic and pulmonary valve closure

5. Isovolumetric ventricular relaxation
6. Rapid ventricular filling
7. Reduced ventricular filling

Question 11

Where is the action potential generated?

Answer 11

The sinus node(SA node), and spread to the atria producing atrial contraction

Question 12

What are the electrical events of the cardiac cycle?

Answer 12

Depolarization

Repolarization

Question 13

What is the mechanical events of the cardiac cycle?

Answer 13

Contraction

Relaxation

Question 14

What are the consequences of the cardiac cycle?

Answer 14

Pressure changes

Valve closure/opening

Blood volume changes

Blood flow

Question 15

What are the useful parameters of the cardiac cycle?

Answer 15

• electrical activity= ECG
• Pressure changes (atrial, ventricular, arterial)(Cardiac Catheterization)
• blood volume changes (atrial, ventricular, arterial) echocardiography
• sounds- phonogram

Question 16

What happens in the P wave?

Answer 16

Atrial depolarization at the beginning

At the peak, atrial contraction begins

Question 17

What occurs in the QRS complex?

Answer 17

Ventricular depolarization

Top priority R wave- ventricular contraction begins

Question 18

What occurs in T wave?

Answer 18

Ventricular repolarization

Then ventricular relaxation begins

Question 19

What does AP stand for?

Answer 19

Aortic pressure

Question 20

What does LVP stand for?

Answer 20

Left ventricular presssure

Question 21

What does what does LAP stand for?

Answer 21

Left atrial pressure

Question 22

What does LVEDV stand for?

Answer 22

Left ventricle end diastolic volume

Question 23

What does LVESV stand for?

Answer 23

LEft ventricle end systolic volume

Question 24

What are the waves of the electrocardiogram?

Answer 24

P wave: atrial depolarization

QRS complex: ventricular depolarization

T wave: ventricular repolarization

Question 25

What are the events of atrial systole?

Answer 25

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%

Question 26

What are the events of the atrial systole?

Answer 26

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.