In a properly functioning circulatory system, the various components of the nervous, neuroendocrine, and renal systems operate together to maintain blood pressures at an adaptive level.

So that organisms can maintain blood flow to all essential body tissues in a variety of physical states, locations, and positions, including physical activity, changes in temperature and climate, and even standing on one’s head.

For some organisms, however, one (or more) of the various regulatory mechanisms outlined above no longer operates to maintain blood pressure in an adaptive range.

In some cases, blood pressure is too low, leading to episodes of lightheadedness and fainting, particularly when one changes positions from sitting to standing.

These are commonly referred to as syncopal or hypotensive episodes and are the result of the circulatory system’s inadequacy in maintaining blood flow to the brain.

In other cases, blood pressure is too high, and in extreme cases can lead to bleeding in weakened locations of the circulatory system, resulting in hemorrhagic stroke (bleeding into the cranium, which damages brain tissue) or the rupture of an aneurysm (a dilated blood vessel).

High blood pressure is commonly referred to as hypertension, and takes two forms: primary or essential hypertension and secondary hypertension.

In cases of secondary hypertension, there is an identified physiological abnormality causing the high blood pressure, such as kidney disease, endocrine disturbances like pheochromocytoma (adrenal tumor) or Cushing’s syndrome, or a blockage of blood circulation that might occur with cardiovascular disease or stenosis (narrowing of the artery).

It is also possible that regular ingestion of various exogenous substances, including amphetamines, oral contraceptives, and licorice, will result in secondary hypertension.

In most cases of hypertension, however, the exact cause of the elevated blood pressure is unknown; in these cases, the heightened blood pressure is called primary or essential hypertension.

Given the association of the word ‘tension’ with emotional states, it is interesting that the word ‘hypertension’ was selected to describe conditions of high blood pressure.

The term ‘hyper’ comes from the Greek word ‘huper,’ which means over, above, or exceeding. The term ‘tension’ comes from the Latin word ‘tensio,’ which refers to the state of tenseness that accompanies stretching or extension.

In this regard, the original use of the word ‘hypertension’ presumably referred to the exaggerated stretching of the blood vessels that accompanied the condition of high blood pressure.

It is interesting that the common use of the word ‘tension’ to refer to emotional distress is derived from the same root Latin word. One might also wonder why the term ‘essential’ was used to describe hypertension with no known origin.

According to Shapiro (1996), the term was initially chosen in the belief that the increase in blood pressure observed across the lifespan was ‘essential’ to maintaining blood flow in an aging circulatory system.