Applied exercise physiology and the environment
Nick Draper, Helen Marshall in Exercise Physiology, 2014
Thermoregulation is the control of body temperature within a narrow range and involves a variety of mechanisms to either increase or reduce body temperature. Humans regulate their body temperature to maintain an optimal internal environment for the cells of the body. Research indicates, for example, that when Tc falls below 37°C there is a concomitant slowing in brain cell activity and a decrease in performance. In addition, the enzymes that catalyse metabolic reactions function optimally within a narrow temperature range. The internal thermal balance is maintained by a variety of mechanisms that are initiated by the hypothalamus in response to sensory input from hot and cold receptors located in the skin, muscles, spinal cord and brain. The body’s thermoregulatory mechanisms attempt to maintain Tc at, or close to, 37°C.
Protocol for Standardized Data Collection in Humans
U. Snekhalatha, K. Palani Thanaraj, Kurt Ammer in Artificial Intelligence-Based Infrared Thermal Image Processing and Its Applications, 2023
According to the second law of thermodynamics, heat flows from high to low levels of temperature, leading to thermal equilibration of objects presenting initially at different temperatures. Thus, the final temperature on the surface of the objects is determined by their starting values. Thermoregulation is a physiological system aiming to maintain a core temperature within a narrow range despite challenges of heat gain from or heat loss to the environment. However, in addition to autonomic thermoregulation, humans extended and modified natural behaviors to achieve thermal comfort, leading already in the early stages of mankind to equivalents of clothing. In the so-called thermoneutral zone, heat exchange with the environment is exclusively controlled via constriction or dilation of cutaneous skin vasculature since neither heat production nor evaporative heat loss is required to keep the inner organs on a constant temperature. Or, in other words, little gains or dissipations of heat may become visible as alterations of local skin temperature. However, not every change in the width of the vascular beds must represent a thermoregulatory response (Marins et al., 2014).
The environment
Francesco E. Marino in Human Fatigue, 2019
Previous chapters outlined the significance and advantages of bipedal locomotion, a characteristic unique to humans and apparently intimately tied to our thermoregulatory strategy (see Chapter 1). This is a key concept since thermoregulation is not just a physiological response to a given environmental challenge but an interactive survival strategy as evidenced by the varying ways in which animals are able to produce and offload heat (Angilletta et al. 2010) – for example, heterothermy, the ability of some animals to switch from having to depend on the environment to adjust their body temperature (poikilothermic) to being able to produce their own body heat (endothermic). Mammals and birds are normally described as having the capacity to maintain a constant temperature (homeotherms). This is undoubtedly an impressive capability which is dependent on the exchange of heat between the body and the environment as given by the equation: Where S is heat storage, M is metabolic rate of the body, W is the mechanical work produced, E is rate of total evaporative loss due to evaporation of sweat and Q is total rate of heat loss from the skin. Although homeotherms are able to maintain a relatively constant body temperature, it is now apparent that they are also able to vary their body temperature over the lifespan, with this variation likely to be relative to the latitude of their habitat (Angilletta et al. 2010)
A review of construction workforce health challenges and strategies in extreme weather conditions
Published in International Journal of Occupational Safety and Ergonomics, 2023
Sanjgna Karthick, Sharareh Kermanshachi, Apurva Pamidimukkala, Mostafa Namian
Human physiology encompasses both physiological and behavioral responses that sustain a reasonable core body temperature (CBT) that ranges from 35 to 40 °C (95–104 °F) despite being exposed to a broad range of ambient temperatures. Thermoregulation is the body’s ability to maintain and adjust its internal temperature. When it is unable to do so, thermal stress causes a series of short-term and long-term health concerns [4]. Therefore, when outdoor workers are exposed to extreme heat or cold and their system is unable to thermoregulate, they experience heat or cold stress that renders them susceptible to various illnesses such as musculoskeletal disorders (MSDs), cardiovascular strain, kidney disease, etc. [4,5]. Factors such as acclimatization, individual heat/cold tolerance levels, water intake capacity and body mass index (BMI) also affect the extent to which workers are impacted. These factors are interrelated and should be considered while evaluating heat-related or cold-related stress [6]. Water intake capacity refers to the amount of fluid consumed by an individual and the frequency with which it is consumed. Workers who drink more fluids are less affected by extreme heat than those who drink less [6]; therefore, it is recommended that those who work outdoors in hot weather drink more than the minimum daily requirement of fluids to avoid related health issues. The amount of water needed by an individual varies according to factors such as age, weight, the intensity of physical work and the temperature, but drinking more water to stay hydrated is always suggested in extremely hot weather [7].
Physiology of sweat gland function: The roles of sweating and sweat composition in human health
Published in Temperature, 2019
Lindsay B. Baker
Eccrine glands were the first type of sweat gland discovered; as they were initially described in 1833 by Purkinje and Wendt and in 1834 by Breschet and Roussel de Vouzzeme, but were not named eccrine glands until almost 100 years later by Schiefferdecker [11]. Eccrine glands are often referred to as the small gland variety, but are by far the most ubiquitous type of sweat gland [12]. Humans have ~2–4 million eccrine sweat glands in total and are found on both glabrous (palms, soles) and non-glabrous (hairy) skin [13–15]. Gland density is not uniform across the body surface area. The highest gland densities are on the palms and soles (~250–550 glands/cm2) [16] and respond to emotional as well as thermal stimuli. The density of eccrine glands on non-glabrous skin, such as the face, trunk, and limbs are ~2–5-fold lower than that of glabrous skin [16], but distributed over a much larger surface area and are primarily responsible for thermoregulation.
When to investigate for secondary hyperhidrosis: data from a retrospective cohort of all causes of recurrent sweating
Published in Annals of Medicine, 2022
Nived Collercandy, Camille Thorey, Elisabeth Diot, Leslie Grammatico-Guillon, Eve Marie Thillard, Louis Bernard, François Maillot, Adrien Lemaignen
Thermoregulatory sweating is a physiological mechanism to maintain thermoregulation homoeostasis in humans. Sweating is triggered by a body temperature increase, which is sensed by peripheral and central thermoreceptors under the central control of the hypothalamus [1,2]. The hypothalamus, in turn, activates the autonomic nervous system through the efferent sympathetic pathway. Sweat is primarily produced by eccrine glands, which are widespread throughout the skin in significant numbers (1.6–4 million on the whole body) with variable density. These glands have muscarinic receptors that can be bound to acetylcholine, a neurotransmitter released from sudomotor nerves. Upon stimulation, human sweat glands can produce an average sweat rate of 1.4 l/h. This rate is regulated by body fluid volume and mechanically by skin hydration status [2].
Related Knowledge Centers
- Bladder
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- Hypothermia
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