Itch and Sensitive Skin
Golara Honari, Rosa M. Andersen, Howard Maibach in Sensitive Skin Syndrome, 2017
In accordance with the existence of dedicated histamine-sensitive primary afferents, cat spinal cord recordings provided evidence for a specific class of dorsal horn neurons projecting to the thalamus, which strongly respond to histamine administered to the skin by iontophoresis (4). The itch-selective units in lamina I of the spinal cord form a distinct pathway projecting to the posterior part of the ventromedial thalamic nucleus, which projects to the dorsal insular cortex (5), a region which has been shown to be involved in a variety of interoceptive modalities such as thermoception, visceral sensations, thirst, and hunger. Thus, the combination of dedicated peripheral and central neurons with a unique response pattern to pruritogenic mediators and anatomically distinct projections to the thalamus provides the basis for a specific neuronal pathway for itch.
Psychobiological foundations of early sensory-motor development and implications for neonatal care
Philip N. Murphy in The Routledge International Handbook of Psychobiology, 2018
The somatosensory system underlies the perception of a wide range of stimuli. It can be subdivided into four functionally distinct subsystems: tactile perception, proprioception, nociception and thermoception. Each has a specific set of peripheral receptors — in the skin, muscles and joints — and neural pathways (for a complete review, see Abraira & Ginty, 2013). The receptors can be distinguished according to the type of stimulus to which they respond, and according to their anatomical situation (exteroceptors or interoceptors). The tactile subsystem is sensitive to the size, shape and texture of objects and their movement on the skin. Four types of tactile cutaneous receptors, distributed throughout the body, were identified. The Merkel discs and the Meissner corpuscules are receptors involved in discriminative touch. They have small and well-defined cutaneous receptive fields and are located in the superficial layers of the skin (dermal–epidermal junction). The Ruffini receptors and the Pacini corpuscules, located in the deeper layers of the skin (dermis) and the subcutaneous tissue, have wide and blurry receptive fields and are involved in non-discriminative touch. Proprioception refers to the perception of one’s body position and movements, and depends on mechanoreceptors in muscles and joints. Neuromuscular spindles are sensitive to muscle length, articular receptors are sensitive to the position of the joints, and Golgi tendon organs are sensitive to muscle tension. Both tactile and proprioceptive information is conveyed to the brain via the lemniscus pathway. Nociception refers to pain perception, and thermoception to the perception of temperature. Both are supported by highly arborized free nerve endings, transmitting information to the brain by slow unmyelinated (C) and fast myelinated (Aδ) fibres through the spinothalamic pathway.
Methodological Considerations
Christoph de Haën in X-Ray Contrast Agent Technology, 2019
The reference dimensions of Dierkes, Hoffmann, and Marz (1996) for the characterization of the modes of production and reproduction of knowledge in different knowledge cultures did not seem to capture the full richness of diversity encountered in this study. Therefore, a number of additional distinctions among modes are introduced here, without claiming thereby to have exhausted the possibilities. A first useful additional differentiation of modes involves preferential use of some of the five classical physiological senses. Given their multiplicity the preferences of a person or a collective may best be captured by a normalized radar chart. When dealing with some diseases the early radiologist with his characteristically visual orientation had to contend with the knowledge culture of the specialist in internal medicine who traditionally reconstructed clinical reality mostly from anamnesis and physical examination, i.e., inspection (vision), manipulation, palpation (touch), auscultation (hearing) and percussion (coordinated touch and hearing) (Lachmund 1997), as well as body temperature sensing (thermoception). The clash in paradigms has been exemplified perceptively in the case of lung tuberculosis with its disputed site of initiation and course of progression (Pasveer 1993; Lerner 1992). Regarding the sense of seeing and visualization, it is worth noting that before the advent of X-ray diagnosis, physicians paid scarce attention to visualization and corresponding communication of their findings. Apparently, it was the advent of X-ray diagnosis that triggered some of them to introduce marked drawings of human torsos into patient medical records (Howell 1986, 1989; Grigg 1965). Eventually this led to the illustrated Röntgen report as a separate document, prepared by the radiologist (Grigg 1965). Pertaining to the sense of hearing, it has been argued that the noise of machines to the adept is a form of music, and as such a source of inspiration of technology (Pacey 1999). The preferential use of senses manifests itself also through preferential choices of communication media such as the voice, the written word, the gesture, body contact, the image, dressing, or music. Even the choice between presenting an argument while writing in real time on a blackboard, flipchart, or overhead projector transparency, a modality today still common among physicists (Ball 2017), versus projecting ready images elaborated using sophisticated software, the dominant manner of physicians, may reflect a difference in the preferred use of senses. Although certainly exceptions, some scientists feel attracted to communicate their PhD work in dance format on occasion of the yearly contest organized by the American Association for the Advancement of Science, a highly respected scientific organization (Bohannon 2010).
Intersegmental differences in facial warmth sensitivity during rest, passive heat and exercise
Published in International Journal of Hyperthermia, 2019
Jung-Hyun Kim, Yongsuk Seo, Tyler Quinn, Patrick Yorio, Raymond Roberge
At the 11th min of each stage, subjective measurements and the warmth sensitivity test were carried out in duplicate. Subjective measures included thermal comfort (TC) obtained using a four-point comfort scale [6] (1: comfortable, 4: very uncomfortable), and overall body thermal sensation (TS) and facial thermal sensation (TSface) utilizing a nine-point sensation scale [7] (–4: very cold, 0: neither warm nor cold, 4: very hot). Immediately following the subjective measurements, facial warmth sensitivity was measured using a thermoception analyzer (Intercross-210, Intercross Co., Tokyo, Japan). The measurement of cutaneous warmth sensitivity using this analyzer has been well described in previous studies [8,9]. In essence, a thermal stimulator probe (25 × 25 mm) of the equipment is built with a Peltier element which transfers power generated heat to a contact surface and measures heat flux between the probe and skin surface. The thermal stimulator probe was placed on the left side of each facial region which was marked with a cosmetic pencil to guide consistent placement. The probe (pre-set at 33 °C) was first stabilized to the skin temperature of the measurement areas with the heat flux maintained within a range of ±30 W·m2. After stabilization, the probe temperature was increased at 0.1 °C·s−1 until subjects detected a warmth sensation, at which time they pressed a hand-held switch in their right hand. The warmth sensitivity was determined as HFdiff (W·m2) between the end-stabilization and detection of a warmth sensation. As heat flows from the warmer probe to the skin, HFdiff is presented as a negative value, so that numerically greater values of HFdiff indicate the need for greater probe warmth to elicit a warmth sensation and thereby reflect decreased thermosensitivity (e.g., –400 W·m2 indicates decreased thermosensitivity compared to –200 W·m2).
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