1.2 the Circulatory System (Circulation of Blood)
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Transcript of 1.2 the Circulatory System (Circulation of Blood)
THE CIRCULATION OF BLOOD
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
Complete double circulation consists of 2 sub-circuits:
PULMONARY CIRCULATION Heart Lung Heart
SYSTEMIC CIRCULATIONHeart Rest of the body Heart
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
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
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
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
Neuromuscular Cells
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
The electrical pathway
STEP 1
The S-A node creates an electrical signal
STEP 2
The movement of electricity stimulates the atria to
contract, which pushes blood into the ventricles.
STEP 3
The electrical signal reaches the A-V node. There, the signal
pauses to give the ventricles time to fill with blood
STEP 4
The movement of electricity causes the ventricles to contract and push blood out to your lungs
and body
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Diastole : Ventricles relax, atria contract Systole: Ventricles contract, atria relax
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Blood pressure & the regulatory system
• Blood pressure:– The force that the blood exerts on the wall
of blood vessels–Measured in mm Hg
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
Tr.Rez@SB2014