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THE CIRCULATION OF BLOOD
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The Circulation of Blood
Human have a closed double circulatory system
CLOSEDblood contained within the heart &
blood vessels
DOUBLE CIRCULATIONbecause blood passes through the
heart twice for each complete circuit of the body
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Complete double circulation consists of 2 sub-circuits:
PULMONARY CIRCULATION Heart Lung Heart
SYSTEMIC CIRCULATIONHeart Rest of the body Heart
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Flow of blood circulation is maintained by:
1) The pumping action of the heart
the ventricles generate sufficient pressure to propel blood through the
arteries into the capillaries
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Flow of blood circulation is maintained by:
2) Contractions and relaxations of skeletal muscles
around the veins during normal body movements propel blood in the veins
to flow towards the heart
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Flow of blood circulation is maintained by:
3) Inhalation movements
during inspiration the thoracic pressure is reduced, and this aids in
drawing blood back to the heart
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MYOGENIC
can contract and relax on its own
does not need nerves to stimulate
Small groups of specialized neuromuscular cells initiate
& conduct impulses
Causing coordinated & synchronized contraction of
the heart muscle
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Neuromuscular Cells
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Cardiac Cycle
• During each heartbeat (cardiac cycle), the heart contracts & the relaxes– Systole: ventricles contract, atria relax (lub sound)– Diastole: ventricles relax, atria contract (dub
sound) Average normal heartbeat is about 72 times
per minute
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The electrical pathway
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STEP 1
The S-A node creates an electrical signal
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STEP 2
The movement of electricity stimulates the atria to
contract, which pushes blood into the ventricles.
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STEP 3
The electrical signal reaches the A-V node. There, the signal
pauses to give the ventricles time to fill with blood
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STEP 4
The movement of electricity causes the ventricles to contract and push blood out to your lungs
and body
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Tr.Rez@SB2014
Diastole : Ventricles relax, atria contract Systole: Ventricles contract, atria relax
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Tr.Rez@SB2014
Blood pressure & the regulatory system
• Blood pressure:– The force that the blood exerts on the wall
of blood vessels–Measured in mm Hg
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Blood pressure & the regulatory system
• Blood pressure:– Typical BP 120/80 mm Hg–1st number represent systole (ventricle
contract)–2nd number represent diastole (ventricle
relax)
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Tr.Rez@SB2014
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Tr.Rez@SB2014
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Tr.Rez@SB2014
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