Blood flow to organs

Prostaglandins play critical roles in a number of physiological processes. These molecules regulate blood flow to organs, stimulate secretion of protective mucosal linings in the gastrointestinal tract, participate in the initiation of platelet aggrega-... 

An important methodology of extrapolating pharmacokinetic or drug properties from one species to another which is relatively independent of such compartmental modeling has been developed by Bischoff and collaborators (13). It is instead based on known anatomical and physiological functions, such as blood flow to organs which either metabolize drugs or are affected by them, the size and... 

The resistance to flow is a strong function of vessel radius Q (x R. As blood vessels become smaller, the resistance to flow increases dramatically (Figure 6.4b). Therefore, an additional consequence of the branching pattern of blood vessels is that the majority of the overall resistance to blood flow resides in the smallest vessels (Figure 6.2b) the majority of the pressure drop ( 80%) occurs in arterioles and capillaries. This natural consequence of the physics of fluid flows is exploited in regulation of blood flow to organs of the body. Local blood flow to a tissue is controlled by constriction and dilation of... 

In other words, the primary purpose of anesthesia care is to maintain adequate delivery of required substrates to each organ and cell, which will hopefully preserve cellular function throughout the body. Surgical retraction may result in diminished blood flow to organ systems, again demonstrating the need to monitor adequacy of perfusion. 

Blood flow to organ A blood flow to organ B cardiac output... 

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. 

The liver is the largest internal organ, weighing about 1.5 kg (3.3 lb) in the adult. The blood flow to the liver is 1350 ml/min (27% of the cardiac output) on average and comes from two sources ... 

Loss of plasma volume leads to a decrease in MAP. Baroreceptors located in the aortic and carotid sinuses detect this fall in MAP and elicit reflex responses that include an increase in the overall activity of the sympathetic nervous system. Sympathetic stimulation of the heart and blood vessels leads to an increase in cardiac output (CO) and increased total peripheral resistance (TPR). These adjustments, which increase MAP, are responsible for the short-term regulation of blood pressure. Although increases in CO and TPR are effective in temporary maintenance of MAP and blood flow to the vital organs, these activities cannot persist indefinitely. Ultimately, plasma volume must be returned to normal (see Table 19.1). 

Blood flow to various tissues or organs (e.g., well-perfused organs usually tend to accumulate more chemical than less well perfused organs). 

The total uptake or release of a substance by an organ is equal to the product of the blood flow to the organ and the arterio-venous concentration difference of the substance. 

Organ blood flow and organ concentration - organ blood flow is an important factor which determines the distribution of a xenobiotic once it has been absorbed. This flow is related to blood pressure and while mammalian pressures are around 100 mm Hg, fish species usually are about one-fifth or less of this value. 

But not everything that norepinephrine and acetylcholine do is opposed. In one case, they cooperate. Acetylcholine stimulates penile erection by increasing blood flow to that organ. Norepinephrine controls ejaculation. In still other cases, the pharmacology of these neurotransmitters is unique. For example, acetylcholine induces urination by causing the bladder to constrict. Acetylcholine also induces secretion of saliva and tears. Norepinephrine has nothing to do with these functions. 

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