Lecture 10 - Overview of Circulation Flashcards
What is the systolic and diastolic pressure in arteries?
Systolic: 120mmHg
Diastolic: 80mmHg
What is the systemic capillary pressure?
10-35 mmHg
What is the pressure at the vena cava?
0 mmHg
What is the systolic and diastolic pressure in the pulmonary arteries?
Systolic: 25 mmHg
Diastolic: 8 mmHg
What is phasic pressure?
- occurs in arteries
- variations in pressure that occurs due to systole and diastole
What is mean arterial pressure?
-time weighted average of the pressure in the arteries
What portion of the total blood is found in each part of the circulatory system?
Systemic circulation: 84%
- veins: 64%
- arteries: 13%
- arterioles and capillaries: 7%
Heart/Lungs: 16%
- lungs: 9%
- heart: 7%
What is the formula for the velocity of blood flow?
V = F / A
V - velocity of blood flow
F - volume of blood flow
A - vascular cross sectional area
What are the three basic functional principles of the circulatory system?
- RATE of blood flow to each tissue is always precisely CONTROLLED in relation to the TISSUE NEED
- the cardiac OUTPUT is controlled mainly by the SUM of all the LOCAL tissue FLOWS
- ARTERIAL PRESSURE regulation is generally INDEPENDENT of either local blood FLOW control or cardiac OUTPUT control
What is pressure gradient?
-pressure difference between the two ends of a vessel
What is resistance?
-impediment to blood flow through a vessel
How is flow through a vessel calculated?
-using Ohm’s law (Poiseuille equation)
- F = ΔP / R
- ΔP = (P1 - P2)
F - flow in mL/min
P1 - upstream pressure
P2 - pressure at end of segment
R - resistance between P1 and P2
What is the overall blood flow of an adult at rest?
- 5000 mL/min
- also referred to as cardiac output
What is laminar flow and when does it occur?
-also called streamline flow
- blood flows at a steady rate in layers (streamlines)
- blood flows slowest in outer layers and fastest at inner layers
- occurs in long, smooth vessels
What is turbulent flow and when does it occur?
- flow is non-layered
- creates a murmur
- higher resistance
Occurs when blood…:
- flow is too great
- passes an obstruction
- makes a sharp turn
- passes over a rough surface
Turbulent flow is __________ (directly/inversely) proportionate to blood flow, __________ proportionate to vessel diameter, __________ proportionate to density, and __________ proportionate to viscosity.
Directly; directly; directly; indirectly
Turbulent flow will occur somewhere in some regions of the vessel when Reynold’s number is above __________ and will occur throughout the vessel when Reynold’s number is above __________.
200-400; 2000
What is blood pressure the measure of?
-the force exerted by blood against an area of the wall of a blood vessel
What is the formula for resistance and what is the unit of resistance?
-R = ΔP / F
or
-R = 8 η l / (π x r^4)
R - resistance ΔP - change in pressure (upstream - downstream) η - viscosity (1/30) l - vessel length r - vessel radius
Unit:
1 PRU = 1 mmHg / 1 mL/sec
Resistance increases when blood flow __________, upstream pressure __________, and down stream pressure __________.
Decreases; increases; decreases
Resistance decreases when blood flow __________, upstream pressure __________, and down stream pressure __________.
Increases; decreases; increases
What is conductance?
- the measure of blood flow through a vessel for a given pressure difference
- calculated using 1 / resistance
Vessels arranged in parallel have a (greater/lesser) __________ resistance than individual vessels.
Lesser
What is viscosity? Describe the viscosity of blood.
-measure of a fluids internal resistance
- viscosity of blood is 3x that of water
- major factor is hematocrit (~42% in men and ~38 in women)
- viscosity of plasma is 1.5x that of water
What is autoregulation?
- the ability of vessels to adjust vascular resistance to maintain blood flow through various blood pressures
- occurs between blood pressures of 75-175 mmHg
What happens when arterial blood pressure is less than 100?
- heart pumps with increase force
- constriction of venous reservoirs
- constrict arterioles
- kidneys may play a role