Isovole contraction: also isovolumetric contraction) Initial phase of ventricular contraction, in which the tension and pressure in the ventricle increase, but no blood is pumped or expelled from the heart Stages 1 and 2 together – “isovolumic relaxation” plus influx (equivalent to “rapid influx”, “diastasis” and “atrial systole”) – include the ventricular period “diastole”, including the atrial system, during which the blood that returns to the heart, flows through the atria into the relaxed ventricles. Stages 3 and 4 together – “isovolumic contraction” plus “sputum” – are the ventricular period “systole”, which is the simultaneous pumping of blood supplies separated from the two ventricles, one to the pulmonary artery and the other to the aorta. Remarkably, towards the end of the “diastole”, the atria begin to contract, and then pump blood into the ventricles; This pressure delivery during ventricular relaxation (ventricular diastole) is called the atrial systemstole, also known as the atrial kick. [Citation needed] The contraction of the atria follows depolarization, represented by the P wave of the ECG. When the atrial muscles contract from the upper part of the atria to the atrioventricular septum, the pressure in the atria increases and blood is pumped into the ventricles through the open ventricular ear (tricuspid and mitral valves or bicuspids). At the beginning of the atrial systole, the ventricles are usually filled with about 70-80% of their capacity due to the influx during diastole. Ear contraction, also known as “ear kicking,” contributes to the remaining 20-30% of the filling (see image below). Atrial systole lasts about 100 ms and ends before ventricular systole, as the atrial muscle returns to the diastole. These venous pressure waves are associated with changes in blood flow. There are two periods of increased venous flow during each cardiac cycle (Fig. 1.18). The first occurs during ventricular systole, when the shortening of the ventricle muscle pulls the tricuspid valve ring towards the end of the heart.
This movement of the valve ring tends to increase the ear volume and decrease the atrial pressure, thereby increasing the flow of extracardiac veins to the atrium. The second phase of increased venous flow occurs after the opening of the tricuspid valve and blood flow from the atria into the ventricles. Venous flow is reduced in the intermediate periods of the cardiac cycle as atrial pressure increases during and shortly after atrial contraction and in the later part of the ventricular systole. Since there are no valves at the junction of the right atrium and vena cava, blood flow in the large thoracic veins temporarily reverses during atrial contraction. The sinus node acting alone produces a constant rhythmic heart rate. Regulatory factors depend on the atrioventricular node to increase or decrease heart rate in order to adjust cardiac output to changing body needs. Most changes in heart rate are mediated by the heart center in the elongated marrow of the brain. The center has sympathetic and parasympathetic components that adjust the heart rate to the changing needs of the body. Cardiac cycle events for the left ventricle, which show changes in left atrial pressure, left ventricular pressure and volume, as well as aortic pressure.
Point A, the opening of the valve AV. Point B, ear contraction. Point C, valve closure AV. Point D, opening of crescent valves. Point E, closing the semi-lunar flap. beads: unusual cardiac tone detected by auscultation; Typically related to septal or valve defects, atrial systole is the contraction of heart muscle cells in both atria after electrical stimulation and conduction of electrical currents through the ear chambers (see above, Physiology). While atrial systole is nominally a component of the cardiac sequence of systolic contraction and sputum of the heart, it actually fulfills the vital role of supplementing the diastole, which is to complete the filling of both ventricles with blood while relaxing and dilating them for this purpose. Atrial systole straddles the end of the diastole and occurs in the subsaturation known as the late ventricular diastole (see cycle graph). At this point, the atrial systemstole exerts contraction pressure to “round” the blood volumes sent to both ventricles; This ear entry closes the diastole immediately before the heart begins to contract again and expel blood from the ventricles (ventricular systole) into the aorta and arteries.  Mitral and tricuspid valves, also called atrioventricular valves or AV, open during the ventricular diastole to allow filling.
Late in the filling period, the atria begin to contract (atrial sysstole) and force a final blood harvest into the ventricles under pressure – see the cycle diagram. Then, triggered by electrical signals from the sinus node, the ventricles begin to contract (ventricular systole), and when the back pressure against them increases, the AV valves are forced to close, which prevents blood volumes from entering or leaving the ventricles; This is called the isovolumic contraction stage.  diastole:: Period of time during which the heart muscle is relaxed and the chambers fill with blood It is not uncommon to sometimes hear a third heart murmur or S3. This is usually caused by a sudden surge of blood into the ventricles of the atria. It is therefore most often an average diastolic sound that occurs after S2. This article discusses the phases of the cardiac cycle and the underlying physiological principles that govern the process. There will be a brief examination of the conductive system of the heart, as well as a discussion of the disorders that affect the cardiac cycle. Heart murmurs and sounds caused by turbulence or vibrations in the heart and vascular system can be innocent or pathological. It is important to understand the timing of events in the cardiac cycle as a prerequisite for understanding heart murmurs. The relationship between the normal cardiac cycle and that of cardiac sounds is recorded in Fig. 8.2. Myocardiocytes are unique cells in the heart that are able to independently generate and distribute electrical activity from one cell to another.
They are able to communicate via lacunar junctions (permeability points) at the interspersed discs (where the cell walls meet). Communication is so effective that cells form syncytium in which ions can flow freely and quickly from one cell to another. Thanks to this network, the heart muscles undergo an almost simultaneous contraction. The period of time that begins with the contraction of the atria and ends with ventricular relaxation is called the cardiac cycle. The period of contraction that the heart goes through when it pumps blood into the circulation is called systole. The period of relaxation that occurs when the chambers fill with blood is called diastole. The atria and ventricles are subject to systole and diastole, and it is important that these components are carefully regulated and coordinated to ensure that blood is pumped efficiently through the body. Isovolumic contraction: the short period of early contraction, when pressure accumulates in the ventricle but has not yet increased enough to allow sputum Increased excitability at points other than the pacemaker site predisposes the heart to the development of ectopic heartbeat.
These can lead to uncoordinated contraction of the ventricles and different types of ventricular arrhythmias. The piping system consists of several components. The first part of the piping system is the sinus node. Without neuronal stimulation, the sinus node rhythmically initiates impulses 70 to 80 times per minute. Because it determines the basic rhythm of the heart rate, it is called the pacemaker of the heart. Other parts of the conduction system include the atrioventricular node, atrioventricular bundle, beam branches, and conduction myofibers. All these components coordinate the contraction and relaxation of the heart chambers. Ventricular systole refers to the period of contraction of the ventricles. The electrical impulse arrives at the atrioventricular node (AV node) shortly after depolarization of the atria. There is a small delay at the AV node that allows the atria to complete the contraction before the ventricles are depolarized.
The action potential descends to the AV node, the bundle of His, and then to the left and right branches of the bundle (conductive fibers that pass through the interventricular septum and branches to supply the ventricles). .