※ 引述《Dejavua (javaua)》之銘言：
: 大家好想請問以下:
: 12. 為什麼B不能選呢? C的訊號放大和relay protein有關, 請問1,2級傳訊是一種relay
: protein 嗎？
: 21. 為什麼不能選D呢? 形成膜電位不是和ECF(Na+)/ICF(K+)有關 嗎？
: 22. 為什麼不能選E?
: 35. D和味覺有關的腦區是頂葉嗎？
: 52. c應該不對吧？
: 謝謝
: http://i.imgur.com/Fw0bwVH.jpg
21題
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.

複習細胞膜電位 將看到不只是與鈉和鉀離子濃度有關
首先 細胞膜兩側 不只有 電位梯度 還有濃度梯度
所以一個離子要進出細胞膜 不只考慮靜電平衡 還有 離子濃度平衡

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.

選擇性通透的離子通道 是主要負責的機制 離子幫浦 則幫助維持




1.隔離 是維持梯度 最重要的特性

2.只考慮鈉和鉀離子是不夠的 兩者都是正離子 實際上當然也要考慮陰離子
In a more formal notation, the membrane potential is the
weighted average of each contributing ion's equilibrium potential.

3.看選項的意思transport 代表主動運輸 那就忽略了離子通道 還有 carrier


ref:
wiki:
https://en.wikipedia.org/wiki/Resting_potential
https://en.wikipedia.org/wiki/Membrane_potential

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: 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 的系統有兩個原因
1. the first messengers 無法直接穿過細胞膜的時候
2. 刺激很微小 需要放大訊號的時候

但是也有缺點
1. 有些scond messanger 需要酵素反應來合成 或活化
Secondary messenger systems can be synthesized and activated by enzymes
離子本身可以進入細胞 則速度更快
2. 多步驟的放大反應 也相較離子直接進入細胞 要花更多時間


: 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

再來是 維生素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. 島葉和額葉 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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