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  • 常态和反馈

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    Steady as She Goes
    ::稳稳如她所去

    This device looks simple, but it controls a complex system that keeps a home at a steady temperature — it's an old-fashioned thermostat. The dial shows the current temperature in the room, and also allows the occupant to set the thermostat to the desired temperature. A thermostat is a commonly cited model of how living systems — including the — maintain a steady state called homeostasis.
    ::这个装置看起来很简单,但它控制着一个复杂的系统,它使一个家庭保持稳定的温度——它是一个老式的自动调温器。拨号显示房间里的当前温度,也让住家将自动调温器设置在理想的温度上。自动调温器是常被引用的关于生活系统如何维持一个稳定状态的模型,这个状态被称为 " 全能 " 。

    What Is Homeostasis?
    ::什么是 " Homeostasis " 吗?

    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 , tissues , organs , and organ systems throughout the body to maintain many different variables within narrow ranges compatible with life. Keeping a stable internal environment requires continually monitoring the internal environment and constantly making adjustments to keep things in balance .
    ::自闭症是某种系统(如人体)维持或多或少稳定状态的条件,是整个身体的组织、器官和器官系统将许多不同的变量维持在与生命相适应的狭窄范围内。 保持稳定的内部环境需要不断监测内部环境并不断调整以保持平衡。

    Set Point and Normal Range
    ::设定点和正常范围

    For any given variable, such as body temperature or glucose level, there is a particular set point that is the physiological optimum value. T he set point for human body temperature, for example, is about 37 degrees C (98.6 degrees F). As the body works to maintain homeostasis for temperature or any other internal variable, the value typically fluctuates around the set point. Such fluctuations are normal, as long as they do not become too extreme. The spread of values within which such fluctuations are considered insignificant is called the normal range . In the case of body temperature, for example, the normal range for an adult is about 36.5 to 37.5 degrees C (97.7 to 99.5 degrees F).
    ::对于任何给定变量,例如身体温度或葡萄糖水平,都有一个特定的设定点,即生理最佳值。例如,人体温度的设定点为约37摄氏度(98.6摄氏度)。由于身体在温度或任何其他内部变量方面保持恒定状态,其值通常在设定点周围波动。这种波动是正常的,只要它们不会变得太极端。认为这种波动微不足道的值的分布被称为正常范围。例如,在体温方面,成年人的正常范围约为36.5摄氏度至37.5摄氏度(97.7摄氏度至99.5摄氏度)。

    Maintaining Homeostasis
    ::保持原状状态

    Homeostasis is normally maintained in the human body by an extremely complex balancing act. Regardless of the variable being kept within its normal range, maintaining homeostasis requires at least four interacting components: stimulus , sensor, control center, and effector.
    ::常态常态通常通过极其复杂的平衡行为在人体中保持。 无论变量是否保持在正常范围内,保持常态至少需要四个相互作用的成分:刺激、传感器、控制中心和效果器。

    1. The stimulus is provided by the variable being regulated. Generally, the stimulus indicates that the value of the variable has moved away from the set point or has left the normal range.
      ::刺激由受监管的变量提供。 一般来说,刺激表明变量的价值已经偏离设定点或离开了正常范围。
    2. The sensor monitors the values of the variable and sends data on it to the control center.
      ::传感器监测变量的值,并将数据发送到控制中心。
    3. The control center matches the data with normal values. If the value is not at the set point or is outside the normal range, the control center sends a signal to the effector.
      ::控件中心将数据与正常值匹配。如果值不位于设定点或超出正常范围,则控制中心向效果器发出信号。
    4. The effector is an organ, gland, muscle, or other structure that acts on the signal from the control center to move the variable back toward the set point.
      ::效果器是一个器官、腺、肌肉或其他结构,它从控制中心对信号起作用,将变量移回设定点。

    Each of these components is illustrated in the cycle diagram . The diagram on the left is a general model showing how the components interact to maintain homeostasis. The diagram on the right shows the example of body temperature. From the diagrams, you can see that maintaining homeostasis involves feedback, which is data that feeds back to control a response. Feedback may be negative (as in the example below) or positive. All the feedback mechanisms that maintain homeostasis use negative feedback . Biological examples of positive feedback are much less common.
    ::这些组成部分中的每一个都在循环图中加以说明。左侧的图表是一个一般模型,显示各组成部分如何相互作用以保持主控状态。右侧的图表显示了身体温度的示例。从图表中可以看出,保持主控状态涉及反馈,即反馈数据,即反馈回馈以控制响应。反馈可能是否定的(如下面的例子)或肯定的。保持主控状态的所有反馈机制都使用负面反馈。积极反馈的生物例子则少得多。

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    Maintaining homeostasis through feedback requires a stimulus, sensor, control center, and effector.
    ::通过反馈保持顺势需要刺激、传感器、控制中心和效果器。

    Negative Feedback
    ::负反馈

    In a negative feedback loop , feedback serves to reduce an excessive response and keep a variable within the normal range. Two  processes controlled by negative feedback are  body temperature regulation and control of blood glucose.
    ::在负面反馈循环中,反馈有助于减少过度反应,使变量保持在正常范围内,两个受负面反馈控制的流程是体温调节和控制血糖。

    Body Temperature
    ::体温

    Body temperature regulation involves negative feedback, whether it lowers the temperature or raises it, as shown in the diagram and explained in the text that follows.
    ::体温调节涉及负面反馈,无论它降低温度还是提高温度,如图表所示,并在以下文字中加以解释。

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    The hypothalamus plays a major role in temperature regulation.
    ::下脑膜在温度调节中起着重要作用。

    Cooling Down
    ::降温

    The human body’s temperature regulatory center is the hypothalamus in the brain . When the hypothalamus receives data from sensors in the skin and brain that body temperature is higher than the set point, it sets into motion the following responses:
    ::人体的温度调控中心是大脑的下丘脑。 当下丘脑从皮肤和大脑的传感器接收到数据时,身体温度高于设定点时,就会引发以下反应:

    • in the skin dilate (vasodilation) to allow more blood from the warm body core to flow close to the surface of the body, so heat can be radiated into the environment.
      ::在皮肤膨胀(血管膨胀)中,允许温暖身体核心的更多血液流到接近身体表面的地方,因此热能可以辐射到环境中。
    • As blood flow to the skin increases, sweat glands in the skin are activated to increase their output of sweat (diaphoresis). When the sweat evaporates from the skin surface into the surrounding air, it takes heat with it.
      ::随着血流向皮肤增加,皮肤中的汗腺被激活来增加汗(糖尿病)的产量。 当汗从皮肤表面蒸发到周围空气时,它会随热。
    • becomes deeper, and the person may breathe through the mouth instead of the nasal passages. This increases heat loss from the lungs .
      ::肺部的热量会增加。 肺部的热量会增加。 肺部的热量会增加。 肺部的热量会增加。 肺部的热量会增加。 肺部的热量会增加。 肺部的热量会增加。
    Heating Up
    ::供暖加热

    When the brain’s temperature regulatory center receives data that body temperature is lower than the set point, it sets into motion the following responses:
    ::当大脑温度调控中心接收到身体温度低于设定点的数据时,就会启动以下反应:

    • Blood vessels in the skin contract (vasoconstriction) to prevent blood from flowing close to the surface of the body, which reduces heat loss from the surface.
      ::皮肤合同(血管压缩)中的血管血管,以防止血液流到身体表面附近,减少表面的热损耗。
    • As temperature falls lower, random signals to are triggered, causing them to contract. This causes shivering , which generates a small amount of heat.
      ::随着温度下降,随机信号被触发,导致它们收缩。这导致颤抖,产生少量热量。
    • The thyroid gland may be stimulated by the brain (via the pituitary gland) to secrete more thyroid . This hormone increases metabolic activity and heat production in cells throughout the body.
      ::甲状腺可能受到大脑的刺激(通过脑垂状腺),以进一步分泌甲状腺。这种荷尔蒙会增加整个身体细胞的代谢活动和热量生产。
    • The adrenal glands may also be stimulated to secrete the hormone adrenaline. This hormone causes the breakdown of glycogen (the used for energy storage in animals) to glucose, which can be used as an energy source. This catabolic chemical process is exothermic, or heat producing.
      ::肾上腺素也可能被刺激以分泌激素肾上腺素。这种激素会导致甘醇(用于动物的能量储存)分解为葡萄糖,而葡萄糖可以用作能源。这种代谢化学过程是异温或热生产。

    Blood Glucose
    ::血糖

    In controlling the blood glucose level, certain endocrine cells in the pancreas (called alpha and beta cells) detect the level of glucose in the blood. They then respond appropriately to keep the level of blood glucose within the normal range.
    ::在控制血糖水平时,胰腺中的某些内分泌细胞(所谓的甲型和乙型细胞)检测血液中的葡萄糖水平,然后做出适当反应,将血糖水平保持在正常范围内。

    • If the blood glucose level rises above the normal range, pancreatic beta cells release the hormone insulin into the bloodstream. Insulin signals cells to take up the excess glucose from the blood until the level of blood glucose decreases to the normal range.
      ::如果血糖水平高于正常范围,胰腺乙型细胞将激素胰岛素释放到血液中。胰岛素信号细胞从血液中提取过量的葡萄糖,直到血糖水平下降到正常范围。
    • If the blood glucose level falls below the normal range, pancreatic alpha cells release the hormone glucagon into the bloodstream. Glucagon signals cells to break down stored glycogen to glucose and release the glucose into the blood until the level of blood glucose increases to the normal range.
      ::如果血糖水平低于正常范围,则胰腺甲型细胞将激素凝胶素释放到血液中。 Glucagon信号细胞将储存的甘醇分解为葡萄糖,并将葡萄糖释放到血液中,直到血糖水平上升到正常范围。

    Positive Feedback
    ::积极反馈

    In a positive feedback loop , feedback serves to intensify a response until an end point is reached. Examples of processes controlled by positive feedback in the human body include blood clotting and childbirth.
    ::在积极的反馈循环中,反馈有助于强化反应,直至达到终点,人体中由积极反馈控制的进程的例子包括血凝结和分娩。

    Blood Clotting
    ::输血衣

    When a wound causes bleeding, the body responds with a positive feedback loop to clot the blood and stop blood loss. Substances released by the injured blood vessel wall begin the process of blood clotting. Platelets in the blood start to cling to the injured site and release chemicals that attract additional platelets. As the platelets continue to amass, more of the chemicals are released and more platelets are attracted to the site of the clot. The positive feedback accelerates the process of clotting until the clot is large enough to stop the bleeding.
    ::当伤口导致出血时,身体会以积极的反馈回路作出反应,凝血并停止血液流失。 受伤的血管墙释放的物质开始血液凝血过程。 血液中的颗粒开始粘贴在受伤的现场并释放化学物质以吸引更多的小块。 随着小块继续聚集,更多的化学物质被释放,更多的小块被吸引到凝血现场。 积极的回路加快了凝血过程,直到血块大到足以止血为止。

    Childbirth
    ::分娩 分娩

    The diagram shows the positive feedback loop that controls childbirth. The process normally begins when the head of the infant pushes against the cervix . This stimulates , which travel from the cervix to the hypothalamus in the brain. In response, the hypothalamus sends the hormone oxytocin to the pituitary gland ,  which secretes it into the bloodstream so it can be carried to the uterus . Oxytocin stimulates uterine contractions, which push the baby harder against the cervix. In response, the cervix starts to dilate in preparation for the passage of the baby. This cycle of positive feedback continues, with increasing levels of oxytocin, stronger uterine contractions, and wider dilation of the cervix until the baby is pushed through the birth canal and out of the body. At that point, the cervix is no longer stimulated to send nerve impulses to the brain, and the entire process stops.
    ::图表显示了控制分娩的积极的反馈环。 这一过程通常从婴儿头部向子宫颈推进时开始。 这刺激了大脑从子宫颈向下脑露骨运动。 作为回应, 下脑膜将荷尔蒙催产素送到垂体腺, 将激素分泌到血液流中, 从而可以携带到子宫。 氧素刺激子宫缩, 将婴儿推到子宫颈上。 作为回应, 子宫颈开始膨胀, 为婴儿的通过做准备。 这种积极的反馈循环在继续, 催产素水平不断提高, 子宫萎缩力更强, 子宫颈变大, 直到婴儿通过出生的罐头和身体被推出。 在这一点上, 宫颈素不再被刺激向大脑输送神经脉冲, 整个过程停止 。

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    Normal childbirth is driven by a positive feedback loop. Positive feedback causes an increasing deviation from the normal state to a fixed end point, rather than a return to a normal set point as in homeostasis.
    ::正常分娩是由积极的反馈循环驱动的。 积极的反馈导致从正常状态向固定终点的偏差越来越大,而不是回到原状状态的正常设定点。

    When Homeostasis Fails
    ::当歇歇止状态衰衰时

    Homeostatic mechanisms work continuously to maintain stable conditions in the human body. Sometimes, however, the mechanisms fail. When they do, homeostatic imbalance may result, in which cells may not get everything they need or toxic wastes may accumulate in the body. If homeostasis is not restored, the imbalance may lead to disease — or even death. is an example of a disease caused by homeostatic imbalance. In the case of diabetes, blood glucose levels are no longer regulated and may be dangerously high. Medical intervention can help restore homeostasis and possibly prevent permanent damage to the organism .
    ::内脏机制不断发挥作用,以保持人体的稳定条件,但有时机制失败,造成内脏不平衡,导致细胞得不到所需的一切,或有毒废物在身体中累积,如果内脏不恢复,这种不平衡可能导致疾病,甚至死亡,这是内脏不平衡造成疾病的例子,在糖尿病方面,血糖水平不再受到管制,而且可能达到危险程度,医疗干预有助于恢复内脏,并可能防止对机体的永久损害。

    Normal aging may bring about a reduction in the efficiency of the body’s control systems, which makes the body more susceptible to disease. O lder people, for example, may have a harder time regulating their body temperature. This is one reason they are more likely than younger people to develop serious heat-induced illnesses, such as heat stroke .
    ::正常衰老可能会降低身体控制系统的效率,从而使身体更容易感染疾病。 比如,老年人可能更难调节体温。 这也是他们比年轻人更可能患严重热诱发疾病的原因之一,如中暑。

    Feature: My Human Body
    ::特质:我的人体

    Diabetes is diagnosed in people who have abnormally high levels of blood glucose after fasting for at least 12 hours. A fasting level of blood glucose below 100 is normal. A level between 100 and 125 places you in the pre-diabetes category, and a level higher than 125 results in a diagnosis of diabetes.
    ::糖尿病被诊断为在服完至少12小时的禁食后血糖含量异常高的人中诊断出糖尿病,血糖浓度低于100的禁食水平是正常的,在糖尿病前的类别中,血糖浓度在100到125之间,糖尿病的诊断结果高于125。

    Of the two types of diabetes, type 2 diabetes is the most common, accounting for about 90 percent of all cases of diabetes in the United States. Type 2 diabetes typically starts after the age of 40. However, because of the dramatic increase in recent decades in obesity in younger people, the age at which type 2 diabetes is diagnosed has fallen. Even children are now being diagnosed with type 2 diabetes. Today, about 30 million Americans have type 2 diabetes, and another 90 million have pre-diabetes.
    ::在两种糖尿病中,2型糖尿病最为常见,占美国所有糖尿病病例的90%左右。 2型糖尿病通常始于40岁之后。 然而,由于近几十年来年轻人肥胖症的急剧增长,2型糖尿病诊断年龄已经下降,甚至儿童现在也诊断患有2型糖尿病。 如今,大约3000万美国人患有2型糖尿病,另有9000万人患有糖尿病前。

    You are likely to have your blood glucose level tested during a routine medical exam. If your blood glucose level indicates that you have diabetes, it may come as a shock to you, because you may not have any symptoms of the disease. You are not alone, because as many as one in four diabetics do not know they have the disease. Once the diagnosis of diabetes sinks in, you may be devastated by the news. Diabetes can lead to heart attacks, strokes, blindness, kidney failure , and loss of toes or feet. The risk of death in adults with diabetes is 50 percent greater than it is in adults without diabetes, and diabetes is the seventh leading cause of death of adults. In addition, controlling diabetes usually requires frequent blood glucose testing, watching what and when you eat, and taking medications or even insulin injections. All of this may seem overwhelming.
    ::在常规体检期间,你很可能要接受血糖水平的测试。如果你的血糖水平表明你患有糖尿病,那么你可能会受到惊吓,因为你可能没有任何这种疾病的症状。你并不孤单,因为4个糖尿病人中多达1人不知道他们有这种疾病。一旦糖尿病被诊断出来,你可能会受到新闻的破坏。糖尿病可能导致心脏病发作、中风、失明、肾衰竭和脚趾或脚的丧失。患有糖尿病的成年人的死亡风险比没有糖尿病的成年人高50%,而糖尿病是成人死亡的第七大原因。此外,控制糖尿病通常需要频繁的血糖测试、观察什么和什么时候吃什么、吃什么、吃什么、吃药或注射胰岛素。所有这些都可能令人难以接受。

    The good news is that changing your lifestyle may stop the progression of type 2 diabetes or even reverse it. By adopting healthier habits, you may be able to keep your blood glucose level within the normal range without medications or insulin. Here’s how:
    ::好消息是,改变你的生活方式可能会阻止二型糖尿病的蔓延甚至逆转。 通过采用更健康的习惯,你可以将血液中的葡萄糖水平保持在正常范围内,而不用药物或胰岛素。 下面是:

    • Lose weight. Any weight loss is beneficial. Losing as little as seven  percent of your weight may be all that is needed to stop diabetes in its tracks. It is especially important to eliminate excess weight around your waist.
      ::减重 。 任何减重都会有好处 。 减肥少于体重的7%可能就是阻止糖尿病的足迹。 尤其重要的是消除腰部的超重。
    • regularly. You should try to exercise for at least 30 minutes, five days a week. This will not only lower your blood sugar and help your insulin work better, but it will also lower your and improve your heart health. Another bonus of exercise is that it will help you lose weight by increasing your basal metabolic rate.
      ::定期锻炼至少30分钟,每星期5天。这不仅会降低你的血糖,帮助胰岛素工作更好,而且会降低你的心脏健康,改善你的心脏健康。另一个奖励是,通过提高鼻涕新陈代谢率,可以帮助减肥。
    • Adopt a healthy diet. Decrease your consumption of refined carbohydrates, such as sweets and sugary drinks. Increase your intake of fiber-rich foods, such as fruits , vegetables, and whole grains. About one-quarter of each meal should consist of high- foods, such as , chicken, dairy products, legumes, or nuts.
      ::采用健康的饮食。 减少对精炼的碳水化合物的消费,比如糖和糖饮料; 增加对富纤维食品的摄取,比如水果、蔬菜和整粒谷物。 每顿饭中大约有四分之一应该包括高营养食品,比如鸡肉、奶制品、豆类或坚果。
    • Control stress. Stress can increase your blood glucose and also raise your blood pressure and risk of heart disease. When you feel stressed out, do breathing exercises or take a brisk walk or jog. T ry to replace stressful thoughts with more calming ones.
      ::控制压力。 压力会增加你的血糖, 也会增加你的血压和心脏病风险。 当你感到压力时, 做呼吸锻炼, 或者做快速的步行或慢跑。 尝试用更冷静的思维来取代压力思维 。
    • Establish a support system. Enlist the help and support of loved ones, as well as medical professionals, such as a nutritionist and diabetes educator. Having a support system will help ensure that you are on the path to wellness, and that you can stick to your plan.
      ::建立支持系统。 加入亲人以及医疗专业人士(如营养学家和糖尿病教育家)的帮助和支持。 拥有支持系统将有助于确保您走上健康之路,并能够坚持您的计划。

    Summary
    ::摘要

    • 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.
      ::自闭症是维持一个系统(如人体)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,例如身体温度,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。
    • Positive feedback loops are not common in biological systems. Positive feedback serves to intensi f y 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。
    • 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, which makes  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,从而使老年人更容易患病。

    Review
    ::回顾

    1. What is homeostasis?
    ::1. 什么是常态?

    2. Define the set point and normal range for physiological measures.
    ::2. 确定生理测量的设定点和正常范围。

    3. Identify and define the four interacting components that maintain homeostasis in feedback loops.
    ::3. 确定和界定在反馈循环中保持统一状态的四个互动组成部分。

    4. Compare and contrast negative and positive feedback loops.
    ::4. 比较和对比负面和正面反馈循环。

    5. Explain how negative feedback controls body temperature.
    ::5. 解释负面反馈控制机构温度如何。

    6. Give two examples of physiological processes controlled by positive feedback loops.
    ::6. 举两个由积极反馈循环控制的生理过程的例子。

    7. A negative feedback loop...
    ::7. 负面反馈循环...

    a. brings a variable’s level back to a normal range
    ::a. 使变量水平回到正常范围

    b. can lower — but not raise — body temperature
    ::b. 能够降低(但不提高)身体温度

    c. is the type of feedback involved in blood clotting
    ::c. 是血凝结所涉的反馈类型。

    d. A and B
    ::d. A和B

     

    8.  During breastfeeding, the stimulus of the baby sucking on the nipple increases the amount of milk produced by the mother. The more sucking, the more milk is usually produced. Is this an example of negative or positive feedback? Explain your answer.  What do you think might be the evolutionary benefit of the milk production regulation mechanism  you described?
    ::8. 母乳喂养期间,婴儿乳头吸奶刺激会增加母亲生产的奶量,吸奶越多,通常产奶量越多,这是负面或正面反馈的例子吗?解释你的答复。你认为牛奶生产监管机制的进化好处是什么?

     

    9. Explain why homeostasis is regulated by negative feedback loops, rather than positive feedback loops.
    ::9. 解释为什么 " 全方位 " 受负面反馈循环而不是正面反馈循环的制约。

     

    10. A set point is usually...
    ::10. 设定点通常.

    a. the top of a normal range
    ::a. 正常幅度的顶部

    b. the bottom of a normal range
    ::b. 正常幅度底部

    c. in the middle of a normal range
    ::c. 在正常范围内的中间

    d. the point at which changes can no longer occur
    ::d. 不能再发生改变的点

     

    11. The level of a sex hormone, testosterone (T), is controlled by negative feedback. Another hormone, gonadotropin-releasing hormone (GnRH), is released by the hypothalamus of the brain, which triggers the pituitary gland to release luteinizing hormone (LH). LH stimulates the gonads to produce T. When there is too much T in the bloodstream, it feeds back on the hypothalamus, causing it to produce less GnRH. While this does not describe all the feedback loops involved in regulating T, answer the following questions about this particular feedback loop.
    ::11. 性激素、睾丸酮(T)水平受负面反馈控制,另一种激素(gonadotropin-releasing holmons(GnRH))由大脑的低脑膜释放,引发脑下垂腺释放润滑荷尔蒙(LH)。LH刺激甲状腺生成T。当血液中T含量过大时,它会回溯到下脑膜上,导致其生成的GnRH减少。虽然这并没有描述调节T的所有反馈循环,但回答关于这一特定反馈循环的以下问题。

    a. What is the stimulus in this system? Explain your answer.
    ::a. 该系统的刺激因素是什么?解释你的答复。

    b. What is the control center in this system? Explain your answer.
    ::b. 这个系统中的控制中心是什么?

    c. In this system, is the pituitary considered the  stimulus, sensor, control center, or effector? Explain your answer.
    ::c. 在这个系统中,垂体是否被视为刺激、传感器、控制中心或影响器?解释你的答复。

    Explore More
    ::探索更多

    You can learn how the body maintains homeostasis in its water content by watching this video:
    ::你可以通过观看这段影片来了解身体如何保持水含量的顺势:

     

     

     

     

     

     

     

     

    Check out this video about the comparisons between positive and negative feedback:
    ::校对:Portnoy