vibrations, while Meissner corpuscles sense low-frequency
vibrations.
Free nerve endings sense the following:
Itc h .
Itch is caused by local inflammatory responses to
certain chemicals.
T ickle.
Tickle is a complex sensation.
C old.
Rapidly adapting cold receptors in the
epidermis respond to temperatures between
10°C and 40°C.
W a rm th .
Rapidly adapting warm receptors
in
the
dermis
respond
to
temperatures
between 32°C and 48°C.
P a in .
Nociceptors
are
found
in
tissues
throughout the body except the brain. Unlike
other sensory receptors, nociceptors do not adapt. Fast
(acute) pain receptors respond within 0.1 s and result in
a sharp or pricking pain. Slow (chronic) pain receptors
respond after 1
s or more and result in a burning, aching,
or throbbing pain. Often, slow pain or pain from internal
organs (visceral pain) is felt over a larger area
than the one stimulated; this phenomenon is
called referred pain (Figure 8.3). (See
W h a t
a H e a lth Provider Sees
for information on the
management of the different types of pain.)
Proprioceptors
are found in skeletal muscles,
tendons, and joints throughout the body. Pro-
prioceptors adapt slowly and only slightly, so
the brain constantly receives information about
head and limb position as well as movements.
nociceptor
(no'-se-
SEP-tor) A free (naked)
nerve ending that
detects painful stimuli.
proprioceptor
(pro'-pre-O-SEP-tor)
A receptor that
provides information
about body position
and movements.
D istribution o f re fe rre d pain
• Figure 8.3
Areas of referred pain for particular visceral organs are indicated by the various colors.
The referred pain usually arises because the innervations of these areas of the skin
share the same spinal cord segment as those of the corresponding visceral organ.
r; "
\
Liver and gallbladder
Gallbladder
Small intestine
Ovary
Kidney
Appendix
Ureter
Heart
Lung and
diaphragm
Heart
Pancreas
Stomach
Ovary
Colon
Urinary
bladder
%
Liver and gallbladder
Stomach
Liver and gallbladder
Kidney
Anterior view
Posterior view
230 CHAPTER 8
Somatic Senses and Special Senses
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