英语听力文摘 English Digest 580、什么是条件反射？

 　　What Are Reflexes?

 

　　If you’ve ever blinked at a sudden light, jerked your hand away from something hot, or jumped at a loud noise, then you know that these are not actions we consciously plan. Rather, they happen involuntarily.

 

　　Such sudden, unconscious movements are a kind of simple neural¹ activity known as a reflex.

 

　　A deliberate action, such as raising a spoon to the mouth, involves consciousness. We decide to raise the spoon, then we do it. Most reflexes, however, do not involve the brain; they are fast, involuntary responses that travel over what is known as a reflex arc. A reflex arc consists of a stimulus², for example extreme heat, which creates an impulse that travels along sensory³ nerves and neurons to the spinal⁴ cord.

 

　　Once it reaches the spinal cord, the impulse is routed speedily back to the muscle originally stimulated⁵. This process occurs almost instantaneously, before we’ve even had time to consciously register that the reflex has happened.

 

　　Although a reflex is automatic, it can change over time, depending on the regularity⁶ of the stimulus. If a stimulus is repeated continuously, the reflex first undergoes sensitization, meaning that it increases in response.

 

　　But if the stimulus is repeated beyond a certain point, the reflex begins to decrease until it disappears. In other words, you can tame a reflex by, for instance, hearing a sudden loud noise repeatedly until you stop jumping.

 

　　什么是条件反射？

 

　　如果你曾因为突如其来的灯光眨眼，碰到烫的东西立刻把手缩回来，或是听到很响的声音吓了一跳，你会发现这些动作并非我们有意识地计划过的，而是不由自主发生的。

 

　　这些突然、无意识的动作是一种简单的神经活动，我们称之为条件反射。

 

　　有意的行为总是包含着意识的参与，比如要把一个勺子送到嘴边，我们先决定拿起勺子，然后再做这个动作。但大部分的条件反射都与大脑无关，它们是快速、无意 识的反应，这种反应沿着我们所熟知的反射弧传递。反射弧包括某种刺激，比如人在极高的温度下会产生一种神经冲动，这种神经冲动会沿着感觉神经和神经元传 递，最后到达脊髓。

 

　　一旦到达脊髓，神经冲动便会迅速沿原路返回至最初受到刺激的肌肉。整个过程几乎是在瞬间完成的，甚至在我们有时间意识到之前，条件反射就已经发生了。

 

　　虽然条件反射是自发形成的，但它会随着时间发生变化，这要取决于刺激发生的频率。如果某种刺激不断地重复，条件反射最开始会对这种刺激变得敏感，换句话说，条件反射的反应次数会增加。

 

　　但如果这种刺激超过了某个临界点时，条件反射次数就会开始减少直至消失。换句话说，条件反射是可以克服的，比如，反复听突如其来的巨响，直到你不会被吓一跳为止。

1 neural   

adj.神经的，神经系统的

参考例句：

• The neural network can preferably solve the non- linear problem.利用神经网络建模可以较好地解决非线性问题。
• The information transmission in neural system depends on neurotransmitters.信息传递的神经途径有赖于神经递质。

2 stimulus   

n.刺激，刺激物，促进因素，引起兴奋的事物

参考例句：

• Regard each failure as a stimulus to further efforts.把每次失利看成对进一步努力的激励。
• Light is a stimulus to growth in plants.光是促进植物生长的一个因素。

3 sensory   

adj.知觉的，感觉的，知觉器官的

参考例句：

• Human powers of sensory discrimination are limited.人类感官分辨能力有限。
• The sensory system may undergo long-term adaptation in alien environments.感觉系统对陌生的环境可能经过长时期才能适应。

4 spinal   

adj.针的，尖刺的，尖刺状突起的；adj.脊骨的，脊髓的

参考例句：

• After three days in Japan,the spinal column becomes extraordinarily flexible.在日本三天，就已经使脊椎骨变得富有弹性了。
• Your spinal column is made up of 24 movable vertebrae.你的脊柱由24个活动的脊椎骨构成。

5 stimulated   

a.刺激的

参考例句：

• The exhibition has stimulated interest in her work. 展览增进了人们对她作品的兴趣。
• The award has stimulated her into working still harder. 奖金促使她更加努力地工作。

6 regularity   

n.规律性，规则性；匀称，整齐

参考例句：

• The idea is to maintain the regularity of the heartbeat.问题就是要维持心跳的规律性。
• He exercised with a regularity that amazed us.他锻炼的规律程度令我们非常惊讶。