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Overview – Introduction to Biochemistry | Lecturio
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标题（采取USMLE标题） （生理学 2级 中文4级 英文三级）
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Biochemistry
Biochemistry Basics
218 Overview – Introduction to Biochemistry
Describe biochemistry at a cellular level with regard to the history of the evolutionary process
Increasing scientific knowledge and improved technology has played significant roles in helping us to better understand the molecular basis of life. In this lecture I will go through a brief overview of the summary of our understanding and our perspective of living system, from ancient times up until today. Life is abundant on planet Earth and as far as we know in the universe that's the only place it exists, although likely it exists in other places as well. Life is diverse and life is widespread. From the deserts in Africa to the farmlands of America. Life has found niches in every land system on earth. In the sea we can look in the deep sea thermal vents, we can look in the top of the ocean and everywhere we look, we see aquatic life. In the air we see birds, we see insects, we see microbes that are floating around. Every available ecosystem on earth that we've examined is abundant with life.
01:02
Now human beings are people who organize and categorize things, and it's only natural therefore that we should be categorizing life systems as well. And one of the things that has happened in the organization of life systems is to create a hierarchical scheme. On the screen you can see one hierarchical scheme that is used to describe essentially every living organism on earth. Starting at the top with the most broad view and narrowing down as we go down through the names, domains of course relate to the very, very broad regions, relating to living systems. Kingdoms are a subdivision of that and phylum are a subdivision of the kingdoms, followed by class, order, family, genus and species. Now it's important to recognize that every life form on earth can be described by this hierarchical system.
01:54
Another system for organizing life is that's shown the screen based on evolutionary distance.
01:59
We think that all life on earth ultimately came from one primordial cell, and that one primordial cell evolved and gave rise to all the life forms that we see today. This plot shows as lines the evolutionary distance each living system is from that primordial cell and by extension how far each living system is evolutionarily from each of the other systems on the screen. On the lower left we can see bacteria. Bacteria of course are the single celled organisms that contain no organelles, they are very simple in their structure and they are very tiny. One of the ways people view bacterias as a bag of enzymes and nucleic acid and that's about what we find in bacteria. The archaeans are the more recently described types of life and they actually exist in some of the most inhospitable places on the planet.
02:53
Environments that other cells would find toxic, the archaeans find home. Like bacteria, they're very simple as well. The eukarya shown on the right include the multicellular organisms we see on eart. This includes the animals, the fungi, the plants and many other multicellular and a few unicellular forms as well. One unicellular form we see in the eukaryotes includes the yeast, makers of bread and ethanol. Now the eukaryotic cells differ from the prokaryotic cells and the archaeon cells in first of all generally being considerably larger than them and second of all, in containing specialized organelles, like the nucleus and like the mitochondrion. These specialized organelles play distinct functions in these cells that are distributed otherwise throughout the entire bacterial or archaean cell.
219 History – Introduction to Biochemistry
00:01 现在我们对生活的看法发生了很大变化 这些年来。可以追溯到文艺复兴时期 人们对理解的兴趣很大 通过了解解剖学来生活。所以解剖 变得很普遍，因为人们感兴趣 理解活着意味着什么 通过了解器官或器官的功能 组织功能。因此，一种普遍的信念 已经有成千上万的人 多年实际上一直是 活力主义。生命主义说发生了什么 在活细胞中是活细胞所独有的 并且无法在宇宙中的其他地方复制。 这个想法基本上被证明是错误的 由屏幕上显示的人弗里德里希 沃勒。 Wöhler能够使用普通 他可以制造尿素的化学反应 已知是由生物体制造的， 在他被发现之前，只有 使细胞成为可能。非常感谢 发现活力，我们现在意识到 细胞发生的事情是一回事 那发生在宇宙的其余部分， 尽管可能以不同的方式。 现在，生命和分子的发现 生活的本质完全取决于 在技术上。第一次技术进步 在帮助我们理解方面很重要 细胞是显微镜的发明。 安东·范·列文虎克（Anton Van Leeuwenhoek）在1650年代发明 第一个显微镜，他是第一个 曾经见过单细胞生物的人， 他称之为动物的生物。他是 这些细胞非常吸引人。 罗伯特·胡克（Robert Hooke）在 Van Leeuwenhoek显微镜，能够 做出一些非常有趣的发现， 包括我们发扬光大的东西 今天是生命的细胞基础。他的 在软木塞上看到的软木解剖图 屏幕在此显示单个单元格并提醒 我们，每个活细胞都来自以前 活细胞。到1850年代， 对分子很重要的分子 生活的基础应运而生。弗里德里希·米歇尔 发现了一种在1850年代工作的化合物， 他称之为核子。现在他很感兴趣 在研究蛋白质，但他所做的是 孤立核，当他分离核 细胞，他发现其中含有某种物质 具有一些非常不寻常的特性。他 不知道这些属性是什么，但是 他知道自己发现了一些新东西， 他称呼核子很重要。我们知道 当然，今天的核子是DNA。奥古斯丁 和尚格里高·孟德尔（Gregor Mendel）很感兴趣，他当时 与Miescher同时学习。 格雷戈尔·孟德尔（Gregor Mendel）对研究 一代人特质的传承 豌豆到另一代人，他做了 非常非常认真的研究和他的研究 意识到有遗传信息 从一代传来的 到下一个。进一步说，遗传信息 具有他称之为隐性的特性 和优势，我们与之相关的特质 基因。孟德尔的作品基本上未被发现 大约30年，但当它变成 被发现，它被揭示为 革命性的发现，当然是它的时代。 到1930年代，分子基础的思想 生活开始实现。 著名物理学家ErwinSchrödinger写道 一本书叫做“生命是什么？”在他的书中 他提出了一个问题，牢房不是 关于最根本的事情 生活。相反，他说分子基础 分子内生命的基础 生命在于分子。在那些分子内 我们可以找到所有可能发生的特征 在生物学上。当时他的想法很激进， 但实际上，它对许多人都有很大的影响 后来发现重大发现的人包括 沃森和克里克在发现DNA方面。 今天我们知道，薛定ding基本上是 正确的，就是生命有一个分子 基础。艾利，麦克劳德和麦卡蒂在 1944年进行了一系列 最终证明的实验 第一次，遗传信息 在几代人之间转移 实际上，细胞数量是DNA。只有几年 1953年下半年，沃森和克里克站在 巨人的肩膀，借用 Rosalind Franklin的数据，能够显示 DNA的结构首次出现。 美丽的双螺旋分子，具有互补性 内部的基础是一个启示，因为 看到它，人们很快意识到 链可以指定另一个的复制 股。通过复制基因 信息可以相同地传输 从一个单元到下一代。的 中枢信条指出，DNA制造RNA，制造 蛋白质，那是因为方式 信息在单元格中传输。 自从第一次出现以来我们就修改了中央教条 在60年代初期描述为合并 今天我们知道的有关RNA的其他一些信息 那时我们不知道。但是中央 教条及其转移的描述 单元内的信息对于 我们所做的一切。我们是否在学习 基因组学，我们是否正在研究转录组学 或者我们是否正在研究代谢组学， 中央教条与今天一样重要 首次描述时。 现在结束本次演讲，我想离开你 与结构有关的一些想法 我之前提到的细菌 “对不起，我为所有 低度细菌。你应该很了解 在它们的微小内部没有细胞器 interia”
220Structure – Amino Acids
00:01 蛋白质是制造蛋白质的重要组成部分 生活可能。
建筑的多样性 蛋白质块与其他大分子相比 为蛋白质提供丰富多样的 功能。在本讲座中，我将讨论 蛋白质从结构单元开始， 组成它们并分解它们的氨基酸 分为不同的组，必要的或不重要的 取决于他们是否可以 由有机体制成。我将讨论基本 每个氨基的结构和立体化学 酸以及每个氨基的侧链如何 酸赋予它个性 它有。最后我给属性 谈论氨基的电离 蛋白质中发现的酸。 蛋白质，我们可以说是主力军 的细胞。他们执行所有必不可少的 细胞需要存活的功能。这些 包括催化，反应的催化 发生，预示着过程 细胞和有机体的一部分可以交流 细胞在生物的另一部分。 蛋白质的结构，例如纤维状 在我们的头发和指甲中发现蛋白质 来自个人的有趣特征 蛋白分子。最后，蛋白质非常 对于产生，创造和 储存能量。地球上所有的蛋白质都是 由约20个氨基酸组成。 20 氨基酸最常见于 地球上的生物。
已知的21位氨基酸 如硒代半胱氨酸，在某些情况下 一些稀有蛋白质。 氨基酸可以分为各种类别， 分类方案之一是除法 氨基酸分为必需基团和非必需基团 取决于生物体是否 可以在其细胞内合成氨基酸。 必需氨基酸是那些氨基酸 细胞需要在饮食中摄取，因为 它本身无法做到。非必需氨基 氨基酸是细胞可以合成的氨基酸。 现在，将基本与否的分类 从一种生物到另一种生物的非必需 甚至随着年龄的增长而变化 例如人类 成年后不同的必需氨基酸 比他们小时候 我们在蛋白质中发现的氨基酸 叫α氨基酸，他们得到这个 名称，
因为使用的每种氨基酸 蛋白质中的特殊碳称为 中间以绿色显示的alpha碳 示意图。所有20个氨基 可以以相同的示意图绘制酸。 现在我要去命名 通过这里，将帮助您更好 了解蛋白质中的氨基酸。
每个Alpha碳都连接到Alpha 羧基，如下所示。而每个alpha 碳也连接到α胺上 这两个给α氨基酸 名称。另外还附有阿尔法碳 您可以在此处看到氢气的顶部 并在R组的左侧R组是 是什么赋予了氨基酸特征 功能，形状，结构和特性。
现在，向您展示一个实际的氨基酸 我要在这里使用的方案 给你看半胱氨酸因此，如果我们看一下 右边的组织方案是 在最后一张幻灯片上，与半胱氨酸进行比较， 我们可以看到例如各种各样的东西。 例如，半胱氨酸具有α碳 如这里所见，一个α羧基，一个 在这种情况下，α胺和一个R基团 含有巯基。在此图中未显示， 但存在于α碳上的是氢 高于α碳。 这是苯丙氨酸。例如苯丙氨酸 有一个α碳，一个α羧基 α胺，它有一个侧链，在这个 盒子里有一个苯环。再次，阿尔法 碳在其上方含有氢。 因为阿尔法碳连接到四个 不同的基团赋予了α碳 一些重要的属性，需要了解。 例如您在有机化学中学习 如果碳有四个不同的分子 附加到它有两种方法 这些原子可以的三维空间 围绕α碳进行组织。 这显示了例如糖D-甘油醛 和L-甘油醛，两种不同形式 含有碳的糖 有四个不同的小组。 这就是所谓的不对称碳， 在此处看到的绿色圆圈中显示。 现在有四个不同的东西 由于这个原因，有两种方法 他们可以组织起来。我画了 蓝色和黄色箭头显示它如何 例如，有两个组织 这里。我们可以在左侧的蓝色箭头下看到 灰色的球正向 观众，而后面的橙色球 正在伸出。在L异构体中，这些 两个位置颠倒了，我们看到橙色 球传到前面和灰色球 向后移动。 氨基酸也用D和L表示 用于糖。有趣的是，几乎 活细胞产生的所有氨基酸 在相同的配置中 L配置。现在，这很有趣 因为如果您举个例子，试管 然后您在测试中化学制造氨基酸 酶未产生的试管 一个单元格，您将得到50％D和50％L的混合物。 我们只获得L的原因 在活细胞中是因为活细胞利用 产生氨基酸的酶，以及那些酶 具有三维的特定结构 只能合成一个 存在两种不同形式。 现在，这真的很有趣 和有用的，因为我们可以告诉我们是否 分析氨基酸是否有混合物 D和L，或仅L，或仅D 问题，因为一种偏向另一种偏见 会暗示它是由酶制成的， 因此是由活细胞制成的。这是用 例如当陨石落到地上 它们含有氨基酸和科学家 对理解非常感兴趣， 生物产生的那些氨基酸，或 由自然化学产生。
Proteins are part and parcel of what makes life possible. The diversity of the building blocks of proteins compared to other macromolecules give proteins a rich and diverse array of functions. In this lecture I will talk about proteins starting with the building blocks, the amino acids that make them up and divide them into various groups, essential or nonessential depending upon whether or not they can be made by the organism. I'll discuss the basic structure and stereochemistry of each amino acid and how the side chains of each amino acid give it the individual characteristics that it have. Last I'll give the properties and talk about the ionization of the amino acids found in proteins. 00:41 Proteins, we can describe as the workhorses of the cell. They perform all the essential functions that cells need to stay alive. These include catalysis, catalyzing of the reactions that happen, signaling the process whereby cells and part of an organism can communicate with cells in another part of the organism. The structure of proteins such as the fibrous proteins found in our hair and our nails arises from interesting features within individual protein molecules. Last, proteins are very important for the generation, creation and storage of energy. All proteins on earth are comprised of about 20 amino acids. The 20 amino acids are most commonly found in every organism on earth. A 21st amino acid known as Selenocysteine, in some cases found in a few rare proteins. 01:36 Amino acids can be divided into various categories, one of the categorization schemes is divide amino acids into essential and nonessential groups, depending upon whether or not the organism can synthesize the amino acid within its cells. Essential amino acids are those amino acids that the cell needs to have in its diet because it can't make those itself. Nonessential amino acids are amino acids that cells can synthesize. Now, the categorization of essential versus nonessential varies from one organism to another and it even varies a little bit with the age of the organism, for example, humans have different essential amino acids as adults than they do as children. 02:23 Amino acids that are found in proteins we call alpha amino acids, and they get this name because every amino acid that's used in proteins has a special carbon call the alpha carbon seen here in green in the center of the schematic diagram. All 20 of the amino acids can be drawn in the same schematic scheme. Now there is nomenclature that I want to go through here that will help you to better understand the amino acids in the proteins. 02:51 Every alpha carbon is attached to an alpha carboxyl group, as shown here. And every alpha carbon is also attached to an alpha amine, these two giving the alpha amino acids their name. The alpha carbon is in addition attached on the top to a hydrogen as you can see here and on the left to an R group. The R group is what gives an amino acid its characteristic, functions, shape, structure and properties. 03:20 Now, to show you an actual amino acid according to the scheme that we're using here, I want to show you cysteine. So if we look at the organizational scheme on the right that was on the last slide and compare to cysteine, we can see for example the various things. 03:34 For example, cysteine has an alpha carbon as seen here, an alpha carboxyl group, an alpha amine and an R group that in this case contains a sulfhydryl. Not shown on this figure, but present on the alpha carbon is a hydrogen above the alpha carbon. 03:55 Here is phenylalanine. Phenylalanine for example, has an alpha carbon, an alpha carboxyl an alpha amine and it has a side chain and in this case contains a benzene ring. Again, the alpha carbon contains a hydrogen above it. 04:13 Because the alpha carbon is attached to four different groups it gives the alpha carbon some properties that are important to understand. You learned in organic chemistry for example that if a carbon has four different molecules attached to it, that there are two ways in three-dimensional space that those atoms can be organized around the alpha carbon. 04:36 This shows for example the sugar D-glyceraldehyde and L-glyceraldehyde, two different forms of a sugar that contain a carbon that have four different groups attached them. 04:46 This is known as an asymmetric carbon and it’s shown in the green circles seen here. 04:52 Now there are four different things attached to this and because of this, there's two ways that they can be organized. I've drawn the blue and the yellow arrows to show how it is that two groups, for example, are organized here. We can see under the blue arrow on the left that the gray ball is projecting towards the viewer whereas the orangish ball in the back is projecting away. In the L isomer, these two positions are reversed, we see the orange ball coming to the front and the gray ball moving to the back. 05:21 Amino acids also are designated by the D and L designation that are used for sugars. Interestingly, almost all of the amino acids made by living cells are in the same configuration, that of the L configuration. Now, this is interesting because if you take for example, a test tube and you make amino acids chemically in a test tube that are not being produced by the enzymes of a cell, you get a mixture of 50% D and 50% L. The reason that we get only L exclusively in living cells is because living cells use enzymes to make amino acids, and those enzymes have a three-dimensional specific structure that will only allow the synthesis of one of the two different forms being present. Now this turns out to be really interesting and useful because we can then tell if we analyze an amino acid whether it has a mixture of D and L, or only L, or only D for that matter, because a bias one way or the other would suggest it was made by an enzyme and therefore made by a living cell. This is used for example when meteorites fall to earth and they contain amino acids and scientists are very interested in understanding, were those amino acids produced biologically, or produced by natural chemistry.
R-group Categories – Amino Acids
Explain the categories of the R-groups of amino acids and cite examples
由自然化学产生。 现在还有其他组织氨基酸的方法 酸和我们组织的方式之一 氨基酸是由它们的R基团决定的。
在这个 例如，我们可以看到分类方案 具有R基团的氨基酸是什么 我们形容为疏水的，这意味着它们 不喜欢与水结合。这包括 色氨酸的芳香氨基酸，苯丙氨酸 和酪氨酸。
它还包括氨基酸 具有脂族侧链，例如蛋氨酸 异亮氨酸，亮氨酸，缬氨酸，甘氨酸，丙氨酸 和脯氨酸。
另一组氨基酸 R基团是那些亲水的， 那就是他们有能力结合 与水结合并与水结合。在这个类别中 我们有含有羟基的氨基酸 侧链中的组；这包括 丝氨酸，苏氨酸和酪氨酸。现在你会 注意酪氨酸已经分为两组 这些群体不是互相排斥的 当您观看和阅读不同的作者时， 您会看到作者将放置氨基酸 根据他们自己的感知在不同的群体中 化学。 在亲水条件下的第二类是 含有巯基，意味着它们含有 与氢连接的硫。只有 该类别中的一种氨基酸，以及 那半胱氨酸。羧酰胺或羧酰胺 也叫氨基酸天冬酰胺 和谷氨酰胺。离子氨基酸是那些 在生理pH下将具有 加号或减号。这些包括 羧酸盐，是天冬氨酸和 谷氨酸。羧酸盐，当它们 电离将带负电荷。 生理pH值的胺含有额外的 质子和额外的质子使这些 胺带正电荷，胺当然 包括赖氨酸，组氨酸和精氨酸。 现在我说过一些氨基酸 不只一个类别，而且这些也不是唯一的 无论如何，我再次提醒您 氨基酸的分类方式确实有所不同。 我现在想做的是 描述每个氨基酸和点
00:00 produced by natural chemistry. 00:01 Now there's other ways of organizing amino acids and one of the ways that we can organize amino acids is by their R groups. In this classification scheme we can see for example amino acids that have R groups that are what we describe as hydrophobic, meaning that they don't like to associate with water. This includes the aromatic amino acids of tryptophan, phenylalanine and tyrosine. It also includes amino acids that have aliphatic side chains, such as methionine, isoleucine, leucine, valine, glycine, alanine and proline. Another grouping of amino acids by R group are those that are hydrophilic, that is that they have an ability to bond with and associate with water. In this category we have the amino acids that contain hydroxyl groups in their side chain; this includes serine, threonine and tyrosine. Now you'll notice that tyrosine has been in two groups and these groups are not mutually exclusive and as you watch and read different authors, you'll see that authors will place amino acids in different groups based on their own perceived chemistries. 01:05 A second category when under hydrophilic is sulfhydryl containing, meaning that they contain a sulfur attached to a hydrogen. There's only one amino acid that's in this category, and that cysteine. The carboxyamides or carboxamides as they are also called, are amino acids asparagine and glutamine. The ionic amino acids are those that at physiological pH will have either a plus or a minus charge. These include the carboxylates, which are aspartic acid and glutamic acid. The carboxylates, when they ionize will have a negative charge. 01:45 The amines at physiological pH contain an extra proton and this extra proton gives these amines a positive charge, the amines of course include lysine, histidine and arginine. 01:57 Now as I said some amino acids appear in more than one category and these aren't exclusive in any way, and again I remind you that authors do differ in how they categorize amino acids. 02:06 What I would like to do now is go through and describe each of the amino acids and point
Which order set of the three amino acids named below are listed in this order: Hydrophobic, Hydrophilic, Ionic?
Arginine, Tyrosine, Asparagine Serine, Glutamine, Proline Histidine, Threonine, Phenylalanine Leucine, Cysteine, Lysine
Hydrophobic R-groups – Amino Acids
Explain the different biochemical categories of hydrophobic amino acids Describe the salient features of all hydrophobic amino acids Define hydrophobic amino acids and cite examples
00:00 我现在想做的是 描述每个氨基酸和点 适当地指出它们的一些显着特征。 氨基酸的芳香族基团包括 酪氨酸，色氨酸和苯丙氨酸。现在， 我已经在酪氨酸上标明了位置 α羧基，α胺和 alpha碳，并再次提醒您 氢在上方投射，但未显示 在这张图片中。酪氨酸被指出具有羟基 基团连接在苯环的末端。
色氨酸以氨基酸闻名 具有最大的R基团，包含苯 环连接到另一个五元环 如您所见。现在这个很大的笨重 色氨酸的人群往往是 限制蛋白质内的空间。 庞大的R基团可能导致蛋白质 必须扭转和适应 结果是更大的结构。
苯丙氨酸 有一个简单的苯环。 现在我在这张幻灯片上所做的就是 在生理pH下标记， 出现在每个分子上。您会在 在每种情况下，α羧基为负 充电，因为它失去了一个质子。每一个 情况下，α胺带正电荷 因为它保留了质子。 pKa 的α羧基大约是2 生理pH当然约为7.4。的 α胺基团的pKa约为9， 因此，由于这个原因，α胺保留了 质子和α羧基已经丢失 它的质子。现在关于酪氨酸的注释 是酪氨酸末端的羟基 可以在高pH下电离，该pH高于 但是是生理范围的。 我想要的第二组氨基酸 谈论的是那些 含有脂族R基团。在这种情况下 在每个绿色方块中再次标记 每个氨基中包含的R基团 酸。以甘氨酸为例，我们 看到甘氨酸有一个不寻常的R基团， 它只含有氢。因此，甘氨酸 具有自然界中最小的R基团 蛋白质中存在氨基酸，但是因为 它包含一个R基团氢，它也 包含附着在 α碳，这意味着只有三个 附着在阿尔法碳上的不同东西 甘氨酸。因此，甘氨酸是 仅存在于20种氨基酸中 没有立体化学的蛋白质。
下一个感兴趣的氨基酸是 脯氨酸。您可以看到脯氨酸具有R 从α碳开始的基团，但是 它也会回来并与 如您所见，α胺形成了五个成员 环。现在，此连接有两点限制 R组脯氨酸旋转的能力。 如果您看一下所有其他的R组 所有其他蛋白质，您会看到它们 只有一个键，可以自由旋转。 脯氨酸受第二键约束 它是由α氨基组成的 结果，脯氨酸不能旋转 它的R基团，意味着脯氨酸 较不灵活的氨基酸。现在有一些 实际发生弯曲的含义 在蛋白质中，我们将在后面描述。
接下来的三个氨基酸异亮氨酸，缬氨酸 和亮氨酸在包含R基团方面相似 含有碳和氢，主要是 如您所见，对它们进行了重新排列。 此处显示的最后一个氨基酸是蛋氨酸， 蛋氨酸很有趣，因为蛋氨酸 含有硫。这是仅有的两个氨基之一 含硫的酸，硫是 可以连接到两个不同的碳上 请参阅此处的分组。那个附件 两种不同的碳意味着硫 在蛋氨酸中是非常没有反应的，不会 做很多，这与硫相反 我们将在半胱氨酸中看到。 现在，如果我们看一下生理上的收费 pH，我们可以看到这些氨基酸都不存在 有电离的R基团，就像我们看到的 在α胺具有正电荷之前 每种情况下，α羧基为负 收费。这些氨基酸各自在生理上 pH值为零。 接下来的两个氨基酸是被离子化的氨基酸， 并且它们的R基团中含有羧基 组。它们包括天冬氨酸，如图所示 左边是谷氨酸， 对。这两个氨基酸实际上是 彼此相同，除了 谷氨酸含有额外的碳 与天冬氨酸相比。在生理上 pH在这里我们看到R基团离子化， 这是因为对于这些 两个氨基酸的pKa值约为4， 表示在生理pH为7的情况下 羧基上的质子丢失了 使分子带有净负电荷 在R组。每个的总费用 这些氨基酸在生理上 pH为-1。
00:00 What I would like to do now is go through and describe each of the amino acids and point out some salient features of them as appropriate. The aromatic group of amino acids includes tyrosine, tryptophan and phenylalanine. Now, I've marked on the tyrosine, the locations of the alpha carboxyl, the alpha amine and the alpha carbon, and remind you again that the hydrogen is projecting above but not shown in this image. Tyrosine is noted has a hydroxyl group attached to the end of benzene ring. Tryptophan is notable for being an amino acid that has the largest R group, contains a benzene ring attached to another five-member ring as you can see here. Now this very large bulky group that's on tryptophan, tends to be a limitation in terms of space within a protein. The bulky R group can cause the protein to have to twist and turn, and accommodate that larger structure as a result. Phenylalanine has a simple benzene ring. 01:03 Now what I've also done on this slide is I've marked at physiological pH, the charges that appear on each molecule. You'll see that in each case the alpha carboxyl has a negative charge because it has lost a proton. In each case, the alpha amine has a positive charge because it is retaining a proton. The pKa of the alpha carboxyl group is about 2, physiological pH of course is about 7.4. The pKa of the alpha amine group is about 9, so for this reason the alpha amine retains the proton and the alpha carboxyl has lost its proton. Now one note about tyrosine and that is that the hydroxyl at the end of tyrosine can ionize at a high pH, this pH is above that of the physiological range however. 01:52 The second group of amino acids that I want to talk about are those that contain aliphatic R groups. In this case I've marked again in the green squares each of the R groups as they are contained in each amino acid. Focusing on glycine for example, we see glycine has an unusual R group, and that it only contains a hydrogen. Glycine therefore has the smallest R group of any of the naturally occurring amino acids in proteins, but because it contains an R group hydrogen and it also contains the hydrogen that's attached to the alpha carbon, it means that there're only three different things attached to the alpha carbon of glycine. For this reason glycine is the only amino acid of the 20 that's found in proteins that does not have a stereochemistry. 02:44 The next amino acid that is of interest is proline. You can see the proline has an R group that goes off of the alpha carbon, but it also comes back around and connects with the alpha amine as you can see forming a five-member ring. Now this connection at two points limits the ability of the R group of proline to rotate. If you look at all of the other R groups of all of the other proteins, you'll see they only have a single bond and can freely rotate. 03:14 Proline is constrained by the second bond that it's making with the alpha amino group and as a consequence, proline cannot rotate its R group, meaning that proline is a much more inflexible amino acid. Now this has some implications for bending that actually happens within proteins as we will describe later. 03:35 The next three amino acids isoleucine, valine and leucine are similar in containing R groups that have carbons and hydrogens and mainly rearrangements of those as you can see. 03:49 The last amino acid as shown here is methionine, and methionine is of interest because methionine contains sulfur. It's one of only two amino acids that contain sulfur and the sulfur is attached to two different carbons as you can see in the grouping here. That attachment to two different carbons means that the sulfur in methionine is very unreactive and doesn't do much, this is in contrast to the sulfur that we will see in cysteine. 04:16 Now, if we look at the charges at physiological pH, we can see that none of these amino acids have R groups that ionize and like we saw before the alpha amine has a plus charge in each case and the alpha carboxyl has a negative charge. Each of these amino acids at physiological pH would have a charge of zero. 04:39 The next two amino acids are those that are ionized, and they contain in their R groups, carboxyl groups. They include aspartic acid, shown on the left and glutamic acid, shown on the right. These two amino acids are virtually identical to each other with the exception that glutamic acid contains one extra carbon compared to aspartic acid. At physiological pH we see here that the R group ionizes, and this is because that the R group for these two amino acids has a pKa value of about 4, meaning that at a physiological pH of 7, the proton on the carboxyl group is lost, leaving the molecule with a net negative charge on the R group. The overall charge of each of these amino acids at physiological pH is -1.
Which of the following is not an aromatic amino acid? (choose all that can apply) Tryptophan Methionine Phenylalanine Tyrosine
Which of the following is the simplest amino acid? Tryptophan Methionine Glycine Histidine Phenylalanine
Which of the following are sulfur-containing amino acids? (More than one correct answer) Glycine Methionine Proline Lysine Cysteine
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https://zhuanlan.zhihu.com/p/50177781
如何学习 生理生化
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生理学（中文）
01 总论
00:00 在这里，我们将讨论生理学及其一般原理。现在你可能在想 在这一点上，生理学到底是什么。因此，让我们先解决这个问题。生理是 生命科学。生理学本质上是相当广泛的，旨在了解其机理 从基因和分子到细胞再到细胞 功能并最终融入整个身体的行为。另一件事是 与生理学相关的重要考虑因素是人体在正常条件下的工作方式。 为什么这很重要，是稍后我们要区分正常生理和 医学生理学。生理几乎用于您在日常生活中所做的一切，从是否 您正在散步或锻炼，无论是阅读还是观看 特别的Lecturio讲座。它几乎完成了所有事情。现在让我们定义什么是 医学生理学与常规生理学的区别。在医学生理学中， 我最喜欢的报价是由一个调查小组完成的，该调查小组首先发现了动脉 在这种情况下，他们决定使用重症监护药物 生理原则来照顾重病患者。因此，在医学生理学上，我们将 更详细地讨论一些主题，并深入探讨，因为它们在医学上更 相关的。生理学中有一些主题，但是，我们将仅解释概念，因此您 了解它是如何工作的，但我们不会以相同的方式进行深入研究，因为它更少 在医学上很重要。好的，现在让我们将这些主题放在一起，然后通过 我们需要讨论的各个领域或系统。一般生理将是那些 经历身体的所有器官系统。神经系统将是大脑，脊柱 绳索和神经，这些有助于控制和调节其他器官系统 其他器官系统包括肌肉骨骼系统。所以就肌肉系统而言 这就是肌肉的收缩，它们如何拉动骨骼杠杆，这样您就可以 走路，走路，做日常生活的各种活动。但是，要做正常的活动 你需要新陈代谢。为了进行新陈代谢，我们需要有氧气，这就是 呼吸系统起作用。在这里，呼吸系统在 环境，进入人体和肺部，您将能够吸收氧气并 您将能够消除二氧化碳。您如何将氧气吸收到体内所有细胞周围 涉及心血管系统。所以在这里，我们将有心脏在抽血。现在就这样 将血液泵送到全身，您需要拥有脉管系统或输液管， 将血液输送到整个身体，每个细胞的扩散距离都足够近 接收氧气。肾脏系统在血液过滤中非常重要。 因此，就像呼吸系统正在添加物质一样，肾脏系统也会被去除 代谢过量或底物。胃肠道系统很好，因为它可以添加各种营养素 根据人体细胞的需要，例如葡萄糖。最后，内分泌系统将 类似于神经系统的调节系统中的另一种控制方法对我们有帮助 将所有各种器官系统整合到体内。现在让我们讨论这些器官系统 以及它们如何在流程图中相互联系。在这里你可以看到身体是 在许多不同的层中进行设置。我们这里的顶层是肺，这是 当然，二氧化碳将离开而氧气将进入。请注意，心脏是 一分为二，心脏的右侧将血液泵入肺部，我们的左侧 心脏在整个系统中移动血液。肾脏系统将位于第三位 梯级，这又是我们的过滤系统。在第二梯级，我们有胃肠道 系统，它将再次成为血液吸收营养的地方 葡萄糖，蛋白质，脂肪，然后可以传递到人体的所有细胞。终于在 最低的横档，我们有毛细血管床，这表示体内的所有不同细胞 以及每个人将如何接受其中含有氧气，营养物质的血液，并且 过滤良好，因此可以进行相应的正常活动 系统，无论是神经系统，肌肉骨骼系统还是内分泌系统。
02 稳态
现在是我们需要按照中心原则进行讨论的过程。中央 生理原理基本上是体内平衡，但我们都需要在同一页面上 稳态实际上意味着。这是生物系统维持的受控过程 在各种压力或压力下动态但相对一致的内部条件 由外部和内部因素引起。有很多事情要考虑，所以让我们谈谈吧 通过这些过程中的每个过程，我们将了解这个定义是什么。 首先要考虑的是身体的哪些变量对您足够重要 真正规范他们。如果您想一想这几秒钟，其中一个 在我看来是葡萄糖。因此，您需要调节血液中的葡萄糖量，以便 最佳量被递送到体内的每个细胞。氧气也是如此。 氧气需要输送到体内的每个细胞，需要进行精确调节。 您如何确保身体各个部位获得足够的氧气和葡萄糖？ 您需要有足够的血压或压力才能将血液推到各个部位。 这些是3个非常好的例子。其他您可能尚未想到的 包括调节体温，调节pH平衡等 我们需要调节的整数变量。现在，关于定义的另一件事是 认为我们应该多讨论一些似乎矛盾的地方，因为两者都是动态的 并保持一致，这就是我们的意思。这不是一个特定的数字，而是 在医学中很重要的一系列数字。例如，葡萄糖水平不 将是一个数字，而是一个范围。血压不仅仅是我们的一个数字 而是一系列血压之后，这就是动态成分， 尽管我们必须始终将其保持在狭窄范围内。有哪些例子 可以改变体内平衡的内部因素？这主要涉及新陈代谢的变化。因此，如果 您进行类似运动的运动会增加新陈代谢，而如果您 睡觉会使您的新陈代谢减少。这是一个内部因素。外部因素是 几乎没有名字可言，这些都是来自外部环境的东西 影响身体。可能是外部，太阳或 从环境以及它如何影响我们的生理。可能会很冷，如何影响寒冷 我们的生理状况，或者处于压力状态，您会感到害怕或制定了 战斗或逃跑反应。这是另一个例子，我们现在需要处理的外部因素 在动态但始终如一的范围内，但保持超调变量。另一件事 我们需要牢牢把握的动态平衡是在什么水平上以及这个水平上 是一个组织层次。所以有原子，这些原子形成分子，然后形成更大的分子 分子，然后最终形成各种细胞成分，例如线粒体， 也可能是其他局部类型的细胞器。最后，我们有了单元。 该单元可能是我们真正需要维持的第一层组织 里面的环境，这就是任何内部的稳态环境 细胞。这调节着进入细胞的物质，调节着细胞质的溶解 将由组成。现在，每个单独的细胞被组合在一起形成一个组织。 在组织水平上，我们也有稳态调节作用，因此特定组织会调节 其中一些参数。器官系统还将调节体内平衡规范。器官 系统共同调节人体的各种体内平衡机制，例如血液和 最后，我们有了需要调节的整个有机体。所以从细胞，组织 器官，器官系统级别，最后是整个有机体，所有这些都需要 个人层面和公司层面的动态平衡。那怎么办？好一 调节体内平衡需要考虑的事情是，这全都基于我们的遗传学。所以 您在每个细胞中都有DNA，因此实际上细胞可以成为体内的任何组织。 恰好发生在当前时间是细胞和组织。所以当我们考虑 组织，器官，器官系统和生物体，我们必须始终意识到每个单独的细胞 经历自身的动态平衡，以及如何相互调节动态平衡 整个生物体的基本遗传密码 组织层次结构。因此，让我们将其重新组合成所有器官系统，然后 讨论此过程如何以集成方式工作。所以请记住你有类似 顶部的神经系统和底部的内分泌系统有助于 整个生物体的调节。肌肉骨骼，呼吸，心血管，肾脏 和GI系统正在帮助进行监管，并且某些监管在 性质意味着它是通过植物神经系统诱发的，其中一些是 行为的。因此，例如，如果天气太热，您可以做一些事情，例如坐在火中 和汗水来尝试调节您的体温，或者您可以简单地起身去 更凉爽的环境。这些是行为和自主反应之间的各种选择 可用来维持体内平衡的物质。我认为动态平衡的最后一个方面 最能帮助您思考的是使您能够 适应不同的环境或压力。最好通过以下方式制定 考虑器官系统可能会做什么。因此，在幻灯片一侧的示例中 这里您的血压升高。因此，如果血压升高，您需要 可以感觉到血压上升的信号，然后再传回心脏， 说“嘿，嘿，压力太大了。”我们要么不得不放慢脚步 特别的心。这可能会更加复杂，不仅仅是与拥有 压力增加和心脏减慢，而是多因素的。所以在这个 在下一个例子中，随着平均动脉血的增加，我们将显示相同的响应 压力感受器会感知到的血压，这些都是压力感受器 或压力感受器。然后将其反馈到脑干，在本例中为髓质。的 然后，髓质组织信息并将信号发送到心脏以及 血管。内心深处，它会发出一个信号，它应该放慢速度，不应该 跳得这么快，也不必灰心。最后对于血管，它会说 “嘿，你可以放松一点，你太紧张了，血压太高了。 系统需要扩张”，这种情况也会降低血压。这会导致两个 东西，心动过缓和血管舒张，并希望两者结合就足够了 将平均动脉血压降低到我们试图调节的值。 同样，这是一个动态的过程，但是我们正在寻找一个稳定的范围。
03 控制和调节
因此，在这种情况下，我们将要调节一个变量。那个调节变量 有些东西会影响它。假设有一个外部压力源，这将 导致您的调节变量发生变化。你需要做什么？你怎么知道 变量是否太高？您体内需要安装各种传感器。就像我们 压力升高时有压力感受器。所以你有一个传感器，你可能有 多个传感器都将收集由该法规生成的数据 变量。现在您有了传感器来收集数据，它需要将其发送到某个地方 因为传感器本身无法确定要做什么。因此它将数据发送到集成 系统，有时甚至是一个协调系统，这将协调我们的响应 调整变量发生的变化，然后将信号发送到 效应器和这些效应器将能够改变或引起我们的改变 调节变量。因此，我们拥有这四类插脚系统 变量，传感器，积分器，协调中心和效应器都在尝试 确保我们的调节变量在一个内部被协调或调节的各个方面 各种范围。好吧，让我们回到我们的内心例子，尝试进一步梳理一下，如此 我们可以表示调节变量在哪里，传感器在哪里，在哪里 集成商和协调系统，以及我们的效应器将要成为的。所以我们将 看看下一张图。因此，我们系统中用于控制动脉血的传感器 压力将成为压力感受器。现在有许多不同的压力感受器 位于血管系统中的血液中或血液外部，而那些位于 颈动脉窦，它们在您的脖子上，主动脉弓位于左上方 心室或血液排出的地方。这些将使我们能够洞悉什么血液 压力是，但是请注意，您到处都没有压力感受器 位于关键地点。那么为什么这是关键？好吧，就主动脉弓而言， 在您将血液挤出到全身循环之后。所以你想知道什么 是心脏排出血液的压力。另一个关键因素是 知道血液流到大脑非常重要。所以你想拥有压力感受器 在颈动脉窦中能够吸收进入大脑的血压。那些是 将成为我们主要的受调节压力感受器。它们通过各种颅神经，迷走神经发送 主动脉弓为颅神经X或舌咽或颅神经IX为 颈动脉窦。他们被送到哪里？他们被送到延髓，这是我们的 整合中心。记住，当我们整合某些东西时，我们会抓住所有 信息，这是由称为NDS或核的特定脑干成分完成的 独尾。这是我们的聚会场所。您可以想到它，例如火车站 所有的信息都回到中心位置，以便我们知道信息在哪里 来自，但仅仅是因为信息正在返回，并不一定意味着 我们知道该怎么做，所以我们需要一些地方，这是一个协调中心 那将能够获取所有这些信息，并让我们决定如何处理它。所以在 以血压为例，我们可能有三个主要位置或效应器 完成。因此，我们有一个心脏减速区，这在副交感神经 系统。我们在交感神经系统中有心脏加速器系统， 交感神经系统中的血管收缩成分。这些是我们所要做的 可以换。那么，如果血压下降怎么办？
副交感神经 神经系统将试图减慢心脏的速度。那你如何减慢 减速器？好吧，你将不得不抑制它。因此，您正在禁止减速器。 您还将向必须做的心脏部分发出积极信号 心率加快，这会增加您的心率。您将增加收缩力。 您将增加发送到小动脉的信号，这些小动脉是血管的一部分 引起血管收缩。您将增加对静脉部分的信号 那也可以收缩。因此，在我们的示例中，我们向 窦房结来自交感神经系统，收缩力，小动脉和静脉。从 副交感神经系统，来自减速区的信号为负 这将使我们能够提高窦房结去极化率。那么这是什么意思 所有这些不同方面？这意味着我们将增加心率，增加 收缩力增加，血管收缩增加，静脉收缩增加 颈动脉窦发送给我们的信号是血压降低。 现在，我们可以想到一些病理生理学实例，这些实例会影响这些 循环，我要指出的其中之一是动脉粥样硬化或其他成分 我们可以想到的是衰老，因为这两种都会使压力感受器反应变钝 因为它们以使血管壁更硬的方式改变血管壁。如果有船只 墙更硬，发生的情况是它在响应时不会扩大或变大 血压变化。因此，如果血压升高，它将拉伸血管。 如果它拉伸血管，就会影响或引起周围神经的变化 该血管，因此，如果您有血管，并且您有正确的神经 在它旁边，当它扩张时，它将推动该神经，并将信号转换回 脑。在这种情况下，如果您的船只较硬，则通过的信息较少 僵硬的血管，因此您对反应的反应程度不同，因此可以更改 人在衰老或动脉粥样硬化中的压力感受器反应，这会影响您的 调节变量，例如动脉血压。
Physiology
Physiology – Introduction & Central Principles
1479.Introduction to Physiology
Define the field of physiology and identify its prominence in medicine Summarize the integrated organ systems approach of medical physiology
It's a science related to physics. The science that aims to understand the mechanisms of living systems, from the molecular to the complex structure of the body. A science that studies higher forms of life. The science that aims to understanding how the body gets sick. The science exclusively aimed at understanding how organs relate to each other.
Answer: B
00:00 Here we are going to talk about physiology and its general principles. Now you may be thinking at this point, well, what exactly is physiology. So let's address that first. Physiology is the science of life. Physiology is fairly broad in nature and it aims to understand the mechanisms of living and this incurs all the way from the genetic and molecular to the cell and to cell function and eventually into integrated behavior of the whole body. The other thing that's important to think about with physiology is it is how the body works under normal conditions. 00:41 Why this is important is later we're going to differentiate between normal physiology and medical physiology. Physiology is used in almost everything you do in daily life from whether you're walking or exercising, whether you're reading or whether you're watching this particular Lecturio lecture. It's done in just about everything. So let's also now define what is medical physiology and difference from regular physiology. In medical physiology, one of the quotes that I like best is done by an investigative team that first discovered what an arterial blood gas is and in this case they decided that critical care medicine is basically applying physiological principles to the care of the seriously ill patient. So in medical physiology, we will talk about some topics in greater detail and drill those down because they are more medically relevant. There are some topics in physiology, however, we will just explain the concept so you understand how this works but we won't drill it down in the same way because it's less medically important. Okay, now let's bring these topics together and go through which are the various areas or systems that we need to discuss. General physiology will be those things that undergo through all organ systems in the body. The nervous system will be the brain, the spinal cord and the nerves and these help control and regulate the other organ systems and those other organ systems include the musculoskeletal system. So in terms of the muscular system this would be the contractions of muscles, how they pull on skeletal levers so that you can ambulate, walk, do the various activities of normal daily living. However, to do normal activities you need to have metabolism. For metabolism, we need to have oxygen and that's where the respiratory system comes into play. Here, the respiratory system exchanges air between the environment and into the body and to the lungs, you will be able to then absorb oxygen and you will be able to eliminate CO2. How you get that oxygen around to all the cells in the body involves the cardiovascular system. So here, we will have the heart pumping blood. Now as it pumps blood throughout the body you need to have a vasculature or a tube system so it delivers blood throughout the whole body and every cell is in close enough diffusional distance to receive that oxygen. The renal system is very important in undergoing filtration of the blood. 03:31 So like the respiratory system was adding substances, the renal system will be removing metabolic excesses or substrates. The GI system is nice in that it adds back various nutrients as needed for the cells in the body such as glucose. Finally, the endocrine system will be another one of those control in regulation systems similar to the nervous system that help us integrate all the various organ systems in the body. So now let's discuss these organ systems and how they relate to each other in more of a flow diagram. Here you can see the body is set up in a number of different layers. The top layer we have here is the lungs and this is of course where the carbon dioxide will leave and oxygen will enter. Notice that the heart is split into two, the right side of the heart pumping blood in to the lungs, we have the left side of the heart moving that blood throughout the system. The renal system will be on the third rung and that's again our filtration system. On the second rung we have the gastrointestinal system and that will be once again the spot in which blood will come to pick up nutrients like glucose, proteins, fats so that then can be delivered to all the cells of the body. Finally at the lowest rung we have the capillary beds and that is to denote all the different cells in the body and how each one of them will receive this blood that has oxygen in it, has nutrients in it and is well filtered and so that can correspond to do the normal activities that are needed for that system, whether it be the nervous system, the musculoskeletal system or the endocrine system.
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Log In subjected to; subjected to also subject to; subjecting to; subjects to Definition of subject to 1: affected by or possibly affected by (something) The firm is subject to state law. The schedule is tentative and subject to change. Clothing purchases over 500 fine. 2: likely to do, have, or suffer from (something) My cousin is subject to panic attacks. I'd rather not live in an area that is subject to flooding. 3: dependent on something else to happen or be true The sale of the property is subject to approval by the city council. All rooms are just $100 a night, subject to availability.
1480 Homeostasis: Definition & Level of Organization
Define homeostasis Name some important physiological variables that must be regulated within the body Recognize the dual dynamic and consistent elements of homeostasis Recognize the numerous internal and external factors that can challenge homeostasis Summarize the levels of organization at which homeostasis occurs, with a focus on the cell as the primary level of organization Recognize the genetic influence on homeostasis at a cellular level Summarize the negative feedback control mechanism involved in blood pressure homeostasis
1 What is homeostasis?
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A process by which a biological system maintains a dynamic but consistently stable internal condition in the face of both internal or external pressures.
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The control system for blood pressure.
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The ability to regulate body fluids.
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A static situation in the body.
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The body’s internal milieu.
Answer:A
2 What variables in the body are important enough to be consistently regulated?
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Urinary output, liver functions, digestion.
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Respiratory rate.
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Oxygen saturation, blood pressure, glucose, pH, body temperature.
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Amount of red cells.
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Blood flow in the muscles.
Answer:C 3 What is the meaning of “dynamic but relatively consistent state”?
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A state maintained within a close range of values.
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A situation that can be safely manipulated.
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A state that may change widely but spontaneously returns to baseline.
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A state that is fixed on one value.
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A state that cannot be manipulated.
Answer: A
4 What inner factors can change homeostasis?
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A salt load
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Changes in metabolism
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Exposure to the sun
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Increasing water intake
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A sugar load
Answer:B
5 Which is the lowest level of organization that needs homeostatic regulation in order to function properly? The whole body
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Organs
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The cell
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Atoms
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Molecules
Answer:C
6 What is the homeostasis mechanism most commonly seen in the body?
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Neuromodulators
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Signal molecules
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Feedback mechanism
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Hormones
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Receptor binding
Answer:C
00:00 This is the process now that we need to discuss in terms of a central principle. The central principle of physiology is basically homeostasis but we all need to be on the same page of what homeostasis actually means. It is a regulated process by which a biological system maintains a dynamic but relatively consistent internal condition during various stresses or pressures incurred both from external and internal factors. That's a lot to think about so let's kind of deal through each of those processes a little bit more so we will understand what this definition is. 00:41 First thing to think about is what variables of the body are important enough for you to actually regulate them. If you think about this for a couple of seconds, one of them that comes to my mind is glucose. So you need to regulate the amount of glucose in the blood so that an optimal amount is delivered to each of the cells in the body. The same goes with oxygen. 01:09 Oxygen needs to be delivered to each cell in the body, it needs to be precisely regulated. 01:14 How do you make sure you get enough oxygen and glucose to the various spots in the body? You need to have enough blood pressure or pressure to push the blood to those various spots. 01:27 So those are 3 really good examples. Other ones that you might not have thought of yet include things like the regulation of body temperature, the regulation of pH balance are also integral variables that we need to regulate. Now, the other thing about the definition that I think we should discuss a little bit more that seems kinds of contradictory is that it's both a dynamic and consistent and what we mean by that. It's not going to be one particular number but rather a range of numbers that's going to be important in medicine. For example, a glucose level is not going to be one number but rather a range. Blood pressure is not just one number that we are after but rather a range of blood pressures and that is what is the dynamic component, although we have to consistently keep it within a narrow range. What are some examples of internal factors that can change homeostasis? This mainly involves changes in metabolism. So if you undergo something like exercise you have an increase in metabolism while if you are sleeping you have a decrease in metabolism. That's an internal factor. External factors are almost too great to even name, these are anything that will be from the external environment impacting the body. That can be something like heat generated from outside, from the sun or from the environment and how that impacts our physiology. It could be cold, how cold impacts our physiology or maybe in a stressful condition in which you are scared or you enacted the fight or flight response. That's another example, that external factor that we need to now deal with but maintain over regulated variables in a dynamic but consistent range. The other thing about homeostasis that we need to have a firm grasp on is at what level are we talking about and this level is a level of organization. So there are atoms and these form molecules which then form larger molecules and then finally form various cellular components like mitochondria in this case, it could be other local types of cellular organelles as well. Then finally we have the cell. 04:00 The cell is probably the first level of organization that we really need to maintain an environment in and this is the homeostatic environment of whatever is going to be within the cell. This is regulating what comes into the cell, it regulates what that cellular cytosol is going to be composed of. Now each individual cell though is combined together to form a tissue. 04:30 At the level of tissue, we also have a homeostatic regulation, so a particular tissue will regulate some of these parameters. Organ systems will also regulate a homeostatic norm. Organ systems together regulate the body's various homeostatic mechanism such as the blood and then finally we have the whole organism that needs to be regulated. So from the cell, tissue, organ, organ system level and finally the organism as a whole, all of these need to have homeostasis both at the individual level and the corporate level. So how is that done? Well one thing to think about with regulation of homeostasis is that it's all based upon our genetics. So you have DNA within each individual cell and so in fact a cell could become any tissue in the body. 05:31 It just so happens it is the cell and tissue that it is at the current time. So when we think about tissues, organ, organ system and organism, we have to always realize that each individual cell undergoes its own homeostasis and how that builds upon each other to regulate the homeostasis of the whole entire organism but the basic genetic code is in each cell of this overall hierarchy of organization. So let's bring it back together as all the organ systems and then discuss how this process works in an integrated fashion. So remember you have something like the nervous system at the top and the endocrine system at the bottom helping out with the regulation of the entire organism. The musculoskeletal, respiratory, cardiovascular, renal and GI systems are helping that regulation occur and some of the regulation is automatic in nature meaning that it's induced through the autonomic nervous system and some of it is behavioral. So for example if it's too hot out you can either do something like sit in the heat and sweat to try to regulate your body temperature or you can simply get up and go to a cooler environment. Those are the various choices between behavior and autonomic responses that are available to try to maintain homeostasis. The last aspect of homeostasis that I think will be most helpful to think about is what are the various components that allow you to regulate to a different environment or a different stressor. That can be best enacted by thinking about what an organ system might do. So in the example on the one side of your slide here you have an increase in blood pressure. So if blood pressure goes up, you need to have something to sense the blood pressure going up and then a signal coming back to the heart to say "Hey, hey that's too much pressure." We're going to either have to slow down that particular heart. This can be more complex to be not just one factor being involved with having an increase in pressure and a slowing down of the heart but rather be multifactorial. So in this next example we're going to show the same response with increase in mean arterial blood blood pressure that's going to be sensed by a pressure receptor and these are baroreceptors or pressure receptors. Then that is fed back to the brainstem, in this case the medulla. The medulla then organizes the information and sends the signal out both to the heart as well as the blood vessels. To the heart, it's going to send a signal that it should slow down, shouldn't beat so fast, it also doesn't have to be disheart. Finally for blood vessels, it's going to say "Hey you can relax a little bit, you're too tensed, there is too much blood pressure in the system you need to dilate" and this case that will also reduce blood pressure. This induces two things, a bradycardia and a vasodilation and hopefully those two in combination are enough to lower mean arterial blood pressure down to a value in which we are trying to regulate. 09:06 Again, this is a dynamic process but we're looking at a consistent range that we're looking for.
1481 Control and Regulation
Describe the control and regulation of physiological variables via sensors, integrators, coordinating centers, and effectors Summarize the control system for arterial blood pressure and describe the sensors, integrator, coordinating centers, and effectors involved Explain how aging and atherosclerosis can affect the body’s ability to regulate arterial blood pressure
1 Which of the following receptors sense pressure? Neuroreceptors Metaboreceptors Thermoreceptors Baroreceptors Ergoreceptors
Answer:D
2 How is a given variable detected in the system for controlling arterial blood pressure? Sensing by one or multiple receptors Direct adaptation to stressors Local responses Stressors themselves Changes in the endothelium of blood vessels
Answer: A
3 Where do data collected by sensors go to maintain homeostasis? To arteries in the neck Back to the stressor To an integrator and coordinating center To the blood vessels where it was collected To veins in the neck
Answer:C
4 What is the function of an effector? To cause alterations in the integrator To cause alterations in the stressor To cause alterations in the sensors To cause alterations in the regulated variable To cause alterations in the coordinating center
Answer: D
5 A rise in blood pressure causes which of the following? Activation of baroreceptors that stimulate the activity of sympathetic neurons Activation of baroreceptors that inhibit the activity of neurons in the dorsal motor nucleus of the vagus and the nucleus ambiguous to influence heart rate Activation of baroreceptors that inhibit the activity of parasympathetic neurons Activation of baroreceptors that inhibit the activity of sympathetic neurons Increase of vasoconstrictive effects of sympathetic innervation on the peripheral blood vessels
Answer: D
6 A rapid drop in blood pressure causes which of the following? Decreased baroreceptor stimulation that increases the activity of sympathetic neurons Activation of baroreceptors that stimulate the activity of neurons in the dorsal motor nucleus of the vagus and the nucleus ambiguous that influence heart rate. Activation of baroreceptors that inhibit the activity of sympathetic neurons Activation of baroreceptors that stimulate the activity of parasympathetic neurons Decrease vasoconstrictive effects of sympathetic innervation on the peripheral blood vessels.
Answer: A
7 Which of the following is caused by aging and atherosclerosis? Delayed effector responses Dilation of the vessels Stiffening of the vessel walls Decreased effectiveness of the integrator and coordinating center Quicker effector responses
Answer: C
00:00 So in this case, we're going to have a variable that's regulated. That regulated variable, something will affect it. So let's say there is an external stressor out there and that's going to cause a change in your regulated variable. What you need to do? How do you know that variable is too high? You need to have various sensors in the body to pick that up. Just like we had baroreceptors when pressure was elevated. So you have a sensor and you may have multiple sensors that all are going to gather the data that is generated by this regulated variable. Now that you have the sensors garnering that data, it needs to send it somewhere because the sensor itself cannot determine what to do. So it sends the data to an integrated system or sometimes also a coordinating system and that is going to coordinate our response to that change that happened to our regulated variable and that signal is then sent to effectors and these effectors are going to be able to then change or cause an alteration in our regulated variable. So we have this four-kind of prong system where we have a regulated variable, sensors, an integrator and coordinating center and effectors all trying to do the various aspects of making sure our regulated variable is coordinated or regulated within a various range. Okay, let's go back to our heart example to try to tease this out further and so we can denote where our regulated variables are, where our sensors are, where our integrator and coordinating system are and what our effectors are going to be. So we will take a look at that in the next diagram. So our sensors in our system for controlling arterial blood pressure are going to be baroreceptors. Now there are a number of different baroreceptors located in the blood or just outside of the blood in the blood vessel system and those are in the carotid sinuses, they are here in your neck, your aortic arch which is just above the left ventricle or where the blood is pushed out. Those will allow us to give us insight into what blood pressure is but notice that you don't have baroreceptors everywhere, you just have them located in key spots. So why would this be key? Well in terms of the aortic arch, it's going to be right after you squeezed out the blood into the systemic circulation. So you want to know what is the pressure in which the heart is pushing out blood. The other key component to this is to know that the blood going to the brain is very important. So you'd want to have baroreceptors in the carotid sinuses to be able to pick up that blood pressure going to the brain. Those are going to be our main regulated baroreceptors. They are sent via various cranial nerves, vagus or cranial nerve X for the aortic arch and the glossopharyngeal or cranial nerve IX for the carotid sinuses. Where are they sent to? They are sent to the medulla and this is our integrating center. Remember when we integrate something, we are grabbing a hold of all the information and this is done from a specific brainstem component called the NDS or the nucleus tractus solitarus. This is our gathering area. You can think of it something like the train depot, all the information is coming back to a central location so that we know where the information is coming from but just because the information is coming back doesn't necessarily mean that we know what to do with it so we need to have some place and this is a coordinating center that is going to be able to take all these information and let us decide what to do with it. So in a blood pressure example, we have three main places or effectors that we might be able to accomplish. So we have a cardiac decelerator region and this is in the parasympathetic nervous system. We have a cardiac accelerator system in the sympathetic nervous system and a vasoconstrictor component in the sympathetic nervous system. These are the things which we can change. So what happens if you have an decrease in blood pressure? The parasympathetic nervous system is going to try to slow down the heart. So how do you slow down a decelerator? Well you're going to have to inhibit it. So you're inhibiting the decelerator. 04:51 You're also going to be giving a positive signal to the portions of the heart that have to do with heart rate and that increases your heart rate. You're going to increase your contractility. 05:07 You're going to increase the signal sent to your arterioles which are part of your blood vessels that cause vasoconstriction. You're going to increase the signal to the portions of the veins that can also venoconstrict. So in our example here, we have an increased signal to the sinoatrial node from the sympathetic nervous system, contractility, arterioles and veins. From the parasympathetic nervous system, we have a negative signal from the decelerator region which will allow us to increase the sinoatrial node depolarization rate. So what does this mean all these different aspects? It means we're going to get an increase in heart rate, an increase in contractility, an increase in vasoconstriction, increase in venoconstriction in response to the signal that was sent to us from the carotid sinuses and that was a decrease in blood pressure. 06:06 Now, there are pathophysiology examples that we can think of that will affect these regulated loops and one of the ones that I will just point out is atherosclerosis or another component that we could think of is aging because both of these can blunt baroreceptor responses because they change the vessel walls in such ways that the vessel walls are stiffer. If a vessel wall is stiffer, what happens is it doesn't distend as much or become bigger in responses to changes in blood pressure. So if blood pressure goes up, it should stretch the blood vessel. 06:45 If it stretches the blood vessel, it impacts or enacts changes in the nerve that's right around that blood vessel and therefore if you have a blood vessel and you have the nerve that's right next to it, as it distends it pushes on that nerve and will transduce the signal back to the brain. In this case if you have a stiffer vessel, less information travels through a stiff vessel and therefore you don't respond to the same extent and so you can change your person's baroreceptor responses in aging or in atherosclerosis and that impacts your ability to regulate a variable such as arterial blood pressure.
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