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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 p. 289
cardiac output and p. 290
equation for p. 737
exercise and p. 688
in pregnancy p. 653
variables in p. 289
V /Q mismatch and p. 687
The main job of the heart is to pump oxygenated blood with nutrients through the arteries to the body’s tissues and receive back deoxygenated blood full of waste products through the veins.
Now, let’s zoom into 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. Then the left ventricle contracts, forcing blood through the aorta and into the whole arterial system. After that is another moment when the left ventricle is fully contracted. It occurs at the end of contraction or systole, also called the end-systolic point, and the volume of blood within the left ventricle is called end-systolic volume, and it’s about 50 milliliters. So, end-diastolic volume minus end-systolic volume, gives us the stroke volume, which is the volume of blood that the left ventricle ejects with every heartbeat, or stroke. In this case, the stroke volume is 120 minus 50, which equals 70 milliliters.
Stroke volume is a useful measurement, but it can vary based on the size of a person. For example, a stroke volume of 50 milliliters might be absolutely fine for a small person with a small heart volume, but may be low for a large person with a bigger heart volume. So another helpful measurement is the ejection fraction, which is the stroke volume divided by the end-diastolic volume, Ejection fraction = Stroke Volume / End- Diastolic Volume. In a normal individual that’s 70/120, or about 58%, but it can fluctuate between 50 and 65% and still be considered normal. In other words, at least half of the blood volume in the left ventricle should get pumped out during each heartbeat. In hearts that have a low contractility - a low force of contraction - the ejection fraction can fall below 50%.
Stroke volume is the amount of blood the heart pumps with each beat. It is the difference between the end-diastolic volume and the end-systolic volume. The ejection fraction is the proportion of the end-diastolic volume that is pumped out with each beat. It is calculated as stroke volume divided by the end-diastolic volume. Cardiac output is the amount of blood the heart pumps in one minute and is equal to the heart rate multiplied by the stroke volume.
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