For example, humans achieve evaporative heat loss primarily by sweating, whereas dogs rely on panting and rodents spread saliva on their fur ( Jessen, 1985). Although feed-forward and feedback signals convey different kinds of information about body temperature, they are thought to converge on a common set of neural substrates in the preoptic area (POA) of the hypothalamus.Įxamples of physiological and behavioral strategies for controlling body temperature.ĭifferent species sometimes use different strategies to achieve the same physiologic effect.
The most common example of feed-forward control is the detection of a change in air temperature by thermoreceptors in the skin, which triggers thermoregulatory responses that precede and prevent any change in core temperature ( Nakamura and Morrison, 2008, 2010 Romanovsky, 2014). Exercise-induced warming in the rat brain and core are sensitive to prevailing ambient temperaturesįeed-forward mechanisms are triggered in the absence of any change in core temperature and instead enable preemptive responses to anticipated thermal challenges. Rat brain and rectal temperatures are tightly correlated during either exercise or external heating.ĭ. Changes in brain and rectal temperature in the rat after 30 minutes of exercise (treadmill, average speed 20 m/min, average ambient temp 27☌) or 30 minutes of heat exposure (average 45☌). Changes in brain or rectal temperatures are typically small during acute external temperature challenges (30-60 minutes) in a range of mammals.ī. Localized heating or cooling of any of these internal structures induces global feedback responses that oppose the applied temperature change.Ĭore temperature during challenges to thermal homeostasisĪ. Such changes in internal temperature are detected by specialized thermoreceptors located throughout the body core, including the viscera, brain, and spinal cord ( Jessen, 1985). Feedback responses are those that are triggered when core temperature deviates from the defended range: for example, exercise generates heat that can increase internal temperature by several degrees Celsius ( Fuller et al., 1998 Walters et al., 2000) ( Figure 1). The core temperature is the regulated variable in the thermoregulatory system ( Hensel, 1973) and is maintained by a combination of feedback and feed-forward mechanisms ( Kanosue et al., 2010).
HOLLOW KNIGHT PATH OF PAIN REWARD SKIN
In studies of thermoregulation, it is common to divide the body into two compartments: (1) the external shell, which includes the skin and largely fluctuates in temperature along with the environment, and (2) the internal core, which includes the central nervous system and viscera and has relatively stable temperature ( Jessen, 1985 Romanovsky et al., 2009). Finally, we highlight some of the key questions that remain to be answered.įeed-forward and feedback regulation of body temperatureīody temperature is not a single value but varies depending on where it is measured. We then describe our current understanding of the circuits in the brain that integrate temperature information and coordinate the behavioral and autonomic response. Next, we summarize what is known about the molecules, cells, and tissues that measure temperature at different sites in the body, and the pathways by which they communicate this information to the brain. First, we outline some of the basic principles of the thermoregulatory system as a whole. In this review, we describe the neural mechanisms that regulate body temperature in mammals.
Whatever the reason, the emergence of elevated but stable body temperature was a key event that accompanied the proliferation of birds and mammals across the globe, and an understanding of the thermoregulatory system is central to understanding our own physiology. Over time, this elevated body temperature may have become defended as a means to enable the optimization of cellular processes for a specific temperature range ( Heinrich, 1977). nocturnal foraging and cold climates) ( Bennett and Ruben, 1979 Crompton et al., 1978 Heinrich, 1977). flight) or occupation of new ecological niches (e.g. One hypothesis is that elevated body temperature evolved as a secondary consequence of the higher metabolic rates needed for sustained activity (e.g. Birds and mammals have the remarkable ability to regulate their internal temperature within a narrow range that is higher than the surroundings.
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