Cardiovascular Physiology 1

Circulatory system as a circuit

systemic circuit

pulmonic circuit

Physical characteristics of blood

hematocrit

blood viscosity ¹

hematocrit and plasma proteins

3× at normal hematocrit, 10× at 70

in small vessels

Fahraeus-Lindqvist effect

rouleux formation

vessel clogging

plasma

about 7% protein

albumins

globulins

fibrinogen

Blood flow

Ohm’s law ²

Q = DP/R

laminar flow

parabolic velocity profile

turbulent flow

additional details on turbulent flow from Guyton’s Physiology

measurement of flow

mL/min

Blood pressure ⁵

an account of pressure measurement written in 1733

standard units

mm Hg

1 mm Hg = 1.36 cm H₂O

Resistance to blood flow

R = DP/Q

1 PRU = (1 mm Hg)/(1 mL/sec)

R (in dyne sec/cm⁵) = (1333 × mm Hg)/(mL/sec)

total pulmonary resistance

Conductance

measure of blood flow for a given DP

conductance = 1/R

effect of vascular diameter

conductance µ diameter⁴

Poiseuille's law

expresses the relationship of all factors in total blood flow ³

mean velocity v = (DPr²)/(8 hl)

Q = vpr²

substitute v, and Q = ( pDPr⁴)/(8 hl)

solve for R

resistance of vessels in series:  R_total = R₁ + R₂ + R₃ + ...

resistance in parallel:  start with conductances

C_total = C₁ + C₂ + C₃ + ...

Vascular distensibility

distensibility = (increase in volume)/((increase in pressure)×(original volume))

veins vs. arteries

Vascular compliance

compliance = (increase in volume)/(increase in pressure)

note that a vessel with a greater original volume will be more compliant

Cardiac cycle

systole and diastole

relationship of the ECG ⁴ to the cardiac cycle

atria as pumps:  a, c , and v waves

ventricles as pumps

ventricular filling

diastasis

isovolumic contraction

period of ejection

isovolumic relaxation

stroke volume output

role of preload and afterload

Cardiac output

cardiac index

metabolism and exercise

age

Regulation of cardiac output

control of cardiac output by venous return

permissive role of heart

sympathetic stimulation

role of total peripheral resistance

Go to beginning

Links

• Referenced sites


• ¹ A quick review of the physics of viscosity



• ² The background is ugly, but here is the physics of Ohm’s law;
  and a Java applet demonstating Ohm’s law



• ³ The physics of blood flow in small vessels;
  a series of slides on fluid dynamics



• ⁴ The 12-lead ECG pages



• ⁵ A very brief history of blood pressure measurement
  NIH and NHLBI have made available the JNC 7 Express publication on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (2003).
  In addition, there is a Physician Reference Card



• Other sites


• Cardiac images



• Cardiology links for just about anything you might want to know



• Various cardiac values; follow the arrows for other pages