Site of highest resistance in cardio system
largest cross sectional and surface area
equation- velocity of blood flow
V= Q / A
q= flow, a= cross-sectional area
Q= ∆P / R
CO= (MAP-R atrial pressure) / TPR
CO=SV x HR
equation- resistance of flow
R = 8 η l / pie r ⁴
C = V / P
capacitance describes distensibility. inversely related to stiffness. think of in terms of vetricular compliace!
Difference between systolic and diastolic pressures?
diastolic pressure + 1/3 (systolic - diastolic)
MAP= CO x TPR
Phase 0 myocytes
upstroke. I (na)
Phase 1 myocytes
initial repolarization - outward K+ ions
Phase 2 myocytes
plateau- I (to) ---> I (Ca)
Phase 3 myocytes
repolarization-large outward I (k)
Phase 4 myocytes
resting membrane potential
Phase 0 P cells
upstroke- I (Ca)
Phase 3 P cells
repolarization I (K) ourward K+ current causes repolarization
Phase 4 P cells
slow depolarization. I (f) inward Na+. turned on by repolarization
Changes in HR are termed?
chronotropic effects increase or decrease HR via SA node
Changes in conduction velocity are termed?
dromotropic effects. affect conduction through AV node and increase or decrease PR interval
How do you increase HR at the SA Node?
norepi at β1 receptors- increase rate of phase 4 depolarization. increased I (f)
How do you increase conduction velocity at the AV node?
increase inward I (Ca) by norepi at β1 receptors
_____ stimulation via _____ receptors decreased force of contraction in atria by decreasing inward Ca++ during plateau
equation- ejection fraction
EF = SV / EDV
equation - stroke work
work the heart performs on each beat
SW = aortic pressure x SV
Finck principle for measuring CO is?
CO = 0₂consum. / (O₂pulm vein - O₂pulm artery)
equation - stroke volume
SV = CO / HR
TPR = (MAP-CVP) / CO
T = P x r
r=radius of tube
T= wall tension