解放军文职招聘考试Muscles and Human

 Muscles and Human

Body It  is in the  joints  of the  human body  that movements of the bones

take  place. The movement itself is  caused  by the pull of sheets and 

cords  of very tough tissue  called  muscle. Muscle tissue has the special

ability to shorten itself so that the bone on which it pulls has to move.

When muscle tissue shortens, it also  bunches up.  Muscle  tissue covers

the  body in sheets and bands that lie between the skin and the skeleton.

The bones are the framework of the body, but the muscles fill out the body

shape. Most muscles extend from one bone to another. When the muscle

between the bones shortens, one bone has to move. The point where the

muscle is fastened to the unmoving  bone is  called the origin  of the

muscle, whereas  the point where the  muscle is not fastened to the bone

that is to be  moved is called  the insertion. Sometimes the muscle is not

attached directly to the bone but to a tough, nonstretchable cord, or

tendon, that is attached to the bone. Muscles do not push; they can only

pull. To bend the arm at the elbow, the muscle at the front of the upper

arm has to shorten and bunch up. To unbend the arm other muscles in the

back of the arm have to shorten. These two sets of muscles - the front and

the back - are said to act in opposition to each other. When one set is

working, the other set is usually relaxed. But there are times when both of

them work. Sometimes muscles are called upon to do more than simply pull in

one direction. They may have to perform a turning motion. To be able to do

this, the muscle must be attached to the bone at an angle. By pulling, the

muscle can cause the bone to pivot. A few muscles have special functions.

The diaphragm, for example, forces the lungs to take in air. This part of

breathing is not primarily a bone moving operation.

肌肉和人体  骨骼运动发生在人体的关节部位。这种运动是由称为肌肉的片状或条状的 强韧组织拖动而引起的。

肌肉组织有一种特殊的收缩能力，可以带动与之相连的骨骼。 肌 肉在收缩的同时，也会聚成团。 肌肉以条状或片状形式布满全身，存在于皮肤与骨架之间。

骨骼是身体的支架，而肌肉则构成了人的体形。  大多数肌肉接两块骨头，但当肌肉收缩时 只有一块骨头运动。

肌肉与不动骨相连的一端叫肌起端，与动骨相连的一端叫附着端。 有 些肌肉不与骨骼直接相连，而是连着附在骨骼上的不能收缩的带状组织或腱上。  肌肉不能

推动而只能拉动骨骼。  要从肘部弯曲手臂，就要收缩上臂正面的肌肉。  要伸直手臂，背面 的肌肉就得收缩。 

这两组肌肉，正面的和背面的，称为相反运动肌肉。  当一组工作时，另 一组就休息。  但有时它们也一起工作。  有时我们要求肌肉不仅仅做简单的单向拖动。

 它 们需要转动。  但只有当肌肉与骨骼形成一定角度时，它们才能转动，从而拖动骨骼绕某个 轴旋转。  有几块肌肉的作用较特殊，例如隔膜肌。 

它带动肺部吸入空气。  呼吸基本上不 是骨骼运动带动的。