1、Introduction to Physiology生理学简介Introduction介绍Physiologyis the study of the functions of living matter. It is生理学是研究生物体功能的科学。它concerned withhow an organism performs its varied activities: how it研究生物体如何进行各种活动，如何饮食，feeds, how it moves, how it adapts to changing circumstances, how it如何运动， 如何适应不断改变的环境， 如何
2、spawns new generations. The subject is vast and embraces the whole of繁殖后代。 这门学科包罗万象， 涵盖了生物life. The success of physiology in explaining how organisms perform their体整个生命过程。生理学成功地解释了生daily tasks is based on the notion that they are intricate and exquisite物体如何进行日常活动，基于的观点是生machines whose operation is g
3、overned by the laws of physics and物体好比是结构复杂而灵巧的机器，其操chemistry.作受物理和化学规律控制。Although some processes are similar across the whole spectrum of尽管从生物学整个范畴看，生物体某biology the replication of the genetic code for or example些活动过程是相似的 如基因编码的复 many arespecific to particular groups of organisms. For this reason it
4、 is necessary制 但许多过程还是某些生物体群组特to divide the subject into various parts such as bacterial physiology, plant有的。鉴于此有必要将这门学科分成不同physiology, and animal physiology.部分研究， 如细菌生理学、 植物生理学和动To study how an animal works it is first necessary to know how it is物生理学。built. A full appreciation of the physiology of
5、an organism must therefore要研究一种动物如何活动，首先需要be based on a sound knowledge of its anatomy. Experiments can then be了解它的构成。要充分了解一个生物体的carried out toestablish how particular parts perform their functions.生理学活动就必须掌握全面的解剖学知Although there have been many important physiological investigations on识。一个生物体的各部分起着什
6、么作用可human volunteers, the need for precise control over the experimental通过实验观察得知。尽管我们对志愿者进conditions has meant that much of our present physiological knowledge行了许多重要的生理调查，但是实验条件has been derived from studies on other animals such as frogs, rabbits, cats, 需要精确控制，所以我们当前大多生理知and dogs. Whenit is clear th
7、at a specific physiological process has a识还是源于对其它动物如青蛙， 兔子，猫和common basis ina wide variety of animal species, it is reasonable to狗等的研究。当我们明确大多数动物物种assume that the same principles will apply to humans. The knowledge的特定生理过程存在共同之处时，相同的gained from thisapproach has given us a great insightinto human生理原理适
8、用于人类也是合理的。通过这physiology and endowed us with a solid foundation forthe effective种方法，我们获得了大量的知识， 从而让我treatment of many diseases.们对人类生理学有了更深入的了解，为我The buildingblocks of the body are the cells, whichare grouped们有效治疗许多疾病提供了一个坚实的基together to formtissues. The principal typesof tissue are epithelial,础。conne
9、ctive, nervous, and muscular, each withits own characteristics.机体的基本组成物质是细胞，细胞结Many connective tissues have relatively few cells but have an extensive合在一起形成组织。组织的基本类型有上extracellular matrix. In contrast, smooth muscle consists of densely皮组织， 结缔组织， 神经组织和肌组织， 每packed layers of muscle cells linked toget
10、her via specific cell junctions.类组织都有各自的特征。许多结缔组织中Organs such as the brain, the heart, the lungs, the intestines, and the liver细胞量相对较少，但是有大量的细胞外基are formed by the aggregation of different kinds of tissues. The organs are质。相比而言， 光滑的肌组织由大量密密麻themselves parts of distinct physiological systems. The hear
11、t and blood麻的肌细胞通过特定的细胞连接组成。各vessels form the cardiovascular system; the lungs, trachea, and bronchi种器官如脑， 心脏，肺，小肠和肝等由不同together with the chest wall and diaphragm form the respiratory system;种类的组织聚集而成。这些器官是不同生the skeleton and skeletal muscles form the musculoskeletal system; the理系统的组成部分。心脏和血管组成心血bra
12、in, spinal cord, autonomic nerves and ganglia, and peripheral somatic管系统； 肺，器官， 支气管， 胸壁和膈肌组nerves form the nervous system, and so on.成呼吸系统；骨骼和骨骼肌组成骨骼肌系Cells differ widely in form and functionbut they allhave certain统；大脑，脊髓，自主神经和神经中枢以及common characteristics. Firstly, they are bounded by a limiting周围躯
13、体神经组成神经系统等等。membrane, the plasma membrane. Secondly, they have the ability to break细胞在形体和功能上差异很大，但是down large molecules to smaller ones to liberate energy for their activities.它们有某些共同的特征。 第一，它们由限制Thirdly, at some point in their life history, they possess a nucleus which contains genetic information
14、in the form of deoxyribonucleic acid (DNA).Living cells continually transform materials. They break down glucose and fats to provide energy for other activities such as motility and the synthesis of proteins for growth and repair. These chemical changes are collectively called metabolism. The breakd
15、own of large molecules to smaller ones is called catabolism and the synthesis of large molecules from smaller ones anabolism.In the course of evolution, cells began to differentiate to serve different functions. Some developed the ability to contract (muscle cells), others to conduct electrical sign
16、als (nerve cells). A further group developed the ability to secrete different substances such as hormones or enzymes. During embryological development, this process of differentiation is re-enacted as many different types of cell are formed from the fertilized egg.Most tissues contain a mixture of c
17、ell types. For example, blood consists of red cells, white cells, and platelets. Red cells transport oxygen around the body. The white cells play an important role in defense against infection and the platelets are vital components in the process of blood clotting. There are a number of different ty
18、pes of connective tissue but all are characterized by having cells distributed within an extensive noncellular matrix. Nerve tissue contains nerve cells and glial cells.The Principal Organ SystemsThe cardiovascular systemThe cells of large multicellular animals cannot derive the oxygen and nutrients
19、 they need directly from the external environment. The oxygen and nutrients must be transported to the cells. This is one of the principal functions of the blood, which circulates within blood vessels by virtue of the pumping action of the heart. The heart, blood vessels, and associated tissues form
20、 the cardiovascular system.The heart consists of four chambers, two atria and two ventricles, which form a pair of pumps arranged side by side. The right ventricle pumps deoxygenated blood to the lungs where it absorbs oxygen from the air, while the left ventricle pumps oxygenated blood returning fr
21、om the lungs to the rest of body to supply the tissues. Physiologists are concerned with establishing the factors responsible for the heartbeat, how the heart pumps the blood around the circulation, and how it is distributed to perfuse the tissues according to their needs. Fluid exchanged between th
22、e blood plasma and the tissues passes into the lymphatic system, which eventually drains back into the blood.The respiratory systemThe energy required for performing the various activities of the body is ultimately derived from respiration. This process involves the oxidation of foodstuffs to releas
23、e the energy they contain. The oxygen needed for this process is absorbed from the air in the lungs and carried to the tissues by the blood. The carbon dioxide produced by the respiratory activity of膜包被， 即细胞质膜； 第二，细胞有把大分子分解为小分子来释放活动所需能量的能力；第三，在生命过程中某个阶段，细胞体内存在一个以脱氧核糖核酸 (DNA) 形式包含基因信息的细胞核。活体细胞不断转化物质。
24、它们为其它活动提供能量分解葡萄糖和脂肪，比如自身生长和修复所需的蛋白质运动和合成。这些化学变化统称为新陈代谢。把大分子分解为小分子的过程称为分解代谢，小分子合成大分子的过程称为合成代谢。细胞在进化过程中不断分化进行不同的功能活动。 有些细胞具有收缩能力 （如肌细胞），有些可以传导电信号（如神经细胞）。进一步进化的细胞能够分泌不同物质如荷尔蒙 （如内分泌细胞） 或酶。胚胎发育过程中，分化的过程由于很多不同细胞来源于受精卵而再次发生。大多数组织包含有不同的细胞类型。比如，血液中含红细胞，白细胞和血小板。红细胞运输全身的氧气。白细胞在抵御感染时起重要作用，血小板是血液凝集过程中重要的成分。结缔组织有
25、多种不同类型，但有一个共同特征，即细胞分布在丰富的细胞外基质中。神经组织含神经细胞和神经胶质细胞。主要的器官系统心血管系统大型多细胞动物体的细胞不能从外界环境中获取直接所需的氧气和营养物质。这些氧气和营养物质必须转运到细胞。这是血液的主要功能之一，血液凭借心脏的泵血作用在血管内流动循环。 心脏、血管和结缔组织组成了心血管系统。心脏包括四个腔，两个心房和两个心室构成了一对并排存在的泵。右心室将脱氧的血液泵至肺中，肺中的血液吸收空气中的氧气，而左心室把从肺回流来的有氧血液泵出至身体其它部位，供应给各组织。生理学家研究促使心脏跳动的因素，心脏如何泵送血液使其循环，心脏如何根据各组织所需分配血液。血浆
26、和组织间的流动液体交换流入淋巴系统，最终回流到血液中。呼吸系统机体进行各项活动所需的能量最终来the tissues is carried to the lungs by the blood in the pulmonary artery where it is excreted in the expired air. The basic questions to be answered include the following: How is the air moved in and out of the lungs? How is the volume of air breathed a
27、djusted to meet the requirements of the body? What limits the rate of oxygen uptake in the lungs?The digestive systemThe nutrients needed by the body are derived from the diet. Food is taken in by the mouth and broken down into its component parts by enzymes in the gastrointestinal tract. The digest
28、ive products are then absorbed into the blood across the wall of the intestine and pass to the liver via the portal vein. The liver makes nutrients available to the tissues both for their growth and repair and for the production of energy. In the case of the digestive system, key physiological quest
29、ions are: How is food ingested? How is it broken down and digested? How are the individual nutrients absorbed? How is the food moved through the gut? How are the indigestible remains eliminated from the body?The kidneys and urinary tractThe chief function of the kidneys is to control the composition
30、 of the extracellular fluid. In the course of this process, they also eliminate non-volatile waste products from the blood. To perform these functions, the kidneys produce urine of variable composition which is temporarily stored in the bladder before voiding. The key physiological questions in this
31、 case are: how do the kidneys regulate the composition of the blood? How do they eliminate toxic waste? How do they respond to stresses such as dehydration? What mechanisms allow the storage and elimination of the urine?The reproductive systemReproduction is one of the fundamental characteristics of
32、 living organisms. The gonads produce specialized sex cells known as gametes. At the core of sexual reproduction is the creation and fusion of the male and female gametes, the sperm and ova (eggs), with the result that the genetic characteristics of two separate individuals are mixed to produce offs
33、pring that differ genetically from their parents.The musculoskeletal systemThis consists of the bones of the skeleton, skeletal muscles, joints, and their associated tissues. Its primary function is to provide a means of movement, which is required for locomotion, for the maintenance of posture, and
34、 for breathing. It also provides physical support for the internal organs. Here the mechanism of muscle contraction is a central issue. The endocrine and nervous systems.The endocrine and nervous systemsThe activities of the different organ systems need to be coordinated and regulated so that they a
35、ct together to meet the needs of the body. Two coordinating systems have evolved: the nervous system and the endocrine源于呼吸。 这一过程包括食物 （主要是糖类和脂肪） 的氧化， 释放它们所含的能量。 这一过程中， 氧气来自于肺中的空气， 经由血液到达全身各组织。组织呼吸活动中释放的二氧化碳由肺动脉中的血液运送至肺，然后呼气排出体外。需回答的基本问题如下：空气是如何进出肺的？呼吸的空气量如何适应机体所需？限制肺吸收氧气频率的因素是什么？消化系统机体所需营养物质来源于饮食。食物经
36、口腔进入体内，在胃肠道内经酶将其分解成小分子物质。这些消化物通过肠壁吸收入血液， 通过门静脉进入肝脏。 经肝脏作用后，这些营养物质能够满足组织生长修复及能量需求。 在消化系统部分， 重要的生理学问题是：食物是如何消化的？食物如何被个体分解消化？个体营养物质如何吸收？食物如何在肠内转运的？未消化的残留如何从体内排出？泌尿系统肾脏主要功能是控制细胞外液体的形成。在这一过程中， 肾脏也会把不可挥发的废物排出去。为行使这一功能，在排出之前，肾脏产生含有各种成分的尿液并将其暂时储存在膀胱中。这一部分主要的生理学问题是：肾脏如何调节血液中的成分？如何排出有毒废物？如何应对像脱水这样的应激反应？以及尿液可以
37、存储和排出体外的机制是什么？生殖系统生殖是活生物体的一个基本特征。生殖腺产生专门的性细胞， 被称为配子。 性生殖的核心是雌雄配子即精子和卵子的产生和融合，因此两个独立个体的基因特征融合而产生一个基因上与双亲不同的后代。运动系统这一系统由骨、 骨骼肌、关节和它们的相关组织组成。其主要功能是提供运动需要，维持姿势及呼吸运动。 它也为内脏器官提供物理支持。 这一部分， 肌肉收缩机制是主要问题。内分泌系统和神经系统不同器官系统的活动需要协作和调system. The nervous system uses electrical signals to transmit information节，以便共同
38、作用满足机体需要。人体有两very rapidly to specific cells. Thus the nerves pass electrical signals to the大调节系统： 神经系统和内分泌系统。神经skeletal muscles to control their contraction.The endocrine system系统通过电信号迅速将信息传导给特定细secretes chemical agents, hormones, which travel in the bloodstream to胞。这样神经将电信号传递给骨骼肌以控the cells upon wh
39、ich they exert a regulatory effect. Hormones play a major制收缩。内分泌系统分泌化学物质 激素。role in the regulation of many different organs and are particularly激素通过血流到达施与调节作用的细胞。important in the regulation of the menstrual cycle and other aspects of激素在许多不同器官中起着重要作用，在reproduction.月经期调节和其它生殖方面尤其重要。The immune system p
40、rovides the body免疫系统通过杀死入侵的有机体，清 s defenses against infectionboth by killing invading organisms and byeliminating diseased or除致病或损伤细胞为机体提供防御功能。damaged cells.虽然研究各器官如何行使功能很有益Although it is helpful to study how each organ performs its functions,处，但我们必须认识到机体作为一个整体it is essential to recognize that the a
41、ctivity ofthe body as a whole is所做的活动依赖于各器官系统间错综复杂dependent on the intricate interactions between the various organ systems.的相互作用。 如果一部分无法正常工作，全If one part fails, the consequences are foundin other organ systems身其它器官系统也会受到影响。例如，如果throughout the whole body. For example, if the kidneys begin to fail,
42、the肾脏出现问题， 内部环境的调节受损， 结果regulation of the internal environment is impaired which in turn leads to导致其它器官系统功能紊乱。disorders of function elsewhere.稳态HomeostasisComplex mechanisms are at work to regulate the composition of the extracellular fluid and individual cells have their own mechanisms for regulati
43、ng their internal composition. The regulatory mechanisms stabilize the internal environment despite variations in both the external world and the activity of the animal. The process of stabilization of the internal environment is called homeostasis and is essential if the cells of the body are to fu
44、nction normally.Taking one example, the beating of the heart depends on the rhythmical contractions of cardiac muscle cells. This activity depends on electrical signals which, in turn, depend on the concentration of sodium and potassium ions in the extracellular and intracellular fluids. If there is
45、 an excess of potassium in the extracellular fluid, the cardiac muscle cells become too excitable and may contract at inappropriate times rather than in a coordinated manner. Consequently, the concentration of potassium in the extracellular fluid must be kept within a narrow range if the heart is to
46、 beat normally.How Does The Body Regulate Its Own Composition?The concept of balance各种复杂机制共同作用调节细胞外液的形成，不同个体细胞有自身机制调节内在组成成分。尽管外界环境和动物活动不停变化，调节机制维持着体内环境的稳定。内部环境的稳定被称为稳态，它是机体能够正常发挥作用所必须的。例如，心脏的跳动依赖于心肌细胞有节律的收缩。 这一活动依赖于电信号， 而电信号反过来依赖存在于细胞外和细胞内液体中钠和钾离子的浓度。如果细胞外液中钾离子过多， 心肌细胞兴奋性增强， 可能出现不规律的收缩。 因此，要维持心脏正常跳动，细胞外液中钾离子的浓度就必须控制在一定范围内。机体如何调节物质成分平衡的概念一天中，一个成人需要消耗约1 千克食物， 23 升液体。 以一个月计算， 这相当于约 30 千克食物， 6090 升液体。然而，In the course of a day, an adult consumes approximately 1 kg of food一般来说， 机体体重是基本不变的。 这类个and drinks 23 liters of fluid. In a month, this is equivalent to around 30体可以说处于平衡状态。食物和液体的摄kg of food and
