Cardiac Blood Flow
o From body
o Through:
♣ Vena cavas
♣ Right atrium
♣ Tricuspid valve
♣ Right ventricle
♣ Pulmonic valve
♣
... [Show More] Pulmonary artery
o To lungs
♣ Pulmonary vein
♣ Left atrium
♣ Mitral valve
♣ Left ventricle
♣ Aortic valve
o Back to body
Cardiac Anatomy
The heart is the size of a closed fist
2/3 of the heart is to the left of the midline
1/3 under the sternum
heart layers
Endocardium ( inner)
myocardium ( middle)
Pericardium ( outer)
Cardiac action potential: phase 0
rapid depolarization
Sodium influx d/t voltage-gated sodium channels opening
Cardiac action potential: phase 1
initial repolarization of cells
voltage gated sodium channels closed
voltage gated potassium channels open
Potassium leaves cell slowly
Cardiac action potential: phase 2
plateau phase
voltage gated calcium channels open
influx of calcium into the cell
balances potassium efflux
calcium influx triggers more calcium from sarcoplasmic reticulum > myocardial contraction
Cardiac action potential: phase 3
Rapid Repolarization w/ potassium efflux
voltage gated potassium channels open
voltage gated calcium channels close
Cardiac action potential: phase 4
resting membrane potential, -85 mV
High potassium permeability from the potassium channels
Potassium imbalance affect on myocardial action potentials
Hypokalemia-increased atrial preload leads to 1-3 degree blocks
Hyperkalemia-slows depolarization, leads to sunus bradycardia and junctional rhythm
Calcium imbalance affect on myocardial action potentials
Hypocalcemia-decreased contractility
Hypercalcemia-increased contractility>ST and PJCs, vasoconstriction
Magnesium imbalance effect on the Cardiovascular system
Magnesium causes vasodilation
Cardiac Output (CO)
Amount of blood pumped in 1 minute (~5 L)
HR x Stroke volume
Stroke Volume (SV)
measurement of the amount of blood ejected from a ventricle in one contraction
depends on preload, endogenous inotropic agents, negative inotropic agents, myocardial oxygenation
Ejection Fraction (EF)
percentage of blood volume in the ventricles at the end of diastole that is ejected during systole; a measurement of contractility
Stroke volume/end diastolic volume
Normal = 55-65%
EF decreases w/ systolic heart failure but no change with diastolic heart failure
Cardiac Cycle: Diastole
Ventricles relaxed
Blood entering atria
Blood flows through AV valves into ventricles
Semilunar valves are closed
Cardiac Cycle: Systole
Ventricles contract
Blood pushes against AV valves and they shut
Blood pushes through semilunar valves into aorta and pulmonary trunk
heart pressure measurement
mmHg
Right side lower
left side higher
Right atrial pressure
0-8 mmHg
right ventricle systolic pressure
Peak systole
15-28 mmHg
right ventricle end diastolic pressure
end diastole before systole
0-8 mmHg
L atrium pressure
4-12 mmHg
Left ventricle systolic pressure
Peak systole
90-140 mmHg [Show Less]