[目的]：理解能量代谢的概念，食物的能量指标，能量代谢的测定

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1 精品课程生理学教案第七章能量代谢与体温 [ 目的要求 ]: 1. 了解食物的能量指标, 能量代谢的测定 ; 2. 掌握影响能量代谢的因素, 基础代谢率及其测定 ; 3. 掌握食物的卡价氧热价呼吸商能量代谢体温等概念 ; 4. 理解影响因素对能量代谢基础代谢体温的作用机制及结果 [ 重点 ]: 1. 食物的能量指标的几个概念 ; 2. 影响能量代谢的因素, 基础状态的概念 ; 3. 散热的不同方式及体温调节 [ 难点 ]: 1. 食物的能量指标 ; 2. 能量代谢的测定 ; 3. 体温调节 [ 基本概念 ]: 能量代谢 (energy metabolism); 合成代谢 (anabolism, 又称同化作用 ); 分解代谢 (catabolism, 也称异化作用 ); 动脉血酮体比率 (arterial ketone body ratio,akbr); 能量负荷 (energy charge, 简称能荷 ); 能量代谢率 (energy metabolic rate); 热价 (thermal equivalent of food); 卡价 (caloric value); 氧热价 (thermal equivalent of oxygen); 呼吸商 (respiratory quotient,rq); 非蛋白呼吸商 (non-protein respiratory quotient, NPRQ); 食物的特殊动力效应 (specific dynamic effect); 基础代谢 (basal metabolism); 基础代谢率 (basal metabolism rate, BMR) ; 体温 (body temperature ); 不感蒸发 (insensibleperspiration) 调定点 (set-point); 热敏神经元 (warm-sensitive neuron); 冷敏神经元 (cold-sensitive neuron); 温度感受器 (thermoreceptors); 致热原 (pyrogen); 体温调节 (thermoregulation) [ 授课学时 ]:3 学时 [ 使用教材 ]: 王庭槐主编. 生理学, 第 1 版, 高等教育出版社,2004 北京第一节能量代谢 (energy metabolism) 定义 : 机体内伴随物质代谢过程而发生的能量的释放转移贮存和利用的过程 1. 新陈代谢的概念新陈代谢 : 维持生命的各种活动过程中化学变化的总称新陈代谢包括 : 物质代谢 ( 同化作用, 异化作用 ); 能量代谢 ( 吸热反应, 放热反应 ) 1

2 图 7-1 能量代谢的场所线粒体 2. 能量贮存形式三大营养物质 ( 糖, 脂肪, 蛋白质 ) 三羧酸循环 ( 产生能量的方式 ) 三磷酸腺苷 (ATP 能量的贮存形式 ) 图 7-2 三羧酸循环呼吸链图 7 3 ATP 生成过程 3. 食物的能量指标 (1) 食物热价 (thermal equivalent of food):1g 某种食物氧化时释放的热量 (2) 食物氧热价 (thermal equivalent of oxygen): 某种食物氧化时消耗 1L 氧所产生的热量 (3) 呼吸商 (respiratory quotient): 各种供能物质氧化时产生的 CO2 量与 O2 的消耗量的比值 (4) 非蛋白呼吸商 (nonprotein respiratory quotient, NPRQ): 将一定时间内产生的 CO 2 量和消耗 O 2 量减去分解蛋白质产生的 CO 2 量和耗 O 2 量, 即为非蛋白质部份 ( 糖和脂肪 ) 氧化产生的 CO 2 量和耗 O 2 量一定时间内, 氧化糖和脂肪产生的 CO 2 量和耗 O 2 量的比值, 称为非蛋白质呼吸商 4. 能量代谢的测定 ( 1 ) 直接测热法 ( direct calorimetry) 特殊的检测环境, 测热装置复杂, 研究肥胖和内分泌系统障碍 2

3 (2) 间接测热法 (indirect calorimetry) 图 7-4 直接测热法遵循定比定律, 测定 CO2 产量和尿氮排出量, 测定耗 O2 量, 测量装置较简单 5. 影响能量代谢的因素图 7-5 间接测热法图 7-6 时间耗氧量 (1) 肌肉活动 : 肌肉活动越强能量代谢越高机体任何轻微活动都会提高代谢率, 剧烈运动时耗 O 2 量比安静时可增加 10~20 倍 (2) 精神活动 : 精神活动越剧能量代谢越高 (3) 食物的特殊动力效应 : 进食后产生的额外的热量现象蛋白质作用最强, 可额外增加 30% 左右, 糖脂肪增加 4-6%, 混合食物为 10% 它可能是肝脏处理蛋白质分解产物时额外消耗的能量 (4) 环境温度 : 环境温度升高或降低均可使能量代谢升高 20~30 稳定肌肉松驰 ; <20 代谢寒战, 肌肉紧张度 <10 代谢寒战, 肌肉紧张度 ; >30 代谢体内化学反应速度, 发汗, 呼吸循环机能 (5) 其他因素 : 年龄性别睡眠激素脂肪组织可分泌瘦素 (leptin) 等细胞因子也参与能量代谢的调节小分子的脑肠肽 Ghrelin 对能量平衡有调节作用 6. 基础代谢率及其测定基础状态 : 清晨, 清醒, 静卧, 未作肌肉活动, 前夜睡眠良好, 测定时无精神紧张, 禁食 3

4 12 小时以上, 室温基础代谢 (basal metabolism): 基础状态下的代谢状况基础代谢率 (basal metabolism rate): 基础状态下单位时间内的能量代谢图 7-7 甲状腺疾病患者的基础代谢与正常人基础代谢的比较第二节体温 (body temperature) 1. 体温的概念恒温动物 (homeothermic animal); 变温动物 (poikilothermic animal) 体表温度 (shell temperature); 体核温度 (core temperature) 图 7-8 不同环境温度下人体体温分布图 2. 产热与散热产热器官肝脏, 骨骼肌产热形式战栗产热 (shivering thermogenesis), 骨骼肌收缩引起非战栗产热 (non-shivering thermogenesis), 代谢产热引起散热部位皮肤, 呼出气, 尿, 粪散热方式 : (1) 辐射散热 (thermal radiation): 人体以热射线的形式将体热传给外界 (2) 传导散热 (thermal conduction): 机体的热量直接传给同它接触的较冷物体 (3) 对流散热 (thermal convection): 通过同皮肤接触的空气流动将机体热量传给外界 4

5 (4) 蒸发散热 (thermal evaporation): 通过体表水份的蒸发来散失体热可分为 : 不感蒸发 (insensible evaporation), 以不显汗的形式蒸发机体水份可感蒸发 (sensible evaporation), 以汗液蒸发的形式带走热量 3. 体温调节自主性调节 (autonomic thermoregulation): 增减皮肤血流量, 发汗, 战栗等生理调节行为性调节 (behavioral thermoregulation): 增减衣着, 开电扇空调等行为外周和中枢温度感受器 : 热敏神经元 (warm-sensitive neuron): 当局部组织温度升高时神经冲动的发放频率增加冷敏神经元 (cold-sensitive neuron): 当局部组织温度降低时神经冲动的发放频率增加 (1) 在过冷环境中冷感受器兴奋中枢紧张性血管收缩血流量散热 ; 另外, 产热维持体温的相对稳定 (2) 在炎热环境中热感受器兴奋中枢紧张性血管收缩血流量散热另外, 产热维持体温的相对稳定图 7-9 由下丘脑视前区导出的温度敏感神经元的放电活动体温调定点 (set-point): 视前区 - 下丘脑前部 (PO/AH) 设定了一个规定的体温值, 即 37 体温调定点学说 (set-point theory): 调定点按照 PO/AH 温度敏感神经元的工作特性来调节体温的高低 5

6 图 7-10 体温调节自动控制示意图思考题 1. 外呼吸的呼吸商与细胞呼吸的呼吸商有何异同点及联系? 2. 能用测定甲状腺激素 (T3,T4) 的水平反映基础代谢率的高低吗? 3. 试解释人精神高度紧张时能量代谢和体温的变化过程? 4. 急性发热 ( 如疟疾发作 ) 时为何常表现出寒战, 高热和大汗退烧的三步曲 5. 试述热环境和冷环境中, 体温维持恒定的调节机制案例 : 患者蔡某,35 岁, 工人 2 天前因淋浴受凉后出现体温升高, 体温达 40.2, 时有寒颤, 伴有流涕咳嗽, 诊断为普通感冒, 经服用阿司匹林后患者大汗淋漓, 随后体温下降至 37.8 问题 : 1 请你解释为什么患者发热时有寒颤现象? 2 用退热药出汗后为什么患者的体温会下降? 3 体温的检测部位及其正常值如何? 机体温度如何维持? 参考文献 1. Hilgemann DW Cytoplasmic ATP-dependent regulation of ion transporters and channels: mechanisms and messengers(review). Annu Rev Physiol, 59:193= Matsuzawa Y Pathophysiology and molecular mechanisms of visceral fat syndrome: the Japanese experience(review). Diabetes Metab Rev, 13(1): Weyer C,Walford RL, Harder IT Energy metabolism after 2 year of energy restriction:the biosphere 2 experiment.am J Clin Nutr,72(4): Jequier E,Tappy L Regulation of body weight in humans(review). Physiol Rev, 79(2): Levine JA, Eberhardt NL, Jensen MD Role of nonexercise activity therogenesis in resistance to fat gain in humans.science, 283(5399): Ganong WF Review of medical physiology.20th ed. 人民卫生出版社 Guyton AC,Hall JE Textbook of medical physiology.10th ed. 北京医科大学出版社 Nakazato M,Murakami N,Date Y,et al A role for rgrelin in the central regulation of feeding. Nature,409(6817):194~ Guyton AC, Hall JE Textbook of Medical Physiology. 10th edition, Philadelphia: WB saunders Co. 10.Lingappa VR, Farey K Physiology medicine. New York, McGraw-Hill 11.Vander A, Sherman J, Luciano D Human Physiology. 8th edition, New York, McGraw-Hill 12.Shier D, Butler J, Lewis R Hole's Human anatomy & physiology. 8th edition, New York, McGraw-Hill 13. Andrew Davies, Asa G.H. Blakeley, Cecil Kidd Human Physiology. Philadelphia, WB saunders. 6

7 14. 姚泰 : 生理学, 第 5 版, 人民卫生出版社,2002,ISBN 王庭槐主编. 生理学, 第 1 版, 高等教育出版社,2004 北京 Summary Metabolism is used to refer to all the chemical and energy transformation occurring in the body, which consists of material metabolism and energy metabolism. Energy metabolism refer to the production, storage, transform, release and utility of energy during the process of material metabolism. The carbohydrates, fats and proteins may become the source of energy of the body. These foods can be oxidized in the cell and produced large amounts of energy in this process. The animal organism oxidizes carbohydrates, fats and proteins principally to CO 2, H 2 O and the energy necessary for life processes. It has been pointed out that carbohydrates, fats and proteins can all be used by cells to synthesize large quantities of ATP, and that the ATP can in turn be used as an energy source for many other cellular functions, including synthesis and growth, muscular contraction, glandular secretion, nerve conduction, active absorption, etc. Energy is stored by forming high energy phosphate bonds. The ATP and the creatine phosphate contain all high energy phosphate bonds. Creatine phosphate can transfer energy interchangeably with ATP. The metabolic rate can be determined by simply measuring the quantity of heat liberated form the body by direct or indirect methods.the metabolic rate is affected by many factors.the most important one is muscular exertion. The ingested food also increases the metabolic rate. After a meal containing a large quantity of carbohydrate or fat, the metabolic rate usually increases by only about 4%. However, after a meal containing large quantity of protein, the metabolic rate usually increases by about 30%. Another factor that stimulates metabolic rate is the environmental temperature. When the environmental temperature is lower than body temperature, heat-conserving mechanisms such as shivering are activated and the metabolic rate rises. When the temperature is high enough to raise the body temperature, there is a general acceleration of metabolic processes. In addition, the metabolic rate is also related to body surface area, age, sex and hormones such as thyroid hormone, epinephrine and norepinephrine, growth hormone etc. Even when a person is at complete rest, considerable energy is required to perform all the chemical reactions of the body. This minimum level of energy required to exist is called the basal metabolic rate (BMR). The measurement of the BMR provides a useful means of comparing one person's metabolic rate with that of another under basal conditions. The temperature of human body includes core temperature and the shell temperature. The core temperature is relatively uniform in the core and is regulated within narrow limits by a negative feedback system. The body temperature in physiology means core temperature, i.e., the mean temperature of deep body. In fact, the body temperature is usually indicated by the temperature in the armpit, the mouth (under the tongue) or the rectum. These values normally vary from 36.0 to 37.4, or 36.4 to 37.4, or 36.9 to 37.9 respectively. Under normal conditions, the body temperature is easily affected by day and night, sex, age, muscle activity and other factors, but does not normally vary by more than 1. Body temperature depends on the production and loss of body heat. The main organs of heat production in human body are the liver, the brain, the heart and the skeletal muscles. The production of heat occurs through basic metabolism and muscle activity and is controlled by 7

8 neural and humoral factors. The heat is lost largely through the skin. The volume of heat loss from the body depends mainly upon the differences in temperature between the skin and the surroundings. The flow of blood to the vessels in the skin controlled by sympathetic nerves can regulate the skin temperature. Skin loses heat to the external environment by means of four processes :radiation, conduction, convection and evaporation. Sweating is an active secretion of water by sweat gland, which removes heat from the skin as it evaporates. The main sweating control centre is located in hypothalamus. Thermoregulation includes autonomic thermoregulation and behavioral thermoregulation. Thermoreceptors are divided into peripheral thermoreceptors and central thermoreceptors, which receive cold or hot stimuli. The information converges to the nervous center, especially PO/AH in hypothalamus. The efferent impulse results in the production or loss of the heat so as to regulate the body temperature. 8

Microsoft PowerPoint - 08-Energy-Lecture.ppt

Microsoft PowerPoint - 08-Energy-Lecture.ppt Energy Metabolism & Body Temperature Wang LinLin M.D. Ph.D E-mail: wanglinlin@zju.edu.cn Rm 608, Block B, Research Building, School of Medicine, Zijingang Campus 学习要求第一节能量代谢一能量的来源转移和利用人体能量的来源, 体内能量的转移