Mechanism of Drug Addiction in the Brain, Animation. · Alila Medical Media
视频通过动画讲解毒品如何影响大脑奖励系统，适合练习医学类词汇和神经科学表达。
Addiction is a neurological disorder that affects the reward system in the brain.
成瘾是一种神经系统疾病，它会影响到大脑中的奖赏机制（即大脑在获得某种奖励时所产生的反应机制）。
In a healthy person, the reward system reinforces important behaviors that are essential for survival such as feeding,
在健康的人体内，奖赏系统会强化那些对生存至关重要的行为（例如进食）。
sexual activity, and social interaction.
性行为、社交互动……
For example, the reward system ensures that you reach for food when you are hungry, because you know that after eating you will feel good.
例如，奖励系统会促使你在饥饿时去寻找食物，因为你知道进食后自己会感到舒适（或：奖励系统会让你在感到饥饿时产生“进食会带来满足感”的心理预期）。
In other words, it makes the activity of eating pleasurable and memorable, so you would want to do it again and again whenever you feel hungry.
换句话说，它让进食这一行为变得愉快且令人难忘；因此，每当感到饥饿时，你就会想要再次进食。
Drugs of abuse hijack this system, turning the person’s natural needs into drug needs.
滥用药物会破坏人体的正常生理机制，使人原本正常的生理需求转变为对药物的需求。
The brain consists of billions of nerve cells, or neurons, which communicate via chemical messages, or neurotransmitters.
大脑由数十亿个神经细胞（即神经元）组成，这些神经元通过化学信号（即神经递质）进行相互交流。
When a neuron is sufficiently stimulated, an electrical impulse called an action potential is generated and travels down the axon to the nerve terminal.
当一个神经元受到足够的刺激时，会生成一种称为“动作电位”的电信号，这种信号会沿着轴突传递到神经末梢。
Here, it triggers the release of a neurotransmitter into the synaptic cleft - a space between neurons.
在这里，该过程会促使一种神经递质释放到突触间隙中（即神经元之间的空隙）。
The neurotransmitter then binds to a receptor on a neighboring neuron, generating a signal in it, thereby transmitting the information to that neuron.
这种神经递质随后会与邻近神经元上的受体结合，在该神经元内产生信号，从而将信息传递给该神经元。
The major reward pathways involve the transmission of a neurotransmitter called dopamine from the ventral tegmental area - the VTA - of the midbrain,
主要的奖赏通路涉及一种名为多巴胺的神经递质的传递。这种多巴胺由中脑的腹侧被盖区（VTA）释放出来。
to the limbic system and the frontal cortex.
这些信号会传递到边缘系统（limbic system）和前额叶皮层（frontal cortex）。
Engaging in enjoyable activities generates action potentials in dopamine-producing neurons of the VTA, causing dopamine release into the synaptic space.
参与令人愉悦的活动会刺激腹侧被盖区（VTA）中产生多巴胺的神经元，从而促使多巴胺释放到突触间隙中。
Dopamine then binds to and stimulates dopamine-receptor on the receiving neuron.
多巴胺随后会与接收神经元上的多巴胺受体结合，并刺激这些受体。
This stimulation is believed to produce the pleasurable feeling or rewarding effect.
人们认为这种刺激会带来愉悦的感觉或满足感。
Dopamine molecules are then removed from the synapse and transported back to the transmitting neuron by a special protein known as dopamine-transporter.
多巴胺分子随后会从突触中被清除，并通过一种名为“多巴胺转运蛋白”的特殊蛋白质被转运回释放多巴胺的神经元。
This clearing of dopamine is to ensure that the postsynaptic neurons are not overstimulated.
多巴胺的这种清除作用是为了确保突触后神经元不会受到过度刺激。
Most drugs of abuse increase the level of dopamine in the reward pathway.
大多数滥用药物都会增加大脑奖赏通路中的多巴胺水平。
Some drugs such as alcohol, heroin, and nicotine indirectly excite the dopamine-producing neurons in the VTA so that they generate more action potentials.
某些药物（如酒精、海洛因和尼古丁）会间接刺激腹侧被盖区（VTA）中产生多巴胺的神经元，从而使这些神经元产生更多的动作电位。
Cocaine acts at the nerve terminal.
可卡因的作用部位是神经末梢。
It binds to dopamine-transporter and blocks the re-uptake of dopamine.
该物质能与多巴胺转运蛋白结合，从而阻止多巴胺的再摄取。
Methamphetamine, a psychostimulant, acts similarly to cocaine in blocking dopamine removal.
甲基苯丙胺是一种中枢兴奋剂，其作用机制与可卡因类似，都能阻止多巴胺的清除。
In addition, it can enter the transmitting neuron, into dopamine-containing vesicles, where it triggers dopamine release even in the absence of action potentials.
此外，这种物质还可以进入传递神经元的含有多巴胺的囊泡中，在那里即使在没有动作电位的情况下也能引发多巴胺的释放。
Different drugs act in different ways but the common outcome is that dopamine builds-up in the synapse to a much greater amount than normal.
不同的药物作用机制各不相同，但它们的共同效果是：多巴胺在突触中的积累量会远高于正常水平。
This causes a continuous overstimulation of receiving neurons and is responsible for prolonged and intense euphoria experienced by drug users.
这种情况会导致接收神经元的持续过度兴奋，从而使得吸毒者体验到长时间且强烈的欣快感。
Repeated exposures to dopamine surges caused by drugs eventually desensitize the reward system.
长期接触由药物引起的多巴胺激增，最终会导致大脑的奖赏系统变得“麻木”（即对多巴胺的刺激不再产生反应）。
The system no longer responds to everyday stimuli; the only thing that is rewarding is the drug.
该系统不再对日常刺激产生反应；唯一能带来“满足感”（即愉悦感）的东西就是毒品了。
That is how drugs change the person’s life priority.
毒品就是这样改变了一个人的人生优先级（即让某些事情变得比其他事情更重要）。
After some time, even the drug loses its ability to reward and higher doses are required to achieve the same pleasurable effect.
过了一段时间后，即使是这种药物也会失去其带来愉悦感的能力；为了达到同样的效果，就需要使用更高剂量的药物。
This ultimately leads to drug overdose.
这最终会导致药物过量服用。