Human brain
hideThe human brain is the center of the human nervous system and is a highly complex organ. Enclosed in the cranium, it has the same general structure as the brains of other mammals, but is over three times as large as the brain of a mammal with an equivalent body size. Most of the expansion comes from the cerebral cortex, a convoluted layer of neural tissue that covers the surface of the forebrain. Especially expanded are the frontal lobes, which are involved in executive functions such as self-control, planning, reasoning, and abstract thought. The portion of the brain devoted to vision is also greatly enlarged in humans.
Brain evolution, from the earliest shrewlike mammals through primates to hominids, is marked by a steady increase in encephalization, or the ratio of brain to body size. The human brain has been estimated to contain 50–100 billion (1011) neurons[citation needed], of which about 10 billion (1010) are cortical pyramidal cells.[citation needed] These cells pass signals to each other via approximately 100 trillion (1014)[citation needed] synaptic connections.
In spite of the fact that it is protected by the thick bones of the skull, suspended in cerebrospinal fluid, and isolated from the bloodstream by the blood-brain barrier, the delicate nature of the human brain makes it susceptible to many types of damage and disease. The most common forms of physical damage are closed head injuries such as a blow to the head, a stroke, or poisoning by a wide variety of chemicals that can act as neurotoxins. Infection of the brain is rare because of the barriers that protect it, but is very serious when it occurs. More common are genetically based diseases[citation needed], such as Parkinson's disease, multiple sclerosis, and many others. A number of psychiatric conditions, such as schizophrenia and depression, are widely thought to be caused at least partially by brain dysfunctions, although the nature of such brain anomalies is not well understood.
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News tagged with human brain
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Medicine & Health / Neuroscience
Aug 25, 2009 |
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Obesity is on a rampage, with the World Health Organization pegging the numbers at more than 300 million worldwide, with a billion more overweight. With obesity comes the increased risk for cardiovascular disease, Type II ...
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Aug 18, 2009 |
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Medicine & Health / Neuroscience
Jul 15, 2009 |
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the ability to think about the minds and mental states of others—is essential for human beings. In the last decade, a group of regions has been discovered in the human brain that are specifically used for social cognition. ...
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Jul 03, 2009 |
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For Mark Changizi, it’s all in the eyes.
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Other Sciences / Social Sciences
Jun 04, 2009 |
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Technology / Computer Sciences
Jun 01, 2009 |
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(PhysOrg.com) -- Recognising objects and groups of objects is something we humans take for granted. For computers, this is far from straightforward. A European project has come up with novel solutions to this conundrum.
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May 13, 2009 |
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Researchers funded by the Biotechnology and Biological Sciences Research Council (BBSRC) have shown that past experience really does help when we have to make complex decisions based on uncertain or confusing information. ...
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Medicine & Health / Psychology & Psychiatry
Apr 28, 2009 |
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New light on bipolar treatment drugs
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Mar 23, 2009 |
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Medicine & Health / Neuroscience
Mar 23, 2009 |
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(PhysOrg.com) -- Most people can easily tell the difference between reality and fantasy. We know that characters in novels and movies are fictitious, and we also understand that historical figures - even if ...
The human brain is on the edge of chaos
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Cambridge-based researchers provide new evidence that the human brain lives "on the edge of chaos", at a critical transition point between randomness and order. The study, published March 20 in the open-access ...
