Question

heart chapter notes working layer funtion cycle and how it pumps blood

Answer 1

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Heart is a muscular organ of your body which is in the left side of your body. It's size is almost equal to that of our fist.
Working of heart
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The deoxygenated blood from whole body comes to heart from the Vena cava ( Large Vein) in the Right Artrium From Right Artrium it goes to Right Ventricle.Now, Right Ventricle pump deoxygenated blood to the Lungs through the Pulmonary Artery( Artery connected to the Lungs). In lungs the blood get oxygenated.This Oxygenated blood comes back into Heart in the Left Atrium through Pulmonary Vein ( The Vein which is connected to the lung).From Left Atrium it goes to the left Ventricle. Now, Left ventricle pumps the oxygenated blood to whole body through Arota(Largest Artery ).


The Rhythmic contraction and relaxation of the Heart is due to the fact that when Atrium of both sides contract at that time the ventricle of both sides releax or vice versa.

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Answer 2

The cardiac cycle refers to series of electrical and mechanical events that occur cyclically. Duration of one cardiac cycle is 0 .8 s (at a heart rate of 75/ Minutes ).
it includes
atrial systole _ 0.1s
atrial diastole _0.7s
ventricular systole _0.3s
ventricular diastole_0.5s
Isovolumetric contraction phase
In the beginning of ventricular contraction ,the semilunar valves are closed but the AV valves are still open. As the ventricles start contracting, the intra ventricular pressure increases and causes the closing of AV valves. The ventricle now become a closed chamber.Here pressure increases but volume does not change.
RAPID EJECTION PHASE
When the pressure in the ventricle exceeds aorta ,aortic valve opens and ejection of blood in to the aorta occurs.Which last for 0.1s.
REDUCED EJECTION PHASE
Ventricular pressure is slightly lower than that of aorta , but the blood flow continues due to momentum. This lasts for 0.15s
PROTODIASTOLE
This phase lasts for only 0.04 sec. During this phase ventricles start relaxing,but the aortic valve is open blood from the aorta tends to flow backward , causes the aortic valve to close sharply.
ISOVOLUMETRIC RELAXATION PHASE
Starts with the closure of semilunar valves. The ventricle is a closed chamber , which is relaxing .The intraventricular pressure falls rapidly when it is below atrial pressure ,the AV valves open. Last for 0.06s.
RAPID FILLING PHASE
As the AV valves open blood rushes from atrium to ventricle. Last for 0.1s.
DIASTASIS
After initial rapid filling ,the blood flow fill gradually decreases. This phase lasts for 0.2s.

ATRIAL SYSTOLE
Lasts for 0.1s. The ventricular flow increases due to atrial systole.