Category Zoology

What is muscle?

Muscles are the body tissue which, because it has the power of contraction, enables the higher animals to move their bodies. Muscles are divided into two great groups, voluntary and involuntary, the former being controlled by the will, while the latter act independently

     Most voluntary muscles are attached to the skeleton and range in size and shape to suit the particular jobs they perform. They can get into action within a few hundredths of a second, exert an enormous pull on the bone to which they are attached and, if necessary, support 1,000 times their own weight. Involuntary muscles include heart muscle and the muscles of the digestive system, and the fibers of which they are composed are very much smaller than those of voluntary muscle.

    Because of its exceptionally rich blood supply, muscle is the most infection-free of the body’s basic tissues. If it is over-taxed it tires and will stop contracting altogether, but if used normally will give little trouble.

Picture credit: google

Why do we sleep?

Some scientists consider that sleep is an instinct, a basic need for the body and mind to relax and to escape from the responses needed while awake. We become tired in body and mind if we do not sleep, and scientists have proved that when we do sleep the electrical activity of the brain slows down, although it may be stimulated when we dream.

     One chemical theory is that a substance needed to maintain the waking state becomes exhausted and may be replenished in sleep. A contrary suggestion is that some poisonous substances built up in wakefulness may be destroyed when we go to sleep.

   Other theories connect the need for increased wakefulness with the development of the more sophisticated areas of the brain. This could explain why new-born babies whose powers of reasoning have not yet developed, spend most of their lives asleep. It has been demonstrated that a particular formation, if severed, causes continues sleep.

     Although we are not sure why we sleep, there is no doubt that we need to do so and so do most other animals. The pattern of sleep and wakefulness is closely connected with our habits and senses. Animals which depend upon sight for food, shelter and defense, like man, are diurnal. That means they are for the most part active during the day and asleep at night.

    The amount of sleep needed by a person to remain in full health varies considerably with age, with different individuals, and even, perhaps, with race. Pre-school children generally need ten to twelve hours sleep schoolchildren nine to eleven hours and adults seven to nine hours. Adults seem to need progressively less sleep as they grow older, and exceptional cases are known of elderly people who have remained healthy on two to three hours a night. It has been said that the Japanese, children and adults, sleep less than Europeans, but that may be due to habit rather than to race.

Picture credit: google

How do we grip?

We take a grip on things by using our muscles to exploit the development of the human thumb. The importance of this thumb is that it can be moved across the palm of the hand to touch the index finger. In contrast the digits of a monkey’s hand are more rigid. This difference explains why a human being can handle an instrument with such precision.

     The mechanism of the hand is operated by way of the wrist, a hinge joint composed of eight small bones (carpals) packed firmly together to give elastic stability. Below the wrist project five small, long bones (metacarpals) which give the palm firmness. Four of the bones have hinge joints and are connected to the thumb allows it to move round and meet the fingers and palm, thus providing a firm grip.

    Possession of such a hand has enabled man to form a society and culture based on the use of tools. It is thought the hand developed from the five-rayed forepaw of an early vertebrate. However, occasionally a child is born with an extra tiny thumb or little finger and some people believe that the forepaw was originally seven-rayed.

    The human thumb has length longer in proportion than that of an ape. About 92% of human being is right handed, but apes tend to use both hands with equal ease.

Picture credit: google

What is the umbilical cord?

 

 

Inside the womb of a pregnant woman or animal a placenta is formed, through which the unborn baby is nourished. The baby is connected to the placenta by the umbilical cord, which is joined to the unborn child at the navel.

     The umbilical cord is the baby’s lifeline. Everything the child needs to survive will pass through it- air, blood and nourishment. At most it is no more than an inch wide and, perhaps, only a foot long.

    Once the baby is born the placenta, which serves a purpose only during the pregnancy, will be discarded.

      The umbilical cord will be cut with scissors a few inches away from the newborn baby’s stomach. This is quite painless because the umbilical cord has no nerves. The baby will now breathe on its own.

Picture credit: google

Where would you catch malaria?

The most likely places to catch malaria would be in tropical and sub-tropical countries, especially in the forested parts of Central Africa, Asia, and southern Europe. This is because the female anopheles mosquito, whose bite transmits the diseases, breeds in the warm, stagnant, marshy pools found in those parts.

    Malaria is said to derive its name from the Italian for “evil air”. It causes chills, fever and anaemia, and is sometimes fatal. In India a million people are likely to die from it every year.

     The first effective remedy for it, quinine, was used in the 16th Century. It is an infusion from the bark of the cinchona tree. Modern drugs, too, have greatly reduced the threat of malaria. In particular the use of sprays on the mosquitoes breeding places has been highly effective.

    In 1955 the world Health Organization started a mosquito-eradication programme of benefit to nearly 1,200 million people.

Picture credit: google

What makes you feel dizzy?

Dizziness most commonly occurs when a person who has been moving around with speed stops suddenly. The sensitive liquid in the inner ear, which mainly controls balance, continues to move around for a time after the body has stopped. So the surroundings appear to be still in motion. However, it takes only a few seconds, for the fluid, and balance, to settle.

    This sensation, which is also called vertigo, may also occur to someone looking down from a height or on board ship. Here the cause is probably not so much physical as a nervous reaction which affects the fluid in the inner ear.

Picture credit: google