Encyclopedia of Health and Medicine

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Preface
among the skin cells, helps maintains fluid and
body temperature, and contains millions of sensory
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 interprets
and responds to sensory information, continuously
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 musculoskeletal
system—the bones, connective tissues,
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 musculoskeletal
system—ranging from injuries such as
sprains and fractures to degenerative processes
such as osteoarthritis—are among the most common
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.