Climate change is negatively affecting many species. The increase in mean air temperature is often associated with shifts in distribution, changes in phenology, and local extinctions. Other factors ...that only partially correlate with air temperature, like water shortage, may also contribute to the negative consequences of climate change. Although the effect of temperature on lizards' ecophysiology is highly studied, many lizards are also at risks of increased water loss and dehydration, which are predicted to increase under climate change. Here we aimed for the first time to explore if lacertid lizards exposed to dehydration thermoregulate less precisely than hydrated lizards and if dehydrated lizards are less active, change the daily pattern of thermoregulation and balance water balance against thermoregulation. We exposed four lizard species with differences in the thermal preference to thermal gradients with or without a source of water. We measured preferred body temperatures, daily pattern of thermoregulation, and the use of space. Dehydration negatively affected thermoregulation in all investigated species. Dehydrated lizards reduced their preferred body temperature and showed a species-specific pattern of hourly change in thermal preference. Furthermore, they more frequently used the colder parts of the gradients and spent more time hidden. Lizards experiencing dehydration may suffer a reduction in survival and fitness because of poor thermoregulation. Similarly, they may spend more time hidden, waiting for more favourable weather conditions. Such inactivity may carry ecological costs especially in those regions that undergo either short or prolonged periods of droughts.
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The regulation of body temperature is one of the most critical functions of the nervous system. Here we review our current understanding of thermoregulation in mammals. We outline the molecules and ...cells that measure body temperature in the periphery, the neural pathways that communicate this information to the brain, and the central circuits that coordinate the homeostatic response. We also discuss some of the key unresolved issues in this field, including the following: the role of temperature sensing in the brain, the molecular identity of the warm sensor, the central representation of the labeled line for cold, and the neural substrates of thermoregulatory behavior. We suggest that approaches for molecularly defined circuit analysis will provide new insight into these topics in the near future.
Tan and Knight review the neural mechanisms that regulate body temperature in mammals. They describe the molecules and cells that sense temperature, the afferent pathways that transmit this information to the brain, and efferent pathways that coordinate the homeostatic response.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Fever has long been recognized as a symptom of disease. Until the past century it was considered a healthy sign; since then this view has changed and the use of drugs to reduce fever has grown quite ...common. Acting on the revival of interest as to whether the effects of fever are beneficial or harmful, Matthew Kluger and other physiologists began a series of experiments designed to resolve this question. This book synthesizes their research, making a case not only for the beneficial function of fever but also for the re-evaluation of current clinical practices regarding fever.
Originally published in 1979.
ThePrinceton Legacy Libraryuses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These paperback editions preserve the original texts of these important books while presenting them in durable paperback editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.
Maintenance of a homeostatic body core temperature is a critical brain function accomplished by a central neural network. This orchestrates a complex behavioral and autonomic repertoire in response ...to environmental temperature challenges or declining energy homeostasis and in support of immune responses and many behavioral states. This review summarizes the anatomical, neurotransmitter, and functional relationships within the central neural network that controls the principal thermoeffectors: cutaneous vasoconstriction regulating heat loss and shivering and brown adipose tissue for heat production. The core thermoregulatory network regulating these thermoeffectors consists of parallel but distinct central efferent pathways that share a common peripheral thermal sensory input. Delineating the neural circuit mechanism underlying central thermoregulation provides a useful platform for exploring its functional organization, elucidating the molecular underpinnings of its neuronal interactions, and discovering novel therapeutic approaches to modulating body temperature and energy homeostasis.
Understanding which species and ecosystems will be most severely affected by warming as climate change advances is important for guiding conservation and management. Both marine and terrestrial fauna ...have been affected by warming
but an explicit comparison of physiological sensitivity between the marine and terrestrial realms has been lacking. Assessing how close populations live to their upper thermal limits has been challenging, in part because extreme temperatures frequently drive demographic responses
and yet fauna can use local thermal refugia to avoid extremes
. Here we show that marine ectotherms experience hourly body temperatures that are closer to their upper thermal limits than do terrestrial ectotherms across all latitudes-but that this is the case only if terrestrial species can access thermal refugia. Although not a direct prediction of population decline, this thermal safety margin provides an index of the physiological stress caused by warming. On land, the smallest thermal safety margins were found for species at mid-latitudes where the hottest hourly body temperatures occurred; by contrast, the marine species with the smallest thermal safety margins were found near the equator. We also found that local extirpations related to warming have been twice as common in the ocean as on land, which is consistent with the smaller thermal safety margins at sea. Our results suggest that different processes will exacerbate thermal vulnerability across these two realms. Higher sensitivities to warming and faster rates of colonization in the marine realm suggest that extirpations will be more frequent and species turnover faster in the ocean. By contrast, terrestrial species appear to be more vulnerable to loss of access to thermal refugia, which would make habitat fragmentation and changes in land use critical drivers of species loss on land.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Body temperature homeostasis is critical for survival and requires precise regulation by the nervous system. The hypothalamus serves as the principal thermostat that detects and regulates internal ...temperature. We demonstrate that the ion channel TRPM2 of the transient receptor potential (TRP) channel family is a temperature sensor in a subpopulation of hypothalamic neurons. TRPM2 limits the fever response and may detect increased temperatures to prevent overheating. Furthermore, chemogenetic activation and inhibition of hypothalamic TRPM2-expressing neurons in vivo decreased and increased body temperature, respectively. Such manipulation may allow analysis of the beneficial effects of altered body temperature on diverse disease states. Identification of a functional role for TRP channels in monitoring internal body temperature should promote further analysis of molecular mechanisms governing thermoregulation and foster the genetic dissection of hypothalamic circuits involved with temperature homeostasis.
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BFBNIB, NMLJ, NUK, ODKLJ, PNG, SAZU, UL, UM, UPUK
Purpose
This study investigated the effects of
l
-menthol mouth rinse and ice slurry ingestion on time to exhaustion, when administered at the latter stages (~ 85%) of baseline exercise duration in ...the heat (35 °C).
Method
Ten male participants performed four time to exhaustion (TTE) trials on a cycle ergometer at 70%
W
max
. In a randomized crossover design, (1) placebo-flavored non-calorific mouth rinse, (2)
l
-menthol mouth rinse (0.01%), or (3) ice ingestion (1.25 g kg
−1
), was administered at 85% of participants’ baseline TTE. Time to exhaustion, core and skin temperature, heart rate, rating of perceived effort, thermal comfort and thermal sensation were recorded.
Results
From the point of administration at 85% of baseline TTE, exercise time was extended by 1% (placebo, 15 s), 6% (
l
-menthol, 82 s) and 7% (ice, 108 s), relative to baseline performance (
P
= 0.036), with no difference between
l
-menthol and ice (
P
> 0.05). Core temperature, skin temperature, and heart rate increased with time but did not differ between conditions (
P
> 0.05). Thermal sensation did not differ significantly but demonstrated a large effect size (
P
= 0.080;
η
p
2
= 0.260).
Conclusion
These results indicate that both thermally cooling and non-thermally cooling oral stimuli have an equal and immediate behavioral, rather than physiological, influence on exhaustive exercise in the heat.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Homeotherms maintain a stable internal body temperature despite changing environments. During energy deficiency, some species can cease to defend their body temperature and enter a hypothermic and ...hypometabolic state known as torpor. Recent advances have revealed the medial preoptic area (MPA) as a key site for the regulation of torpor in mice. The MPA is estrogen-sensitive and estrogens also have potent effects on both temperature and metabolism. Here, we demonstrate that estrogen-sensitive neurons in the MPA can coordinate hypothermia and hypometabolism in mice. Selectively activating estrogen-sensitive MPA neurons was sufficient to drive a coordinated depression of metabolic rate and body temperature similar to torpor, as measured by body temperature, physical activity, indirect calorimetry, heart rate, and brain activity. Inducing torpor with a prolonged fast revealed larger and more variable calcium transients from estrogen-sensitive MPA neurons during bouts of hypothermia. Finally, whereas selective ablation of estrogen-sensitive MPA neurons demonstrated that these neurons are required for the full expression of fasting-induced torpor in both female and male mice, their effects on thermoregulation and torpor bout initiation exhibit differences across sex. Together, these findings suggest a role for estrogen-sensitive MPA neurons in directing the thermoregulatory and metabolic responses to energy deficiency.
Ectotherms may experience large body temperature (Tb) variations. Higher Tb have been reported to increase baroreflex sensitivity in ectotherm tetrapods. At lower Tb, pulse interval (PI) increases ...and diastolic pressure decays for longer, possibly resulting in lower end-diastolic pressures and mean arterial pressures (Pm). Additionally, compensatory baroreflex-related heart rate modulation (i.e. the cardiac branch of the baroreflex response) is delayed due to increased PI. Thus, low Tb is potentially detrimental, leading to cardiovascular malfunctioning. This raises the question on how Pm is regulated in such an adverse condition. We investigated the baroreflex compensations that enables tegu lizards, Salvator merianae, to maintain blood pressure homeostasis in a wide Tb range. Lizards had their femoral artery cannulated and pressure signals recorded at 15°C, 25°C and 35°C. We used the sequence method to analyse the heart rate baroreflex-related corrections to spontaneous pressure fluctuations at each temperature. Vascular adjustments (i.e. the peripheral branch) were assessed by calculating the time constant for arterial pressure decay (τ)-resultant from the action of both vascular resistance and compliance-by fitting the diastolic pressure descent to the two-element Windkessel equation. We observed that at lower Tb, lizards increased baroreflex gain at the operating point (Gop) and τ, indicating that the diastolic pressure decays at a slower rate. Gop normalized to Pm and PI, as well as the ratio τ/PI, did not change, indicating that both baroreflex gain and rate of pressure decay are adjusted according to PI lengthening. Consequently, pressure parameters and the oscillatory power fraction (an index of wasted cardiac energy) were unaltered by Tb, indicating that both Gop and τ modulation are crucial for cardiovascular homeostasis.
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