Cardiovascular System Flashcards
Systemic system
delivery depends on pressure via reducing resistance. The neural system can override the organ system to shunt blood to the brain Ex. during hemorrhage
True/false: blow flow is arranged in series and systemic vasculature is arranged parallel
true
when distances are short AND large surface area for exchange
diffusion
pressure formula
h x p x g
True/False: hydrostatic pressure is caused by effects of gravity on the fluid, so P and h are not proportional and is dependent of the vessel shape.
False: hydrostatic pressure is caused by effects of gravity on the fluid, so P ∞ h and is independent of the vessel shape.
pressure from cardiac pump. This energy moves blood through blood vessels and is dissipated in overcoming the resistance to blood flow offered by the blood vessels and the blood itself
hydrodynamic pressure (blood pressure is static and dynamic)
How do you measure fluid pressure in fluid column?
height difference P2-P1 represents pressure of Hg
formula of flow (darcy’s equation)
Flow = difference of pressure / resistance
What influences blood flow through any vessel?
pressure gradient because blood flows from high to low, in systemic circulation it’s pressure difference between aorta and CVP. Also, resistance which comes from arterioles
What are factors affecting resistance?
viscosity- friction between molecules so that each layer of lamina slows the flow and slowest layer is closest to vessel, vessel length, vessel radius, and if in series or parallel
True or false: viscosity is constant
true, however blood doesn;t count because when the vessel diameter decreases the viscosity decreases because hematocrit decreases ONLY in small vessels such as capillaries (Fahraeus effect)
blood flow into smaller vessels, RBCs bend, spin and align – along with plasma spinning – lowers viscosity in smaller vessels
Axial streaming (Fahreus effect)
How does length of vessel affect flow?
If tube length doubles that the resistance would double and the flow would decrease by 1/2 (flow = 1/L, ex. so if length triples the flow reduces by 1/3)
How does radius affect flow?
In smaller diameter vessel, a given volume of blood comes into contact with more of the surface area of the wall than a larger-radius vessel, resulting in greater resistance with smaller radius.
How are resistance and radius related?
resistance is inversely proportional to 4th power of radius. So doubling the radius reduces resistance to 1/16 (2^4). That’s why contraction of arterioles is most important for regulating flow
What does a closed circulatory system mean?
This means that the total volume of blood (~5 Liters) contained within the heart and vasculature cannot change as it moves through the various classes of vessels in CV system
how are flow and velocity related?
Flow = velocity x area
How do area and velocity affect flow?
if velocity increases then area will decrease this is how flow remains constant from arteries> arterioles> capillaries. Velocity is slowest in the capillaries and area is largest for diffusion purposes.
What does resistance of blood flow depend on?
dimension of vessels
How is resistance different in series vs parallel?
resistance in series is added which increases it. resistance decreases in parallel because you add the reciprocals
When does flow become turbulent?
When pressure increases the flow can exceed critical velocity becoming turbulent
Turbulence due to vessel plague (A), stenotic (B) or leaky heart valves (C)
What are the noises you hear during blood pressure recording?
When cuff is pumped no sound heard, blood flows through creates systolic noise (turbulence), once blood becomes laminar no sound is heard and that’s diastolic
Compliance
volume/pressure, the greater the compliance the greater in change of volume for pressure
