when the blood vessels going to the heart to supply it with blood (so it can keep on beating) get smaller in size and so, not enough blood gets to the heart causing problems
, can be due to the or not enough blood going to the heart
can be due to an that gets stuck in the and doesn't let brain get enough blood
the blood vessels open up, get weak at places, and form balloon like structures that can burst
a that will move from its place in the vessel and get stuck in an organ somewhere else, causing damage to that organ by not providing it blood
Several things can increase the risk of atherosclerosis. Both high levels of cholesterol (hypercholesterolemia) and high levels of triglycerides (hypertriglceridemia) are important risk factors. Diabetes can promote the development of atherosclerosis and family history is an obvious factor. Finally, Cigarette smoking can also increase the risk as atherosclerosis of the coronary arteries and the aorta is more severe among than among non-smokers. Other factors are increasing age, post-menopausal women, male gender, and stressful life patterns. (McKinley Heath Centre: Factors That affect Blood Pressure)
One consequence of atherosclerosis is high blood pressure (hypertension). Hypertension is a condition in which the blood pressure in either arteries or veins is abnormally high. Blood pressure is the force exerted by the blood against the walls of the blood vessels. High blood pressure is caused by a variety of reasons, the blood vessels may lose their flexibility, or the muscles surrounding them may force them to contract. Consequently, the heart must pump more forcefully to move the same amount of blood through the narrowed vessels into the capillaries, thereby increasing the blood pressure. Over time, this higher pressure, or hypertension, can damage the arterioles (the small terminal twigs of an artery that end in capillaries) in such organs as the liver, kidney, or brain and can also weaken the overworked heart. The increased risk of death from congestive heart failure, kidney failure, or stroke is the chief danger of hypertension. (Microsoft, 1996, Encarta 97 Encyclopedia)
From Heartpoint: High Blood Pressure Information I found that 90 percent of people who have high blood pressure have something called essential hypertension. This type of high blood pressure has no known cause. However, studies have pointed out several contributing factors. Included among these are family history, obesity, high salt intake, smoking, high alcohol consumption, and emotional and physical stress.
Another type of high blood pressure that occurs is called secondary hypertension. This may result from a wide range of uncommon causes
- A number of kidney diseases cause high blood pressure.
- Disorders of the adrenal glands:
- Pheochromocytoma, This tumour produces adrenaline and/or similar substances. Patients with this disorder typically have spells of high blood pressure which are accompanied by strong and rapid heart beats, sweating and headaches.
- Cushing's syndrome is caused from the overproduction of glucocorticoids – steroids that participate in regulating the metabolism of glucose and other food substances. The site of this overproduction is in the adrenals.
- Adrenal adenomas (non-malignant tumours) or hyperplasia (too much tissue growth) can be responsible for excess levels of "mineralcorticoids" -- steroids that participate in the regulation of sodium, potassium, and other minerals. Their effect is primarily from holding onto too much sodium.
- An obstruction to the arteries to the kidneys (Renal Artery Stenosis). In this situation, the kidney that is blocked doesn't detect enough blood pressure, and releases chemicals causing the blood pressure to go up. In this way, that kidney may produce enough blood pressure to satisfy itself, while the rest of the body sees very high pressures as a result. This obstruction can come from atherosclerosis (blockage with cholesterol) or from a congenital disorder of the connective tissue in the blood vessels (Fibromuscular Dysplasia).
- A "Coarctation" (or narrowing) of the aorta can cause high blood pressure in a manner similar to Renal Artery Stenosis noted above. Blood has to find a way around the obstruction, but the pressure is low, including the pressure to the kidneys. They behave in exactly the same way they do in Renal Artery Stenosis, releasing chemicals to raise their own pressure. However, the pressure in other parts of the body, particularly the heart and the brain, see very high pressures and can therefore have all of the complications of high blood pressure.
If high blood pressure is not controlled or treated, it can cause; heart attacks (from blockages in the heart arteries), strokes (blockages or weakening of vessels to the brain) or kidney failure from injury to the kidney and its blood vessels. Heart failure is a frequent occurrence in long term hypertension. The heart initially compensates for the increased work of pushing against the elevated pressure in the vessels by becoming thick (hypertrophied). The person with this thickening may not notice any problems even at this stage. Eventually the muscle can weaken, and heart failure can occur. Retinal haemorrhages (blood leaking in the back of the eye) also occurs. Untreated hypertension can slowly lead to death. In order to treat such diseases of the sympathetic nervous system, doctors usually subscribe diuretics, sympathetic nerve blockers or in severe cases vasodilators. Beta-blockers (In full Beta-adrenergic Blocking Agent) are nerve blockers.
Beta blockers block mainly adrenaline's effects on the body's beta receptors. There are two primary beta-receptors appropriately named beta 1 and beta 2. Some beta-blockers are 'selective' meaning that they block beta 1 receptors more than they block beta 2 receptors.
Beta 1 receptors are found primarily in the heart. Stimulating beta 1 receptors causes the heart to beat faster, beat stronger, and causes nerve-muscle conduction velocity to increase. Therefore, blocking the beta 1 receptor (and all beta blockers block the beta 1 receptor) results in the heart rate slowing down and the heart beating less forcefully. This causes the heart to require less oxygen, less blood is ejected from the heart, and blood pressure is lowered. Beta blockers are a fundamental treatment in myocardial infarctions ("Heart Attacks"). The main beta 1 selective drugs used are metoprolol (Lopressor) and atenolol (Tenormin). These drugs do not allow the hormones that cause the blood vessels to constrict (norepinepherine and epinephrine) bind to their site on the blood vessel. Because these hormones cannot bind, the blood vessels do not contract and the blood pressure is lowered.
Stimulating the beta 2 receptor causes smooth muscle (muscles that control body functions which you do not have control over) to relax. This means that lungs relax (bronchodilation), uterus relaxes, and arterioles (a type of blood vessel) relax. They also cause skeletal muscles (as in biceps, triceps, etc.) to become activated and large. Therefore, drugs which block the beta 2 receptor have adverse effects and uses in addition to the effects mentioned for beta 1 blockade. The classic non-selective beta blocker is propranolol (Inderal).
Other examples include:
Nadolol
Acebutolol
Labetolol
(About - Marshall U. (US))
Bibliography
- Roberts, Reiss and Monger, 1993, Biology principles and processes
- Microsoft, 1996, Encarta 97 Encyclopedia CD ROM (Hypertension, Arterial plaque)
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COHIS: cardiovascular diseases: vessel disorder (http://web.bu.edu/cohis/cardvasc/vessel.htm)
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Heartpoint: High Blood Pressure Information (http://www.heartpoint.com/highbloodpage.html)
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McKinley Heath Centre: Factors That Affect Blood Pressure (http://www.uiuc.edu/departments/mckinley/health-info/dis-cond/bloodpr/fact-bp.html)
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About - Marshall U. (US) (http://musom.marshall.edu/CHH/DrugInfo/Review/Beta-Bl.htm)
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Encyclopaedia Britannica (http://www.britannica.com/bcom/eb/article.html)
- KIB, 1999, cardiovascular diseases
