Introduction to Physiology
Introduction
加工误差Physiology is the study of the functions of living matter. It is concerned with how an organism performs its varied activities: how it feeds, how it moves, how it adapts to changing circumstances, how it spawns new generations. The subject is vast and embraces the whole of life. The success of physiology in explaining how organisms perform their daily tasks is bad on the notion that they are intricate and exquisite machines who operation is governed by the laws of physics and chemistry.
Although some process are similar across the whole spectrum of biology—the replication of the genetic code for or example—many are specific to particular groups of organisms. For this reason it is necessary to divide the subject into various parts such as bacterial physiology, plant physiology, and animal physiology.
To study how an animal works it is first necessary to know how it is built. A full appreciation of the physiology of an organism must therefore be bad on a sound knowledge of its anatomy. Experiments can then be carried out to establish how particular parts perform their functions. Although there have been many important physiological investigations on human volunteers, the need for preci control ov
er the experimental conditions has meant that much of our prent physiological knowledge has been derived from studies on other animals such as frogs, rabbits, cats, and dogs. When it is clear that a specific physiological process has a common basis in a wide variety of animal species, it is reasonable to assume that the same principles will apply to humans. The knowledge gained from this approach has given us a great insight into human physiology and endowed us with a solid foundation for the effective treatment of many dias.
The building blocks of the body are the cells, which are grouped together to form tissues. The principal types of tissue are epithelial, connective, nervous, and muscular, each with its own characteristics. Many connective tissues have relatively few cells but have an extensive extracellular matrix. In contrast, smooth muscle consists of denly packed layers of muscle cells linked together via specific cell junctions. Organs such as the brain, the heart, the lungs, the intestines, and the liver are formed by the aggregation of different kinds of tissues. The organs are themlves parts of distinct physiological systems. The heart and blood vesls form the cardiovascular system; the lungs, trachea, and bronchi together with the chest wall and diaphragm form the respiratory system; the skeleton and skeletal muscles form the musculoskeletal system; the brain, spinal cord, autonomic nerves and ganglia, and peripheral somatic nerves form the nervous system, and so on.
Cells differ widely in form and function but they all have certain common characteristics. Firstly, they are bounded by a limiting membrane, the plasma membrane. Secondly, they have the ability to break down large molecules to smaller ones to liberate energy for their activities.
生理学简介
介绍
生理学是研究生物体功能的科学。它研究生物体如何进行各种活动，如何饮食，如何运动，如何适应不断改变的环境，如何繁殖后代。这门学科包罗万象，涵盖了生物体整个生命过程。生理学成功地解释了生物体如何进行日常活动，基于的观点是生物体好比是结构复杂而灵巧的机器，其操作受物理和化学规律控制。
尽管从生物学整个范畴看，生物体某些活动过程是相似的——如基因编码的复制——但许多过程还是某些生物体群组特有的。鉴于此有必要将这门学科分成不同部分研究，如细菌生理学、植物生理学和动物生理学。
要研究一种动物如何活动，首先需要了解它的构成。要充分了解一个生物体的生理学活动就必须掌握全面的解剖学知识。一个生物体的各部分起着什么作用可通过实验观察得知。尽管我们对志愿者进行
了许多重要的生理调查，但是实验条件需要精确控制，所以我们当前大多生理知识还是源于对其它动物如青蛙，兔子，猫和狗等的研究。当我们明确大多数动物物种的特定生理过程存在共同之处时，相同的生理原理适用于人类也是合理的。通过这种方法，我们获得了大量的知识，从而让我们对人类生理学有了更深入的了解，为我们有效治疗许多疾病提供了一个坚实的基础。
机体的基本组成物质是细胞，细胞结合在一起形成组织。组织的基本类型有上皮组织，结缔组织，神经组织和肌组织，每类组织都有各自的特征。许多结缔组织中细胞量相对较少，但是有大量的细胞外基质。相比而言，光滑的肌组织由大量密密麻麻的肌细胞通过特定的细胞连接组成。各种器官如脑，心脏，肺，小肠和肝等由不同种类的组织聚集而成。这些器官是不同生理系统的组成部分。心脏和血管组成心血管系统；肺，器官，支气管，胸壁和膈肌组成呼吸系统；骨骼和骨骼肌组成骨骼肌系统；大脑，脊髓，自主神经和神经中枢以及周围躯体神经组成神经系统等等。
细胞在形体和功能上差异很大，但是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 posss a nucleus which contains genetic information in the form of deoxyribonucleic acid (DNA).
Living cells continually transform materials. They break down gluco and fats to provide energy for other activities such as motility and the synthesis of proteins for growth and repair. The chemical c
hanges are collectively called metabolism. The breakdown of large molecules to smaller ones is called catabolism and the synthesis of large molecules from smaller ones anabolism.
In the cour of evolution, cells began to differentiate to rve different functions. Some developed the ability to contract (muscle cells), others to conduct electrical signals (nerve cells). A further group developed the ability to crete 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.
情海无边
Most tissues contain a mixture of cell 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 defen against infection and the platelets are vital components in the process of blood clotting. There are a number of different types 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 Systemsk线图基础知识
The cardiovascular system
The cells of large multicellular animals cannot derive the oxygen and nutrients 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 vesls by virtue of the pumping action of the heart. The heart, blood vesls, and associated tissues form 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 from 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 perfu the tissues according to their needs. Fluid exchanged between the blood plasma and the tissues pass into the lymphatic system, which eventually drains back into the blood.
The respiratory system
冷爵士The energy required for performing the various activities of the body is ultimately derived from respir
ation. This process involves the oxidation of foodstuffs to relea 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。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。松饼的简单做法
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 adjusted to meet the requirements of the body? What limits the rate of oxygen uptake in the lungs?
The digestive system
The 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 digestive 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 ca of the digestive system, key physiological questions 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 tract
The chief function of the kidneys is to control the composition of the extracellular fluid. In the cour of this process, they also eliminate non-volatile waste products from the blood. To perform the functions, the kidneys produce urine of variable composition which is temporarily stored in the bladder before voiding. The key physiological questions in this ca are: how do the kidneys regulate the composition of the blood? How do they eliminate toxic waste? How do they respond to stress such as dehydration? What mechanisms allow the storage and elimination of the urine?
The reproductive system阿依努人
Reproduction is one of the fundamental characteristics of living organisms. The gonads produce specialized x cells known as gametes. At the core of xual 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 parate individuals are mixed to produce offspring that differ genetically from their parents.
The musculoskeletal system
This 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 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 systems
The activities of the different organ systems need to be coordinated and regulated so that they act 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？张仪受笞
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 us electrical signals to transmit information very rapidly to specific cells. Thus the nerves pass electrical signals to the skeletal muscles to control their contraction. The endocrine system cretes chemical agents, hormones, which travel in the bloodstream to the cells upon which they exert a regulatory effect. Hormones play a major role in the regulation of many different organs and are particularly important in the regulation of the menstrual cycle and other aspects of reproduction.
The immune system provides the body’s defens against infection both by killing invading organisms and by eliminating diad or damaged cells.
Although it is helpful to study how each organ performs its functions, it is esntial to recognize that the activity of the body as a whole is dependent on the intricate interactions between the various organ systems. If one part fails, the conquences are found in other organ systems throughout the whole body. For example, if the kidneys begin to fail, the regulation of the internal environment is impaired which in turn leads to disorders of function elwhere.
Homeostasis
Complex mechanisms are at work to regulate the composition of the extracellular fluid and individual cells have their own mechanisms for regulating 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 esntial if the cells of the body are to function 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 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. Conquently, the concentration of potassium in the extracellular fluid must be kept within a narrow range if the heart is to beat normally.
How Does The Body Regulate Its Own Composition?
The concept of balance
In the cour of a day, an adult consumes approximately 1 kg of food and drinks 2~3 liters of fluid. In a month, this is equivalent to around 30 kg of food and 60~90 liters of fluid. Yet, in general, body weight remains remarkably constant. Such individuals are said to be in balance; the intake of food and drink matches the amounts ud to generate energy for normal bodily activities plus the loss in urine and feces. In some circumstances, such as starvation, intake does not match the needs of the body and muscle tissue is broken down to provide gluco for the generation of energy. Here, the intake of protein is less than the rate of breakdown and the 节，以便共同作用满足机体需要。人体有两大调节系统：神经系统和内分泌系统。神经系统通过电信号迅速将信息传导给特定细胞。这样神经将电信号传递给骨骼肌以控制收缩。内分泌系统分泌化学物质―激素。激素通过血流到达施与调节作用的细胞。激素在许多不同器官中起着重要作用，在月经期调节和其它生殖方面尤其重要。
免疫系统通过杀死入侵的有机体，清除致病或损伤细胞为机体提供防御功能。
虽然研究各器官如何行使功能很有益处，但我们必须认识到机体作为一个整体所做的活动依赖于各器官系统间错综复杂的相互作用。如果一部分无法正常工作，全身其它器官系统也会受到影响。例如，如果肾脏出现问题，内部环境的调节受损，结果导致其它器官系统功能紊乱。
稳态
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，2~3升液体。以一个月计算，这相当于约30千克食物，60~90升液体。然而，一般来说，机体体重是基本不变的。这类个体可以说处于平衡状态。食物和液体的摄入量相当于正常机体活动消耗的能量加上尿液和粪便中丢失的能量。在一些情况下，如饥饿状态，摄入量与机体所需量并不相当，肌组织断裂，提供葡萄糖产生能量。蛋白质的摄入低于肌组织断裂的速度，机体处于负氮平衡。同样地，如果机体组织正处于生长期，如生长期的儿童，孕妇和早期训
冻疮药individual is said to have a negative nitrogen balance. Equally, if the body tissues are being built up, as is the ca for growing children, pregnant women and athletes in the early stages of training, the daily intake of protein is greater than the normal body turnover and the individual is in positive nitrogen balance.
This concept of balance can be applied to any of the body constituents including water and salt and is important in considering how the body regulates its own composition. Intake must match requirements and any excess must be excreted for balance to be maintained. Additionally, for each chemical constituent of the body there is a desirable concentration range, which the control mechanisms are adapted to maintain. For example, the concentration of gluco in the plasma is about 4~5mmol/L between meals. Shortly after a meal, plasma gluco ris above this level and thi
s stimulates the cretion of the hormone insulin by the pancreas, which acts to bring the concentration down. As the concentration of gluco falls, so does the cretion of insulin. In each ca, the changes in the circulating level of insulin act to maintain the plasma gluco at an appropriate level. This type of regulation is known as negative feedback. During the period of insulin cretion, the gluco is being stored as either glycogen or fat.
A negative feedback loop is a control system that acts to maintain the level of some variable within a given range following a disturbance. Although the example given above refers to plasma gluco, the basic principle can be applied to other physiological variables such as body temperature, blood pressure, and the osmolality of the plasma. A negative feedback loop requires a nsor of some kind that responds to the variable in question but not to other physiological variables. Thus an osmoreceptor should respond to changes in osmolality of the body fluids but not to changes in body temperature or blood pressure. the information from the nsor must be compared in some way with the desired level by some form of comparator. if the two do not match ,an error signal is transmitted to an effector, a system that can act to restore the variable to its desired level .the features of negative feedback can be appreciated by examining a simple heating system .the controlled variable is room temperature, which is nd by a thermostat. the effector is a heater of some kind .when th
e room temperature falls below the t point, the temperature difference is detected by the thermostat which switches on the heater .this heats the room until the temperature reaches the per t level whereupon the heater is switched off.
To summarize, the body is actually a social order of about 100 trillion cells organized into different functional structures, some of which are called organs. each functional structures its share to the maintenance of homeostatic conditions in the extracellular fluid, which is called the internal environment.as long as normal conditions are maintained in this internal environment ,the cells of the body continue to live and function properly. Each cell benefits from homeostasis, and in turn, each cell contributes its share toward the maintenance of homeostasis. This reciprocal interplay provides continuous automaticity of the body until one or more functional systems lo their ability to contribute their share 练阶段的运动员，那么蛋白质的日常摄入量比正常机体所需要的多。相反，此时个体处于正氮平衡。
平衡的概念可以应用到机体的任何构成成分上，包括水和盐，而且平衡在机体调节其自身成分上是非常重要的。摄入必须等于所需，为维持机体平衡，任何多余的能量都必须排出。此外，因为机体的每种化学成分都有一个可取的浓度范围，控制机制维持这个范围。例如，两餐间血糖浓度大约为4~5mmol/L。进食后不久，血糖含量超过这一范围，刺激胰腺分泌胰岛素，降低浓度。随着葡萄糖浓
度的下降，胰岛素分泌减少。在此情况下，循环胰岛素水平的改变都是为了使血浆中的葡萄糖维持在一个合适的范围内。这种调节称为负反馈机制。在胰岛素分泌期间，葡萄糖像肝糖原或脂肪一样被储存。
负反馈调节是在机体出现紊乱时，将一些变量控制在限定范围内的一个控制系统。虽然上面的例子讲到血糖，但这一基本原则可以应用到其它生理变量中如体温、血压和血浆的渗透浓度。负反馈调节需要一种能对不确定的变量做出反应而对其它生理变量不应答的传感器。因此，渗透压感受器应该能对机体体液渗透的变化而不是体温和血压的变化产生应答。感受器传递的信息必须和理想水平（系统的调定点）以比较者的身份，以某种方式进行比较。如果两者不相符，一个错误信号就会传递给效应器，效应器是一种能使变量保持在理想水平的系统。负反馈的这些特点可以通过检测一种简单的加热系统来理解。被控制的变量是室温，它可以由一个温度计检测到，效应器是一种加热器。当室温降低到调定点以下时，温度计就可以监测到温度的变化而开启加热器，对室内进行加温，直到室温升高到先前调好的调定点，加热器关闭。
总而言之，机体实际上是由100万亿细胞有序组成了不同的功能结构，其中一些被称为器官。每个功能结构都在维持细胞外液稳态方面发挥其作用，这称之为内环境。只要内部环境处于正常状态，机体细胞继续生存并正常运行。每个细胞都从稳态中获益，反过来，每个细胞都为稳态做出贡献。这种相互作用促使机体持续自主运行，直至一个或多个功能系统不能正常运转。此时，机体所有细胞都会受
损。功能极
