The control of body temperature | 体温调节

📚 The control of body temperature | 体温调节

Homeotherms, including humans, maintain a stable internal body temperature regardless of external fluctuations. This homeostatic regulation is known as thermoregulation. The normal core temperature in humans is approximately 37 °C, a value that provides an optimal environment for enzyme-catalysed reactions. Even small deviations from this set point can disrupt metabolic processes and pose serious health risks. The thermoregulatory system involves a feedback loop integrating sensory information, processing in the hypothalamus, and effector responses that balance heat production and heat loss.

恒温动物，包括人类，无论外界温度如何波动，都能维持稳定的体内温度。这种稳态调节称为体温调节。人类正常的核心体温约为 37°C，这一温度为酶催化反应提供了最佳环境。即使偏离这个设定点很小的幅度，也可能扰乱代谢过程，带来严重的健康风险。体温调节系统涉及一个反馈回路，整合感觉信息，在下丘脑进行处理，并通过效应器反应来平衡产热与散热。

1. Introduction to Thermoregulation | 体温调节简介

Thermoregulation is the physiological process by which homeothermic organisms maintain their core body temperature within a narrow, optimal range. In humans, the set point is around 37 °C, although it can vary slightly with circadian rhythm (lower in the early morning, higher in the late afternoon). This constancy is essential because the rates of most biochemical reactions are highly temperature-dependent; enzyme activity peaks at around 37 °C and declines sharply below 35 °C or above 40 °C.

体温调节是恒温生物维持其核心体温在一个狭窄的、最佳范围内的生理过程。人类的体温设定点约为 37°C，尽管会随着昼夜节律略有波动（清晨较低，午后较高）。这种恒定性至关重要，因为大多数生化反应的速率高度依赖温度；酶活性在约 37°C 时达到峰值，低于 35°C 或高于 40°C 时会急剧下降。

The body can be divided into two thermal compartments: the core (deep organs, brain, thorax, abdomen) and the shell (skin, limbs). Core temperature is tightly regulated, while the temperature of the shell can vary considerably depending on environmental conditions and vasomotor adjustments.

人体可划分为两个热区：核心区（深部器官、脑、胸腔、腹腔）和外壳（皮肤、四肢）。核心温度被严格调控，而外壳温度则会随着环境条件和血管舒缩调节而发生较大变化。

2. Why Core Temperature Must Be Kept Constant | 为什么必须维持核心温度恒定

Enzymes and other proteins are finely tuned to function within a narrow temperature window. A rise in temperature increases kinetic energy, initially speeding up reactions, but beyond a certain point (usually above 40 °C) enzymes begin to denature; their tertiary structure unfolds, active sites lose shape, and metabolic pathways fail. Conversely, a drop in temperature reduces molecular motion, slowing enzyme activity and overall metabolism; at very low core temperatures, essential processes such as nerve conduction and cardiac contraction become impaired.

酶和其他蛋白质被精密调节以在狭窄温度窗口内发挥作用。温度升高会增加动能，最初加快反应速率，但超过一定限度（通常高于 40°C），酶便开始变性；其三级结构展开，活性位点变形，代谢途径受阻。相反，温度下降会降低分子运动，减缓酶活性和整体代谢；在核心温度极低时，神经传导和心脏收缩等基本过程会受损。

Moreover, membrane fluidity is temperature-sensitive. Excess heat makes membranes too fluid, potentially leaking ions, while cold makes them too rigid, hindering the function of transport proteins and receptors. Thus, maintaining a stable core temperature is fundamental for homeostasis.

此外，膜的流动性也受温度影响。过热会使膜流动性过强，可能导致离子泄漏；过冷则使膜过于僵硬，妨碍运输蛋白和受体的功能。因此，维持稳定的核心温度对稳态至关重要。

3. The Hypothalamus as the Control Centre | 下丘脑作为调控中枢

The hypothalamus integrates thermal information and compares it to the set point. The preoptic area of the anterior hypothalamus acts as the main thermostat, containing warmth-sensitive and cold-sensitive neurones. When blood temperature deviates, these neurones change their firing rate and drive appropriate effectors. The posterior hypothalamus then orchestrates the effector responses by modulating sympathetic nervous output and hormonal signals.

下丘脑整合温度信息并与设定点进行比较。前下丘脑的视前区充当主恒温器，含有热敏和冷敏神经元。当血液温度偏离设定点时，这些神经元的放电频率发生变化，并驱动相应的效应器。随后后下丘脑通过调节交感神经输出和激素信号来协调效应器反应。

The anterior hypothalamus is often referred to as the heat-loss centre; stimulation provokes vasodilation and sweating. The posterior hypothalamus is the heat-production and conservation centre, triggering vasoconstriction, shivering, and the release of thermogenic hormones. Together, these nuclei maintain the delicate balance required for homeothermy.

前下丘脑通常被称为散热中枢；其兴奋会引发血管舒张和出汗。后下丘脑则是产热和保温中枢，能触发血管收缩、颤抖以及释放生热激素。这些神经核团共同维持恒温动物所需的精细平衡。

4. Detecting Temperature Change: Thermoreceptors | 检测温度变化：温度感受器

Peripheral thermoreceptors are located in the skin and mucous membranes. Cold receptors increase their firing rate when skin temperature falls, peaking around 25–30 °C; warm receptors fire more as temperature rises, especially in the range of 30–45 °C. These signals travel via sensory neurones to the spinal cord and then up to the hypothalamus.

外周温度感受器位于皮肤和黏膜中。冷感受器在皮肤温度下降时放电频率增加，峰值在 25–30°C 左右；热感受器在温度升高时放电增多，尤其在 30–45°C 范围内。这些信号通过感觉神经元传到脊髓，再上传至下丘

Published by TutorHao | A-Level Biology Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）