Factors Affecting Stroke Volume
Stroke volume is a term used in cardiovascular physiology to refer to blood volume pumped with every heartbeat from one ventricle to another. It is calculated through use of ventricle volumes from echocardiogram and subtracted from the blood volume in that ventricle by the end of the beat. It is an essential cardiac output determinant and what is more, it is used for purposes of calculating ejection fraction which refers to stroke volume at the end of diastolic volume. Stroke volume is known to decrease when an individual has certain disease or conditions hence, it is correlated to cardiac function.
Determinants
On average, men record high stroke volumes compared to women and this is attributed to the fact they have larger hearts. While this is the case, there are several factors that influence stroke volume such as the size of the heart, preload, afterload as well as the contraction duration.
Exercising
Long periods of aerobic exercise can lead to increased stroke volume which results to a low heart rate. Reduction in the heart rate leads to ventricular diastole, increased end diastolic volume and in the end, permits ejection of more blood.
Preload
intrinsically, stroke volume is influenced by preload. Increased speed of volume and venous increases pre-load and this increases the stroke volume. A decrease in venous however causes the reverse effect and causes stroke volume decrease.
Afterload
Whenever there is an elevated afterload which is measured as aortic pressure, the stroke volume reduces. While it does not affect healthy individuals, an increase in afterload inhibits the ventricles from ejecting blood and causes reduction in the stroke volume. Increase in afterload is count in arterial hypertension and aortic stenosis.
The central nervous system as well as hormonal release also affects stroke volume. According to the book, “Physiology of Sport and Exercise, impulses travel from the brain to the nervous system and increase stroke output. For instance when one is stressed psychologically, cortisol hormone is released to the blood stream resulting to increase in the heart rate and also preparing the body for required action. Excitement can also cause release of epinephrine hormone causing the constriction of blood in vessels consequently lowering stroke volume while at the same time increasing the heart rate.
Other factors
There are other aspects that also influence stroke volume like the environment, sex and age of an individual. With an increase in age, people are likely to experience low maximum stroke volume. Females are also more likely to have high cardiac output because they have a low heart volume. Other factors that also affect the stroke volume include extremes in temperature, noise, altitude as well as pollution.
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Sources:
http://www.livestrong.com/article/246579-factors-that-influence-stroke-volume-heart-rate/