Heart AS biology

heart and how it works. i made these notes after referring to my 4 textbooks and number of websites. hope you find it usefull. 

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  • Created by: Minko Syd
  • Created on: 05-12-11 16:37
Preview of Heart AS biology

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Heart as a pump
It's the organ that moved the blood around the body
Its four chambered muscular and sits in the chest protected by the ribs and the
sternum. Its contained in a tightly fitting membrane called the pericardium.
Its divided into four chambers, right side is separate from the left by a septum.
Two upper chambers are thin walled and are called atria. They receive blood into
the heart.
The two lower chambers are thick walled ventricles which blood pumped out of
the heart.
Left ventricle is thicker than right ventricle.
The heart muscle receives oxygenated blood via coronary arteries.
The valves of the heart prevent backflow of the blood, thereby maintaining
direction of flow through the heart.
Atrioventricular valves prevent backflow from ventricles to atria.
Semi lunar valves prevent back from aorta and pulmonary artery into ventricles.

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Cardiac Cycle
1. Right atrium receives blood from the veins. Pressure builds up, and
tricuspid valve opens and blood begins to seep into ventricle. When atrium
is full its contracts, forcing the blood into the ventricle. (atrium has thin
walls because it receives blood at low pressure)
2. The right ventricle is filled with blood, then the ventricles contract. Its
walls produce pressure and force the blood out of the pulmonary arteries.
This carries the deoxygenated blood to the capillary beds of the lungs.…read more

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Atrium has thin walls because it receives blood at low pressure)
The tendentious cords make sure the valves are not inside out by the great
pressure when ventricles contract
The wall of the left side of the heart is thicker than the right, because right side
pumps blood to the lungs. Which is relatively close to the heart,
Semilunar valves prevent the backflow from aorta to ventricle.…read more

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The contraction of the heart is called a systole
Systole is divided into atrial systole, when the atria contact forcing blood into
ventricles, and ventricular systole when the ventricles contract.
Between contractions the heart relaxes and the atria fill with blood. This stage is
called a diastole.…read more

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Pressure graph
At the start of the cycle, the pressure in the atrium and ventricle is almost zero
as the muscles are relaxed.
As the muscles of the atrium contract, the pressure rises. The pressure also
rises slightly during atrial systole as the blood is pushed through the
atrioventricular valves into the ventricle.
the atrium now relaxes and the pressure falls. The pressure in the atrium
gradually rises again as blood is pushed into the atrium from the pulmonary
At A.…read more

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Blood pressure
Blood pressure is a measure of hydrostatic force of the blood against the walls of
blood vessel.
There is friction between the blood and the walls of vessels. This friction is called
the peripheral resistance and it slows down the flow of blood.
Little pressure is lost in arteries because they are wide.
The arterioles and capillaries offer a greater surface area, resisting more flow,
slows down the blood, the peripheral resistance increases and blood pressure
falls.…read more

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Formation of tissue fluid
the formation of tissue fluid assist in delivery of nutirents to all cells and
removal of waste products.
the hydrostatic pressure generated drives out fluid from the capillaries
arterial end of a capillary is under high pressure. this forces the fluid and small
molecules in plasma through capillary walls into the intercellular spaces forming
tissue fluid.
the capillary walls prevent blood cells and larger plasma proteins from passing
through, so these stay inside capillaries.…read more

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