sinoatrial (SA) node A small cluster of specialized nerve and muscle fibers located in the upper wall of the heart's right atrium. The SA node initiates the electrical pacing impulse that causes the heart to contract. In the healthy heart the electrical impulse spreads in an orderly and synchronized pattern through the two atria, causing them to contract. The atrioventricular (av ) node, a second small cluster of specialized nerve and muscle fibers located in the wall of the heart between the atria and the ventricles, picks up the impulse, amplifies it, and sends it through the ventricles to cause them to contract.
For further discussion of the SA node within the context of cardiovascular structure and function please see the overview section "The Cardiovascular System."
See also bundle branch; bundle branch block; cardiac cycle; sick sinus syndrome.
smoking and cardiovascular disease Cardiovascular disease (cvd) is the most frequent and significant consequence of cigarette smoking, with smoking accounting for one in six deaths due to CVD. Smoking significantly increases the risk for hypertension (high blood pressure), atherosclerosis, and coronary artery disease (cad). The combination of cigarette smoking and using oral contraceptives (birth control pills) presents a particular risk of blood clot formation in women, especially women over age 35. This raises the risk for stroke and heart attack such that many doctors will not prescribe oral contraceptives for women who smoke. Smoking is also a key factor in numerous pulmonary diseases, affecting the cardiovascular system's ability to circulate oxygen-rich blood.
The US Surgeon General offered the first conclusive evidence of the correlations between smoking and cardiovascular disease in the landmark 1964 report, Smoking and Health: Report of the Advisory Committee to the Surgeon General of the Public Health Service. Researchers have since continued to accumulate knowledge and understanding of the mechanisms through which smoking affects cardiovascular health. Cigarette smoke contains more than 2,000 identifiable chemicals, dozens of which are carcinogenic (CANCER-causing) or have other deleterious actions on health. Two in particular, nicotine and carbon monoxide, are highly toxic to the cardiovascular system.
Nicotine and Cardiovascular Function
Nicotine is a central nervous system stimulant that acts on nerves throughout the body. In the cardiovascular system, nicotine stimulates the nerves that regulate smooth muscle tissue, causing smooth muscle cells to contract. This constricts blood vessels, notably arteries, reducing the channel for blood flow. Nicotine further stimulates the baroreflex sensors (clusters of nerve cells in the major arteries and the heart that sense the flow
and pressure of blood). These actions result in increased blood pressure, HEART RATE, and cardiac workload. Nicotine further acts as an irritant within the arteries, causing INFLAMMATION of the inner layer of the arterial wall. Researchers believe such inflammation may be the foundation for atherosclerosis.
Carbon Monoxide and Cardiovascular Function
Carbon monoxide is a poison. It has a greater affinity than oxygen for HEMOGLOBIN and binds with hemoglobin, blocking hemoglobin from carrying oxygen. This reduces the amount of oxygen that enters the bloodstream from the LUNGS. By the end of a cigarette, a smoker can have concentrations of carbon monoxide as high as 7 percent; 10 percent is the level at which symptoms of carbon monoxide poisoning begin to become apparent. Carbon monoxide in the bloodstream deprives cells in the BRAIN and heart, which rely on oxygen for fuel.
Environmental Smoke Exposure
Cigarette smoke also raises the risk for health problems, including cardiovascular disease, among people who are themselves nonsmokers though live or work in a smoking environment. Children are at particular risk. Numerous studies show the children of smokers have more EAR infections, sinus infections, and upper respiratory infections than children who live in smoke-free environments. Long-term exposure to ENVIRONMENTAL CIGARETTE SMOKE, called passive smoking, has the same health consequences as active smoking.
The health risks of cigarette smoking diminish within 30 to 40 minutes of the last puff. With sustained SMOKING CESSATION, the risk for cardiovascular disease gradually diminishes over 5 to 10 years, finally reaching a level consistent with the risks for a nonsmoker. Any damage that has already occurred to the cardiovascular system is permanent, however.
See also ANTISMOKING EFFORTS; CARDIOVASCULAR DISEASE PREVENTION; CONTRACEPTION; HEALTH RISK FACTORS; INHALED TOXINS; LIFESTYLE AND CARDIOVASCULAR HEALTH; SMOKING AND CANCER; SMOKING AND HEALTH.
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… PACs take place when another region from the atria depolarizes before the particular sinoatrial node and thus causes a premature heartbeat. Crystal clear as mud? In The english language, another element of…
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Atrioventricular client, i believe.
Purkinje materials run through the atrial nodes to cause contractions.
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The particular signals are produced in the very center itself.
The particular SA node is an inbuilt pacemaker, it discharges activity potentials regularly on its own. This process possible
To begin with, those devices are not accurate. In case you are concerned you need to go see a physician.
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Electrical conductivity of the Coronary heart
www.handwrittentutorials.com — This tutorial looks at the road by which the transmission to contract is sent with the heart. It discusses the SA client, the AV client, the Bundles, and also the Purkinje fibers. Fo
Photograph Puzzle, Illustration showing the particular nerves of the the heart. Illustration of the section through the the heart, displaying (in yellow) the nerve fibres th
Aging is associated with a decrease in the function from the sinoatrial client (SAN; there is certainly decrease in intrinsic cardiovascular rate) and an increase within the incorporation
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