Hemodynamics Flashcards
Describe series arrangement
series arrangement is a closed system loop, seen in pulmonary circulation. Lower pressure. Total resistance in series of vessels is higher than the resistance of any individual vessel (largest proportion of total resistance is in arterioles)
Rt=Rartery+Rarteriole+Rcapillaries
Therefore, the blood flow is constant but the pressure drops
Describe parallel arrangement
found is systemic circulation. Higher pressure, decreased total vascular resistance. The total resistance is lower than any individual resistance.
1/Rt=1/R1+1/R2+1/R3
Oxygenated blood visits only one organ system before returning to the heart. Allows for fine tuning the blood supply depending on the demand of the organ.
The flow equation
Flow=difference in pressure/resistance to flow
Analogous to Ohm’s Law (V=IR)
Flow vs. Velocity
Flow is constant throughout the system and reflects in cardiac output. Velocity is a distance per unit time (cm/sec) and reflected in v=Q/A (velocity=flow/area)
Velocity is highest in aorta, lowest in the capillaries
cardiac output
the volume of blood pumped per minute by the heart (about 5 L per minute) -> corresponds to the total flow in the cardiovascular system.
CO=(mean arterial pressure - venous pressure)/total peripheral resistance
Poiseulle’s Law
Vascular resistance=decreases blood flow
Blood viscosity=decreases blood flow
Vessel length=longer decreases blood flow
Vessel radius = MOST IMPORATANT. r^4 effect. The greater the radius, the greater the blood flow.
Explain how pulsatile flow of blood produced by the heart is converted into steady flow in the capillary beds
Laminar flow -> most efficient, velocity fastest at the center, zero at the edges.
Turbulent flow -> irregular, promotes shearing forces. (can be a result of artherosclerotic plaque)
Pulsatile flow -> flow is continous in the capillaries, no pulse variation so its a steady flow. The smaller they get, the less variation there is.
Define vascular compliance
C=V(change in volume)/P(change in pressure)
REPRESENTS THE ELASTIC PROPERTIES OF ARTERIES
Transports pulsatile flow into continous flow. Veins are more compliant than arteries. Lose compliance w/ time=ARTERIOSCLEROSIS
LaPlace’s Law
Tension (or wall stress)=(transmural pressure X radius)/wall thickness.
Basically this means that greater tension=increased radius=less thickness!
Tension increases as radius and pressure increase.
The larger the vessel radius, the larger the wall tension required to withstand a given internal fluid pressure.
Fick’s Principle
VO2=the rate at which oxygen is consumed in the body, basically calciulating by Q(flow) multiplies by (initial-final amount) of oxygen in the blood
Starling’s Equation
Filtration and reabsorption - two opposing forces that determine solume movement. Hydrostatic pressre and oncotic pressure drive transcapillary flux.
Hydrostating pressure=fluid pressure. Favors filtration
Oncotic pressure favors reabsorption (more protein in the blood than interstitial fluid)
Cardiac Output
Heart rate x SV (amount of blood ventrible ejects w/ each beat)
Afterload
the pressure that the ventricles are pushing against to eject the blood. On the left side of the heart, this is aortic pressure
Frank Starling Relationship
An increased preload = increased contraction. The greater the end diastolic volume, the greater the volume of blood ejected during systolic contraction is.
Its basically a nice little length tension relationship. Peak tension of the sarcomere is somewhere between lengths of 2.2 to 2.3 mM. More ability to crossbridge between actin and myosin.
Inotropy
The strength of contraction
