1. Cell Biology and Physiology Quiz #2 Review
Matthew L. Fowler, Ph.D.
Cell Biology and Physiology Block 4
MT: Application only

2. Review Topics Circulation Biophysics Action Potentials
Frank-Starling Relationship

3. Circulation Biophysics
Cell Biology and Physiology – Quiz #2 Review
Circulation Biophysics

4. Circulation Biophysics
Objectives
Where is the blood?
Blood Dynamics
Blood Pressure
Cardiac Output
Regulation of Cardiac Output
Factors Affecting Blood Flow

5. Where is the blood? Most of the blood is in the systemic circulation
Veins, venules, and venous sinuses
Blood reservoir

6. Blood Dynamics
Active tissues may require 20 to 30 times more blood than when it is at rest.
The heart cannot normally increase its cardiac output to more than ~7 times resting levels.

7. Blood Pressure
Needs to average ~100 mm Hg
Autonomic control

8. Cardiac Output CO = HR (beats/min) x SV (mL) SV ≅ 70 mL/beat
Example: where HR = 80 beats/min CO = 80 beats/min x 70 mL/beat = 5600 mL/min

9. Regulation of Cardiac Output
Cardiac output is determined by peripheral input (venous return)
Large Venous Return  Stretched Heart  More Forceful Contraction  Increased HR
 Venous Return =  HR

10. Blood Flow Flow = CO (mL/min) CO at rest ~5000 mL/min (~5 L/min)
Aortic flow at rest ~5000 mL/min (~5 L/min)
Blood flows from high pressure to low pressure
Down the pressure gradient

11. Flow, Pressure, Resistance
Flow (F) = ΔP/ΔR
ΔP = P1 – P2
P = Force/Area
Pressure is created by the heart at the start of circulation.

12. Pressure Flow (F) = ΔP/ΔR Therefore: ΔP = ΔR x F
A moving fluid has no pressure unless it encounters some resistance

13. Resistance R = 8/π x nl/r4 Factors affecting flow Vessel geometry
Length (l) (this cannot change quickly)
Radius (r)
Fluid viscosity (n)

14. Laminar Flow (Velocity)
Affected by radius and viscosity
 Radius =  Laminar flow

15. Viscosity/Shear and Flow
Affected by layers and contacts
Vessel Wall Contact
Blood contacts wall
Velocity along vessel walls is 0
Layer Contact
Less contact with layers at center
Velocity max at center
Remember: Velocity = Flow

16. Cause of Viscosity
High viscosity of blood is almost entirely related to the hematocrit (RBCs)

17. Resistance in Series Resistance in series is additive
Rtotal = R1 + R2 + …

18. Resistance in Parallel
Resistance in parallels is inversely summed
Rtotal = 1/R1 + 1/R2 + …

19. Circuit Resistance
Resistance in parallel will always be less than resistance in a series.
Fact: Total resistance for all vessels is far less than the resistance of any single blood vessel
Implications: Varicose veins, amputation, thrombosis…all increase Resistance

20. Directional Flow of Blood

21. Total Flow and Velocity
Total vessel cross-sectional area changes throughout the circulation, however, overall blood flow must remain the same (~5L/min)
Mathematically, the velocity of blood flow must change in order to maintain constant flow (~5L/min) in each segment.
Velocity in the capillaries is low to maximize nutrient, waste, and gas exchange

22. Turbulent Flow Increases resistance Modifiable via velocity
Results in increases in pressure to overcome
Modifiable via velocity
Velocity is modified via pressure
low pressure = low velocity = laminar flow

23. Turbulent Flow in the Vessels
Turbulence causes the parabolic profile of the linear velocity across the diameter of a cylinder to become blunted (blue arrow) compared to normal laminar flow (Vmax)
Sounds
Murmurs
Sounds of Korotkoff