Cardiovascular Homeostasis Flashcards
Describe the pulmonary circulation:
blood pumped from heart to the lung
distance is short
pressure requirements are low (pulmonary artery pressure is low)
Describe the systemic circulation:
blood pumped from the heart to rest of the body
Long distance - large area to cover with extensive vascular network
Pressure requirements are high (aortic pressure is high)
function of the heart?
to pump blood at a pressure high enough that it is able to circulate throughout the entire body and reach all the target organs on time
how is the cardiac cycle accomplished?
through the regulation of pressure and volume within the chambers of the heart over a period of time
what is the cardiac cycle defined as?
defined as the events occurring from the state of one heart beat to the start of another heart beat - a full cycle
what is the cardiac cycle divided into?
into two major events
diastolic phase - relaxation of ventricles
systolic phase - contraction of ventricles
the description of the cardiac cycle is typically related to…?
to events that are occurring in the ventricle (specifically the left ventricles)
describe what happens during the diastolic phase of the cardiac cycle:
relaxation causes drop in ventricular pressure
when ventricular pressure drops lower than atrial pressure - AV valves open
blood fills ventricle
when the blood fills the ventricle in the diastolic phase - where is this blood coming from?
initially filled with blood that has been accumulating inside atria
then by blood from venous side flowing directly through atria into ventricles
and finally by the actual contraction of the atria, hence atrial contraction not entirely important for normal cardiac output
Significance in AF or during exercise
AF?
atrial fibrillation
describe what the aorta is doing during the diastolic phase:
aortic valve is closed because pressure in the aorta is higher than LV
over time, the aortic pressure falls as blood is sent to other parts of body + to the venous side
at the same time, LV pressure due to filling is beginning to rise
what happens during the systolic phase when ventricles contract?
as ventricles start contracting, ventricular pressure also starts rising quickly
this rise quickly exceeds atrial pressure
AV valve will close (prevents backflow)
for a brief period - all valves are closed - aortic valve also closed but pressure here is slowly reducing
cardiac muscle length is same but force exerted due to the stretch will further increase the pressure inside ventricle
When LV pressure exceeds aortic pressure aortic valve opens
Blood flows out
As blood leaves LV, the LV muscles start to shorten and this aids to keep expelling blood from LV
During systolic phase of cardiac cycle, what happens as soon as ventricles start contracting:
the ventricular pressure also starts rising quickly
During systolic phase of cardiac cycle, the rise in ventricular pressure does what quickly?
it will rise very quickly and exceeds atrial pressure and then AV valve will close (prevents backflow)
what happens for a brief period during systolic phase of cardiac cycle?
all valves are closed - aortic valve are closed by pressure here is slowly reducing
During systolic phase of cardiac cycle, what happens as the LV begins to relax?
the pressure drops significantly and blood from aorta will attempt to flow back in but this is when the aortic valve will close and this further propels blood forward into systemic circulation
after LV begins to relax during systolic phase of cardiac cycle, what happens?
LV pressure remains higher than atrial pressure so AV valves still remains closed and here the force exerted by the LV muscles on the blood falls
left atrial pressure indicators used for?
monitoring anaesthesia
During systolic phase of cardiac cycle, what happens when LV pressure falls below atrial pressure?
the AV valves open and filling begins
and this cycle is repeated for every beat
75% of blood entering the atrium flow directly into?
into ventricle
atrial contraction adds what percentage of blood?
adds 25% of volume (hence atrial contraction only essential in exercise)
3 ways when atrial pressure increases:
when atrium contracts
as ventricle contracts - bulging of AV valve into atria
increases slowly as atrium fills with blood from periphery
what can be used to measure LAP?
pulmonary capillary wedge pressure can be used to measure LAP - a surrogate marker
when does aortic pressure increase?
it increases during LV systole - blood ejected out
Increased when aortic valve closes - blood built up from backflow
Falls in ventricular diastole
