Your Body Cares for Itself: Internal Blood Pressure Regulators
At the moment, the internal, physiological regulation of blood pressure is not completely understood. Yes, the heart is the main focus of blood pressure, as its contractions start the flow of blood throughout the body. However, there are other factors at work in the body that also regulate blood pressure. There are currently three mechanisms of blood pressure regulation within the body that have been well-categorized: Baroreceptor reflexes, the Renin-angiotensin system, and aldosterone release.
Baroreceptors (or baroceptors) are located in the body’s organs and detect the pressure of blood flowing through them. If they detect a change in pressure that could result in bodily harm, signals are sent to the heart that will then adjust the average arterial pressure by changing both the force and the speed of the hearts contractions. This is called the baroreceptor reflex, or baroflex for short. So, when blood pressure is high, the baroflex will lower it, and vice versa.
While the baroflex is good for short term changes in the body’s blood pressure, the renin-angiotensin system (RAS) works well for more long-term regulation. The RAS kicks in when blood pressure begins to drop to a dangerous low, and works to bring blood pressure up by activating angiotensin II. Angiotensin II is what is known as a vasoconstrictor. Basically, it narrows blood vessels, which results in more pressure being placed on them. Angiotensin II is activated when the RAS uses the kidney to help bring up blood pressure.
Not all of these regulation processes are independent of each other. In fact, there is a very strong link between the RAS system and the release of aldosterone in the body. Aldosterone, a steroid hormone, is released from the adrenal cortex once either angiotensin II begins to work or a high level of potassium is detected. Aldosterone helps stimulate the release of sodium, which just so happens to be the main ion that determines the amount of fluid in the blood. Thus, aldosterone indirectly will increase blood pressure when such a change is necessary.
While other regulators and regulation processes involved with blood pressure are sure to be present, the three mentioned here is what is best known to occur. Other processes are being researched, though no other way to regulate the blood pressure has been so clearly defined. Baroflexes, the RAS, and aldosterone are, at the moment, all we know about in regards to internal blood pressure regulation.
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