Circulation 1 and 2 Flashcards
Which cardiac artery is most important and why?
Left anterior descending artery b/c it feeds blood to the majority of the front wall of the heart (feeds a much greater area than the other coronary arteries)
Stroke Volume Formula
SV = Starting Volume - Ending Volume
= End Diastolic Volume - End Systolic Volume
= EDV - ESV
* Answer should be positive
What is Ejection Fraction and how is it calculated?
Percent of blood ejected each heartbeat
EF = (EDV - ESV)/EDV * 100
= SV/EDV * 100
* Normally 55-70%
What is considered high arterial pressure? What is considered normal arterial pressure?
High: >160 mmHg
Normal: 80 - 160 mmHg (Varies based on age, exercise, etc)
Calculating Cardiac External Work
Cardiac Work = Pressure x Volume
where
Pressure = Mean Arterial Pressure = 2/3 diastolic + 1/3 systolic
Volume = Stroke Volume = EDV - ESV
Diastolic Pressure vs Systolic Pressure
Diastolic is pressure between beats (resting)
Systolic is during contraction
What are the units of cardiac external work (stroke work)
Work = Pressure x Volume
= mmHg x ml
= N/m^2 x m^3
= Joules (J)
Cardiac Power Formula
Power = Cardiac External Work/Time
= Joules x Beats/Second
Poiseuille’s Law
Blood flow depends on the pressure difference ΔP, length l, viscosity n, and very strongly on the radius
Q (blood flow) = πΔPr^4/8nl
Resistance to Blood Flow (Formula)
R = 8Ln/πr^4
Resistance in Series vs in Parallel
Series: Rtotal = R1 + R2 + R3…
Parallel: 1/R1 + 1/R2 + …
Why is blood doping bad?
Increases the viscosity of the blood which leads to increase chances of heart disease/stroke/blood clots
What are the 3 methods of measuring cardiac output?
Fick’s Method, Indicator Dilution, Echocardiography
Relationship between blood pressure, volume, and blood flow
Δ𝑃 = (Blood flow) * Resistance
- Increase in blood pressure means a proportional increase in blood flow
- Increase in blood volume proportionally increases blood pressure
Name the transition of blood vessels from artery to vein
artery, arteriole, capillary, venule, vein
Precapillary sphincters
Contractile band of cells at the point where each capillary branches from the arteriole
- Vasomotion - cyclical opening and closing of precapillary sphincters
Vasoconstriction vs Vasodilation
Constriction - contraction of smooth muscle to decrease lumen diameter
Dilation - relaxation of vascular smooth muscle to increase lumen diameter
What are the 3 control types?
Local control - mechanisms to regulate blood flow to specific tissues (local, acute or long term)
Humoral - control by substances secreted or absorbed into the body fluids (local or systemic, acute or intermediate duration)
Neural - control of circulation by autonomic nervous system (systemic, acute to long term)
Types of Local Control
Acute Control
- Metabolic Control: regulate blood flow to meet metabolic demands of a tissue
- Autoregulation: regulate blood flow during arterial pressure changes
- Endothelium-derived Factors
Long-term Control
- Angiogenesis: formation of new blood vessels
Metabolic Acute Local Control Regulation Types
Active Hyperemia - local blood flow temporarily increases to compensate for an increase in tissue metabolism or a decrease in O2 availability
Reactive Hyperemia - temporary elevation of blood flow to repay the tissue oxygen deficit after a period of reduced or blocked blood flow
Is adenosine a vasodilator or vasoconstrictor
vasodilator (important especially in the heart)
What is the Oxygen demand theory
- Metabolic mechanism for acute local regulation of blood flow
- The degree of vessel contraction depends on the availability of oxygen and nutrients to vascular smooth muscle
What is autoregulation
- Acute local regulation of blood flow due to blood pressure change
- allows blood flow to a tissue/vessel to remain constant despite variations in arterial pressure
- Myogenic and Metabolic mechanism
What are the 2 main endothelium-derived factors
Nitric Oxide (vasodilator) and Endothelin (vasoconstrictor)
