Lecture 9 - Overview of Circulation Flashcards
Arterial P range
80-120 mmHg
Systemic capillary pressure range
10-35 mmHg
Systemic circulation P at the vena cavae
0 mmHg
Pulmonary systolic P
25 mmHg
Pulmonary diastolic pressure
8 mmHg
What “propels” blood forward during diastole?
Elasticity of arteries
What part of the circulatory system acts as “control conduits” by changing vessel diameter?
Arterioles
The functional portion of the circulatory system where nutrient/waste exchange occurs.
Capillaries
Act as a “blood reservoir”
Veins
Give blood distribution (%) in systemic circulation
64% veins
13% arteries
7% arterioles/capillaries
Give blood distribution (%) in pulmonary circulation
9% lungs
7% heart
Formula for blow flow in circulation.
V=F/A
V-velocity
F-blood flow
A-cross sectional area
Blood flow to tissues is precisely controlled according to tissue needs. This is accomplished by _____.
Changing the diameter of the muscular arterioles
Cardiac output is determined by the sum of all tissue flow/needs. How is this accomplished?
By the heart’s response to tissue needs (primarily through SNS/PNS control)
What are the two major, rapidly occurring mechanisms for increasing pre-load during hypotension?
- constriction of skeletal m. compresses veins (skel m. Pump)
- construction of arterioles
Kidneys increase BP after continued hypoTN and take time to do so
What two variables primarily determine blood flow?
- pressure gradient (P1-P2: between vessel ends)
- resistance (controlled by changing vessel diameter)
Flow through a vessel formula
F=(P1-P2)/R
The two “functional parts” of the circulatory system.
Pulmonary and systemic circulation
Smooth (“streamlined”) blood flow.
laminar
Along what area (center of vessel or outer edges of vessel) is blood flow velocity greater?
center (less turbulent)
This is rough (or “eddy current”) blood flow
turbulent
List some causes of turbulent blood flow:
- vessel length is very long
- blood passes an obstruction/rough surface
- blood must make sharp turn
Turbulent blood flow is measured by what eqiatopm?
Reynold’s number
Turbulent blood flow is directly proportional to what factors?
velocity of flow, vessel diameter, and blood density
Turbulent blood flow is inversely proportional to what factor?
Viscosity (increased viscosity -> more “sticky” -> decreased flow)
What blood component determines blood density?
Red blood cell concentration; protein concentration
What is meant by “viscosity” of blood?
The “stickiness” of blood
The tendency for turbulence is measured by _____.
The Reynold’s number
Turbulence increases with?
velocity, blood density, and vessel diameter
The tendency for turbulence is inversely proportional to?
Blood viscosity
Force exerted by blood against a unit area of vessel wall.
Blood pressure
Pressure difference from systemic arteries to systemic veins
100 mmHg (why important?)
Constriction of blood vessels strongly _____ resistance; this mechanism of constriction occurs through the _______.
increases; sympathetic nervous system
Formula for resistance of vessels in parallel
1/Rtotal=1/R1+1/R2+1/R3…
Formula for resistance of vessels in series:
Rtotal=R1+R2+R3…
Measure of blood viscosity is called the _____
Hematocrit (HCt)
Viscosity is a measure of a fluid’s _____.
Internal resistance
Blood vessels can undergo autoregulation between what arterial pressures?
70-175 mmHg
The factors that determine blood flow resistance.
Radius, viscosity, length
At any time time, our heart contains what % of circulating blood volume?
7%
At any time time, our lungs contain what % of circulating blood volume?
9%
