How is Blood Pressure Maintained?
The mechanisms by which blood pressure is maintained are very complicated and are not fully understood.
Blood pressure is primarily controlled by the brain, the autonomic nervous system (ANS), the kidneys, the endocrine glands, the arteries, and last but not least, the heart itself.
The brain is the centre from which the blood pressure is mainly controlled. It instructs the other organs in concurrence or in response to the body’s demands and needs. The Autonomic Nervous System or ANS (which is mainly made up of nerve fibres) brings signals from various parts of the body to inform the brain of the status of the blood pressure, the volume of blood and all the special needs of all the different organs. This information is processed by the brain, decisions taken by it and the message is sent out via the outgoing nerve fibres. These nerve fibres from the brain reach different organs which include the blood vessels, where the signals cause narrowing or opening of the vessels. These nerves function automatically, without our knowledge, unlike other nerves that we can control, such as those needed for physical movements of the body. The blood pressure can be affected at many levels in the brain centre, on the way to and from the autonomic nervous system or during the process of sending messages to the blood vessels.
The kidneys make a hormone called renin that causes the blood pressure to rise in response to anything that lowers the blood pressure and thereby threatens the normal function of the kidneys. Renin from the kidneys stimulates the formation of angiotensin. Angiotensin causes blood vessels to constrict, and in turn the blood pressure rises.
Hormones from several organs also affect the blood pressure.
A small gland, Adrenal Glands, secrete several hormones that can raise the blood pressure including Cortisone, Adrenaline and Aldosterone.
The Thyroid Gland produces thyroid hormones or Thyroxine which plays an important part in blood pressure control.
Ovaries secrete estrogen which increases the blood pressure.
The heart which is a muscular pump, and whose main job is to supply blood to all the different parts of the body, also functions as an endocrine gland. It secretes a hormone called Natriuretic hormone, which functions by getting rid of the excess salt from the body and also in helping the blood vessels to dialate, thus helping in controlling the blood pressure.
All the hormones mentioned above are secreted in very specific amounts and are necessary for the body functions. They can create many health problems when secreted in abnormal amounts. They can cause blood pressure to become inappropriately elevated.
The arteries themselves also contribute to blood pressure control. These are elastic tubes which supply blood to all the organs of the body. They can dialate and increase the blood supply to a particular organ, or contract to shunt blood away to distribute it where it is most needed.
The functions of the kidney, hormones and arteries are not isolated, and all are directed by the brain.
To keep this system working and all of the 11 pints of blood in your body moving, a certain amount of pressure is required. Your blood pressure is the force that is exerted on your artery walls as blood passes through. This force helps to keeps blood in your arteries flowing smoothly.
Shows have the organism solves the problem of adjusting the pressure and distribution of arterial blood to the constantly changing blood supply needs.
Regulators of Blood Pressure
Several factors help to control your blood pressure and keep it from increasing too high or decreasing too low. They include three major organs: your heart, your arteries and your kidneys.
Each time your heart beats, blood is released from the left side of your heart (left ventricle) into the large blood vessel (aorta) that transports blood to your arteries. Blood returns to your heart through your veins. Before being circulated again, blood from your veins is sent to your lungs to load up on fresh oxygen.