• Circulation in series
 
  • Circulation in parallel
 
  • Two important hemodynamic principles
 
  • Poiseuille-Hagen Law: Flow = (P1-P2) πr4/8ηL
  • R = (P1-P2)/Flow = 8ηL/Nπr4
  • Pa-Pv = CO x TPR
  • Cardiac output = Heart rate x Stroke volume
  • Total peripheral resistance = Blood viscosity x Vascular resistance
 
  • Capacity C = V/P.
  • Capacitance or Compliance Cd = ΔV/ΔP
  • Artery has low capacity and vein has high capacity.
  • Arterial capacitance = Stroke volume/Pulse pressure
 
  • Diastolic pressure ~ Mean arterial pressure
  • Systolic pressure = Diastolic pressure + Pulse pressure
  • Pulse pressure = Stroke volume/Arterial capacitance
  • Mean arterial pressure = Cardiac output x Total peripheral resistance
  • Cardiac output = Heart rate x Stroke volume
  • Total peripheral resistance = Blood viscosity x Vascular resistance
 
  • Autonomic Nervous System
  • Structures innervated: Cardiac Muscle, Smooth Muscle & Glands
  • Location of cell bodies: Ganglia outside CNS
  • Myelination: Preglionic (+), Postganglionic (-)
  • Voluntary control: No
  • Peripheral inhibition: Yes
  • Effectors after denervation: Automaticity, no atrophy
  • General function: Homeostasis
 
  • Sympathetic: Thoracolumbar outflow
  • Parasympathetic: Craniosacral outflow
  • Sympathetic: Solid lines
  • Parasympathetic: Broken lines
  • +: Excitation
  • -: Inhibition
  • Sympathetic: Mobilization of energy; signs of alarm
  • Parasympathetic: Conservation of energy; elimination of waste product
 
 
  • Control of blood pressure consists of efferent system, afferent system, and the integrating center in medulla
 
 
 
 
  • Arterioles and venules have one layer of smooth muscle; capillaries do not have smooth muscle.
  • The precapillary sphinctors determine how many capillaries open. When precapillary sphinctors relax, there are more capillaries open (recruitment phenomena).
  • Note that there are no postcapillary sphinctors.
 
 
  • The glycocalyx layer at lumen surface is now considered as the macromolecular sieve; the intercellular junction is considered as the barrier of water flow.
  • The characteristic features of capillary are the plasmalemmal vesicles and the tight junction between endothelial cells.
  • Serial sectioning EM suggests that the vesicles are all connected to outside; they do not shuttle between the two surfaces. The tight junctions are not a real transport barrier; they are disrupted in the three dimensional view.
  • When vesicles form channel, they can serve as a large pore system of transcapillary transport.
 
 
  • Water flow (filtration/reabsorption) follows the Starling's hypothesis; the rate of filtration is:
    Jv = Kf[(Pc-Pif) - σ(πc-πif)]
  • Pc is high in renal glomeruli; Pc is low in lungs.
  • Kf is determined by the permeability of intercellular junction; σ is determined by the integrity of the glycocalyx layer and the size of plasma proteins.
 
 
  • Light mechanical stimuli: Vasoconstriction
  • Noxious stimuli: Triple response
  • Red line: Release of histamine/kinins
  • Flare: Axon reflex causes release of vasodilator substance
  • Wheal: edema formation
 
  • The lymphatics endothelium is a discontinuous endothelium; lymphatics flow is facilitated by muscle pump and respiratory pump.
  • Edema results from: 1) increased Jv per Starling's hypothesis; 2) blockage of lymphatics
 
  • Venous pooling decreases venous return, decreases stroke volume, decreases cardiac output, decreases mean arterial pressure, increases sympathetic activation, increases heart rate/increases cardiac contractility/venoconstrction/arteriolar constrction, increases blood pressure.