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69 Interesting Facts About . . .

The Human Brain

  1. The human brain weighs approximately 3.0 pounds. Human skin (all three layers) weighs approximately 20 pounds, intestines 7.5 pounds (large intestine: 4.0 lbs., small intestine: 3.5 lbs.), lungs 5 pounds (2.5 lbs. each), the liver 3.2 pounds, and the heart 0.6 pounds.e
  2. Déjà vu (French for “already seen”) has never been fully explained, though some scientists believe that a neurological glitch causes an experience to be registered in the memory before reaching consciousness.i
  3. brain doctor In 1955, Einstein’s brain was preserved for research
  4. Albert Einstein’s brain was removed within seven hours of his death by Princeton pathologist Thomas Stoltz Harvey (1912-2007). Harvey sectioned the preserved brain into 240 blocks and removed the eyes and gave them away. He kept pieces of the brain for himself and gave other pieces to other prominent pathologists. He was fired from Princeton Hospital because he refused to return the brain. Other brains that have been preserved include German mathematician Carl Friedrich Gauss, Vladimir Lenin, and the Native American Ishi.g
  5. While Einstein’s brain weighed 1,230 grams, which is within normal human range, the brain had no parietal operculum in either hemisphere and had an enlarged Sylvan fissure. Certain parts of his brain also had more glial cells in relation to neurons.g
  6. A mother’s illness may severely affect fetal brain cells; studies suggest that influenza or malnutrition during pregnancy may be associated with the development of schizophrenia. Damage to developing cells may also occur from maternal smoking and drinking, prenatal exposure to chemicals, or excess heat.i
  7. The brain takes the longest of any organ to develop and goes through more changes than any other organ.f
  8. A UCLA study found that both Caucasians and African Americans have similar brain activity when seeing photographs of African Americans. Both races showed more activity in the amygdala, an area of the brain associated with alarm, when shown expressionless photographs of African Americans than when they were shown expressionless photographs of Caucasians.j
  9. What appears as random bursts of light when people hit their heads is actually caused by a jolt to the brain cells responsible for vision. Stars most often appear following a blow to the back of the head because that is the location of the visual cortex.i
  10. A human brain is 75% water and has the consistency of tofu or gelatin.e
  11. The human brain consists of approximately 100 billion neurons (which is as many cells as there are stars in the Milky Way). Each neuron has somewhere between 1,000 and 10,000 synapses, equaling about 1 quadrillion synapses. If all the neurons in the human brain were lined up, they would stretch 600 miles. As a comparison, an octopus has 300,000 neurons, a honeybee has 950,000, and a jellyfish has no brain at all.a
  12. Eyeballs are a direct physical extension of the brain.e
  13. brain lightbulb The human brain generates enough energy to power a light bulb
  14. While awake, a human brain can generate enough energy to power a light bulb (between 10-23 watts).g
  15. Adults have between 125-150 ml of cerebrospinal fluid. An infant has 50 ml. The total volume of cerebrospinal fluid is replaced three to four times per day with a rate of production of .35 ml/min, or 500 ml/day.a
  16. A fold or fissure in the brain is called a sulcus (Latin for “furrow”). The smooth area between the folds is called a gyrus (Latin for “circle”).e
  17. A 20-year-old man has around 109,000 miles (176,000 km) of myelinated axons in his brain, which is enough to wrap around the earth’s equator four-and-a-half times. A 20-year old woman’s brain is typically smaller than a male’s, and, consequently, requires less wiring, with approximately 92,600 miles (149,000 km) of myelinated axons in her brain.i
  18. Men have a sexual pursuit area that is 2.5 times larger than in the female brain.h
  19. The human brain is the largest and most powerful sex organ.d
  20. The newest part of the cerebral cortex in terms of evolution is the neocortex (“new bark”), which scientists believe is responsible for the development of human intelligence.e
  21. The surface area of the human brain is about 230-470 square inches (1,500-3,000 sq. cm). The average length of a spinal cord is about 19 inches (45 cm).a
  22. Scientists claim that the most complicated and mysterious thing in the universe is the human brain. Scientists know more about stars exploding billions of light years away than they know about the brain.g
  23. Ancient people thought that other organs, including the stomach and the heart, were more important than the brain. During the mummification process, for example, the ancient Egyptians would pull out pieces of the brain through the nose with a long iron hook and throw them away. They would, however, keep the stomach, liver, intestines, and heart.i
  24. The first description of the anatomy of the brain is found in the 1700 B.C. Edwin Smith Surgical Papyrus, but it most likely contains information that was much older, perhaps from a thousand years earlier. In the document, ancient Egyptian doctors describe 26 different head injuries and treatments, wrinkles and fluids in the brain, its outer wrapping, and even the fluid inside it.i
  25. skull hole Trepanation is derived from the Greek word trypanon, meaning “to bore”
  26. In South America, scientist have discovered deliberately made “skull holes” that may have been made to treat painful headaches, brain disease, or to let “evil spirits” out of the head. Called “trepanation,” the process of making those holes was incredibly painful. The high number of trepanized skulls suggests that this brain surgery was commonplace.g
  27. Aristotle (384 BC-322 BC) believed that the center of thought was the heart and that the brain’s function was merely to cool the heart. He was correct, however, in his observation that the processes involved in short-term memory differ from those involved in long-term memory.g
  28. An early Greek physician, Alcmaeon of Croton (c. 6th century B.C.), was the first to claim that the brain, not the heart, is the central organ of sensation and thought. He also argued that the eyes themselves hold light and that the optic nerves are light-bearing paths to the brain.i
  29. René Descartes (1596-1650) argued that the brain functioned like a machine but that it cannot account for some higher mental faculties in humans, such as emotion and intellect. Descartes argued for a dualist system in which the brain is separate from an “immaterial mind.”i
  30. During the Middle Ages, the Catholic church banned human dissection and the study of human anatomy; consequently, study on the brain slowed considerably. However, roaming barbers offered primitive brain surgery to remove “the stone of madness.”i
  31. In 1862, Paul Broca determined the location of the speech center in the brain when he dissected the brain of a man who could only say “Tan! Tan!” and discovered that the left side of his brain had been eaten away by disease. The section of the brain responsible for speech was named “Broca” in honor of his research. i
  32. side of the brain The two brain hemispheres are highly complementary
  33. Eduard Hitzig (1839-1907) and Gustav (1838-1927) Fritsch discovered that the right side of the brain controls the left side of the body and vice versa.g
  34. Wilder Penfield (1891-1976) created a drawing that became known as a homunculus, which shows what we would look like if our body parts were as big as the brain space they take up. The homunculus has huge eyes, lips, hands, feet, and a tiny chest, little hips, and small shoulders.i
  35. The lobotomy, from the Greek lobe=of brain + tome=slice, was one of the most popular types of brain surgery ever invented. Neurologist and psychiatrist Walter Freeman (who was not a surgeon) simplified the surgery by taking an icepick through the eye sockets instead of through drilled holes in the skull. He chose an icepick because regular surgical tools made at the time kept snapping off inside of people’s heads.i
  36. President John F. Kennedy’s sister, Rosemary, was given a lobotomy for her mild retardation. A famous actress named Frances Farmer was given a lobotomy to make her easier to get along with, even though she may not have been mentally insane. Howard Dully discovered late in life that he had been lobotomized in 1960 at the age of 12 by Walter Freeman—simply because, it appears, his stepmother didn’t like him but she convinced Freeman something was wrong with the boy.i
  37. Researchers at Baylor University have found that children deprived of touch, play, and interaction with others have brains 20-30% smaller than normal for their age. Child abuse can inhibit brain development in a child and permanently negatively affect brain development.g
  38. During the first few weeks of life, a babbling baby utters almost every sound of every known language. Later, the ability to make some sounds vanishes, which is a case of neural pruning.f
  39. There are more than 100,000 chemical reactions happening in the human brain every second.i
  40. While general vocabulary and knowledge about the world often stays sharp through one’s 70s, memory for names begins to decline as early as age 35. The ability to recognize faces and find one’s car has already begun to wane by the 20s. However, research shows that brain stimulation not only stops cells from shrinking, but it can also increase brain cell and dendrite branching.i
  41. Neurological complications occur in at least 70% of patients who are diagnosed with AIDS. At autopsy, 80-90% have neurological abnormalities.i
  42. Anencephaly is the congenital absence of the brain, top of the skull, and spinal cord. Most infants born with this disease are stillborn or die a few hours after birth. It occurs in about 5 of every 1,000 pregnancies.i
  43. The brain does not have any pain receptors and, consequently, cannot feel pain.i
  44. Wearing a helmet can reduce the risk of brain injury by as much as 80%.g
  45. The human brain has around 100,000 miles of blood vessels.i
  46. The human brain consists of 60% fat, making it one of the fattiest organs in the body.g
  47. During early pregnancy, approximately 250,000 neurons develop per minute. After birth, a newborn’s brain nearly triples in size in its first year.f
  48. Approximately 20% of the total oxygen in the human body is used by the brain. The brain also uses 20% of the body’s total blood.i
  49. The human brain can process information as fast as 268 miles/hr. Information travels to the brain at different speeds because neurons are built differently.i
  50. Humans have more brain cells at the age of two than at any other time of their lives.i
  51. The first known writing about the brain was found in ancient Sumeria around 4000 B.C. The anonymous writer describes the euphoric, mind-altering feeling caused by eating poppies.i
  52. brain woman Everyone’s brain starts out female
  53. Everyone’s brain starts out as female. The brain of males begins to become masculinized around eight weeks after conception by the male hormone testosterone.f
  54. Research indicates that men and women have different structures and wiring in the brain. For example, the frontal lobe—which is responsible for problem solving and decision making, and the limbic cortex—which is responsible for regulating emotion, are larger in women. Women also have about 10 times more white matter than men.b,d
  55. A woman’s brain shrinks during pregnancy and takes up to six months to regain its full size.d
  56. If brain cells were replaced, like skin or liver cells, scientists hypothesize we would lose our memories.i
  57. In humans, the left side of the brain controls speech. In birds, the left side of the brain controls song. At least in this way, humans are “bird brained.”e
  58. A human adult brain weighs about 3.5 pounds, slightly less than a large bag of flour. The sperm whale has the largest brain of all animals, weighing up to 20 pounds. An elephant’s brain weighs 11 pounds, while a mouse’s weighs only a few ounces.a
  59. Swiss researchers have discovered that certain types of brain lesions lead average eaters to become addicted to thinking about and eating gourmet foods.g
  60. Research shows that those who are clinically depressed or suicidal have abnormal levels of the brain chemicals serotonin and norepinephrine. Flaws in the brain’s serotonin levels have been linked to violent suicide attempts and aggression.i
  61. When a person diets or deprives himself of food, the neurons in the brain that induce hunger start eating themselves. This “cannibalism” sparks a hunger signal to prompt eating.g
  62. Humans grow faster at night than they do during the day because a small part of the brain, the pituitary gland, releases a growth hormone at night while a person sleeps.i
  63. The sense of smell connects to the part of the brain that also controls emotions and memories. This is why smells often evoke strong memories.g
  64. If the human cortex (the outer layer of the cerebrum) were unfolded, it would cover an area roughly the size of a pillowcase.g
  65. Scientists note that children with autism have normal-sized brains at birth, but at some point—usually at the end of the first year of life—a part of the brain called the amygdala grows on average 13% larger than in non-autistic children.c
  66. In biblical times, the lentil was thought to have the power to improve the brain. During the Middle Ages, popular brain food included eagle hearts and crushed lizard. During the reign of Louis XI, people hoped gold leaf would enhance the power of the brain.i
  67. Fetal brain tissue has been used to repair brain damage by implanting cerebral tissue from aborted fetuses.f
  68. On an ongoing basis, even during sleep, electrical signals are constantly flashing over the brain. These signals can be detected and measured by an encephalograph. Because the tissues of the body conduct electricity well, metal sensors attached to the skin of the head can detect the signals passing from the brain through the muscles and skin.i
  69. The heaviest known normal human brain belonged to the Russian Writer Ivan Turgenev, who died in 1883. His brain weighed 4.43 pounds, more than a pound heavier than the average male brain.i
  70. The smallest known normal brain belonged to a woman who died in 1977. Her brain weighed just 2.41 pounds.i
  71. foot feather The cerebellum prevents us from self-tickling
  72. Brain scientists have identified the cerebellum as the part of the brain that prevents us from tickling ourselves. It helps us distinguish between expected and unexpected sensations.g
  73. Experts estimate that in a lifetime, a human brain may retain one quadrillion separate bits of information.i
  74. Contrary to the popular belief that humans use just 10% of their brain capacity, humans actually use virtually every part of the brain, and most of the brain is active all the time. If 90% of the brain were removed, leaving just 10%, that would leave 140 grams (0.3lbs) of brain tissue, which is the same size as a sheep’s brain.i
  75. Chronic exposure to stress overloads the brain with powerful hormones that are intended for short-term functions in emergency situations. Long-term exposure has a cumulative effect that kills brain cells.i
    Average Brain Weights a
    Animal Weight (g)
    Human Adult 1,300-1,400
    Human Newborn 350-400
    Sperm Whale 7,800
    Fin Whale 6,930
    Killer Whale 5,620
    Elephant 4,783
    Humpback Whale 4,675
    Gray Whale 4,317
    Camel 762
    Giraffe 680
    Hippopotamus 582
    Pig 180
    Dog 72
    Cat 30
    Goldfish 0.097
    Green Lizard 0.08

    Proportions of the Brain in Rats and Humans by Volume (%)
    Rat Human
    Cerebral Cortex 31 77
    Diencephalon 7 4
    Midbrain 6 4
    Hindbrain 7 2
    Cerebellum 10 10
    Spinal cord 35 2

-- Posted December 14, 2011

References

a Chudler, Eric. “Brain Facts and Figures.” November 1, 2011: Accessed: November 17, 2011.

b Cohen, Elizabeth. “Loving with All Your . . . Brain.” CNN. February 5, 2007. Accessed: November 17, 2011.

c Dellorto, Danielle. “Toddler Brain Difference Linked to Autism.” CNN. May 4, 2009. Accessed: November 17, 2011.

d Edmonds, Molly. “Do Men and Women Have Different Brains?” Discovery. 2011. Accessed: November 17, 2011.

e Juan, Stephen. 2011. The Odd Brain: Mysteries of Our Weird and Wonderful Brain Explained. Riverside, NJ: Andrews McMeel Publishing.

f McDonald, Ann. “Prenatal Development–The Dana Guide.” The DANA Foundation. November 2007. Accessed: November 17, 2011.

g Newquist, H.P. 2004. The Great Brain Book. New York, NY: Scholastic Inc.

h Schaefer, Laura. “The Male Brain, Explained.” MSCN. 2011. Accessed: November 17, 2011.

i Turkington, Carol. 1996. The Brain Encyclopedia. New York, NY: Checkmark Books.

j Wolpert, Stuart. “African Americans and Caucasians Have Similar Emotional Brain Activity When Seeing African Americans, UCLA Psychologists Find.” UCLA Newsroom. May 9, 2005. Accessed: November 17, 2011.