The cerebrum is divided into a right and left half, as shown inFigure20.5. Each half of the
cerebrum is called ahemisphere. The two hemispheres are connected by a thick bundle
of axons called the corpus callosum. It lies deep inside the brain and carries messages back
and forth between the two hemispheres. The right hemisphere controls the left side of the
body, and the left hemisphere controls the right side of the body. This would be impossible
without the corpus callosum.
Dr. Jill Bolte Taylor is a brain scientist. At the age of 37, she suffered massive
brain damage when blood vessels burst inside her brain. It took Dr. Taylor
almost ten years to recover from the damage to her brain. She had to relearn
even basic skills, like walking and talking. To share her story of recovery with
others, Dr. Taylor wrote a popular book describing what she went through. Her
story gave other people so much inspiration thatTime Magazinenamed her one
of the world’s 100 most influential people in 2008.Each hemisphere of the cerebrum is divided into four parts called lobes. The four lobes are
the frontal, parietal, temporal, and occipital lobes (Figure20.5). Each lobe has different
functions. Some of the functions are listed inTable(20.1).
Table 20.1:Cerebral Lobes and Their FunctionsLobe Main Function(s)
Frontal Speech, thinking, touch
Parietal Speech, taste, reading
Temporal Hearing, smell
Occipital SightThe Spinal Cord
Thespinal cordis a long, tube-shaped bundle of neurons. It runs from the brain stem to
the lower back. The main job of the spinal cord is to carry nerve impulses back and forth
between the body and brain. The spinal cord is like a two-way highway. Messages about
the body, both inside and out, pass through the spinal cord to the brain. Messages from the
brain instructing the body how to respond pass through the spinal cord to the body.
Peripheral Nervous System
Theperipheral nervous system (PNS)consists of all the nerves of the body that lie
outside the central nervous system. The network of nerves that make up the peripheral
system is shown inFigure20.6. They include nerves of the hands, arms, feet, legs, and