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

Tr.Rez@SB2014

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)

Tr.Rez@SB2014

Tr.Rez@SB2014

Tr.Rez@SB2014