Stress: What are the changes in the body that make blood pressure increase?

Stress is part of life and evolved to serve a purpose. On seeing that saber tooth tiger over there, we need a quick strong response! There are a number of changes in the body, including increased blood pressure, that are all part of our response system to increase our ability to survive.

Unfortunately, these stress responses if prolonged also have negative consequences such as a weaken immune system and blood pressure remaning high.

A result of stress is the release of increased quantities of a number of hormones. Increased levels of many of these hormones, either directly or directly, results in raised blood pressure.

Adrenaline (epinephrine)

Adrenaline is the fight or flight hormone. We are all familiar with the feelings of sudden stress. One of these effects is the increase in heart rate. This increase in heart rate causes an increase in blood pressure. Additionally there is contraction of most blood vessels of the body, causing an additional local increase in blood pressure. In other areas of the body, mainly in skeletal muscle, there is a widening of blood vessels. The result is that there is more blood and hence oxygen and glucose (energy) in the skeletal muscles ready for fight or flight and less in many other areas of the body. However, the overall result for most of the body is an increase in blood pressure.

Norepinephrine

With regards to blood flow and blood pressure, norepinephrine has the same effects as adrenaline, causing increased heart and rate and blood pressure.

Vasopressin (anti-diuretic hormone)

One class of drugs used to treat high blood pressure function is diuretics. They work by causing the volume of urine to increase, so there is less fluid in the body including blood. Less blood volume results in lower blood pressure (see explanation of diuretic action).

As an anti-diuretic hormone, vasopressin acts on the kidney to decrease the volume of urine, resulting in more water being retained by the body. As the volume of blood increases there is an increase in blood pressure. In addition, vasopressin also causes some contraction of blood vessels so that the inside is narrower. The contraction, known as vasoconstriction, also increases blood pressure.

Cortisol (stress hormone)

Cortisol is often called the stress hormone. When cortisol is made in the lab it is known as hydrocortisone, and is used mainly for treatment of inflammation and allergy. In the body cortisol is made by the adrenal glands. Naturally, the levels of cortisol change through the day with the highest levels early in the morning. Cortisol has a wide range of effects on many parts of the body. Its effects on blood pressure are indirect. It makes blood vessels more sensitive to adrenaline (epinephrine) and norepinephrine. This increases the effects of adrenaline and norepinephrine, including raising blood pressure.

In conclusion

Increased levels of cortisol, adrenaline (epinephrine), norepinephrine and vasopressin all cause an increase in blood pressure. Chronic stress leads to a lasting increase of these hormones and hence an continued increase in blood pressure.