by 
irochka
ANSWERS: 2
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Do your own homework the next time. http://serendip.brynmawr.edu/bb/kinser/Structure1.html
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The brain is made up of approximately 100 billion neurons.A neuron is a nerve cell. There are approximately 1 quadrillion synapses in the human brain. That's 1,000,000,000,000,000 synapses! This is equal to about a half-billion synapses per cubic millimeter. The adult human brain weighs between 1300 g and 1400 g (approximately 3 lbs). A newborn human brain weighs between 350 and 400 g. Some neurons are very short...less than a millimeter in length. Some neurons are very long...a meter or more! The axon of a motor neuron in the spinal cord that innervates a muscle in the foot can be about 1 meter (3 feet) in length. Information travels at different speeds within different types of neurons. Transmission can be as slow as 0.5 meters/sec or as fast as 120 meters/sec. Traveling at 120 meters/sec is the same as going 268 miles/hr!!! The first recorded use of the word "brain" belongs to the ancient Egyptians. The word for "brain" and other "neuro" words appear in the Edwin Smith Surgical Papyrus which was written by an unknown Egyptian surgeon around 1,700 BC.
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