31 You've Got a Lot of Nerve!-Mid

You've Got a Lot of Nerve! FOCUS Question How does the brain control behavior?

你胆子真大!大脑是如何控制行为的?

Getting Connected Have you thanked your nervous system lately? You owe your best ideas—and even your survival—to your nervous system. It controls everything. Your nervous, system is made up of hundreds of billions of cells called neurons, or nerve cells. Neurons gather and transmit messages throughout your body. A neuron has three main parts. The cell body contains the nucleus and other tiny parts. The axon carries messages over long distances to other cells. Fingerlike dendrites receive messages from other neurons. Axons send messages to the dendrites of other neurons across tiny gaps called synapses. Synapses are where chemicals trigger electrical pulses. When neurons "fire," electrical pulses zip away.

最近你感谢过你的神经系统吗? 你最好的想法——甚至你的生存——都要归功于你的神经系统。 它控制着一切。你的神经系统是由数千亿个叫做神经元或神经细胞的细胞组成的。 神经元在你全身收集并传递信息。 神经元有三个主要部分。 细胞体包含细胞核和其他微小部分。 轴突将信息远距离传送到其他细胞。 指状树突接收来自其他神经元的信息。 轴突通过称为突触的微小间隙向其他神经元的树突发送信息。 突触是化学物质触发电脉冲的地方。 当神经元“放电”时，电脉冲迅速消失。

The brain and spinal cord make up the central nervous system. The spinal cord is a bundle of nerves that travels from the brain down through the backbone. Spinal nerves fan out to the rest of the body. These side branches form the peripheral (puh-RIF-er-uhl) nervous system. There are two kinds of nerve cells in the peripheral nervous system. Sensory neurons gather information from the senses. They carry messages to the central nervous system. Motor neurons send messages from the central nervous system to muscles. All vertebrates—animals with backbones—have similar nervous systems. For example, both frogs and humans have a brain, spinal cord, and peripheral nerves. Word Wise The word peripheral means "to the side."

大脑和脊髓组成中枢神经系统。 脊髓是一束神经，从大脑向下穿过脊柱。 脊神经呈扇形伸展到身体的其他部位。 这些侧分支形成了外周神经系统(puh-RIF-er-uhl) 周围神经系统中有两种神经细胞。 感觉神经元从感官中收集信息。 它们将信息传递到中枢神经系统。 运动神经元从中枢神经系统向肌肉发送信息。 所有脊椎动物——有脊椎的动物——都有相似的神经系统。 例如，青蛙和人类都有大脑、脊髓和周围神经。 “peripheral”这个词的意思是“在一边”。

The Great Brain The brain has many important jobs. How does it keep track of them all? Different areas of the brain take care of each job. The brain stem and cerebellum are two key areas. They control autonomic (AH-tow-NAH-mick) functions. These functions include breathing, balancing, and other important functions that we don't have to think about. The cerebrum is another key area of the brain. Each of the five senses has its own region in the cerebrum: sight, hearing, smell, taste, and touch. In human brains, there are also well-developed regions for communication and higher-level thinking.

大脑有许多重要的功能。 它是如何跟踪它们的? 不同的大脑区域负责不同的工作。 脑干和小脑是两个关键区域。 它们控制自主(AH-tow-NAH-mick)功能。 这些功能包括呼吸、平衡和其他我们不需要考虑的重要功能。 大脑是大脑的另一个关键区域。 五种感官在大脑中都有各自的区域:视觉、听觉、嗅觉、味觉和触觉。 在人类的大脑中，也有非常发达的区域用于交流和高级思维。

Every animal's brain is different. Each brain is developed for the actions and senses that are important for each animal. For example, bats make sound waves and listen for the echoes. This is called echolocation. A bat's brain has a larger region for hearing than a human's brain. Bats survive by using echolocation to find and capture food. Humans survive because our cerebrum allows us to think and communicate complex thoughts. Math Moment Your brain uses about 20% (or .20) of your energy. If you eat 2,000 calories in a day, how much energy goes toward "feeding" your brain?

每种动物的大脑都是不同的。 每一个大脑都是为对每一种动物都很重要的动作和感觉而发育的。 例如，蝙蝠会发出声波并聆听回声。 这叫做回声定位。 蝙蝠大脑的听觉区域比人类大脑更大。 蝙蝠靠回声定位来寻找和捕捉食物。 人类之所以能生存下来，是因为我们的大脑允许我们思考和交流复杂的思想。 你的大脑消耗了你20%(0.20)的能量。 如果你一天吃2000卡路里，有多少能量是“喂养”你的大脑?

Reflex Action Some actions are so basic and important that the brain doesn't need to be involved at all. Suppose you accidentally touched the handle of a hot pan. Without thinking, you'd pull back your hand. The sensory nerves in your hand would sense that the pan was hot, and an electric pulse would flash through your neurons to your spinal cord. Motor neurons would respond, and muscles would pull back your hand. The whole process happens in an instant. That's a reflex. Reflexes help animals to avoid danger and survive.

有些动作是非常基本和重要的，根本不需要大脑参与。 假设你不小心碰到了热锅的把手。 你会不假思索地缩回手来。 你手上的感觉神经会感觉到锅是热的，电脉冲会通过你的神经元闪到你的脊髓。 运动神经元会做出反应，肌肉会缩回你的手。 整个过程在瞬间发生。 这是条件反射。反射帮助动物躲避危险并生存下来。