What hurts when you have a headache? The bones of
the skull and tissues of the brain itself never hurt,
because they lack pain-sensitive nerve fibers.
Several areas of the head can hurt, including a
network of nerves which extends over the scalp and
certain nerves in the face, mouth, and throat. Also
sensitive to pain, because they contain delicate
nerve fibers, are the muscles of the head and blood
vessels found along the surface and at the base of
the brain.
The ends of these pain-sensitive nerves, called
nociceptors, can be stimulated by stress, muscular
tension, dilated blood vessels, and other triggers
of headache. Once stimulated, a nociceptor sends a
message up the length of the nerve fiber to the
nerve cells in the brain, signaling that a part of
the body hurts. The message is determined by the
location of the nociceptor. A person who suddenly
realizes "My toe hurts," is responding to
nociceptors in the foot that have been stimulated by
the stubbing of a toe.
A number of chemicals help transmit pain-related
information to the brain. Some of these chemicals
are natural painkilling proteins called endorphins,
Greek for "the morphine within." One theory suggests
that people who suffer from severe headache and
other types of chronic pain have lower levels of
endorphins than people who are generally pain free.
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