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肌肉系统的工作原理 – 译学馆
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肌肉系统的工作原理

How your muscular system works - Emma Bryce

“他完全被生命的汹涌 潮汐的存在 每一块单独的肌肉的完美喜悦所掌控…”——杰克·伦敦《野性的呼唤》
每当你迈出一步
Each time you take a step,
200块肌肉同时工作使你抬起脚
200 muscles work in unison to lift your foot,
并向前推进
propel it forward,
然后放下
and set it down.
这只是肌肉系统成千上万个任务中的一个
It’s just one of the many thousands of tasks performed by the muscular system.
这个肌肉网 是由覆盖全身的650块肌肉组成
This network of over 650 muscles covers the body
而这是我们可以眨眼
and is the reason we can blink,
微笑
smile,
奔跑
run,
跳跃
jump,
和站立的原因
and stand upright.
它甚至为心脏的稳定工作负责
It’s even responsible for the heart’s dependable thump.
首先 肌肉系统到底是什么?
First, what exactly is the muscular system?
它主要有三种肌肉组成:
It’s made up of three main muscle types:
骨骼肌 通过肌腱连接在我们的骨骼上
skeletal muscle, which attaches via tendons to our bones,
心肌 仅在心脏中被发现
cardiac muscle, which is only found in the heart,
平滑肌构成了血管和某些器官的内壁
and smooth muscle, which lines the blood vessels and certain organs,
比如肠跟子宫的内壁
like the intestine and uterus.
这三种都是由肌肉细胞组成的
All three types are made up of muscle cells,
紧紧聚集在一起的肌细胞又叫肌纤维
also known as fibers, bundled tightly together.
这些肌束从神经系统得到
These bundles receive signals from the nervous system
收缩纤维的信号 依次产生力和动作
that contract the fibers, which in turn generates force and motion.
这通常是我们所有的动作所经历的过程
This produces almost all the movements we make.
运动不受肌肉系统支配的身体部分
Some of the only parts of the body whose motions aren’t governed by the muscular system
只有精子细胞
are sperm cells,
呼吸道中的毛状纤毛
the hair-like cilia in our airways,
和某些白细胞
and certain white blood cells.
肌肉收缩可以分成三种主要形式
Muscle contraction can be split into three main types.
前两种分别是缩短肌纤维和拉长肌纤维
The first two, shortening muscle fibers and lengthening them,
由此产生相反的力
generate opposing forces.
所以当举起胳膊并在肘部弯曲
So the biceps will shorten while the triceps will lengthen or relax,
会使二头肌缩短 三头肌呈现拉长或是放松状态
pulling up the arm and making it bend at the elbow.
这是拿起书本的动作
This allows us to, say, pick up a book,
如果肌肉关系相反就是放下书本的动作
or if the muscle relationship is reversed, put it down.
这种互补的合作关系在整个肌肉系统中存在
This complementary partnership exists throughout the muscular system.
第三种收缩会产生一种稳定力
The third type of contraction creates a stabilizing force.
在这种情况下 肌肉纤维在长度上不会发生变化
In these cases, the muscle fibers don’t change in length,
但肌肉会保持刚硬状态
but instead keep the muscles rigid.
这让我们能紧握一杯咖啡或斜靠在墙上
This allows us to grip a mug of coffee or lean against a wall.
它还使我们能够保持直立状态
It also maintains our posture by holding us upright.
在肌肉系统中 有大量的骨骼肌
Skeletal muscles form the bulk of the muscular system,
其重量为体重的30-40%
make up about 30-40% of the body’s weight,
人体的大多数动作都是由骨骼肌完成的
and generate most of its motion.
有些肌肉对我们来说很熟悉 像胸肌和二头肌
Some muscles are familiar to us, like the pectorals and the biceps,
其他的则不熟悉 像颊肌
Others may be less so, like the buccinator,
它是连接你面颊跟牙齿的肌肉
a muscle that attaches your cheek to your teeth,
还有身体中最小的骨骼肌——
or the body’s tiniest skeletal muscle,
被称为镫骨肌的一毫米长的组织块
a one-millimeter-long tissue fragment called the stapedius
它位于耳朵极深的内部
that’s nestled deep inside the ear.
全身的骨骼肌都与躯干神经系统相连
Wherever they occur, skeletal muscles are connected to the somatic nervous system,
神经系统几乎完全控制了骨骼肌的运动
which gives us almost complete control over their movements.
肌肉群包括两种改善动作的肌肉纤维
This muscle group also contains two types of muscle fibers
分别是慢肌纤维和快肌纤维
to refine our motions even further, slow-twitch and fast-twitch.
快肌纤维能够迅速做出反应
Fast-twitch fibers react instantly when triggered
但是会迅速用尽能量并疲劳
but quickly use up their energy and tire out.
相反 慢肌纤维是有耐力的肌细胞
Slow-twitch fibers, on the other hand, are endurance cells.
它们反应迟缓 耗能慢 所以它们能够长时间工作
They react and use energy slowly so they can work for longer periods.
一个短跑选手的腿部会积累大量快肌纤维
A sprinter will accumulate more fast-twitch muscles in her legs
通过连续练习
through continuous practice,
使她能够迅速 简单地加快步伐
enabling her to quickly, if briefly, pick up the pace,
然而背部肌肉含有更多的慢肌纤维
whereas back muscles contain more slow-twitch muscles
能够保持你一整天的姿势
to maintain your posture all day.
不像骨骼肌 身体中的心肌和平滑肌
Unlike the skeletal muscles, the body’s cardiac and smooth muscles
由自主神经系统控制
are managed by the autonomic nervous system
不由我们直接控制
beyond our direct control.
你的心脏在一生当中
That makes your heart thump roughly 3 billion times
跳大概30亿次
over the course of your life,
这为身体提供了血液和氧气
which supplies the body with blood and oxygen.
自主神经系统能按一定的周期
Autonomic control also contracts and relaxes smooth muscle
来控制平滑肌的收缩和放松
in a rhythmic cycle.
自主神经系统使心脏泵出的血液穿过平滑的血管内壁
That pumps blood through the smooth internal walls of blood vessels,
使肠道收缩 并将食物推入消化系统
enables the intestine to constrict and push food through the digestive system,
并且在生育时能使子宫收缩
and allows the uterus to contract when a person is giving birth.
肌肉运动时消耗能量并产生重要的副产物 热量
As muscles work, they also use energy and produce an important byproduct, heat.
事实上 肌肉提供了人体大约85%的热量
In fact, muscle provides about 85% of your warmth,
被心脏跟血管通过血液
which the heart and blood vessels then spread evenly across the body
均匀地输送到全身
via the blood.
如果没有它 我们将不能保持
Without that, we couldn’t maintain the temperature necessary
生存所必须的温度
for our survival.
肌肉系统大部分是不可见的
The muscular system may be largely invisible to us,
但它几乎参与了我们的一切行动
but it leaves its mark on almost everything we do,
不论是眨眼或是跑到终点线
whether it’s the blink of an eye or a race to the finish line.

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肌肉系统是如何工作的?肌肉分为几种?每种都在哪里发现?一起来看看吧!

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