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Cardiovascular System:
Published in Michel R. Labrosse, Cardiovascular Mechanics, 2018
The properties of the blood vessels change as the blood moves from the elastic arteries into the muscular arteries. The muscular arteries have the thickest tunica media layer and contain relatively more smooth muscle and less elastic tissue than the elastic arteries. Thus, they are less distensible than the elastic arteries but are able to contribute to vasoconstriction. They range in size from 3 to 10 mm in diameter. The smallest arteries are called the arterioles, ranging in size from 10 µm to 0.3 mm. The larger arterioles contain all three tunicae, but as they decrease in size closer to the capillary bed, they become more like the capillary walls. Like the muscular arteries, they contain a high proportion of smooth muscle, which usually has some vascular tone (a condition of partial vasoconstriction). The diameter of the arterioles is a large determinant in the amount blood flow entering a connecting capillary bed. Vasoconstriction can be triggered by a change in sympathetic tone or by local effects such as a rise in O2, decrease in CO2, and cold. Conversely, vasodilation occurs when the smooth muscle relaxes, in response to local effectors such as high CO2, high temperature, and histamine. As the blood leaves the arterioles, the pulsatile flow reduces to smooth flow.
Work Capacity, Stress, Fatigue, and Recovery
Published in R. S. Bridger, Introduction to Human Factors and Ergonomics, 2017
Under stressful conditions, breathing exceeds metabolic requirements. According to Schleifer and Ley (1994), this causes a drop in the carbon dioxide concentration in the end-tidal expired air (the last air to be expired when breathing out). Stress-induced hyperventilation decreases the concentration of carbon dioxide in the blood. This has a number of physiological effects. Vasoconstriction of blood vessels reduces the flow of blood to the heart and brain and the amount of oxygen that hemoglobin in the red blood cells can release to the tissues. This is accompanied by feelings of dizziness and heart palpitations. Theoretically, end-tidal carbon dioxide measurement should be a powerful way of measuring nonphysical stress. Unlike heart and ventilation rate measurements which increase both under stress and during exercise, end-tidal pCO2 measurements decrease when the person is under stress but not when physical work is carried out (breathing does not exceed physical work requirements under these conditions). The authors compared these stress indices during self-relaxation, relaxation using a stress management technique known as progressive relaxation and during data entry work at a visual display terminal (VDT). As predicted, end-tidal pCO2 more closely tracked self-reported mood states than the other variables. It seems to be a useful means of investigating the stress of VDT work and might be used as biofeedback in stress management programs.
Treatment
Published in Herman Staudenmayer, Environmental Illness, 2018
The cardiovascular pathway of the stress response provides another example. Heart rate, blood pressure, and respiration usually increase to maintain greater cardiac output to accommodate heightened arousal. Through vasoconstriction, blood is shunted away from the peripheral vascular beds to increase flow to the large muscles and the brain, supplying oxygen and nutrients required for efficient action. The skin of the hands and feet will cool as a consequence of peripheral vasoconstriction. This is the rationale for monitoring skin temperature of the fingers or toes in psychophysiologic stress profiling and biofeedback for cardiovascular disorders.
Physiological and thermoregulatory effects of oral taurine supplementation on exercise tolerance during forced convective cooling
Published in European Journal of Sport Science, 2022
Richard Simmonds, James Cole, Jamie Tallent, Owen Jeffries, Nicola Theis, Mark Waldron
Exercise in cold environments presents a significant challenge to thermoregulation, with exaggeration of the thermal gradient from core-to-environment facilitating heat loss, primarily via convective and conductive pathways (Young & Castellani, 2001). Cold exposure elicits reflex increases in efferent skin sympathetic activity, leading to peripheral vasoconstriction and reductions in skin blood flow to delay heat losses (Castellani & Young, 2016). These thermoregulatory reflexes occur when skin surface temperature decreases ∼3–4°C below a thermoneutral threshold of ∼34°C (Greaney, Stanhewicz, Kenney, & Alexander, 2015). During prolonged cold exposure, shivering becomes important for thermoregulation to generate metabolic body heat (Castellani & Young, 2016). Initial vasoconstriction leads to increased intra-thoracic pressure, central blood pressure, cardiac output and myocardial oxygen demand (Doubt, 1991). Thus, coupled with the thermogenic (shivering) responses, the primary effects of cold exposure increase the net O2 cost at rest and exercise (Cheuvront & Haymes, 2001). Higher rates of glycogenolysis are also observed in cold, driven by increased activation of the sympathetic nervous system due to cold exposure (Jacobs et al., 1985; Martineau & Jacobs, 1988). Collectively, these acute physiological responses to moderately cold exposure could have negative effects on exercise efficiency, potentially leading to an earlier onset of fatigue and impaired endurance performance (Galloway & Maughan, 1997).
A summertime thermal analysis of New Zealand Homestar certified apartments for older people
Published in Building Research & Information, 2022
Cold air inflames the lungs and inhibits circulation, increasing the risk of respiratory conditions. It also induces vasoconstriction, which causes stress to the circulatory system that can lead to cardiovascular effects and death (World Health Organization, 2018a). Additionally, heat exposure can affect sleep quality (Van Loenhout et al., 2016) with poor sleep quality associated with an increased risk for mortality (Sivertsen et al., 2014). While a direct relationship between sleep quality and heat-related mortality remains to be assessed, it has been established that elevated temperature and humidity can reduce thermal comfort, which is highly correlated with sleep quality (Kenny et al., 2019).