What is the difference between systole and diastole?

Question

Understanding the definitions of cardiovascular function.

Answer 1

This question needs 4 pages of answer at least, but let's make it simple.

Systole: Contraction of the heart.. and since the heart is filled with blood, then this contraction is associated with pumping of blood to the Aorta.

Diastole: Relaxation of heart after contraction.

Systolic pressure: The force of heart produced to pump blood against resistant thick arterial walls "Aorta" (Top number)

Diastolic pressure: The pressure in the blood vessels when the heart is relaxed.(bottom number)

So when we say Normal blood pressure is 120/80 (120 is systolic and 80 is diastolic).

Answer 2

Systole and diastole are measurements of cardiovascular function and can be easily explained by the following:

1. Systole represents the amount of force needed to contract against a certain volume of blood in the right and left ventricles
2. Diastole represents the amount of volume against which the cardiac chambers must contract.

These measurements follow along with the Frank - Starling law, which states that, with an increase in the given amount of blood volume in the cardiac chambers, the cardiac myocytes will increase their contractile force against that volume, if all other variables are held constant.

Systole and diastole are also representative of the top and bottom numbers, respectively, when we measure a blood pressure.

Answer 3

The "big picture" of the cardiac cycle can be broken down into two phase. These stages repeat over and over again to both fill the ventricles with blood (diastole) and eject blood out of the heart (systole).

Systole (beginning with the first heart sound "lub" or S1) is the ejection of blood from both the left and right ventricles. This is accomplished by a coordinated contraction of the cardiac muscle surrounding the ventricles, along with open aortic ( left ventricle) and pulmonic (right ventricle) valves. The "lub" or S1 sound is made from the closing of the mitral (left ventricle) and tricuspid (right ventricle) valves which when open allow blood to flow into their respective ventricles during the 2nd phase, diastole.

Diastole (beginning with the second heart sound "dub" or S2) is ejection of the blood from the left and right atria into their respective ventricles, filling them in the process. This phase is usually longer than systole. The "dub" sound heard when listening to the heart is actually from closing of the aortic and pulmonic valves. The closing of these valves, along with opening of the mitral and tricuspid, allows blood to flow from the atria to the ventricles, in preparation for systole, when this blood will leave the heart and into the arteries.

By measuring blood pressure during each stage, we can get a sense for how hard the heart is having to push to get blood out into circulation (systolic) and how much the arteries are pushing back when the heart is relaxed (diastolic). Commonly, this number is around or below 120/80.