- There are about 10 million nerve cells in the brain
and nerves.
- There are 12 pairs of nerves that join directly to the
brain called cranial nerves.
- The brain and spinal cord together are called the
central nervous system (CNS) because they are in the center of
the body and at the center of the control coordination processes.
- The other nerves branching outward are the
peripheral nervous system or PNS because they reach the
periphery(outer parts) of the body.
- The nerves near the center of the body, controlling
automatic processes, are the subdivision of the PNS. They are called the
automatic nervous system, or ANS.
- Inside the spinal cord is an area of gray matter
shaped like a butterfly. This is mainly the cell bodies and dendrites of
nerve cells linked together at the synapses. The white matter
surrounding the gray matter consists of axons of nerve cells running up
and down the cord.
- All nerve fibers in a nerve look similar, but they are
divided into 2 main types. These types are the sensory and motor nerve
fibers.
- Peripheral nerves spread to all parts of the body and
are linked to the central nervous system. The largest peripheral nerves,
such as the sciatic nerve near the lower hip, are as thick as your
thumb.
- The ANS(automatic nervous system) is the body's
control system, it has parts inside the brain, spinal cord, and the
peripheral nerves. It also has its own nerves, nerve junctions, and
links, which run mainly outside the spinal column.
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Perry