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Cardiovascular system anatomy and physiology
Lymphatic system anatomy and physiology
Abnormal heart sounds
Normal heart sounds
Changes in pressure-volume loops
Cardiac and vascular function curves
Altering cardiac and vascular function curves
Law of Laplace
Measuring cardiac output (Fick principle)
Stroke volume, ejection fraction, and cardiac output
Physiological changes during exercise
Cardiovascular changes during hemorrhage
Cardiovascular changes during postural change
Cardiac conduction velocity
Electrical conduction in the heart
ECG normal sinus rhythm
ECG QRS transition
ECG rate and rhythm
ECG cardiac infarction and ischemia
ECG cardiac hypertrophy and enlargement
Control of blood flow circulation
Microcirculation and Starling forces
Blood pressure, blood flow, and resistance
Compliance of blood vessels
Laminar flow and Reynolds number
Pressures in the cardiovascular system
Resistance to blood flow
Action potentials in myocytes
Action potentials in pacemaker cells
Cardiac excitation-contraction coupling
Excitability and refractory periods
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Cardiac output is defined as the volume of blood ejected by the left ventricle per unit time.
The volume of blood is called the stroke volume, and the unit used to measure cardiac output is one minute.
So cardiac output can be calculated as stroke volume which is the volume of blood pumped out of the left ventricle per beat, times the number of heartbeats per minute, which is around 70.
Another way to calculate cardiac output is by using the Fick Principle, which simply states that at rest, the oxygen going into an organ minus the oxygen left out of an organ must equal how much oxygen that organ has used.
Using the Fick Principle’s equation of (cardiac output = oxygen consumption/arterio-venous oxygen difference), cardiac output can be calculated.
Both methods render normal cardiac output to around 5 litres per minute on average.
To measure cardiac output, we first have to take a look at the left ventricle.
There’s a moment when the left ventricle is fully relaxed.
It occurs at the end of filling or diastole, also called the end-diastolic point, and the volume of blood within the left ventricle is called the end-diastolic volume, and it’s about 120 milliliters.
The Fick principle is a mathematical equation that calculates cardiac output by multiplying the difference between arterial and venous oxygen partial pressures by the blood flow through the vascular bed. In other words, it takes into account how much oxygen is being delivered to and removed from the tissues. This makes it a more accurate measure of cardiac output than simply measuring heart rate or blood pressure.
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