英语听力练习下载mp3文本

2022-03-21 06:15:20 文档大全网 [ 字体：小中大 ] [ 阅读： ]

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英语听力练习下载mp3文本

Heart Rate： What A Baby’s Heart Rate Should Be

Picture new parents cooing at their baby on the couch. The baby’s quiet and calm, and everyone’s at rest. So their heart rates are low, maybe 60 or 70 beats a minute for the adults. What about the baby? How do you think the baby’s heart rate compares to the parents’? Baby Bliss

Newborns have resting heart rates around 100 to 150 beats per minute, way higher than that of adults. In fact, a newborn’s resting heart rate is in the ballpark of the target heart rate for an adult doing a heavy workout. What gives? Why do newborns’ hearts beat so much faster than adults’?

Part of the answer lies in the fact that babies grow so dramatically. They burn food in every cell of their bodies to fuel that growth.

The process requires not only an abundance of milk but also oxygen, and it produces large amounts of carbon dioxide as waste.

Babies’ hearts work overtime to keep supplying oxygen and removing carbon dioxide to fuel their amazing growth. The Animal World

But growth isn’t the only factor, because it’s not just baby animals we’re talking about. Adult Chihuahuas have much higher heart rates than adult elephants. Why? Chihuahuas have

a greater surface to volume ratio. In other words, the Chihuahua has a greater proportion of skin than internal tissue, which means it loses more heat to the environment, relatively speaking, than a larger animal.

Babies’ hearts beat much faster than their parents’, both to fuel their growth and make up for greater heat loss to the environment.

So little hearts maintain a higher metabolic rate, pound for pound, than big hearts. 婴儿的心率应该为多少呢？

想象这样一个画面，刚为人父母的他们正坐在沙发上温声细语的哄着孩子。孩子安静了不吵了，所有人都处于静息状态。所以这时他们的心率处于最低水平，对于成年人来说大约每分钟60到70次。那么婴儿的心率是多少呢？你认为婴儿的心率与父母的心率比起来是高还是低？婴儿福气。

新生儿的静息心率大约在100到150次每分钟，比同等条件下的成年人要高。事实上，一个新生儿的静息心率大致相当于一个成年人干重活时的心率。

这种现象出于什么目的？为什么新生儿的心率要比成年人的要快？部分原因在于新生儿生长的非常快。他们身体上的每个细胞都要消耗能量来维持生长。

在生长的过程中不但需要牛奶还需要氧气，而且会产生大量的代谢废物二氧化碳。

为了提供充足的氧气并将二氧化碳运出体外，以达到快速生长的目的，婴儿的心脏都是超负荷工作的。

动物世界。

但是生长不是的原因，因为它不但仅发生在我们正在谈论的婴儿身上。成年吉娃娃犬的心率要比成年大象快的多。为什么？吉娃娃犬有一个较大的表面体积比。换句话说，吉娃娃犬的皮肤面积比内部组织面积要大，这就意味与一个大型动物相比，它会向周围散失更多的热量。

婴儿的心率比他们父母的心率快，是因为生长和补充散失到环境中的大量能量的双重原因造成的。

在均等的条件下，小心脏要承受比大心脏更高的代谢速率。