human nervous system

SOME INTERESTING FACTS ABOUT NERVOUS SYSTEM

• When we accidentally touch a hot object, the nerves that are connected to our skin transmit the message of pain to the brain. In response, the brain directs the muscles of the affected area to pull away from the source of pain. The whole process is executed in fractions of a second -- lot lesser than the time you will take to read these two lines. There are several such facts about the human nervous system; a few of these are listed below.

1.  There are billions of nerve cells in the human body; whether their number is actually more than the number of stars in the Milky Way galaxy is debatable, but their number is definitely more than the number of people on Earth.
2.  The human brain alone consists of about 100 billion neurons on an average. If all these neurons were to be lined up, it would form a 600-mile long line.
3.  While most of the sources maintain that the average number of neurons in the human brain is 100 billion, a 2009 study by neuroscientist, Herculano - Houzel revealed that the same is actually 86 billion.
4.  The human spinal cord, with an average length of 19 inches, consists of around 13,500,000 neurons. All the messages relayed between the brain and other parts of the body go via the spinal cord.
5.  The diameter of these neurons ranges between 4 to 100 microns. Though they are the largest cells in the human body, they do not undergo the process of mitosis like the other cells.
6.  The nervous system is able to transmit impulses at the speed of 100 meters per second. In fact, the speed of message transmission to the brain can be as high as 180 miles per hour.

SOURCE: http://www.buzzle.com/articles/interesting-facts-about-nervous-system.html