Cardiovascular system heart

Chronic dextroamphetamine use and abuse can cause sexual dysfunction (impotence). Because of the stress amphetamines place on the cardiovascular system, heart attack, cardiovascular shock, and cerebral hemorrhage may also occur with chronic use. 

The entire cardiovascular system—heart, arteries, and veins—is dependent upon the capillaries. These minute-sized vessels, averaging about 1/2,000 of an inch in diameter, are a part of the microcirculation system— the connecting link between the smallest branches of the arteries and the connecting veins. The segments of this small vessel system in order from the arterial to the venous side are (1) arteriole, (2) terminal arteriole, (3) metarteriole, (4) capillary, and (5) venule (see Fig. B-28). 

Histamine in the Cardiovascular System. It has been known for many years that histamine is present in sympathetic nerves and has a distribution within the heart that parallels that of norepinephrine (see Epinephrine and norepinephrine). A physiological role for cardiac histamine as a modulator of sympathetic responses is highly plausible (15). A pool of histamine in rat heart located neither in mast cells nor in sympathetic nerves has been demonstrated. The turnover of this metaboHcaHy active pool of histamine appears to be maintained by normal sympathetic activity. 

The heart, a four-chambered muscular pump has as its primary purpose the propelling of blood throughout the cardiovascular system. The left ventricle is the principal pumping chamber and is therefore the largest of the four chambers in terms of muscle mass. The efficiency of the heart as a pump can be assessed by measuring cardiac output, left ventricular pressure, and the amount of work requHed to accomplish any requHed amount of pumping. 

Mean arterial pressure and cardiac output, an expression of the amount of blood that the heart pumps each minute, are the key Indicators of the normal functioning of the cardiovascular system. Mean arterial pressure is strictly controlled, but by changing the cardiac output, a person can adapt, e.g., to increased oxygen requirement due to increased workload. Blood flow in vital organs may vary for many reasons, but is usually due to decreased cardiac output. However, there can be very dramatic changes in blood pressure, e.g., blood pressure plummets during an anaphylactic allergic reaction. Also cytotoxic chemicals, such as heavy metals, may decrease the blood pressure. 

Angiotensin converting enzyme (ACE) plays a central role in cardiovascular hemostasis. Its major function is the generation of angiotensin (ANG) II from ANGI and the degradation of bradykinin. Both peptides have profound impact on the cardiovascular system and beyond. ACE inhibitors are used to decrease blood pressure in hypertensive patients, to improve cardiac function, and to reduce work load of the heart in patients with cardiac failure. 

Cardiovascular system—hypertension, edema, congestive heart failure, and thromboembolism ... 

Pathological observations indicate that lesions of the cardiovascular system can be a cause of death in patients with anaphylaxis [2], Myocardial lesions might be the anatomical basis for the irreversible cardiac failure occasionally associated with systemic anaphylaxis [3]. There is compelling evidence that the heart is directly and/or indirectly involved in several forms of anaphylaxis in man [1,4,5]. 

Anaphylaxis is the most dramatic and potentially catastrophic manifestation of allergic disorders. It can affect virtually any organ including the cardiovascular system. Cardiovascular collapse and hypotensive shock in anaphylaxis have been attributed to peripheral vasodilation, enhanced vascular permeability and plasma leakage, rather than any direct effect on the myocardium. However, there is increasing experimental and clinical evidence that the human heart is a site and target of anaphylaxis. 

Heart and cardiovascular system Atherosclerosis Red blood cells... 

The cardiovascular system includes the heart, which serves as a pump for the blood, and the blood vessels, which transport blood throughout the body. Under normal conditions, this system is a continuous, closed circuit, meaning that the blood is found only in the heart and blood vessels. 

Vasomotor center. Autonomic nervous activity to the cardiovascular system is regulated by the vasomotor center (see Figure 15.4). Located in the lower pons and the medulla of the brainstem, the vasomotor center is an integrating center for blood pressure regulation. It receives several sources of input, processes this information, and then adjusts sympathetic and parasympathetic discharge to the heart and blood vessels accordingly. 

Although typically asymptomatic, the dominant organ systems involved are the neuromuscular and cardiovascular systems. Symptoms include heart palpitations, tetany, twitching, and generalized convulsions. 

Cardiovascular Effects. There were no histopathological effects on the heart after inhalation or oral exposure at any concentration tested (15-5,900 ppm for the inhalation route and 1-750 mg/kg/day for the oral route) and with acute, intermediate, or chronic exposure durations (Gorzinski et al. 1985 NTP 1977, 1989 Weeks et al. 1979). The risk that humans will experience adverse effects on the cardiovascular system as the result of exposure to hexachloroethane through the environment seems to be relatively low. 

One of the pollutants known to interfere with cardiovascular development is 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD). TCDD is a persistent, bioaccumulative environmental contaminant, as well as a potent developmental toxicant and human carcinogen [30]. Piscine, avian, and mammalian cardiovascular systems are sensitive to TCDD toxicity, with effects including cardiac enlargement, edema, and several dysfunctions. In zebrafish embryos, these effects include areduction in cardiomyocyte number at 48 hpf, decreased heart size, altered vascular remodeling, pericardial edema, and decreased ventricular contraction culminating in ventricular standstill [31-34]. 

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