The spinal cord begins at the base of the brain and extends
into the pelvis. Many of the nerves of the peripheral nervous system,
or PNS, branch out from the spinal cord and travel to various parts of the
Information from the senses travels through the nerves of the PNS to the
spinal cord and then to the brain for processing, and commands from the brain
travel down the spinal cord and then to the appropriate part of the PNS, where
nerves transport the instructions to the appropriate body part where action is
To facilitate this process, the spinal cord is divided into two kinds of
pathways called tracts. Ascending tracts carry sensory input
from the body to the brain, and descending tracts carry commands from the brain
down to specific tissues and organs.
The spinal cord is also essential for reflex function. Reflexes are the
body’s way of coping with stimuli that require an immediate response. For
example, jerking away from something hot or sharp is a reflex action. It
happens immediately because instructions come from the spine (rather than the
brain) to avoid injury.
The spinal cord, like the brain, has two major layers of protection. First
are the vertebrae of the spine, and underneath those are three layers of tough
membrane called the meninges.
The meninges surround both brain and spinal cord and are
filled with a liquid called cerebrospinal fluid. The fluid has several
functions, and one of them is shock absorption.
The spinal cord can suffer physical damage that can hamper or even halt
communication between brain and body. If the spinal cord is severed, the part
of the body below the damage is cut off from the commands of the brain, which
The spinal cord can also be afflicted by disease or disorder. Among these is
the birth defect spina bifida, which is the incomplete development of the
central nervous system, including the spine. This can affect movement of the
legs, incomplete sensation, or loss of bladder control.
The spinal cord can also be damaged by tumors. Whether
cancerous or benign, they can put pressure on the cord and impair sensory or