※ 引述《Dejavua (javaua)》之铭言： : 大家好想请问以下: : 12. 为什麽B不能选呢? C的讯号放大和relay protein有关, 请问1,2级传讯是一种relay : protein 吗？ : 21. 为什麽不能选D呢? 形成膜电位不是和ECF(Na+)/ICF(K+)有关 吗？ : 22. 为什麽不能选E? : 35. D和味觉有关的脑区是顶叶吗？ : 52. c应该不对吧？ : 谢谢 : http://i.imgur.com/Fw0bwVH.jpg 21题 Membrane potential (also transmembrane potential or membrane voltage) is the difference in electric potential between the interior and the exterior of a biological cell. Any voltage is a difference in electric potential between two points-for example, the separation of positive and negative electric charges on opposite sides of a resistive barrier. An electric potential (also called the electric field potential or the electrostatic potential) is the amount of electric potential energy that a unitary point electric charge would have if located at any point in space, and is equal to the work done by an electric field in carrying a unit of positive charge from infinity to that point. 复习细胞膜电位 将看到不只是与钠和钾离子浓度有关 首先 细胞膜两侧 不只有 电位梯度 还有浓度梯度 所以一个离子要进出细胞膜 不只考虑静电平衡 还有 离子浓度平衡 resting potential of animal cells is determined by predominant high permeability to potassium and adjusted to the required value by modulating sodium and chloride permeabilities and gradients. 选择性通透的离子通道 是主要负责的机制 离子帮浦 则帮助维持 1.隔离 是维持梯度 最重要的特性 2.只考虑钠和钾离子是不够的 两者都是正离子 实际上当然也要考虑阴离子 In a more formal notation, the membrane potential is the weighted average of each contributing ion's equilibrium potential. 3.看选项的意思transport 代表主动运输 那就忽略了离子通道 还有 carrier ref: wiki: https://en.wikipedia.org/wiki/Resting_potential https://en.wikipedia.org/wiki/Membrane_potential ----------------------------------------------------------- : http://i.imgur.com/Sb31QGI.jpg The cell releases second messenger molecules in response to exposure to extracellular signaling molecules—the first messengers. Because peptide hormones and neurotransmitters typically are biochemically hydrophilic molecules, these first messengers may not physically cross the phospholipid bilayer cell membrane to initiate changes within the cell directly—unlike steroid hormones, which usually do. This functional limitation necessitates the cell to devise signal transduction mechanisms to transduce first messenger into second messengers, so that the extracellular signal may be propagated intracellularly. An important feature of the second messenger signaling system is that second messengers may be coupled downstream to multi-cyclic kinase cascades to greatly amplify the strength of the original first messenger signal 所以通常使用second messanger 的系统有两个原因 1. the first messengers 无法直接穿过细胞膜的时候 2. 刺激很微小 需要放大讯号的时候 但是也有缺点 1. 有些scond messanger 需要酵素反应来合成 或活化 Secondary messenger systems can be synthesized and activated by enzymes 离子本身可以进入细胞 则速度更快 2. 多步骤的放大反应 也相较离子直接进入细胞 要花更多时间 : http://i.imgur.com/7tlVjnR.jpg Animal Physiology: From Genes to Organisms 作者：Lauralee Sherwood，Hillar Klandorf，Paul Yancey Parathyroid hormone (PTH), the principal regulator of Ca2+ metabolism, acts directly or indirectly on all three effector sites. It is the primary hormone responsible for maintaining Ca2+ homeostasis and is essential for maintaining Ca2+ balance PTH是essential 再来是 维生素D 第三位才是 The third Ca2+-influencing hormone, calcitonin, is not essential for maintenance of Ca2+ homeostasis in birds and mammals, though has roles in other vertebrates. : http://i.imgur.com/5mjRNuR.jpg The primary gustatory cortex is a brain structure responsible for the perception of taste. It consists of two substructures: the anterior insula on the insular lobe and the frontal operculum on the inferior frontal gyrus of the frontal lobe. 岛叶和额叶 各有一部份 http://www.austincc.edu/apreview/NursingPics/CNSPics/Picture14.jpg : http://i.imgur.com/V4cDlno.jpg the magnitude of the depolarization diminishes with distance from the site of initial depolarization, as some of the excess cations leak back across the membrane through resting cation channels ...... Another strategy to improve the passive flow of electrical current is to insulate the axonal membrane, reducing the ability of current to leak out of the axon and thus increasing the distance along the axon that a given local current can flow passively (see Box C). REf http://www.ncbi.nlm.nih.gov/books/NBK21668/ --

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