第七章 能量代谢，体温与麻醉

【目的要求】了解机体能量代谢的概况，能量代谢的测定原理，温度习服。熟悉测定能量代谢的几个基本概念（食物的热价、氧热价、呼吸商、非蛋白呼吸商），体温的测定方法和生理性波动，维持体温相对稳定的机制。掌握影响能量代谢的主要因素，基础代谢和基础代谢率等概念，测定基础代谢的条件，体温的概念，机体主要产热的器官和散热的方式。了解麻醉和手术期间影响体温的因素。掌握术中体温升高和降低的危害。了解恶性高热及低温生理学。

【教学内容】

1.        能量代谢的概念。机体能量的来源，在机体代谢过程中能量的释放、储存、转化及利用，能量平衡。

2.        食物的热价、氧热价、呼吸商、非蛋白呼吸商概念。间接测热法的原理。影响能量代谢的主要因素。基础代谢、基础状态和基础代谢率的概念、测定方法及临床意义。

3.        体温的概念，体温的测定方法和生理性波动。机体产热过程和散热过程的平衡，主要产热器官、产热形式及产热活动的调节。散热的主要部位，散热的方式（辐射、传导、对流、蒸发）。汗液的成分特点，汗腺的神经支配和分泌调节，散热反应的调节。

4.        自主性体温调节，体温调节的控制系统，丘脑下部的整合作用。体温相对稳定的负反馈调节机制，体温调定点，温度习服。

5.   麻醉和手术期间影响体温的因素：麻醉用药的影响（全身麻醉药，肌肉松驰剂，神经阻滞剂，交感神经兴奋药），室温的影响及各种操作的影响。术中体温升高和降低的的危害：体温升高－代谢加强；体温降低－麻醉药需要量减少－术后苏醒时间延迟。

6.  恶性高热及低温生理学；人工低温对代谢的影响；对神经系统的影响；对呼吸系统的影响；对循环系统的影响；对肝、肾功能的影响；对血液系统的影响；对水电平衡的影响。

【计划学时】4学时。

Chapter VII Energy Metabolism and Temperature

 In adults the rates at which molecules are synthesized (anabolism) and broken down (catabolism) are approximately equal, and so the chemical composition of the body does not change appreciably. The energy released during a chemical reaction is either released as heat or is transferred to other molecules. In all cells, energy is transferred from the catabolism of fuel molecules to adenosine triphosphate (ATP). The hydrolysis of ATP to adenosine triphosphate (ADP) and Pi then transfers this energy to cell functions. ATP is formed by oxidative phosphorylation and substrate phosphorylation.

Regulation of Total Body Energy Balance

The energy liberated during a chemical reaction appears either as heat or work. Total energy expenditure = heat produced + external work done + energy stored. Metabolic rate is influenced by the muscular activity, environmental temperature, emotional state, food intake, age, sex, height, weight, body surface area and body temperature. Basal metabolic rate is increased by the thyroid hormones and epinephrine.

Energy storage, as fat, can be positive or negative when metabolic rate is less than or greater than, respectively, the energy content of ingested food. Energy storage is regulated mainly by reflex adjustment of food intake to metabolic rate. In addition, metabolic rate increases or decreases, to some extent, when food intake is chronically increased or decreased, respectively.

Regulation of Body Temperature

   Body temperature, measured as rectal temperature, shows a circadian rhythm, being highest during the day and lowest at night. Body temperature is regulated by altering heat production and/or heat loss so as to change total-body heat content. Heat production is altered by increasing muscle tone, shivering, and voluntary activity. Heat-loss mechanisms include radiation, conduction, convection, and evaporation of water from the body surface. Heat loss by radiation, conduction, and convection depends on the difference in temperature between the skin surface and the environment. . In response to cold, skin temperature is decreased by decreasing skin blood flow through reflex stimulation of the sympathetic nerves to the skin. In response to heat, skin temperature is increased by inhibiting the nerves. Behavioral responses such as putting on more clothes also influence heat loss.

  Evaporation of water occurs all the time as insensible loss from the skin and respiratory lining. Additional water for evaporation is supplied by sweat, stimulated by the sympathetic nerves to the sweat glands. Increased heat production is essential for temperature regulation at environmental temperatures below the thermoneutral zone, and sweating is essential at temperatures above this zone. The hypothalamus and other brain areas are the integrating centers for temperature-regulating reflexes. Both peripheral and central thermoreceptors participate in these reflexes.

  The most common causes of hyperthermia are fever and exercise. Fever is due to a resetting of the temperature set point so that heat production is increased and heat loss is decreased in order to raise body temperature to the new set point and keep it there. The stimulus is endogenous pyrogens, probably including IL-I, TNF, and IL-6. The hyperthermia of exercise is not due primarily to a changed set point but to the increased heat produced by the muscles.

内容提要

（一）能量代谢

1. 能量代谢是指生物体内物质代谢过程中所伴随的能量释放、转移、贮存和利用的过程。机体生命活动所需的能量物质，最终来自于食物中的糖、脂肪和蛋白质。能量转化和利用的关键环节是三磷酸腺苷(ATP)，它既是体内重要的储能物质,又是直接的供能物质。通过食物的热价、氧热价、呼吸商和非蛋白呼吸商，可测定机体在一定时间内所消耗的食物种类和量，或测定机体所产生的热量与所做的外功，从而测算出整个机体的能量代谢率，即单位时间内所消耗的能量。

2. 影响能量代谢的主要因素有肌肉活动、精神活动、食物的特殊动力效应和环境温度等。

3. 人体在基础状态下的能量代谢称为基础代谢，而基础状态下，单位时间内的能量代谢称为基础代谢率。基础代谢率随性别、年龄等不同而有生理变动。

（二）体温

1. 人和高等动物机体保持一定的温度，是机体进行新陈代谢和正常生命活动的必要条件。体温是指机体深部的平均温度。临床上通常用直肠、口腔和腋窝等部位的温度来代表机体的深部温度（即体温）。直肠温度的正常值为36.9～37.9℃，口腔（舌下部）温度的正常值为36.7～37.7℃，腋窝温度的正常值为36.0～37.4℃。

2. 正常情况下，人体温保持相对稳定，但可受昼夜变化、性别、年龄和肌肉活动等因素的影响而发生波动。

3. 正常体温的维持是机体在体温调节机构的控制下，使产热和散热两个生理过程处于动态平衡的结果。机体的主要产热器官是内脏、脑和骨骼肌等。安静时机体以内脏器官（肝脏产热量最多）产热为主；运动或劳动时以骨骼肌产热为主。人体的主要散热部位是皮肤。当环境温度低于人体表层温度时，大部分的体热通过皮肤的辐射、传导和对流散发。当外界气温等于或高于皮肤温度时，机体唯一有效的散热方式就是通过蒸发来散失体热。

4. 环境温度或机体功能状态的变化，都可使体温产生波动。但人和高等动物能够在体内外环境温度变化的情况下始终保持体温的相对稳定，是因为机体内具有完善而精确的体温调节机制。包括自主性体温调节和行为性体温调节两种方式，二者相互配合，通过调节机体的产热和散热过程，维持体温的相对稳定，以确保生命活动的正常进行。自主性体温调节过程是通过生物自动控制系统完成的。