Internal & External Factors That Regulate the Cardiovascular System

The cardiovascular system is regulated internally. However, external factors can cause these internal factors to change the heart rate or dilate or constrict the blood vessels. Under normal or stressful circumstances, internal factors that regulate the cardiovascular system respond to other parts of the body to determine an appropriate response.

Internal Factors

• Internally, the cardiovascular system is regulated by three main pathways. Autoregulation of the cardiovascular system is the normal means by which the body regulates heart rate. If blood flow is slowed or occluded to an organ or tissue, the body works on its own to correct it over the course of a few minutes. If autoregulation is unsuccessful, two other pathways take over. Hormone secretion into the blood stream occurs to make long-term changes in circulation like shunting of blood to high-priority tissues, breaking up of emboli or stimulation of blood cell development. Neural integration and receptors play an active part in short-term cardiovascular changes. Baroreceptors detect changes in arterial and venous pressures. Chemoreceptors detect changes in blood chemistry---things like pH and oxygen saturation. All internal mechanisms of cardiovascular regulation act in response to external stimuli.

External Factors

• The cardiovascular system regulates blood flow to necessary tissues during different external situations. Under high levels of stress, hormonal secretion causes blood to be shunted to the muscles and away from other less immediately important tissues. Also, baroreceptors in blood vessels cause dilation or constriction depending upon which tissues the vessels supply. Stress situations include any number of situations. Danger, exercise and sexual intercourse all cause elevated heart rates. In dangerous situations and during exercise, blood is shunted toward skeletal and cardiac muscle tissue and blood flow to organs like the stomach and intestines decreases. Sleep is another external factor that changes cardiovascular function, as is the level of physical fitness. Both cause a decrease in heart rate; however, the decrease during sleep is only short term.

Disease

• Disease is another factor that affects the regulation of cardiovascular function. How it affects the heart is fairly disease specific. Diseases such as chronic obstructive pulmonary disease and coronary artery disease cause an overall increase in resting heart rate and blood pressure. Some arrhythmias can cause a dangerous decrease in resting heart rate. Bacterial or viral infection can also cause acute or long-term cardiovascular function changes.