heart and cardiac cycle Flashcards
what does the heart consist of
two muscular pumps
what does the right side of the heart do
pumps deoxygenated blood to the lungs
what does the left side do
pumps oxygenated blood to the whole body
adaption of the left ventricle
thicker and has more muscular walls than the right ventricle, this is because it needs to contract powerfully to pump blood all the way round the body
the right side only needs to get blood to the lungs which are near
ventricle adaption
thicker walls than the aria
this is because they have to push blood out of the heart whereas the atria just needs to push blood a short distances into the ventricles
atroventricular values
link the atria to the ventricles and stop blood flowing back into the atria when the ventricles contract
semi-lunar values
link the ventricles to the pulmonary artery and aorta, and stop blood flowing back into the heart after the ventricles contract
cords
attach the atrioventricular values to the ventricles to stop them being forced up into the atria when the ventricles contract
how do the vales work
vales only open one way
whether they’re open or closed depends on the relative pressure of the heart chambers
if higher pressure behind a value, it’s forced open but if pressure is higher in front of the value it’s forced shut
this means blood only flows in one direction through the heart
what does the cardiac cycle do
pumps blood around the body
- ongoing sequence of contraction and relaxation of the atria and ventricles that keeps blood continuously circulating
volume of atria and ventricles change
pressure changes also occur
first stage of cardiac cycle
the ventricles relax
atria contract - decreasing the volume of the chambers and increasing the pressure inside the chambers
this pushes the blood into the ventricles
there’s a slight increase in ventricular pressure and chamber volume as the ventricles receive the ejected blood from the contracted atria
second stage of cardiac cycle
the atria relaxes
the ventricles contract - increasing the pressure
the pressure becomes higher in the ventricles than the atria, which forces the AV values shut to prevent back-flow
the pressure in the ventricles is also higher than in the aorta and pulmonary artery, which forces open the SL values and blood is forced out into these arteries
third stage of cardiac cycle
the ventricles and the atria both relax
the higher pressure in the pulmonary artery and aorta closes the SL vales
Blood returns to the heart and the atria fill again due to the higher pressure in the vena cava and pulmonary vein
this causes increase of pressure in the atria
ventricles continue to relax, their pressure falls below the pressure of the atria so the AV values open
This allows blood to flow passively into the ventricles from the atria
the atria contract and process begins again
cardiac cycle graph
pls learn
