Lecture 21 Cardiovascular system 2: Cardiac Function Flashcards
Systole
contraction phase
ventricular systole 1/3 of cycle
Diastole
relaxation phase
ventricular diastole 2/3 of cycle
5 specific phases of cardiac cycle
ventricular filling atrial systole isovolumic contraction ventricular ejection isovolumic relaxation
Ventricular Filling
mid to late diastole low Pressure in ventricle AV valves open, semilunar valves closed ventricular volume increased this is the P wave
Atrial systole
end of ventricular diastole
atrial contraction “tops off” ventricles after passive phase of ventricular filling
AV valves are still open
Isovolumic Contraction
beginning of ventricular systole
pressure rapidly increases as ventricles contract
AV valves close -> 1st hear sound “LUB”
semilunar valves still closed, so volume stays constant as Pressure increases
Volume is maximal
QRS phase
Ventricular Ejection
mid to late systole Pressure increase to maximal semilunar valves open blood ejected to arteries and ventricular volume decreases S-T segment (Plateau)
isovolumic relaxation
beginning of diastole P rapidly decrease AV valves stay closed until ventricular Pressure < atrial Pressure volume is the lowest T wave
Pressure in LV ranges
from about 0 during diastole to 120 mm Hg at peak of systole
Atrial BP in aorta and large arteries ranges
from 80 (diastolic) to 120 mm Hg (systolic) BP is sustained in diastole by closure of semilunar valves and elastic recoil of arteries
Volume in ventricles
is highest at end of diastole
lowest at end of systole
Wiggers cardiac output diagram correlates
electrical events (ECG) pressure changes in atria, ventricles, and aorta, volume and heart volume changes in ventricles heart sounds
Cardiac Output
total blood flow per minute from one ventricle
RV and LV have the same output
CO is totaly blood flow to all tissues of the body (systemic circuit)
increased demand for O2 and nutrients is accommodated by increase in CO
Cardiac output (CO) =
hear rate (HR) X stroke volume (SV)
Stroke Volume
amount of blood ejected from each ventricle
end-diastolic volume (EDV) - end-systolic volume (ESV) = SV
resting values: 130 mL 60mL 70mL
