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Mechanisms of Controlling Body Temperature in Animals

Major Mechanisms that Animals use to Control Body Temperature (Thermoregulatory Mechanisms in Animals)

by Yadav Sharma Bajagai

Major Impacts of climate change on animals are due to thermal stress resulting from increased ambient temperature. This article has been posted to illustrate how animals control their body temperature. This will help to find/design adaptation methods against climate change effects. 

The first line of defense animal use to maintain body temperature in unfavorable ambient temperature is behavioral response to manage heat loss or gain [1]. Seeking shelter in hot day or sun in cold day and altering body posture according to temperature to minimize or maximize relative body surface area to alter heat loss or gain are major behavioral response to maintain body temperature by cattle [1].

Animals can maintain its body temperature within narrow range irrespective of ambient temperature due to metabolic heat production [2, 3]. Control in heat production is mediated either with autonomic or voluntary thermoregulatory process.

Control of body temperature during cold


During cold weather, animal should produce more metabolic heat to maintain body temperature [4]. When ambient temperature is low, the thermoreceptors in skin  sends signals to the thermoregulatory centers in brain (hypothalamus) which in turn stimulate motor neuron causing increase in muscle metabolism producing more metabolic heat [3]. In long run, animal can maintain the heat production without muscular heat production either by increased activity of the sympathetic nervous system or increased secretion of thyroid hormones [3]

Control of body temperature during hot


Feed intake is generally decreased when ambient temperature is increased which results in reduced metabolic heat production and animal prefer to eat (and graze) during cooler part of the day [5, 6].

Similarly, loss of heat from animal body to surrounding is hastened during hot ambient temperature. During hot weather blood circulation to the skin is increased to transfer more heat from core to skin surface [4]. Evaporative heat loss by sweating is the key mechanism to regulate body temperature when ambient temperature increases above normal body temperature [4]. Vaporization of water from sweat causes temperature heat loss which in turn reduces body temperature. Heat loss through evaporation is account for loss of heat from metabolic activities and part of that for loss of heat obtained from environment [4].

Physiological mechanism to control heat production


i) Nervous control of heat production


Both central and peripheral nervous system have role to control heat production in animal body through secretion of some neurotransmitters [7]. Peripheral neurons sends the signal from neuroreceptors in skin to thermoregulatory center central nervous system (hypothalamus) [3, 7]. Thermoregulatory center modifies the endocrinal and autonomic nervous activities [3, 7]. Stimulation of sympathetic nervous system produces catecholamines (epinephrine and nor-epinephrine), prostaglandins, acetylcholine, and 5-hydroxytrytamine which modify metabolism and production of heat [3, 7, 8, 9]. Lin [10] has showed that inhibition of dopaminergic receptors reduces body temperature by reducing heat 

ii) Endocrinal control of heat production


Thermoregulatory center also influence the production of some metabolic hormones like thyroid hormones (thyroxine and triiodothyronine), adrenal hormones (glucocorticoides) and growth hormone which in turn modifies the heat production from body tissues [3, 7].