You must have heard that your blood flows to one part of the body than the other, or at one point in time, blood flows at high pressure, and it doesn't at another time. I remembered writing a post about the intake of caffeine and an experience a friend of mine had with a pounding heart and an adrenaline rush. It is very surprising how we can overlook the metabolic activities of our body. The Blood is important for the transportation of material in the body, starting with taking oxygen, vitamins and other nutrients, to our body, while taking carbon dioxide, and other waste product away from the body. It is important that you know that your cardiovascular system cannot be overlooked. According to the World Health Organization, you are more likely to die of a cardiovascular system related disease, than any other type of system disease. There are a lot of things that can lead to an increase in blood pressure, and these things includes emotional stress, physical stress, dehydration, taking caffeine and so on. But before we start to explain how blood pressure increases, it is good that you know how blood is taken to the body.
https://commons.wikimedia.org/wiki/File:Blood_pressure_monitoring
Oxygenated blood is transported from the lungs where it is oxygenated to the left atrium of the heart. The left atrium contracts and pumps the blood to the left ventricle, after which the blood is pumped from the heart to the aorta, then to the arteries, then the arterioles which then distributes blood to the capillaries where it is distributed to the various tissues. The heart is responsible for the pumping of the blood, and this is done by the left ventricle, which contracts at a particular amount of beats per minute which is known as Heart Rate The normal heart rate of a human is 60 to 100 beat to minute. When there is a pump, it is important to identify the amount of blood that is being pumped. What is known as Stroke Volume. The product of the Heart Rate and the stroke volume is what is known as Cardiac Output (the heart pumps about 5 liters of blood per minute). When the blood is pumped out of the heart, it is distributed to the Coronary (the Heart itself), the Brain, the Gastrointestinal tract, the Renal (Kidney), the Muscles, and the Skin. The brain requires about 15 percent of the heart’s cardiac output, the Gastrointestinal tract gets about 25%, the Muscles get 20%, the skin gets 5% of the blood from the heart, the Renal system gets about 25%, the coronary system (which is the heart) gets 5%, and the rest goes to the other tissues.
Blood movement can change as a result of viscosity (the thicker the blood the slower it moves, and the lighter the blood, the more it moves fast) or the length and diameter of the vessel. What is very important in the pressure of blood is the diameter of the vessel in which the blood flows through.
Blood flow = Difference in blood pressure/resistance
Blood Pressure = Blood flow X Resistance
For the blood to get to every part of the body, the diameter of the vessels carrying the blood is important. The wider the vessel, the lesser the pressure of the blood, and the narrower the vessel, the higher the pressure of the blood and the easier the blood can reach every part of the body. In other for the pressure of increase also, vessels have smooth muscles that can constrict thereby causing the push of blood. The hypothalamus which responsible for homeostasis of the endocrine system helps in the autonomic nervous system. The hypothalamus using the sympathetic nervous system releases the Norepinephrine / Noradrenaline to the vessels to which have alpha-1 (α-1) receptors on their smooth muscles, allowing them to constrict causing the pressure of the blood to increase. Constriction also occurs during exercises as it triggers the stress response (sympathetic nervous) which causes the muscles of other part of the body to constrict, but the norepinephrine triggers the alpha-2 (α-2) receptor which causes the vessels of the muscles to dilate allowing blood to get into it the muscles. When the muscles undergo exercise, the vessels of the digestive organs constricts, causing resistance of blood, and allowing more blood to go to the vessels of the muscles.
One way blood pressure is being controlled is via the kidney, which helps to regulate the volume of blood in the body. With hormones such Renin and angiotensin, which are responsible for the regulation of fluids in the body by constricting and relaxing blood vessels, as well as regulating sodium level in the body. Angiotensin is responsible for vasoconstriction and dilation of the blood vessel and increase of aldosterone, which helps to regulate sodium and water concentration in the body. You see, when there is a high blood pressure, the kidney causes excessive water in the body to be excreted, thereby reducing the volume of blood in the body.
Conclusion
While there is need for constrictions and dilations of the heart chambers for the release of blood, as well as the constriction and dilation of the blood vessels for the blood to increase in pressure and reduce accordingly, it is important that an extremely high blood pressure could lead to the damage to the heart and the blood vessels that has to withstand the blood pressure. Chronic high blood pressure can lead to death of heart muscles (heart failure), myocardial infarction (heart attack), arteriosclerosis, aneurysm, and organ damages.
https://www.ncbi.nlm.nih.gov/books/NBK279250/
https://www.ncbi.nlm.nih.gov/books/NBK547686/
https://www.medicalnewstoday.com/articles/321122
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4389556/
https://www.who.int/news-room/fact-sheets/detail/cardiovascular-diseases