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The Venous System
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
Artin A. Shoukas and Carl F. Rothe
Gravimetric techniques can be used to measure changes in blood volume. If the organ can be isolated and weighed continuously with the blood vessels intact, changes in volume can be measured in response to drugs or reexes. With an important modication, this approach can be applied to an organ or the systemic circulation; the tissues are perfused at a constant rate, and the outow is emptied at a constant pressure into a reservoir. Because the reservoir is emptied at a constant rate for the perfusion, changes in reservoir volume reect an opposite change in the perfused tissue blood volume [7]. To measure compliance, the outow pressure is changed (2−5 mmHg) and the corresponding change in reservoir volume noted. With the inow and outow pressure held constant, the pressure gradients are assumed to be constant so that 100% of an outow pressure change can be assumed to be transmitted to the primary capacitance vessels. Any reex or drug-induced change in reservoir volume may be assumed to be inversely related to an active change in vascular volume [7-9]. If resistances are also changed by the reex or drug, then corrections are needed and the interpretations are more complex.
Toxic Responses of the Blood
Published in Stephen K. Hall, Joana Chakraborty, Randall J. Ruch, Chemical Exposure and Toxic Responses, 2020
The circulatory system is the transport system that supplies substances absorbed from the gastrointestinal tract and oxygen to the tissues, returns carbon dioxide to the lungs and other products of metabolism to the kidneys, functions in the regulation of body temperature, and distributes hormones and other agents that regulate cell function. The cellular elements of the blood—red blood cells, white blood cells, and platelets—are suspended in plasma. The normal total circulating blood volume is about 8% of the body weight, or 5600 mL in a 70-kg man. About 55% of this volume is plasma.
Diagnostic Devices
Published in Laurence J. Street, Introduction to Biomedical Engineering Technology, 2016
Physical exertion increases pressure as the heart pumps harder and more rapidly in order to maintain adequate blood supply to muscles. Various diseases, usually related to the renal system, can cause increases in blood volume, which in turn increases blood pressure (hypertension). Hypertension can also be produced by abnormal responses of the autonomic nervous system.
Fluid and electrolyte balance considerations for female athletes
Published in European Journal of Sport Science, 2022
Paola Rodriguez-Giustiniani, Nidia Rodriguez-Sanchez, Stuart D.R. Galloway
The role of thirst, sodium balance, and renal function are integrated to help regulate body water volume and maintain circulating blood volume and cardiovascular function (Armstrong & Johnson, 2018; Leib et al., 2016; McKinley & Johnson, 2004). Thirst is a crucial component of this body water regulatory mechanism. Key physiological signals for thirst are plasma hyperosmolality with consequential cellular dehydration and hypovolemia (Thompson, Bland, Burd, & Baylis, 1986). The need to drink can be driven by habitual, cultural, and psychogenic drivers, as well as by the regulatory response to a decrease in body water. Hypertonicity of the extracellular fluid, or increases in the circulating concentration of certain dipsogenic hormones (such as angiotensin and aldosterone) and neural signals from low- and high- pressure baroreceptors all regulate the thirst response (Johnson & Thunhorst, 1997). Under normal conditions these physiological regulators ensure that plasma volume and osmolality are preserved within normal limits. However, certain situations such as exercise can increase sweat losses and insensible water losses (respiratory water losses). In summary, body fluid and electrolyte balance are regulated by a complex integration of multiple physiological responses (Figure 1). How these responses are influenced by other hormonal fluctuations such as oestrogen and progesterone will now become the focus in the remaining sections of this review.
The need for an alternative method to determine intravascular volumes
Published in European Journal of Sport Science, 2018
L. M. Lobigs, P. Peeling, B. Dawson, Y. O. Schumacher
Blood volume in humans is the sum total of red cell- and plasma-volume. Plasma is the liquid component of blood and plays a critical role in countless physiological processes. Both red cell volume and plasma volume (PV) fluctuate independently and are influenced by exercise, environmental stressors, trauma, and illness (Sawka, Convertino, Eichner, Schnieder, & Young, 2000). For example, exercise results in a PV expansion, claimed to aid in muscle perfusion, increase stroke volume and cardiac output, and enhance the body’s thermoregulatory response (Convertino, 1991; Harrison, 1985; Sawka et al., 2000).