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Asynchronous cardiac events
Cardiac Dynamics
Atria contract asynchronously
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Why?
Right side first
Left side second
Volumes are EQUAL on both sides.
Ventricles contract asynchronously
- Left side first
- right side second
Right side (pulmonary valve) opens first
Left side (aortic valve) opens second
Why?
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It turned out that the right atrium contracts
slightly earlier due to electrical signals from the
sinoatrial node reaching the right side first.
left ventricle provides a much stronger
contraction and has morework to do,since it is
sending out the blood to the systemic circuit,
while the right goes out to the pulmonary circuit.
CONFUSING* & DISTORTING FACTORS
All entering & leaving vessels attach towards one end of the heart, so these two
circulations - for the lungs & the systemic - are close together
The left ventricle has to do more work than the right (more territory to send
blood to), so it is larger and thicker-walled, resulting in a heart that tips down
towards the left, and is rotated.
The rotation causes the left of the heart to lie towards the back (posterior),
whereas the right atrium and right ventricle lie frontwards or anterior.
The blood-flows out of the heart are not in parallel, but are angled to cross
each other.
The two circulations are oriented in the body differently - for the lungs it is
crosswise in the chest (left & right); for the systemic, it is lengthwise to upper &
lower body. These patterns affect how the major vessels come off the heart.
The two sides of the heart are working simultaneously
The 'arterial' blood leaving for the lungs goes first into a trunk, not an artery
Confusing* - not for the heart: It’s had millions of years to optimise its form