[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Physiology](https://durgical.com/en/physiology/) › [Temperature, exercise and metabolism](https://durgical.com/en/physiology/#s-integrative) › Body temperature regulation [Physiology](https://durgical.com/en/physiology/) · [Temperature, exercise and metabolism](https://durgical.com/en/physiology/#s-integrative) # Body temperature regulation - Regulation - Exam priority: high The brain keeps the body core near 37 °C: it sweats and opens skin vessels when hot, shivers and closes them when cold. Updated 2026-11-01 Also called: Thermoregulation **See it in 3D:** [Hypothalamus](https://durgical.com/en/anatomy/hypothalamus/) · [Skin](https://durgical.com/en/anatomy/skin/) ## Key points - Integrating centre: preoptic area/anterior hypothalamus (heat loss); the posterior hypothalamus organizes heat conservation and shivering. - Four routes of heat loss: radiation (largest at rest), conduction, convection and evaporation. - When air is hotter than skin, only sweat evaporation cools; in high humidity (Caribbean coast) that fails too. - Sweat: eccrine glands with sympathetic cholinergic innervation (acetylcholine on muscarinic receptors). - Brown fat: UCP1 uncouples the respiratory chain to make heat without shivering (newborns, via β3). ## What it is The preoptic area of the anterior hypothalamus compares core temperature with a set point (≈37 °C) and integrates input from skin and visceral thermoreceptors. When hot, it boosts heat loss through the skin; when cold, it cuts heat loss and makes more heat. The skin is the radiator and skin blood flow is the valve. ## How it works, step by step - Thermoreceptors in skin, spinal cord and viscera, plus warm-sensitive preoptic neurons, report temperature. - If core temperature rises above the set point, sympathetic vasoconstrictor tone falls and warm blood floods the skin. - Sympathetic cholinergic fibres switch on sweating; evaporation removes ≈0.58 kcal per gram of water. - If temperature falls, norepinephrine closes skin arterioles and arteriovenous anastomoses, and hairs stand up. - Motor neurons receive a rhythmic drive (shivering) that can raise heat production several-fold. - Over longer periods norepinephrine activates brown fat (UCP1) and thyroid hormone raises the basal metabolic rate. ## Responses to heat and cold | Response | Heat | Cold | | --- | --- | --- | | Skin vessels | Vasodilation | Vasoconstriction | | Sweating | Increases (up to 1–2 L/h when acclimatized) | Suppressed | | Heat production | Falls slightly | Shivering, non-shivering thermogenesis | | Behaviour | Seek shade, less activity | Wrap up, curl up | | Acclimatization (days–weeks) | Earlier, more dilute sweat (aldosterone) | Limited in humans | ## Clinical notes - Newborns: large surface area and little insulating fat; they rely on brown fat and cool quickly. - Older adults, high spinal cord injury and anticholinergic drugs impair sweating or vasoconstriction and raise the risk of heat stroke or hypothermia. - Hypothyroidism: cold intolerance; hyperthyroidism: heat intolerance with warm, moist skin. ## Memory aid «Skin is the radiator, hypothalamus the thermostat, blood the coolant». ## Test yourself Think of the answer, then tap the question to see it. ## Why does the body heat up on a 38 °C, 90%-humidity day in Cartagena despite heavy sweating? With air hotter than skin only evaporation cools, and high humidity stops sweat evaporating: it drips off without removing heat. ## Which transmitter drives eccrine sweat glands, and what does that mean for anticholinergic drugs? Acetylcholine from sympathetic postganglionic fibres acting on muscarinic receptors; anticholinergics dry the skin and favour hyperthermia. ## How does brown fat make heat without muscle contraction? UCP1 lets protons return to the mitochondrial matrix bypassing ATP synthase, so the gradient's energy is released as heat. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/physiology/body-temperature-regulation/) ## See it in 3D The structures of Durgical's 3D anatomy where it happens. - [Hypothalamus](https://durgical.com/en/anatomy/hypothalamus/) - [Skin](https://durgical.com/en/anatomy/skin/) ## Related topics - [Fever](https://durgical.com/en/physiology/fever/) - [Heat exhaustion and heat stroke](https://durgical.com/en/physiology/heat-exhaustion-and-heat-stroke/) - [Hypothermia and cold injury](https://durgical.com/en/physiology/hypothermia-and-cold-injury/) - [Energy metabolism and basal metabolic rate](https://durgical.com/en/physiology/energy-metabolism-and-basal-metabolic-rate/) ## Related conditions - [Hypothyroidism](https://durgical.com/en/conditions/hypothyroidism/) ## In Biochemistry - [UCP1 (thermogenin)](https://durgical.com/en/biochemistry/enzymes/ucp1/) [← All of physiology](https://durgical.com/en/physiology/) Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given. Sources: [24.6 Energy and Heat Balance](https://openstax.org/books/anatomy-and-physiology-2e/pages/24-6-energy-and-heat-balance) (OpenStax (Rice University), 2022); [1.5 Homeostasis](https://openstax.org/books/anatomy-and-physiology-2e/pages/1-5-homeostasis) (OpenStax (Rice University), 2022); [5.3 Functions of the Integumentary System](https://openstax.org/books/anatomy-and-physiology-2e/pages/5-3-functions-of-the-integumentary-system) (OpenStax (Rice University), 2022); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 74). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/physiology/body-temperature-regulation/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/physiology/body-temperature-regulation/