Key Definitions Flashcards
What is the stroke volume?
The volume of blood ejected from each ventricle during systole
What is cardiac output?
The volume of blood each ventricle pumps as a function of time i.e. litres per minute
Which term is given to the total resistance to flow in systemic blood vessels from aorta to vena cava?
Total peripheral resistance
What is preload?
The volume of blood in the left ventricle which stretches the cardiac myocytes before contraction (basically how much blood is in the ventricle before it pumps).
Aortic stenosis = increase in preload
Dilate veins = decrease in preload
What is afterload?
The pressure the left ventricle must overcome to eject blood during contraction.
Dilated arteries = decrease in afterload
What is contractility?
The force of contraction and the change in fibre length i.e. how hard the heart pumps.
Which property does the myocardial tissue have that enables it to recover normal shape after systolic stress?
Elasticity
Which term describes how easily the heart chamber expands when filled with blood volume?
Compliance
Give Starling’s Law.
The force of contrition is proportional to the end disastolic length of cardiac muscle fibre i.e. the more the ventricle fills, the harder it contracts.
increased venous return > increased end diastolic volume > increased preload > increased sarcomere stretch > increased force of contraction > increased stroke volume + force of contractions
What is intrinsic autoregulation?
When the arterioles either vasoconstrict or vasodilate in response to changes in resistance. Has the aim of maintaining constant blood flow.
What is myogenic autoregulation?
When increased blood flow stretches vascular smooth muscle, the muscle constricts until the diameter is normalised.
Which term is given to an increase in blood flow?
Hyperemia
Which term is given to an increase in blood flow when metabolic activity is increased?
Active hyperemia
