CARDIAC CYCLE IN MAMMALIANS
The bigger organisms, the smaller surface area compared to their volume. Therefore, if they rely only on diffusion, the rate of it will be extremely slow to sustain the life of their cells. Single or open circulatory system is not the system we need - as blood will move too slowly at a very low pressure, it wouldn't be able to provide efficient, rapid blood supply of - oxygen, nutrients and vital substances to the located far away much more complex systems that depend on each other for the maintaining the body homeostasis. Then - glucose and oxygen levels will be insufficient - the organism will be unable to produce as much ATP at it needs for crucial processes anabolism - it will simply die. Therefore, in order to speed up diffusion, larger organisms, as well as humans, have developed specialized organs of gas exchange and blood transport system.
The existence of strongly determinated and structured cardio vascular systems in mammalinas is the key for their survival. Double circulation is only way of blood transport that can effectively deal with the problems listed above.
Double or closed circulation means that the blood flows through specialized tubes called blood vessels but also in a complete cardiac cycle it is pumped by the heart twice. With one complete cardiac cycle two things are achieved:
Blood is pumped by the heart to the lungs. There, it is turned from carbon dioxide rich into oxygen rich - pulmonary circulation. The oxygenated blood is then turned back to the heart and pumped again but now at a very higher pressure to the whole body - systematic circulation.
Cardiac cycle consists of three main phases - atrium systole - 0.1 s, ventricle systole - 0.3s, diastole - 0.4s. In other words cardiac...