通过比较细胞内部和外部的电位来测量细胞膜上的电势,因为在细胞内部称为离子的带电粒子的浓度或浓度梯度存在差异。这些浓度梯度反过来导致电子和化学不平衡,驱动离子平衡不平衡,更多不同的不平衡提供更大的动力或驱动力,以弥补不平衡。为此,离子通常从膜的高浓度侧移动到低浓度侧。动作电位的两个感兴趣的离子是钾阳离子(K +)和钠阳离子(Na +),它们可以在细胞内外发现。相对于外部,细胞内的K +浓度更高。细胞外侧的Na +浓度相对于内部浓度高,约为10倍。当没有进行中的动作电位时(即,细胞“静止”),神经元的电位处于静息膜电位,其通常被测量为约-70mV。这意味着电池内部的电位比外部低70 mV。应该注意的是,这指的是一种平衡状态 – 离子仍然进出细胞,但是以一种使静息膜电位保持在一个相当恒定的值的方式。静息膜电位可以维持,因为细胞膜含有形成离子通道的蛋白质 – 允许离子流入和流出细胞的孔 – 以及能够将离子泵入和离开细胞的钠/钾泵。离子通道并不总是打开;某些类型的渠道仅在特定条件下开放。这些通道因此被称为“门控”通道。泄漏通道随机打开和关闭,有助于维持细胞的静息膜电位。钠泄漏通道允许Na +缓慢进入细胞(因为Na +的浓度在外部相对于内部更高),而钾通道允许K +移出细胞(因为K +的浓度在内部更高)相对于外面)。然而,钾的泄漏通道比钠更多,因此钾以比钠进入细胞更快的速度移出细胞。因此,细胞外部有更多的正电荷,导致静息膜电位为负。钠/钾泵通过将钠从细胞或钾移回细胞中来维持静息膜电位。然而,该泵为每三个Na +离子带来两个K +离子,保持负电位。电压门控离子通道对动作电位很重要。当细胞膜接近其静息膜电位时,大多数这些通道保持闭合。然而,当细胞的电位变得更正(负更少)时,这些离子通道将打开。

美国布朗大学生物工程代写:外部的电位

The potential on the cell membrane is measured by comparing the potentials inside and outside the cell because there is a difference in the concentration or concentration gradient of charged particles called ions inside the cell. These concentration gradients in turn lead to electronic and chemical imbalances that drive ion balance imbalances, and more different imbalances provide greater power or drive to compensate for imbalances. For this reason, ions generally move from the high concentration side of the membrane to the low concentration side. The two ions of interest at the action potential are potassium cation (K + ) and sodium cation (Na + ), which can be found both inside and outside the cell. The concentration of K + in the cells is higher relative to the outside. The Na + concentration outside the cell is high relative to the internal concentration, which is about 10 times. When there is no action potential in progress (ie, the cell is “stationary”), the potential of the neuron is at a resting membrane potential, which is typically measured to be about -70 mV. This means that the potential inside the battery is 70 mV lower than the outside. It should be noted that this refers to an equilibrium state – the ions are still in and out of the cell, but in a way that maintains the resting membrane potential at a fairly constant value. The resting membrane potential can be maintained because the cell membrane contains proteins that form ion channels – pores that allow ions to flow into and out of the cell – and a sodium/potassium pump that can pump ions into and out of the cell. Ion channels are not always on; some types of channels are only open under certain conditions. These channels are therefore referred to as “gated” channels. The leaking channels are randomly turned on and off to help maintain the resting membrane potential of the cells. The sodium leak channel allows Na+ to slowly enter the cell (since the concentration of Na+ is higher externally relative to the interior), while the potassium channel allows K+ to move out of the cell (because the concentration of K+ is higher internally) relative to the outside). However, potassium leaks more channels than sodium, so potassium moves out of the cell at a faster rate than sodium enters the cell. Therefore, there is more positive charge outside the cell, resulting in a negative resting membrane potential. The sodium/potassium pump maintains the resting membrane potential by moving sodium from the cells or potassium back into the cells. However, the pump brings two K + ions to every three Na + ions, maintaining a negative potential. Voltage-gated ion channels are important for action potentials. Most of these channels remain closed as the cell membrane approaches its resting membrane potential. However, when the potential of the cells becomes more positive (less negative), these ion channels will open.

 

 

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