Pain and Temperature Sensations Flashcards
Core Body Temperature
37⁰ C
Body temperature has a
circadian fluctuation of
- 5-
0. 7°C (1-1.5° F)
Temperature is lowest at
—, highest in the —
6:00am
evening
Temperature regulation is less
precise in
young children;
normally have a temperature
that is 0.5°C or so above adults.
Thermal Receptors (thermoreceptors) are on
free nerve endings
& commonly found in the skin. Also in hypothalamus, spinal cord,
& deep tissues.
Categorized by their different sensitivities: (2)
cool
warm
Cool and warm receptors innervate
discrete regions of skin
There are – times as many cool receptors at any skin surface
3-10
— are activated by extreme cold or heat
Nociceptors
Which do you perceive first- a thermal or mechanical sensation?
mechanical
After thermoreceptors are activated,
Warm signals are transmitted by:
Cool signals are transmitted by:
C and Aδ fibers
Aδ and C fibers
The mechanism of thermal sensation is most likely achieved by
sensing a change in
metabolic rate
— increases the rate of intracellular chemical
reactions
Temperature
Several Transient Receptor Potential (TRP) channels
have been identified, each sensitive to a different
temperature range. Some chemicals (Capsaicin, Menthol)
elicit thermal sensations, too.
Temperature Perception
Based on the Activation of a
Combination of the Receptors
COLD PAIN: (5)
Tickling, Pricking, Aching, Burning, Numbing
HOT PAIN: (5)
Sharp, Pricking, Stinging, Burning, Throbbing
If skin reaches —, cold/pain fibers are no longer stimulated.
freezing
At ~ –°C, heat/pain fibers are activated.
Sometimes cold fibers are activated, too—
45
paradoxical cold
Average skin
temperature =
34-35ºC;
equal activation of cool
and warm receptors.
Adaptation of Thermoreceptors • They mostly (but never completely) adapt to --- ---; BUT they quickly change their activity in response to ---
constant temperature
changes in temperature.
They are very sensitive to changes
in temperature.
Adaptation of Thermoreceptors
• If the temperature reaches one of the
pain thresholds, the sensation
becomes
more persistent throughout
the stimulus
Sensitivity of Thermoreceptors
• Warm and Cool receptors are best able to detect a change at the
— of their temperature sensitivity (that is where they are
most sensitive)
mid-range
Sensitivity of Thermoreceptors
• If nociceptors are simultaneously activated, the system is even
better able to
discern small changes in temperature