Blood flow heart

The same applies to pathologically-disturbed function. A simulated reduction in coronary blood flow (heart attack) would lead to reduced oxygen supply to the cells in the virtual heart, which would reduce efficiency of cardiac contraction and possibly give rise to heart rhythm disturbances. Ventricular pressure development would be compromised, as would the blood supply to all organs of the body, including the heart. All these implications can be studied in a virtual heart. 

At present, we suspect that toxin-LR causes heart failure in mice, perhaps due to suddenly increased resistance to pulmonary blood flow. Heart failure in mammals is known to cause engorgement of the liver with blood. Pulmonary vascular occlusion may also cause secondary hypoxemia and shock. However, biochemical pathways that are initiated by toxin-LR and that lead to the onset of discernable signs of illness after 30 min are unidentified. The 30 min asymptomatic period following toxin injection may be associated with a toxin-initiated cascade of biochemical events which lead to overt signs of illness. 

Naliboff, B. D., Rickies, W. H., Cohen, M. J., and Naimark, R. S. (1976). Interactions of marijuana and induced stress Forearm blood flow, heart rate, and skin conductance. Psychophysiology 13,... 

Lower-extremity blood flow Heart rate... 

The pumping action of the heart rather than gravity is responsible for blood flow hence the term pgl can be set equal to zero in Eq. (9.29) and the result solved for 77 ... 

One of the remarkable features of the heart, which is about the size of a fist, is that the pumping action or contractions (- 70 times/min) of atria and ventricles are simultaneous. Deoxygenated blood is pumped out to the lungs from one side of the heart at the same time oxygenated blood is pumped out from the other side to the aorta and onward through the body. The entire process of blood flow between the atria, ventricles, and the principal vessels is in unison, controlled in part by four one-way valves. The atrioventricular valves, tricuspid on the right and mitral on the left, prevent blood from flowing... 

In addition to its internal blood flow operation, the heart has its own system of blood vessels to keep the muscle wall of the heart, the myocardium, supphed with oxygenated blood (Fig. 3a). The coronary arteries, which branch from the aorta to the right and left sides of the heart, are vital to maintaining that supply. The heart is an extraordinary electromechanical muscle that can be trained to increase blood flow to the body sixfold. It can range from 5 to 30 L /min during exertion. 

Ca.rdia.c-AssistDevices. The principal cardiac-assist device, the intra-aortic balloon pump (lABP), is used primarily to support patients before or after open-heart surgery, or patients who go into cardiogenic shock. As of the mid-1990s, the lABP was being used more often to stabilize heart attack victims, especially in community hospitals which do not provide open-heart surgery. The procedure consists of a balloon catheter inserted into the aorta which expands and contracts to assist blood flow into the circulatory system and to reduce the heart s workload by about 20%. The disposable balloon is powered by an external pump console. 

Some P-adrenoceptor blockers have intrinsic sympathomimetic activity (ISA) or partial agonist activity (PAA). They activate P-adrenoceptors before blocking them. Theoretically, patients taking P-adrenoceptor blockers with ISA should not have cold extremities because the dmg produces minimal decreases in peripheral blood flow (smaller increases in resistance). In addition, these agents should produce minimal depression of heart rate and cardiac output, either at rest or during exercise (36). 

Moreover, digitahs has indirect effects on the circulation, which in normal hearts results in a small increase in arterial pressure, peripheral resistance, and cardiac output (114). The effects of digitahs on the circulation of an individual experiencing congestive heart failure are much more dramatic, however. The increased cardiac output, for example, increases renal blood flow which can reheve in part the edema of CHF associated with salt and water retention (114). 

P-Adrenoceptor Blockers. There is no satisfactory mechanism to explain the antihypertensive activity of P-adrenoceptor blockers (see Table 1) in humans particularly after chronic treatment (228,231—233). Reductions in heart rate correlate well with decreases in blood pressure and this may be an important mechanism. Other proposed mechanisms include reduction in PRA, reduction in cardiac output, and a central action. However, pindolol produces an antihypertensive effect without lowering PRA. In long-term treatment, the cardiac output is restored despite the decrease in arterial blood pressure and total peripheral resistance. Atenolol (Table 1), which does not penetrate into the brain is an efficacious antihypertensive agent. In short-term treatment, the blood flow to most organs (except the brain) is reduced and the total peripheral resistance may increase. 

Verapamil (Table 1), the first slow channel calcium blocker synthesized to selectively inhibit the transmembrane influx of calcium ions into cells, lowers blood pressure in hypertensive patients having good organ perfusion particularly with increased renal blood flow. Sustained-release verapamil for once a day dosing is available for the treatment of hypertension. Constipation is a prominent side effect. Headache, dizziness, and edema are frequent and verapamil can sometimes cause AV conduction disturbances and AV block. Verapamil should not be used in combination with -adrenoceptor blockers because of the synergistic negative effects on heart rate and contractile force. 

Methyldopa. Methyldopa reduces arterial blood pressure by decreasing adrenergic outflow and decreasing total peripheral resistance and heart rate having no change in cardiac output. Blood flow to the kidneys is not changed and that to the heart is increased. It causes regression of myocardial hypertrophy. 

Cromakalim. Cromakalim has along half-life (254). Cromakalim at an oral dose of 1.5 mg ia humans significantly lowers blood pressure 19/12 mm Hg (systohc/diastoHc pressure). It iacreases reaal blood flow, PRA, and heart rate. Cromakalim has bronchodilating activity that is beneficial for hypertensive asthmatic patients. Because of some undesirable effects seen ia cardiac papillary muscles of animals oa long-term treatmeat, future clinical trials are to be carried out usiag the active enantiomer, lemakalim (BRL 38227). 

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. 

Coronary vasodilator. A drug that enhances blood flow through the blood vessels of the heart. 

Myocardial infarction. Blockage of the blood flow to a portion of the heart muscle leading to tissue damage. 

Nitric oxide (NO) is a minor but villainous component of the atmosphere. It is involved in the formation of both smog (Chapter 11) and acid rain (Chapter 14). You may be surprised to learn that small amounts of NO are also produced in the human body, where it has a generally beneficial effect. In particular, it has the ability to dilate blood vessels, lowering blood pressure and reducing the likelihood of strokes or heart attacks. Beyond that, NO is effective in treating what television commercials refer to as erectile dysfunction it increases blood flow to the penis. 

Hypertension /cardiac ischemia/vaso cons trie tion/central 4- blood pressure Hypertension/cardiac ischemia/skel. muscle blood flow Cardiac inotropy bronchospasm/heart rate/ventricular fibrillation Fascil. cardiac arrest/impairs cardiac perform... 

The cardiotonics are dm used to increase the efficiency and improve the contraction of the heart muscle which leads to improved blood flow to all tissues of the body. The drug s have long been used to treat congestive heart failure (CHF), a condition in which the heart cannot pump enough blood to meet the tissue needs of the body. While the term congestive heart failure continues to be used by some, a more accurate term is simply heart failure. ... 

Glyceryl trinitrate is used in medicines for its effects on blood flow. Physicians use it as a coronary vasodilator for their heart patients. 

Ongoing work is devoted to the accurate description of the origin and spread of excitation from the natural pacemaker to the rest of the heart. Computations of ventricular pressure development are being extended to account for blood flow dynamics in adjacent blood vessels. The thorax... 

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