In: Anatomy and Physiology
Describe all the events (steps) that occur during a cardiac cycle for mammals (organisms with a double circulation), as well as the opening and closing of all heart valves and the signals arising from the SA and AV nodes How does this cycle contribute to metabolic homeostasis for our cells, and what is the purpose of the valves?
Events occuring during cardiac cycle:-
1. ATRIAL SYSTOLE :
The atria contracts due to wave of contraction stimulated by SA Node. The blood is forced into ventricles as Bicuspid and Tricuspid valve are open.
2. BEGINNING OF VENTRICULAR SYSTOLE:
The ventricles begin to contract due to wave of contraction, stimulated by AV NODE . The bicuspid and tricuspid valve close immediately producing the first heart sound.
3. COMPLETE VENTRICULAR SYSTOLE:
When the ventricles complete the contraction, blood flows into the pulmonary trunk and aorta as semi-lunar valves open.
4. BEGINNING OF VENTRICULAR DIASTOLE:
Ventricle relax and semi-lunar valves are closed. This cause second heart sound.
5. COMPLETE VENTRICULAR DIASTOLE:
The tricuspid and bicuspid valve open when the pressure in the ventricle fall and blood flow from artia into ventricles. Contraction of heart does not cause this blood flow. It is due to the fact that pressure within the relaxed ventricle is less than that of atria and vein.
PATH OF SIGNAL ARISING FROM SA NODE:-
Sequence of transmission of impulse fron SA Node are as follows:-
1. SA NODE
2. AV NODE
3. BUNDLE OF HIS
4. PURKINJE's FIBRES
CONTRIBUTION OF CARDIAC CYCLE TO METABOLIC HAEMOSTASIS:-
Cardiac cycle performs an essential function of pumping blood in our body.
It sends the oxygenated blood to the body for its metabolism and sends the deoxygenated blood to the lungs for their oxygenation.
PURPOSE OF VALVES:
The main purpose of valve is to prevent the back flow of blood during cardiac cycle.
Major valves assocated with human heart are as follows :-
1. Bicuspid valve - Present between left atrium and left ventricle.
2. Tricuspid valve - Present between right atrium and right ventricle.
3. Semilunar valve - Present at opening of aorta and Pulmonary artery