The Cardiac Cycle Flashcards
Broken down into 0.8s - now
What happens in diastole (relaxation)
What happens in atrial systole (contraction)
What comes after atrial systole
Where does the ‘lub’ in the lub dub sound come
Lub = as the blood is forced against the atrioventricular valves as the ventricles contract
Where does the ‘dub’ in the ‘lub dub’ sound come from
dub = as a backfliw of blood closes the semilunar valves in the aorta & pulmonary artery as the ventricles relax
How does the heart act as a natural pacemaker
Heart SAN AVN action steps
What happens in terms of the SAN during atrial systole
The SAN on the right atruum sends a wave of electrical activity (depolarisation) through the atria
This causes atria walls to contract
Blood is forced out through the bicuspid and tricuspid valves into the ventricles
What happens in ventricular systole in terms of electrical excitation
The AVN picks up the SAN wave & sends its own depolarisation wave down the His Bundle & Purkinje fibres -> causing the ventricular walls to contract
- blood = forced out of the aorta + pulmonary valves (semi-lunar)
Advantage of increase in cardiac output in pregnant mothers
- delivers more blood to maternal cells /tissues
- delivers more oxygen to feral cells / tissues
Meets the need for higher metabolic rate of mother
Explain how the different affinities of maternal & feral haemoglobin enable transfer of oxygen from maternal circulation to the fetus
Low pO2 in placenta
But @ same pO2, foetal hb has a higher affinity for oxygen
So oxygen dissociates from maternal Hb and diffuses to the feta l blood from the maternal blood
