L20 - Cardiovascular System 3 Flashcards
Why are valves integral to healthy heart function?
ensure unidirectional flow
open / close passively
What causes the opening and closing of valves in the heart?
pressure differences between components of the heart
When do the atrioventricular valves close?
when the ventricles start to contract
When do the semilunar valves close?
when the ventricles relax
When do valves close in general?
when pressure in current compartment becomes greater than pressure in previous compartment
What are the sounds of the heart? What causes these sounds?
sound 1 and sound 2
occur when heart valves close (sudden turbulent flow and vibration)
What is sound 1 caused by?
closure of atrioventricular (AV) valves (contraction)
What is sound 2 caused by?
closure of semilunar valves (relaxation)
What will cause the AV valves to close? (contraction or relaxation of ventricles / greater pressure in ventricles than atria or greater pressure in atria than ventricles)
pressure in ventricles become greater than pressure in atria
ventricles start contracting
What affects the movement of blood?
heart - source of energy gravity skeletal muscle diaphragm movements elastic tissue
What is systolic BP?
max pressure exerted in arteries when blood is ejected into them during systole (heart contracting phase)
What is diastolic BP?
min pressure within arteries when blood draining off into remainder of vessels during diastole (heart relaxing / filling phase)
What is pulse pressure?
a measure of strength of pressure wave
difference between systolic and diastolic BP
What is mean arterial pressure?
average pressure responsible for driving blood forward into tissues throughout cardiac cycle
Why is regulation of MAP important?
essential for efficient function and life
low BP = dizziness, organ failure
high BP = stroke, aneurysm
What determines MAP?
how much blood is pumped out per unit time
how difficult / easy is it for the blood to move through the system
What determines how much blood is pumped out per unit time?
stroke volume x heart rate = cardiac output
What determines how difficult / easy it is for the blood to move through the system?
total peripheral resistance (TPR) = resistance of the peripheral circulation
What is MAP proportional to?
cardiac output x total peripheral resistance
How is stroke volume calculated? How can stroke volume be increased?
end diastolic volume minus end systolic volume
increasing end diastolic volume or decreasing systolic volume via more forceful contractions resulting in less blood leftover in the heart
What is cardiac output?
volume of blood pumped by one ventricle in a given period of time
What is stroke volume?
amount of blood pumped by one ventricle during a contraction
What is stroke volume? What affects stroke volume?
force of ventricular contraction
affected by:
length of muscle fiber (volume of blood in chamber at start of contraction)
contractility of heart (neural influences)
What is the stretch-force relationship in heart? (Frank-Starling Law)
as more blood enters the heart, length of muscle fibres stretches towards optimum length resulting in increased contractile force
