Friday, February 26, 2021
Cold Thermogenesis

Thermoregulation in mammals | thermoregulation in mammals class 12

Thermoregulation in mammals | thermoregulation in mammals class 12 | MDCAT

Regulatory Strategies
Mammals including human maintain their high body temperature within a narrow range of about
36-38 °C because of their endothermic characteristics. The origin of endothermy in birds and
mammals have provided the opportunity to keep high metabolic rate and availability of energy
round the clock, thus has acquired greater ability to adaptations and has assisted in much of their
wider diversity and distribution in diversified regions of the earth.
These regulate the rate of metabolic heat production, balancing it with the rate at which they
gain or lose heat from the surroundings. The rate of heat production is increased by increased
muscle contraction by movements or shivering so-called as shivering thermogenesis. Also
hormones trigger the heat production as do thyroid hormones and are termed as non-shivering
thermogenesis. Some mammals possess brown fat, which is specialized for rapid heat production.
An overproduction of heat, it is dissipated through exposed surfaces by increasing blood low or
the evaporative cooling. In mammals, it is observed that skin has been adapted as the organ of
thermoregulation. (Fig. 15.14)
In Cold Temperature: Mammals have various mechanisms that regulate heat exchange with
their environment. Vasodilation and vasoconstriction effect heat exchange and may contribute to
regional temperature differences within an animal. On a cool day, a human’s temperature may
be several degrees lower in the arms and legs than in the trunk, where the most vital glands are
situated. Most land mammals respond to cold by raising their furs thereby trapping the thicker
layer of still air and it acts as a good insulator between animal skin and the surroundings. Human
mostly rely on a layer of fat just insulating beneath the skin as insulating material against heat loss.
Similarly, marine mammals such as whales and seals inhabit much colder water than their body
temperature, have a very thick layer of insulating fat called blubber just under the skin.


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