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  • 案例研究结论:压力下

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    Case Study Conclusion: Under Pressure
    ::案例研究结论:压力下

    As you learned in this chapter, the human body consists of many complex systems that normally work together efficiently — like a well-oiled machine — to carry out life’s functions. For example, the image above illustrates how the brain and spinal cord are protected by layers of membrane called meninges and fluid that flows between the meninges and in spaces called ventricles inside the brain. This fluid is called cerebrospinal fluid (CSF), and as you have learned, one of its important functions is to cushion and protect the brain and spinal cord, which make up most of the central nervous system (CNS). Additionally, CSF circulates nutrients and removes waste products from the CNS. CSF is produced continually in the ventricles, circulates throughout the CNS, and is then reabsorbed by the bloodstream. If too much CSF is produced, its flow is blocked, or not enough is reabsorbed, the system becomes out of balance and CSF can build up in the ventricles. This causes an enlargement of the ventricles called hydrocephalus that can put pressure on the brain, resulting in the types of neurological problems that former professional football player Jason, described in the beginning of this chapter, is suffering from.  
    ::正如你在本章中所了解到的,人体由许多复杂的系统组成,通常能够高效地一起工作——像一个油污良好的机器一样——来完成生命的功能。例如,上面的图像展示了大脑和脊髓如何受到脑膜的层层保护,这些层叫做脑膜和流体,在脑中流出,在脑室中流出。这种流体被称为脑骨液(CSF ) , 正如你所知道的那样,它的重要功能之一是缓冲和保护大脑和脊髓,而脑脊髓是中央神经系统(CNS)中的大部分成分。此外,CSF循环着营养素,从CNS中清除废物产品。CSF在呼吸室中不断生产,在CNS中循环,然后通过血液流中再吸附。如果CSF生产过多,其流量就会被阻塞,或者没有足够的再吸附剂,那么CSF系统就可以在心血管中形成平衡,而CSFSF可以形成一个更大的脑脊椎,这导致称为氢纤维素, 并且从大脑中开始产生压力。

    Recall that Jason’s symptoms included loss of bladder control, memory loss, and difficulty walking. The cause of his symptoms was not immediately clear, although his doctors suspected that it related to the nervous system, since the nervous system acts as the control center of the body, controlling and regulating many other organ systems. Jason’s memory loss directly implicated the brain's involvement, since that is the site of thoughts and memory. The urinary system is also controlled in part by the nervous system, so  the inability to hold urine appropriately can also be a sign of a neurological issue. Jason’s trouble walking involved the muscular system, which works alongside the skeletal system to enable movement of the limbs. In turn, the contraction of muscles is regulated by the nervous system. You can see why a problem in the nervous system can cause a variety of different symptoms by affecting multiple organ systems in the human body.
    ::记得杰森的症状包括膀胱控制丧失、记忆丧失和行走困难。 他的症状原因并不十分明确,尽管他的医生怀疑其症状与神经系统有关,因为神经系统是身体的控制中心,控制和调节许多其他器官系统。杰森的记忆丧失直接涉及到大脑的参与,因为这是思想和记忆的场所。 尿道系统也部分受神经系统控制,因此不能适当保持尿液也可能是神经问题的一个征兆。 杰森的肌肉系统行走困难与肌肉系统有关,而肌肉系统与骨骼系统一起运作,可以使四肢运动。 反过来,肌肉的收缩由神经系统调节。 你可以看到为什么神经系统的问题会通过影响人体的多个器官系统而造成不同的症状。

    To try to find the exact cause of Jason’s symptoms, his doctors performed a lumbar puncture (or spinal tap), which is the removal of some CSF through a needle inserted into the lower part of the spinal canal. They then analyzed Jason’s CSF for the presence of pathogens (such as bacteria) to determine whether an infection was the cause of his neurological symptoms. When no evidence of infection was found, they used an MRI to observe the structures of his brain. This is when they discovered his enlarged ventricles, which are a hallmark of hydrocephalus.  
    ::为了寻找杰森症状的确切原因,他的医生做了一个腰部刺穿(或脊椎水龙头 ) , 也就是通过插入脊髓下部的针将一些骨折解开。 他们随后分析了杰森的骨折,以了解病原体(如细菌)的存在,以确定感染是否是其神经症状的原因。 当没有发现感染的证据时,他们用磁共振仪观察他的大脑结构。 这正是他们发现他的脑部变大时,这是脑积水的标志。

    To treat Jason’s hydrocephalus, a surgeon implanted a device called a shunt in his brain to remove the excess fluid. An illustration of a brain shunt is shown below. One side of the shunt consists of a small tube, called a catheter, which was inserted into Jason’s ventricles. Excess CSF is then drained through a one-way valve to the other end of the shunt, which was threaded under his skin to his abdominal cavity, where the CSF is released and can be reabsorbed by the bloodstream.
    ::为了治疗杰森的脑积水,一名外科医生植入了一个叫“分流”的装置,以去除脑部中的过量液体。下面举例说明了一次脑分流。 分流的一面是一个小管子,叫做导管,插入杰森的腹腔。 然后,过量的CSF通过一个单向阀门排到转流的另一端,从他的皮肤到他的腹腔腔,中央立体系统被释放,并被血液吸附。

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    Implantation of a shunt is the most common way to treat hydrocephalus, and for some people, it can allow them to recover almost completely. However, there can be complications associated with a brain shunt. The shunt can have mechanical problems or cause an infection. Also, the rate of draining must be carefully monitored and adjusted to balance the rate of CSF removal with the rate of its production. If it is drained too fast, it is called overdraining, and if it is drained too slowly, it is called underdraining. In the case of underdraining, the pressure on the brain and associated neurological symptoms will persist. In the case of overdraining, the ventricles can collapse, which can cause serious problems, such as the tearing of blood vessels and hemorrhaging. To avoid these problems, some shunts have an adjustable pressure valve, where the rate of draining can be adjusted by placing a special magnet over the scalp. You can see how the proper balance between CSF production and removal is so critical – both in the causes of hydrocephalus and in its treatment.
    ::切口的植入是治疗脑积水的最常见的方法,对一些人来说,它可以使他们几乎完全恢复。然而,可能会有与脑部切口有关的并发症。 切口可能会有机械问题或造成感染。 此外,必须仔细监测并调整排水速度,以平衡CSF清除速度与生产速度之间的平衡。 如果排水速度过快,它就被称为过度排水,如果排水过慢,它就被称为排水过慢。在排水过慢的情况下,脑部压力和相关神经症状将继续存在。在过度排水的情况下,脑部和神经症状可能会崩溃,这可能造成严重的问题,如血管撕裂和出血。为避免这些问题,有些流口会有一个可调整的压力阀,通过在头顶上放置特殊的磁铁来调整排水速度。你可以看到CSF的生产和排出之间的适当平衡是如何如此关键的 — 两者都是由于流气压造成的。

    In what other ways does your body regulate balance, or maintain a state of homeostasis? In this chapter you learned about the feedback loops that keep body temperature and blood glucose within normal ranges. Other important examples of homeostasis in the human body are the regulation of the pH in the blood and the balance of water in the body. You will learn more about homeostasis in different body systems in the coming chapters.
    ::你的身体以何种其他方式调节平衡,或保持一种顺势状态?在本章中,你了解了将身体温度和血糖保持在正常范围的反馈循环。人体的顺势的其他重要例子是血液中的pH值调节和身体中水的平衡。在接下来的章节中,你会更多地了解不同身体系统中的顺势。

    Thanks to Jason’s shunt, his symptoms are starting to improve, but he has not fully recovered. Time may tell whether the removal of the excess CSF from his ventricles will eventually allow him to recover normal functioning or whether permanent damage to his nervous system has already been done. The flow of CSF might seem simple, but when it gets out of balance, it can easily wreak havoc on multiple organ systems because of the intricate interconnectedness of the systems within the human “machine."
    ::由于杰森的分流,他的症状开始开始好转,但他还没有完全恢复。 时间可能会决定从他的心血管中去除多余的CTF是否最终能使他恢复正常功能,或者是否已经对其神经系统造成了永久性的损伤。 CTF的流量看起来可能很简单,但是,当它失去平衡时,它很容易对多个器官系统造成破坏,因为人类“机器”内部的系统错综复杂的相互联系。

    Chapter Summary
    ::章次摘要

    This chapter provided an overview of the organization and functioning of the human body. You learned that:
    ::本章概述了人体的组织和运作。

    • The human body consists of multiple parts that function together to maintain life. The biology of the human body incorporates the body’s structure — or anatomy — and the body’s functioning, or physiology.
      ::人体由多个部分组成,它们共同发挥作用,维持生命。 人体的生物学包含身体的结构——或解剖学——和身体的功能,或生理学。
    • The organization of the human body is a hierarchy of increasing size and complexity, starting at the level of atoms and molecules and ending at the level of the entire organism.
      ::人体的组织是一个规模和复杂性越来越大的等级,从原子和分子的层次开始,到整个生物体的层次结束。
    • Cells are the level of organization above atoms and molecules, and they are the basic units of structure and function of the human body. Each cell carries out basic life functions, as well as other specific roles. Cells of the human body show a lot of variation.
      ::细胞是原子和分子以上的组织层次,它们是人体结构和功能的基本单位,每个细胞发挥基本的生命功能和其他特定作用,人体细胞存在许多差异。
      • Variations in cell function are generally reflected in variations in cell structure.
        ::细胞功能的变化通常反映在细胞结构的变化中。
      • Some cells are unattached to other cells and can move freely. Others are attached to each other and cannot move freely. Some cells can divide readily and form new cells, and others can divide only under exceptional circumstances. Many cells are specialized to produce and secrete particular substances.
        ::有些细胞不与其它细胞相连,可以自由移动,另一些细胞彼此相连,不能自由移动,有些细胞可以随时分裂,形成新的细胞,另一些细胞只能在特殊情况下才能分裂,许多细胞专门生产并秘密保存特定物质。
      • All the different cell types within an individual have the same genes. Cells can vary because different genes are expressed depending on the cell type.
        ::个人内所有不同的细胞类型都有相同的基因。 细胞可以不同,因为不同的基因因细胞类型而不同。
      • Many common types of human cells consist of several subtypes of cells, each of which has a special structure and function. For example, subtypes of bone cells include osteocytes, osteoblasts, osteogenic cells, and osteoclasts.
        ::许多常见的人类细胞类型由若干子型细胞组成,每个子型细胞都有特殊的结构和功能,例如,骨骼细胞的子型细胞包括骨质素、骨质激素、骨质细胞和骨质激素。

      ::细胞功能的变异一般反映在细胞结构的变化中,有些细胞不与其他细胞相连,可以自由移动,另一些细胞相互连接,不能自由移动,有些细胞可以随时分割,形成新的细胞,另一些细胞只能在特殊情况下才能分离。许多细胞专门生产和分解特定物质,个人中所有不同的细胞类型都有相同的基因。细胞可以不同,因为不同的基因会因细胞类型而不同。许多常见的人类细胞类型是由几个子类型的细胞组成,每个细胞都有特殊的结构和功能。例如,骨细胞的子类型包括骨骼细胞、骨骼细胞、骨质细胞、骨质细胞和骨质细胞。
    • A tissue is a group of connected cells that have a similar function. There are four basic types of human tissues that make up all the organs of the human body: epithelial, muscle, nervous, and connective tissues.
      ::组织是一组相互联系的细胞,其功能相似。有四种基本人体组织构成人体的所有器官:上皮、肌肉、神经和连接组织。
      • Connective tissues, such as bone and blood, are made up of living cells that are separated by non-living material, called extracellular matrix.
        ::骨骼和血液等连接组织由活细胞组成,由非生物物质(称为外细胞基体)分离。
      • Epithelial tissues, such as skin and mucous membranes, protect the body and its internal organs and secrete or absorb substances.
        ::皮肤和粘膜等环境组织保护身体及其内脏器官,并秘密或吸收物质。
      • Muscle tissues are made up of cells that have the unique ability to contract. They include skeletal, smooth, and cardiac muscle tissues.
        ::肌肉组织由具有独特能力的细胞组成,包括骨骼、光滑和心脏肌肉组织。
      • Nervous tissues are made up of neurons, which transmit messages, and glial cells of various types, which play supporting roles. 
        ::神经组织由神经元组成,神经元传递信息,而气球细胞则有各种类型,发挥辅助作用。

      ::骨骼和血液等连接组织由活细胞组成,这些细胞由非活性物质(称为外细胞基体)分离,皮肤和粘膜等动物组织保护身体及其内脏器官和秘密或吸收物质,肌肉组织由具有独特能力的细胞组成,包括骨骼、光滑和心肌肉组织,神经组织由神经元组成,它们传递信息,而各种类型的滑翔细胞则发挥辅助作用。
    • An organ is a structure that consists of two or more types of tissues that work together to do the same job.  The brain and the heart are two examples.
      ::一个器官是由两种或两种以上的组织组成的结构,它们一起工作,做同样的工作。大脑和心脏就是两个例子。
      • Many organs are composed of a major tissue that performs the organ’s main function, as well as other tissues that play supporting roles.
        ::许多器官由履行该器官主要功能的主要组织以及发挥辅助作用的其他组织组成。
      • The human body contains five organs that are considered vital for survival: the heart, brain, kidneys, liver, and lungs. If any of these five organs stops functioning, death of the organism is imminent without medical intervention.
        ::人体包含五种被认为对生存至关重要的器官:心脏、大脑、肾、肝和肺。 如果这五种器官中的任何一种停止功能,生物体的死亡在没有医疗干预的情况下即将发生。

      ::许多器官是由一个履行器官主要功能的主要组织以及发挥辅助作用的其他组织组成的主要组织组成的。 人体包含五个被认为对生存至关重要的器官:心脏、大脑、肾脏、肝脏和肺。 如果这五个器官中的任何一个停止功能,生物体的死亡在没有医疗干预的情况下就迫在眉睫。
    • An organ system is a group of organs that work together to carry out a complex overall function. For example, the skeletal system provides structure to the body and protects internal organs.
      ::器官系统是由共同履行复杂整体职能的机关组成的小组,例如,骨骼系统为身体提供结构,保护内部机关。
      • There are 11 major organ systems in the human organism. They are the integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, and reproductive systems. Only the reproductive system varies significantly between males and females.
        ::人体有机体有11个主要器官系统,它们是营养系统、骨骼系统、肌肉系统、神经系统、内分泌系统、心血管系统、淋巴系统、呼吸系统系统、消化系统、小便系统和生殖系统,只有生殖系统在男性和女性之间差别很大。

      ::人体有机体有11个主要器官系统,它们是营养系统、骨骼系统、肌肉系统、神经系统、内分泌系统、心血管系统、淋巴系统、呼吸系统系统、消化系统、小便系统和生殖系统,只有生殖系统在男性和女性之间差别很大。
    • The human body is divided into a number of body cavities. A body cavity is a fluid-filled space in the body that holds and protects internal organs. The two largest human body cavities are the ventral cavity and dorsal cavity.
      ::人体分为若干个体腔,一个体腔是身体内装有液体的空间,保存和保护内部器官,最大的两个人体腔是呼吸腔和口腔。
      • The ventral cavity is at the anterior (or front) of the trunk. It is subdivided into the thoracic cavity and abdominopelvic cavity.
        ::口腔腔在后备箱前部(或前部),再细分为胸腔和腹腔。
      • The dorsal cavity is at the posterior (or back) of the body, and includes the head and the back of the trunk. It is subdivided into the cranial cavity and spinal cavity.
        ::背腔腔位于身体的后部(或后部),包括后备箱的头部和后部,再分为脊椎腔和脊椎腔。

      ::口腔腔在后备箱前部(或前部),再分为胸腔和腹腔,背部和脊椎腔,后部或后部为背部,头部和后部为后部,后部为脊椎和脊椎。
    • Organ systems of the human body must work together to keep the body alive and functioning normally. This requires communication among organ systems. This is controlled by the autonomic nervous system and endocrine system. The autonomic nervous system controls involuntary body functions, such as heart rate and digestion. The endocrine system secretes hormones into the blood that travel to body cells and influence their activities.
      ::人体器官系统必须共同努力,保持身体的活力和正常运转,这需要器官系统之间的交流,由自主神经系统和内分泌系统控制,自主神经系统控制非自愿身体功能,如心率和消化,内分泌系统将荷尔蒙分泌到血液中,进入身体细胞并影响它们的活动。
      • Cellular respiration is a good example of organ system interactions, because it is a basic life process that occurs in all living cells. It is the intracellular process that breaks down glucose with oxygen to produce carbon dioxide and energy. Cellular respiration requires the interaction of the digestive, cardiovascular, and respiratory systems.
        ::细胞呼吸是器官系统相互作用的一个很好的例子,因为它是所有活细胞中发生的基本生命过程。 细胞内过程是用氧气分解葡萄糖以产生二氧化碳和能量。 细胞呼吸需要消化、心血管和呼吸系统之间的相互作用。
      • The fight-or-flight response is a good example of how the nervous and endocrine systems control other organ system responses. It is triggered by a message from the brain to the endocrine system and prepares the body for flight or a fight. Many organ systems are stimulated to respond, including the cardiovascular, respiratory, and digestive systems.
        ::战斗或飞行反应是神经和内分泌系统如何控制其他器官系统反应的一个很好的例子,它是由大脑向内分泌系统传递的信息引发的,并且使身体准备飞行或战斗。许多器官系统,包括心血管、呼吸和消化系统,都受到激励来作出反应。
      • Playing softball or doing other voluntary physical activities may involve the interaction of nervous, muscular, skeletal, respiratory, and cardiovascular systems.
        ::玩垒球或从事其他自愿体育活动可能涉及神经、肌肉、骨骼、呼吸和心血管系统的相互作用。

      ::细胞呼吸是器官系统相互作用的一个很好的例子,因为它是所有活细胞中发生的基本生命过程,是用氧气分解葡萄糖以产生二氧化碳和能量的细胞内过程。细胞呼吸需要消化、心血管和呼吸系统的互动。战斗或飞行反应是神经和内分泌系统如何控制其他器官系统反应的一个很好的例子。它是由大脑向内分泌系统传递的信息触发的,并且为人体飞行或战斗做好准备。许多器官系统受到刺激,以作出反应,包括心血管、呼吸和消化系统。玩软球或从事其他自愿的物理活动,可能涉及神经、肌肉、骨骼、呼吸和心血管系统的互动。
    • Homeostasis is the condition in which a system such as the human body is maintained in a more or less steady state. It is the job of cells, tissues, organs, and organ systems throughout the body to maintain homeostasis.
      ::自闭症是像人体这样的系统维持或多或少稳定状态的条件,是整个身体细胞、组织、器官和器官系统维持自闭症的工作。
      • For any given variable (such as body temperature), there is a particular set point that is the physiological optimum value. The spread of values around the set point that is considered insignificant is called the normal range.
        ::对于任何给定变量(如体温),有一个特定的设定点,即生理上的最佳值。在设定点周围被认为微不足道的数值的分布被称为正常范围。
      • Homeostasis is generally maintained by a negative feedback loop that includes a stimulus, sensor, control center, and effector. Negative feedback serves to reduce an excessive response and to keep a variable within the normal range. Negative feedback loops control body temperature and the blood glucose level.
        ::常态常态通常由负反馈循环维持,包括刺激、传感器、控制中心和效果器。 负反馈有助于减少过度反应并将变量保持在正常范围内。 负反馈循环控制身体温度和血糖水平。
      • Sometimes homeostatic mechanisms fail, resulting in homeostatic imbalance. Diabetes is an example of a disease caused by homeostatic imbalance. Aging can bring about a reduction in the efficiency of the body’s control system, making the elderly more susceptible to disease.
        ::有时,自闭症机制失败,导致自闭症失衡。 糖尿病是自闭症失衡造成的疾病的例子。 老龄化可以降低人体控制系统的效率,使老年人更容易患病。

      ::对于任何给定变量(如体温),都有一个特定的设定点,即生理最佳值。在被认为是微不足道的设定点周围的值的分布被称为正常范围。 Homeostacis 通常由负面反馈循环维持, 包括刺激、 传感器、 控制中心和效果。 消极反馈有助于减少过度反应, 并将变量保持在正常范围内。 消极反馈循环控制着身体温度和血糖水平。 有时,家庭主机机制失灵,导致家庭主治不平衡。 糖尿病是家庭主治不平衡造成的疾病的例子。 老龄化可以降低身体控制系统的效率,使老年人更容易患病。
    • Positive feedback loops are not common in biological systems. Positive feedback serves to intensify a response until an end point is reached. Positive feedback loops control blood clotting and childbirth.
      ::积极的反馈回路在生物系统中并不常见。 积极的反馈有助于强化反应,直到达到终点。 积极的反馈回路控制血液凝结和分娩。

    The severe and broad impact of hydrocephalus on the body’s systems highlights the importance of the nervous system and its role as the master control system of the body. In the next chapter, you will learn much more about the structures and functioning of this fascinating and important system.
    ::脑积水对身体系统的严重和广泛影响凸显了神经系统的重要性及其作为身体控制系统的作用。 在下一章中,你将更多地了解这个令人着迷的重要系统的结构和功能。

    Chapter Summary Review
    ::" 概述 " 章次

    1. Compare and contrast tissues and organs.
    ::1. 比较和对比组织和器官。

    2. Osteocyte cells are part of which type of tissue and organ system?
    ::2. 骨质细胞是哪种类型的组织和器官系统的一部分?

    3. Adipose tissue, or body fat, is the same general type of tissue as:
    ::3. 脂肪组织,或身体脂肪,与下列组织相同的一般组织类型:

    a. mucous membranes
    ::a. 粘膜

    b. gray matter
    ::b. 灰物质

    c. skin
    ::c. 皮肤

    d. blood
    ::d. 血血

    4. Which type of tissue lines the inner and outer surfaces of the body?
    ::4. 何种类型的组织将身体的内表和外表划成直线?

    5. True or False:  The extracellular matrix that surrounds cells is always solid.
    ::5. 真实或假:细胞周围的外细胞矩阵始终是固体的。

    6. True or False:  Skin is an organ.
    ::6. 真实或假:皮肤是器官。

    7. What is a vital organ? What happens if a vital organ stops working?
    ::7. 重要器官是什么?如果重要器官停止工作会怎样?

    8. Name three organ systems that transport or remove wastes from the body.
    ::8. 列出运输或从身体中清除废物的三个器官系统。

    9. Name two types of tissue in the digestive system.
    ::9. 在消化系统中列出两类组织。

    10. For each of the following body functions, choose the organ system that is most associated with the function.
    ::10. 对于下列每个机构的职能,请选择与该职能关系最密切的机关系统。

    Organ systems: integumentary; skeletal; muscular; nervous; endocrine; cardiovascular; lymphatic; respiratory; digestive; urinary; reproductive
    ::器官系统:内脏系统;骨骼系统;肌肉系统;神经系统;内分泌系统;心血管系统;淋巴系统;呼吸系统;消化系统;小便系统;生殖系统;生殖系统;

    a. processes sensory information
    ::a. 过程感官信息

    b. secretes hormones
    ::b. 分泌激素

    c. releases carbon dioxide from the body to the outside world
    ::c. 将二氧化碳从身体释放到外部世界

    d. produces gametes
    ::d. 产生调子

    e. controls water balance in the body
    ::e. 控制身体水平衡;

    11. The spleen is part of the _________________ system.
    ::11. 脾脏是系统的一部分。

    a. digestive
    ::a. 消化

    b. lymphatic
    ::b. 淋巴体

    c. integumentary
    ::c. 半导体

    d. urinary
    ::d. 尿 尿

    12. Describe one way in which the integumentary and cardiovascular systems work together to regulate homeostasis in the human body.
    ::12. 说明营养系统和心血管系统共同努力调节人体自闭症的一种方式。

    13. Name the two largest body cavities in humans. Describe their general locations.
    ::13. 列出人类两个最大的体腔,说明其一般位置。

    14. What are the names given to the three body cavity divisions where the reproductive organs are located?
    ::14. 生殖器官所在的三个身体腔部的名称是什么?

    15. True or False:  There are two pleural cavities.
    ::15. 真实或假:有两种胸腔。

    16. True or False:  Body cavities are filled with air.
    ::16. 真实或假:身体空洞充斥空气。

    17. In which organ system is the pituitary gland ?  Describe how the pituitary gland increases metabolism.
    ::17. 哪个器官系统是垂死腺?描述垂死腺是如何增加新陈代谢的。

    18. When the level of thyroid hormone in the body gets too high, it acts on other cells to reduce production of more thyroid hormone. What type of feedback loop does this represent?
    ::18. 当体内甲状腺激素水平过高时,它会对其他细胞采取行动,以减少更多的甲状腺激素的生产。

    19. Hypothetical organ A is the control center in a feedback loop that helps maintain homeostasis. It secretes molecule A1 which reaches organ B, causing organ B to secrete molecule B1. B1 negatively feeds back onto organ A, reducing the production of A1 when the level of B1 gets too high.
    ::19. 假设器官A是反馈循环中的控制中心,有助于保持自足状态,它会将分子A1隐藏到器官B,导致器官B将分子B1.B1秘密化,使器官B对分子B1.B1负向回馈到器官A,当B1水平过高时,A1的产量会减少。

    a. What is the stimulus in this feedback loop?
    ::a. 这一反馈循环的刺激因素是什么?

    b. If the level of B1 falls significantly below the set point, what do you think happens to the production of A1? Why?
    ::b. 如果B1水平大大低于设定点,那么你认为A1的生产会发生什么情况? 为什么?

    c. What is the effector in this feedback loop ?
    ::c. 这一反馈循环的效应是什么?

    d. If organs A and B are part of the endocrine system, what type of molecules do you think A1 and B1 are likely to be?
    ::d. 如果器官A和B是内分泌系统的一部分,那么你认为A1和B1可能属于何种分子?

    20. What are the two main systems that allow various organ systems to communicate with each other?
    ::20. 允许不同机关系统相互交流的两个主要系统是什么?

    21. The hypothalamus is part of the...
    ::21. 下脑膜是...

    a. s pinal cord
    ::a. 脊髓

    b. t horacic cavity
    ::b. 胸腔

    c. k idneys
    ::c. 肾脏

    d. b rain
    ::d. 大脑

    22. What are two functions of the hypothalamus?
    ::22. 下丘脑的两种功能是什么?