10 Quick Facts About the Brain

There are still many mysteries about the human brain, but researchers have uncovered a number of interesting facts about how the brain works. Here are ten quick facts to get you started on the path to a better understanding of the brain.

1. The average adult human brain weights approximately 3 pounds.

2. The human brain is composed of approximately 75 percent water.

3. The average weight of a newborn human infant brain is about 350 to 400 grams.

4. Recent estimates suggest that the average adult brain contains approximately 86 billion neurons.

5. Only about 10 percent of the brain is made up of neurons; the other 90 percent is mostly composed of glial cells. Glial cells perform a range of functions, including acting as a "glue" to hold neurons together. They also perform housekeeping functions by cleaning up excess neurotransmitters and supporting synaptic growth.

6. The brain continues to form new connections between neurons throughout life. Old beliefs suggested that the brain was fairly set in stone early in life, but neuroscientists now know that the brain never stops changing.

7. Among children and adults between the ages of 1 and 44, traumatic brain injury is the leading cause of disability and death.

8. The most common causes of traumatic brain injury include falls, motor vehicles crashes, and assaults.

9. The average size of the human brain has decreased by about 9 cubic inches over the past 5,000 years.

While it represents only about 2 percent of the body's total weight, it requires about 20 percent of the body's oxygen and 25 percent of the body's glucose.