Facts on File Encyclopedia of Health and Medicine

among the skin cells, helps maintains fluid and
body temperature, and contains millions of sen-
sory nerve cells. Most of the body’s pain receptors
are among these nerve cells. Remarkably resilient
and flexible, the skin continually renews itself.

The Nervous System
The nervous system is both command central (the
brain) and intercellular highway (the nerves),
orchestrating every function within the body—
more often than not without conscious awareness
of its myriad activities. The nervous system inter-
prets and responds to sensory information, contin-
uously adjusting and accommodating its functions.
These functions require chemical messengers—
neurotransmitters—as well as electrical activity
among cells. Nerves range in size from microscopic
to several feet in length.

The Musculoskeletal System

Giving the body the ability to resist the force of
gravity to provide shape and mobility is the mus-
culoskeletal system—the bones, connective tis-
sues, and muscles. These structures have density

and strength. They use leverage and oppositional

function to move the body—walk, run, jump,

skip, and even turn cartwheels. These functions

require coordination with the nervous system,

sensory systems, and balance structures within the

inner ear. Health conditions that affect the muscu-

loskeletal system—ranging from injuries such as

sprains and fractures to degenerative processes

such as osteoarthritis—are among the most com-

mon reasons people seek medical care.

Pain and Pain Management

The final section in Volume 1 is “Pain and Pain

Management”—not, of course, a body system but

rather a discipline (specialty) within the practice

of medicine that examines the interactions of the

foundational body systems that, when disrupted,

result in pain. A complex physiologic experience,

pain typically arising from multiple causes that

cross these body systems. Consequently, so must

its treatment approaches. The entries in “Pain and

Pain Management” cover the mechanisms of pain

as well as health conditions in which pain is the

primary symptom.

xiv Preface