动作电位是静息膜电位的暂时逆转,从阴性到阳性。动作电位“尖峰”通常分为几个阶段:响应信号(或刺激),如神经递质与其受体结合或用手指按键,一些Na +通道打开,允许Na +流入细胞到期到浓度梯度。膜电位去极化或变得更正。一旦膜电位达到阈值 – 通常约-55 mV-动作电位继续。如果未达到潜力,则不会发生动作电位,细胞将恢复其静息膜电位。达到阈值的这一要求是动作电位被称为全有或全无事件的原因。达到阈值后,电压门控Na +通道打开,Na +离子涌入电池。膜电位从负转变为正,因为细胞内部现在相对于外部更为正。随着膜电位达到+ 30 mV  – 动作电位的峰值 – 电压门控钾通道打开,并且K +由于浓度梯度而离开细胞。膜电位复极化或移回负静息膜电位。随着K +离子导致膜电位变得比静息电位稍微负一点,神经元暂时变得超极化。 神经元进入不应期,其中钠/钾泵使神经元返回其静息膜电位。动作电位沿着轴突的长度向轴突终端传播,轴突终端将信息传递给其他神经元。传播的速度取决于轴突的直径 – 其中较宽的直径意味着更快的传播 – 以及轴突的一部分是否被髓鞘覆盖,髓鞘是一种类似于电缆线覆盖的脂肪物质:它的鞘轴突并防止电流泄漏,使动作电位更快发生。

英国拉夫堡大学Essay代写:脂肪物质

The action potential is a temporary reversal of the resting membrane potential, from negative to positive. The action potential “spike” is usually divided into several stages: a response signal (or stimulus), such as a neurotransmitter that binds to its receptor or a finger press, and some Na+ channels open, allowing the Na+ influent cell to expire to a concentration gradient. The membrane potential is depolarized or becomes corrected. Once the membrane potential reaches the threshold – usually about -55 mV – the action potential continues. If the potential is not reached, the action potential will not occur and the cell will resume its resting membrane potential. The requirement to reach the threshold is why the action potential is called an all-or-nothing event. After the threshold is reached, the voltage-gated Na+ channel turns on and Na+ ions flood into the cell. The membrane potential changes from negative to positive because the interior of the cell is now more positive relative to the outside. As the membrane potential reaches + 30 mV – the peak of the action potential – the voltage-gated potassium channel opens and K+ leaves the cell due to the concentration gradient. The membrane potential is repolarized or moved back to the negative resting membrane potential. As the K + ion causes the membrane potential to become slightly more negative than the resting potential, the neurons temporarily become hyperpolarized. The neurons enter a refractory phase in which the sodium/potassium pump returns the neurons to their resting membrane potential. The action potential propagates along the length of the axon to the axon terminal, which transmits information to other neurons. The speed of propagation depends on the diameter of the axon – where a wider diameter means faster propagation – and whether a part of the axon is covered by the myelin, a fat that resembles a cable covering: its sheath Axons prevent current leakage and allow action potentials to occur faster.

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