Write notes on the working of the heart of human.
A hollow muscular organ, consists of four chambers in which two are atria and two are ventricles, that pumps the blood through the circulatory system by rhythmic contraction and dilation is called Heart in Humans. It provides continuous blood circulation through the cardiac cycle. Human heart is myogenic. It contains a specialized cardiac musculature called the nodal tissue. Nodal tissue shows the following tissues.
- Sinoatrial node(SAN) – present in the right upper content of right atrium.
- Atrioventricular node (AVN) – present in the lower left corner of the right atrium.
Working of heart can be understood in terms of the Cardiac cycle.
Cardiac cycle: The sequence of cardiac events that occur from the beginning of one heart beat to the beginning of next is called Cardiac cycle. In the beginning, all the four chambers of the heart are in a relaxed state. Cardiac cycle shows three phases, namely a)Atrial systole b)Ventricular systole c)Cardiac diastole
Atrial systole: The contraction of the atria by which blood is forced into the ventricles; it precedes the true or ventricular systole and is indicated by the fourth heart sound. extrasystole. ventricular systole contraction of the ventricles, forcing blood into the aorta and pulmonary artery. It lasts about 0.1 seconds. Sino atrial node now stimulates an action potential which stimulates both the atria to contract simultaneously causing the atrial systole. This increases the flow of blood into the ventricles by about 30%, the remaining blood flows into the ventricle before the atrial systole.
Ventricle systole: The contraction, or period of contraction, of the heart, especially of the ventricles, during which blood is forced into the aorta and pulmonary artery. Atrial systole contraction of the atria by which blood is forced into the ventricles; it precedes the true or ventricular systole.
The action potential from the Sino-atrial node reaches the atrioventricular tissue, from where they are conducted through the bundles of His, its branches and the purkinje fibres, to entire ventricular musculature. This causes the simultaneous ventricular systole increases the pressure causing closure of AV valves preventing the backflow of blood, results in the production of first heartbeat sound ‘Lub’. When the pressure in ventricles exceeds the pressure in aortic arches, semilunar valves open. It results in the flow of blood from ventricles into aortic arches.
Cardiac diastole: It is a period of relaxation of the heart muscle, accompanied by the filling of the chambers with blood. The ventricles now relax and ventricular pressure falls causing the closure of the semilunar valves which prevent the backflow of blood. This results in the production of second heart sound known as’ Dup’. When pressure in ventricles falls below atrial pressure, AV valves open and ventricular filling begins. All the chambers are now again in relaxed state. Soon another cardiac cycle sets in.
A hollow muscular organ, consists of four chambers in which two are atria and two are ventricles, that pumps the blood through the circulatory system by rhythmic contraction and dilation is called Heart in Humans. It provides continuous blood circulation through the cardiac cycle. Human heart is myogenic. It contains a specialized cardiac musculature called the nodal tissue. Nodal tissue shows the following tissues.
- Sinoatrial node(SAN) – present in the right upper content of right atrium.
- Atrioventricular node (AVN) – present in the lower left corner of the right atrium.
Working of heart can be understood in terms of the Cardiac cycle.
Cardiac cycle: The sequence of cardiac events that occur from the beginning of one heart beat to the beginning of next is called Cardiac cycle. In the beginning, all the four chambers of the heart are in a relaxed state. Cardiac cycle shows three phases, namely a)Atrial systole b)Ventricular systole c)Cardiac diastole
Atrial systole: The contraction of the atria by which blood is forced into the ventricles; it precedes the true or ventricular systole and is indicated by the fourth heart sound. extrasystole. ventricular systole contraction of the ventricles, forcing blood into the aorta and pulmonary artery. It lasts about 0.1 seconds. Sino atrial node now stimulates an action potential which stimulates both the atria to contract simultaneously causing the atrial systole. This increases the flow of blood into the ventricles by about 30%, the remaining blood flows into the ventricle before the atrial systole.
Ventricle systole: The contraction, or period of contraction, of the heart, especially of the ventricles, during which blood is forced into the aorta and pulmonary artery. Atrial systole contraction of the atria by which blood is forced into the ventricles; it precedes the true or ventricular systole.
The action potential from the Sino-atrial node reaches the atrioventricular tissue, from where they are conducted through the bundles of His, its branches and the purkinje fibres, to entire ventricular musculature. This causes the simultaneous ventricular systole increases the pressure causing closure of AV valves preventing the backflow of blood, results in the production of first heartbeat sound ‘Lub’. When the pressure in ventricles exceeds the pressure in aortic arches, semilunar valves open. It results in the flow of blood from ventricles into aortic arches.
Cardiac diastole: It is a period of relaxation of the heart muscle, accompanied by the filling of the chambers with blood. The ventricles now relax and ventricular pressure falls causing the closure of the semilunar valves which prevent the backflow of blood. This results in the production of second heart sound known as’ Dup’. When pressure in ventricles falls below atrial pressure, AV valves open and ventricular filling begins. All the chambers are now again in relaxed state. Soon another cardiac cycle sets in.
