Sanjeev Bhasin
The Mechanics of Hypertension: How Your Heart, Arteries, and Kidneys Control Blood Pressure
The Lowdown on High Blood Pressure
Even standing up after sitting for an extended period causes a temporary increase in blood pressure. According to Harvard Health, hypertension is a circulatory disease that can affect many organs, including the brain. High blood pressure is not connected to personality traits. According to the American Heart Association, while stress itself can contribute to risk factors for high blood pressure, such as unhealthy eating habits and excessive alcohol use, there is no evidence that calm individuals are more likely to develop high blood pressure or that people who are tense will always have normal levels.
Blood shoots out of the heart’s aorta, or largest blood vessel, at the phenomenal rate of 15 inches per second. According to a study by Klarhöfer and colleagues, capillary blood flow velocity in the human finger is measured with high precision, though the specific rate of 0.02 inches per second is not reported. Many factors can temporarily raise blood pressure, including eating, drinking alcohol, stress, and strong emotions such as fear and anger. According to the Mayo Clinic, blood pressure follows a daily pattern. It usually starts to rise a few hours before waking, peaks around midday, and tends to be lower in the late afternoon and evening, reaching its lowest levels at night during sleep. These fluctuations are normal and generally do not pose a health risk. Concern arises only when blood pressure gradually exceeds healthy levels and remains elevated over extended periods.
The Goldilocks Syndrome
Optimal blood pressure is neither excessively high nor too low. The body maintains this balance through the coordinated actions of the heart, arteries, and kidneys.
How Your Heart Works
Your heartbeat has two stages: Systole, when your heart pumps blood from the ventricles, right side to your lungs, left to the aorta and arteries. During diastole, your heart muscle relaxes, letting blood flow into the ventricles from the atria.
Did You Know? If you work the night shift, your blood pressure rises when you rise, not when the sun does. That’s because your body has shifted its daily, or circadian, rhythms, including your blood pressure, to match your new sleep/wake cycle.
Atherosclerosis
Atherosclerosis, the clogging of arteries with fatty deposits, can elevate your blood pressure. Here’s how it works: Plaque deposits gradually accumulate in the lining of your arteries. As deposits enlarge, blood flow decreases, and blood pressure rises. This elevates your risk for heart attack, stroke, and other vascular problems.
The Role of the Heart and Arteries – Your heart
The pumping action of the heart directly influences blood pressure. Increased physical or emotional stress, such as during strenuous activity or anxiety, elevates arterial pressure. Conversely, relaxation and calmness reduce heart rate and lower blood pressure.
Your arteries
Wider, more elastic arteries provide less resistance, resulting in lower blood pressure. Reduced arterial elasticity increases cardiac workload and raises blood pressure.
How Your Kidneys Regulate Blood Flow
The kidneys regulate sodium and water retention in the body. Increased fluid retention elevates blood pressure, while reduced retention lowers it.
Your brain weighs in.
While the heart, arteries, and kidneys are primary regulators of blood pressure, the brain, hormones, and enzymes also play significant roles.
Baroreceptors, specialised nerve endings located in the walls of major arteries, the heart, and lungs, monitor blood pressure and relay information to the brain. In response to changes, the brain directs the release of hormones that adjust heart rate and arterial diameter to maintain stable blood pressure.
Epinephrine and norepinephrine, also known as adrenaline and noradrenaline, are hormones released by the adrenal glands in response to signals from the brain during periods of stress. These hormones increase heart rate and constrict arteries, elevating blood pressure.
A terrible trio. Three other hormones—renin, angiotensin, and aldosterone—also team up to regulate blood pressure. The process starts with the enzyme renin, produced mainly by kidney cells. Once released into the blood, renin searches for and eventually reacts with the protein angiotensin (produced by the liver) to form a new, much more powerful compound, angiotensin II.
Raising blood pressure is one of angiotensin II’s key jobs, and it does so in two ways: first, it orders blood vessels to narrow. Second, it helps produce aldosterone, a hormone that causes the kidneys to retain sodium (salt). The more fluid retained, the higher the blood pressure.
Some medications—ACE (angiotensin-converting enzyme) inhibitors and angiotensin II receptor blockers—lower blood pressure by blocking the actions of this trio of hormones.
Saying NO to High Blood Pressure
In recent years, scientists have added nitric oxide, a molecule in the body, to the known arsenal of blood-pressure regulators. Made from an amino acid called L-arginine, nitric oxide has been found to relax and open blood vessels, and that, of course, helps lower blood pressure.
A 1993 study found that L-arginine's effect on blood pressure varies among individuals with hypertension, suggesting that not everyone may benefit from L-arginine supplementation due to differences in nitric oxide production. The reasons for these differences are still not fully understood.
