Lecture 10: Cardiovascular System, Hemodynamics Flashcards
Heart valve flow order
R: tricuspid (AV) -> semilunar pulmonary
L: mitral (AV) (aka bicuspid) -> semilunar aortic
L vs R ventricle
L ventricle wall is thicker than the right due to greater systemic resistance vs pulmonary
Valve opening/closing
Opening/closing depends on ΔP between areas; valves themselves have little resistance. Creates unidirectional flow. Leakage = incompetent valves
Types of CV vessels
- Large artery
- Arteriole
- Capillary
- Venule
- Vein
Large artery
Low resistance conducting vessel; elastic/pressure reservoir
Arteriole
Primary effector of peripheral resistance to control blood distribution via dilation/constriction
Capillary
Highest total cross-sectional area and smallest individual radius. Fluid/gas/nutrient exchange; uptake of waste/secreted products
Venule
Migration site for WBCs, capacitance vessels; high compliance
Vein
Low R high capacitance vessels; high compliance
Compliance
ΔV / ΔP; defines change in volume for a given change in pressure.
Windkessel effect
Refers to the elastic pressure reservoir property of the aorta. During ejection the aorta stretches out as flow in > runoff. When the heart relaxes, runoff continues and the aorta shrinks.
Hydrostatic pressure
P = ρgh
Weight of water column (note the static part)
Lateral pressure
Outward pressure of MOVING fluid
Laminar vs turbulent flow
Laminar flow is smooth and ordered, turbulent is chaotic. Turbulent flow is what produces sounds (blood colliding w/ vessel walls)
Flow equation
Q = ΔP / R
For CVS, CO = P_aorta - P_Ratrium / TPR
Resistance of a vessel
R = 8ηL / πr^4
Most important is radius^4; other factors don’t change much physiologically
Features of a system in series
- Q is the same everywhere
- Total ΔP = sum of ΔP in each segment
- Total R = sum of R in each segment
- Greatest ΔP drop occurs in highest R segment
2 pumps in series
The CVS is 2 pumps (L + R heart) in series; thus Q is the same everywhere; CO = venous return
Features of a system in parallel
- Total Q = sum of Qs in each branch
- Total ΔP = sum of ΔP in each branch
- 1 / total R = 1 / R_A + 1 / R_B + …
- Largest Q goes to path with least R
Flow velocity
v = Q / A; flow per cross-sectional area. Thus capillaries, w/ most cross-sectional area, have slowest flow allowing more gas exchange.
Bernoulli’s equation and total fluid energy
E total = E lateral + KE + gravitational PE + heat energy loss to R
Energy is conserved. In terms of P, P1 (lateral) + 1/2ρv^2 (KE1) + ρgh (PE1) = P2 + KE2 + PE2
Reynold’s number
N_R = ρdv / η
Describes propensity of laminar flow to become turbulent. >4000 usually turbulent; most notable is with change in diameter/velocity e.g. stenosis
Reticulocytes
Young RBCs; still have ribosomes, lose after ~1 day
Required substances for RBCs
- Iron
- Folic acid + Vit. B12
Iron (RBCs)
Hemochromatosis = excess accumul.
Binds to ferritin for liver storage, transported in plasma by transferrin. Homeostatic control mostly by intestines.
Erythropoietin
Hormone that directly controls erythropoiesis in bone marrow; erythrocyte progenitor proliferation.
Anemia
Decreased blood ability to carry O2, due to:
-Fewer total RBCs
-Less Hb per RBC
-Combo
Polycythemia
More RBCs than normal; more O2 carrying capacity but also thicker blood putting more strain on heart.
Blood cells
-RBCs
-Leukocytes (WBCs)
-Platelets (megakaryocyte fragments)
Hematopoietic growth factors
HGFs stimulate proliferation/differentiation of various blood cell progenitors
Bulk flow
Movement of all blood constituents together
2 halves of circulation
- Pulmonary
- Systemic
Microcirculation
Arterioles + capillaries + venules
Systemic circuit
L vent -> aorta -> artery branches -> arterioles -> capillaries -> venules -> veins -> inf/sup vena cava -> R atrium
Pulmonary circuit
R vent. -> pulmonary trunk -> 2x pulmonary arteries (1 per lung) -> arteries -> microcirculation -> 4x pulm. veins -> L atrium
Parallel arrangement of systemic artery branches
Parallel systemic arteries ensure all organs/tissues get fresh oxygenated blood; all get fraction of L vent blood. Allows independent regulation of blood flow
Portal systems
Exceptions usual anatomical path with 1st capillary bed, veins, then 2nd capillary bed before veins and heart return. E.g. liver, anterior pituitary
Hemodynamics
Blood pressure, flow, resistance. Q = ΔP / R
Poiseuille’s Law
Describes factors for R; more friction = more resistance. Viscosity = intermolecular friction, length/radius = surface-molecule friction. Viscosity increases w/ hematocrit
Pulse pressure
Systolic - diastolic pressure
Factors for magnitude of pulse pressure
Everything affecting systolic and diastolic P
Stroke volume, ejection seed, arterial compliance
Mean Arterial Pressure
MAP = DP + 1/3(pulse P)
Average pressure driving blood over entire cardiac cycle. Same throughout entire body, remember relative arteriole P determines different arteriole flow
Intrinsic tone
Aka basal tone. Baseline spontaneous contractile activity of arteriolar smooth muscle. External stim. increase/decrease this tone
