Quickly gobbling up cold ice cream may result in “brain freeze,” also know as an ice cream headache. When the cold object touches the roof of your mouth, the blood vessels contract in order to prevent loss of body heat. As the coldness stops, the blood vessels relax again, quickly increasing blood flow to the brain.
This sudden release is What causes the intense headache sensation. You can relieve brain freeze by quickly warming the roof of your mouth: Touch your tongue to the top of your mouth or, if you can roll your tongue in a ball, press the underside of your tongue (which is warmer) to the roof of your mouth. Slowly sipping room-temperature water or pressing a warm thumb against the roof of the mouth also works for some people.
The human body is a complicated living machine in which various systems work together as a functioning whole. All the parts of the body—including hundreds of rock-hard bones and quarts of blood—are made up of cells, about 100 trillion (100,000,000,000,000) cells in all! Twenty-two internal organs—the large body parts like the heart, lungs, liver, and kidneys—perform special jobs and work together to form the different body systems. There are eight key systems in the body. The muscular system, made up of more than 600 muscles, enables our bodies to make all of their movements. The circulatory system carries oxygen-rich blood throughout the body. The skeletal system is made of the bones that form the skeleton and give the body its shape. People breathe using the respiratory system. The body’s heat-control system is called the integumentary system, which is made up of skin, hair, nails, and sweat glands. The reproductive system creates new life.
The nervous system processes information from both inside and outside the body and sends messages, via its nerves, to different parts of the body. And the digestive system helps us digest our food and nutrients and gives us energy to go through the day. There are other systems, too, that help the body sustain life, including the immune system, which fights off invading viruses and diseases, and the urinary system, which helps keep the inside of the body clean and eliminates waste. The endocrine system, made up of glands, sends hormones around the body to trigger growth and to control other activities. These body systems work together to keep all human beings alive and healthy.
Just as telephones are connected by a worldwide phone system, home and work computers can connect with a global computer communications network known as the Internet. Each computer that is linked to the system has its own Internet address, as individual as a phone number. Home computer users buy the services of an Internet provider, which is an organization with powerful computers that link all its subscribers to the Internet.
Many large organizations and companies have computers that link them directly to the network. Internet users can visit the World Wide Web, which is a global network of Web sites providing information, entertainment, products, and other services.
In Victorian times, to “go to The Devil” was to visit a bar on Flat Street near the London Civil Courts. The Devil was a favourite pub for lawyers, who seemed to spend more time in that bar than in their offices. If a client thought his money had “gone to The Devil” to pay for his lawyer’s drinks, he might visit the legal offices to ask for an explanation, where he would be told that the absent lawyer had indeed “gone to The Devil.”
A virus is a malicious software program that infects computer files or hard disk drives and then makes copies of itself. Many activities that kids do online can leave computers vulnerable to viruses. E-mail attachments are a common means of distributing viruses, but viruses can also be downloaded when you share files and open instant message attachments. In order to keep your computer safe, never open an e-mail attachment you haven’t requested.
Send an e-mail to friends to confirm that they meant to send you an attachment. Also, you can configure your instant messaging program so you can’t receive files from other users. Never download any program without checking with a parent first. You can protect your computer by always running up-to-date firewall software, by running antivirus software regularly, and by periodically scanning your computer for spyware or other unwanted software and immediately removing it.
The deepest hole ever made by humans is in Kola Peninsula in Russia, where in 1989 geologists dug a hole 7.6 miles (12.2 kilometers) deep. The Kola Superdeep Borehole began in the 1970s.
Russian teams used special drilling techniques to dig into the Baltic continental crust, presumed to be about 22 miles (35 kilometers) thick, exposing rocks 2.7 billion years old at the bottom.
Often it is a group of people with something in common, whose members identify with one another, that makes up a country. It may be a shared race, religion, language, history, or culture that makes people feel that they belong together as a nation. Because of its uniqueness, the group feels that it should govern itself as an independent country. This feeling of shared identity and loyalty to the group is frequently behind the rise of nations. Some countries are so large and have such complicated histories of war and conquest that they are home to many different groups of people who have their own separate beliefs, languages, and customs.
The differences between these groups sometimes make it difficult for them to get along. A nation is weakened by such groups if they put their own interests ahead of those of their country. But a population of many different groups can also enrich a country with diverse ideas and cultures if a spirit of acceptance and cooperation exists.
Walking with your dog strengthens the bond between you and your pet, and it is also the healthy thing to do. Dogs, like people, benefit from exercise to help control weight and to maintain a healthy heart, lungs, and muscles. They love going for a walk, running and jumping, and retrieving a ball or Frisbee. Aging pets must be kept as agile and fit as possible, but may not be motivated to exercise without encouragement. The pleasure of your company is one of your dog’s greatest motivations to exercise.
In addition to exercise, dogs also need social interaction, positive attention from their owner, and mental stimulation. Many of these needs can be met by simply taking your dog for a walk. Always remember to walk your dog on a secure leash (with identification tags) and pick up after your pet. During warm weather carry water for your pet, and always pause when your dog needs a rest.