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Dynamic Speckle
Published in Hector J. Rabal, Roberto A. Braga, Dynamic Laser Speckle and Applications, 2018
The influence of light on the functioning of living matter depends on the degree of homeostasis of the bioobject and the evolution level. It is the lowest for biological molecules, and the highest for vertebrates.30 Homeostasis is the property of either an open system or a closed system, especially a living organism that regulates its internal environment so as to maintain a stable, constant condition. Multiple dynamic equilibrium adjustments and regulation mechanisms make homeostasis possible. Low-intensity radiation does not activate the adaptation mechanisms of a biosystem and does not affect its homeostasis. Thus, at small intensities, it is possible to study the processes occurring in living objects without any serious perturbation in their behavior. In our case we can employ biospeckle techniques, which do not need strong light and do not distort the measurement results because the homeostasis of living matter remains intact even at the local level.
General Systems Theory
Published in Slobodan P. Simonović, Managing Water Resources, 2012
A basic example of a feedback system is a simple thermostat and the maintenance of constant temperature. The thermostat senses a difference between desired and actual room temperature, and activates the heating unit. The addition of heat eventually raises the room temperature to the desired level. Then the thermostat automatically shuts off the heater. The system description used for the thermostat applies equally well to many systems: the electric eye of a camera, a thermostatically controlled oven, the automatic pilot of an airplane and the speed governor of a turbine all follow this pattern. Although these are all mechanically controlled systems, there are also equivalents in the biological world. The human body contains numerous self-regulating physiological processes that enable it to maintain a relatively constant internal environment. This self-regulation, called homeostasis, maintains, for example, a normal body temperature through the continual alteration of metabolic activities and blood flow rates. Goal-directed action is fundamental to human social behaviour too.
Circadian Rhythms and Mental Performance
Published in Gerald Matthews, Paula A. Desmond, Catherine Neubauer, P.A. Hancock, The Handbook of Operator Fatigue, 2017
Homeostasis, keeping the internal environment within narrow limits, is a key concept in biology, and failure in this process can lead to death. This stability is normally achieved by reflex mechanisms acting via negative feedback loops. In spite of the importance of homeostasis, however, repeated measurements during the course of a day have indicated that daily rhythms are superimposed upon this stability. For example, in humans, normally active in the daytime and asleep at night, core temperature is 1–2oC higher in the daytime; day–night changes are observed in physiological variables in general (Minors & Waterhouse, 1981; Reilly, Atkinson & Waterhouse, 1997; Waterhouse & DeCoursey, 2004a).
Redox homeostasis in sport: do athletes really need antioxidant support?
Published in Research in Sports Medicine, 2019
Ambra Antonioni, Cristina Fantini, Ivan Dimauro, Daniela Caporossi
Homeostasis is the tendency of organisms to auto-regulate and to maintain their internal environment in a stable state. This condition is essential for cells so that intracellular environment remains optimal for the manufacturing and processing tasks that take place within. Redox homeostasis is essential for the maintenance of many cellular processes including responses to ROS, signaling, protection of protein thiols, oxidation–reduction reactions as well as the removal of xenobiotics (Holmstrom & Finkel, 2014). Despite the extensive defense system, an increase in ROS production or decrease of antioxidants can lead to a homeostatic imbalance and thereby the redox state becomes more pro-oxidizing. This condition is called oxidative stress and it refers to a disturbance in the pro-oxidant/antioxidant balance in favour of the oxidants, leading to a disruption of redox signaling and control and/or molecular damage (Sies, 2017).
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
Homeostasis to maintain a constant water and electrolyte balance involves the coordination of many inputs/outputs, including neural pathways and integrative centres in the brain and peripheral effectors (Zimmerman et al., 2016; Figure 1). Total body water (TBW) can be most simply subdivided into extra cellular fluid (ECF) and intra cellular fluid (ICF) compartments. ECF is composed of three major compartments: plasma, interstitial, and connective tissue water. The largest component is ICF which has been reported to be around 26 litres (59% of TBW) or 34% of total body mass in an average male and around 19 litres (61% of TBW) or 31% of total body mass in an average female (Ritz et al., 2008). At rest, a water deficit increases the ionic concentration of the extracellular fluid compartment (increased osmolality, decreased plasma volume) and this draws water from the intracellular compartment (Nose, Mack, Shi, & Nadel, 1988). Two receptors also sense this osmotic stimulus in the brain, one regulating drinking behaviour (thirst) and the other controlling renal function (Fitzsimons, 1998; Kanbay et al., 2019; Leib, Zimmerman, & Knight, 2016; Thornton, 2010). A fluid deficit will lead not only to a decrease in glomerular filtration rate and a subsequent renin-angiotensin-aldosterone system (RAAS) response to decrease sodium excretion but also will increase the release of arginine vasopressin (AVP) from the posterior pituitary to alter renal tubular water reabsorption (Stockand, 2010). These actions counter the reduced effective circulating volume and, when combined with the thirst response, drive increased fluid intake to restore body water balance. If there is an excess of water, the lower ionic concentration of body fluids (reduced osmolality, increased plasma volume) will result in the opposite actions. Thus, the kidneys play a central role in regulating inorganic ion composition and fluid volume in the internal environment.