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Thermal Physiology and Thermoregulation
Published in James Stewart Campbell, M. Nathaniel Mead, Human Medical Thermography, 2023
James Stewart Campbell, M. Nathaniel Mead
The hypothalamus integrates inputs from thermoreceptors in both the skin and core organs. Activation of warm thermoreceptors may cause inhibition of cold receptors.16 Specialized neuronal thermoreceptors in the hypothalamus constantly compare arterial blood temperature to an internal set point. This temperature setting may vary with individuals and with circadian rhythms; core temperature typically fluctuates between average values of 36.4°C (97.5°F) in the morning and 36.9°C (98.4°F) in the evening.17 Various pathological processes can induce either systemic or local thermal anomalies; for example, core temperature may increase due to infection, inflammation, trauma, and malignancy, while limb temperature may decrease due to ischemia or increase due to inflammation.
Behind the Scenes
Published in Ivana Špelić, Alka Mihelić-Bogdanić, Anica Hursa Šajatović, Standard Methods for Thermal Comfort Assessment of Clothing, 2019
Ivana Špelić, Alka Mihelić-Bogdanić, Anica Hursa Šajatović
The thermoreceptors are located immediately under the skin at discrete separated spots. The cold-sensitive thermoreceptors are most numerous and most superficially situated. Usually, all skin areas have 3 to 10 times more cold spots than warmth spots. Their number varies from 15 to 25 cold spot/cm2 in the lips to 3 to 5 cold spot/cm2 in the fingers to less than 1 cold spot/cm2 in some broad surface areas of the trunk. Humans are able to perceive different gradations of cold and heat, from freezing cold to cold, to cool to indifferent to warm sensations, from warm, to hot, to burning hot (Guyton and Hall, 2016). The cold sensors are closer to the surface than the warm, so these peripheral sensors are more dedicated to the rapid detection of cold than of warmth. The thermoreceptors are located in the dermis, with the cold receptors placed immediately beneath the epidermis and the warmth receptors placed within the upper layer of the dermis. The average depth for cold receptors is 0.15 to 0.17 mm, and 0.3 to 0.6 mm for warmth receptors (Arens and Zhang, 2006).
Human and Biomimetic Sensors
Published in Patrick F. Dunn, Fundamentals of Sensors for Engineering and Science, 2019
A stimulus can be characterized by its energy, location, intensity, and duration. Human sensory receptors respond to mechanical, chemical, thermal, and electromagnetic energy, as presented in Table 3.1. These are called mechanoreceptors, chemoreceptors, thermoreceptors, and photoreceptors, respectively. The stimuli of chemoreceptors are molecules that bind to the receptor site. Stimuli include oxygen, hydrogen (thus, pH), and more complex molecules. Mechanoreceptor stimuli are strain, vibration, acceleration, pressure, and sound. Light photons (electromagnetic energy) stimulate photoreceptors. Thermoreceptors are stimulated by temperature and changes in temperature. Each sensor description, its signal pathway, and sensor characteristics are presented in the following.
A proposed long-term thermal comfort scale
Published in Building Research & Information, 2021
Sormeh Sharifi, Wasim Saman, Alemu Alemu, John Boland
Both temperature and pain are felt through the skin and share common physiology (Krantz, 2012). Both have receptive fields that cover large areas of the skin with sensory receptors connected to free nerve endings (Krantz, 2012). Both receptors are categorized as somatic sensory nerves in the Peripheral Nervous System (PNS), which is outside the brain and spinal cord (Marieb & Hoehn, 2015) associated with conscious perceptions (Canavero & Vincenzo, 2013; Ebner & Kaas, 2015; Waldman, 2009). Two groups of somatic sensory nerves, thermoreceptors and nociceptors conduct the impulses of temperature and pain, respectively from the receptors to the Central Nervous System (CNS) (Cuevas, 2011; Hees & Gybels, 1981; Marieb & Hoehn, 2015; Ochoa & Torebjork, 1989; Waldman, 2009). Both types of impulses are transmitted to the tissue outside of the brain (Apkarian et al., 2005; Ebner & Kaas, 2015; Pribram, 2011) by lateral parts of the spinothalamic tract, which is an ascending pathway of the spinal cord (KENHUB, 2018; Krantz, 2012; Rea, 2015). Temperature and pain are processed for perception in different columns of the somatosensory cortex (Krantz, 2012; Oi et al., 2017). The final output is a perception of the senses. Due to the similarities of thermal perception and pain perception in terms of their receiving, transmitting portals and processing, it is rational to consider the currently accepted use of the long-term pain reporting method for reporting long-term thermal comfort perception.
Does detailed hygrothermal transport analysis in respiratory tract affect skin surface temperature distributions by thermoregulation model?
Published in Advances in Building Energy Research, 2020
Chong Wang, Sung-Jun Yoo, Kazuhide Ito
The controlling system of the Stolwijk model was developed based on studies of the coupling function between sensor signals and effector action (Stolwijk & Hardy, 1966b). The system can be divided into three parts: thermoreceptors, effectors, and the coupling function between them. In the regulation process, the thermoreceptors recognize the difference between the instantaneous temperature and reference temperature (temperature at which the whole controlled system maintains thermal balance with no thermoregulatory actions) in different body parts, and generate error signals. The signals are then used to derive effector actions, which are distributed to different body parts and modified according to local conditions if necessary. The effector actions are vasoconstriction, vasodilation, shivering, and sweating. The commands for these actions were modelled as multiple functions of integrated skin temperature signals and temperature signals from the hypothalamus by means of statistical regression, using measured data obtained from numerous experiments.
Heat, moisture and air transport through clothing textiles
Published in Textile Progress, 2020
It was reported that thermoreceptors in the skin, i.e. the receptors which respond to changes in temperature, are responsible for thermal comfort sensations. Other factors that can have an influence on the wearer comfort are softness, stickiness, roughness, itchiness, heaviness, stiffness and prickliness which involve the mechanoreceptors, i.e. the receptors which respond to mechanical stimuli. In the presence of moisture, the friction between the skin and fabric increases and the receptors in the skin are stimulated. It was reported that an even pressure applied to someone wearing tight clothing in a cold environment made a person feel damp even though the fabric was dry (Li, 2001).