What hurts when you have a headache? 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 bones of the skull and tissues of the brain itself, however,
never hurt, because they lack pain-sensitive nerve fibers.
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.