Thermoregulation and thermoregulatory functions in humans and other organisms

Thermoregulation and thermoregulatory in humans and all living organisms that helps in studies for students of school and colleges as well as masters students. We also can enhance your knowledge by making best slides and pptx for the understanding the topics in easy ways.
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1. Thermoregulation By:- Harsh Solanki

2. Synopsis Definition of thermoregulation Impact of temperature on animals life How animals exchange their heat with the environment Classification based on source of heat Classification based on heat maintenance Temperature regulation in Invertebrates Temperature regulation in Vertebrates Heat production in birds and mammals Control of thermogenesis Adaptive Hypothermia Conclusion References

3. Thermoregulation : Thermoregulation is the ability of an organism to maintain a core body temperature, which is 37° C (98°F) within an optimal physiological range. The hypothalamus, a portion of a brain which plays an important role in regulating body temperature by acting as a thermostat. . It is also called “heat production” . THE IMPACT OF TEMPERATURE ON ANIMAL LIFE: Optimal temperature: The temperature at which procedure is best carried out. Example – Action of an enzyme If optimal temperature increases the enzyme begins to denature due to this reason metabolic activity will be stop. If optimal temperature decreases it may cause membranes to change from fluid to a solid state. Body temperature = (Heat produced metabolically + Heat gained from the environment) – Heat lost to the environment.

4. How animals exchange their heat with the environment ? Conduction- Direct heat transfer between environment & the body surface of an animal. Convection - The movement of air ( or a liquid) over the surface of a body. Radiation- Emission of electromagnetic wave that objects such as Sun, Animals etc. Evaporation - Loss of heat from a surface as water molecules escape in the form of a gas.

5. Classification of animals based on sources of heat: Ectotherm- Derive most of their body heat from the environment. CHARACTERS: They have low rates of metabolism. They are poorly insulated. Ectotherm tend to move about the environment and find places that minimize heat or cold stress to their bodies. Example- Reptiles, Amphibians, Fishes and Invertebrates. ( Although a few reptiles, insects & fishes can raise their internal temperature.) Endotherm- Obtain their body heat from cellular processes. CHARACTERS : A constant source of internal heat allows them to maintain a nearly constant core temperature, despite the fluctuating environmental temperature. Most endotherms have bodies insulated fur or feathers and a relatively large amount of fat. Example- Birds and Mammals.

6. Classification based on heat maintenance: Homeotherms ( warm blooded): Maintain a relatively constant body temperature. Most endotherms are homeotherms . Exception – Some endotherms vary their temperatures seasonally (e.g. hibernation); other vary on it a daily basis (e.g. daily topor ). Example – Hummingbird Poikilotherms ( Cold blooded) : Have a variable temperature. Most ectotherms are heterotherms . Exceptions – Some reptiles that can maintain fairly constant body temperature by changing position and location during the day to equalize heat gain and loss. Example – Desert lizards

7. Temperature regulation in invertebrates : Many invertebrates have relatively low metabolic rates and have no thermoregulatory mechanism. They passively conform to the temperature of their external environment. These invertebrates are called thermoconformers. However many arthropods have unique mechanism for surviving temperature extremes. The temperature of an insect can be varied from ambient either behaviorally using external heat or by physiological mechanism. PHYSIOLOGICAL MECHANISM: Temperate-zone insects avoid freezing by reducing the water content in their tissues as winter approaches. Other insects can produce glycerol or other glycoproteins that acts as an antifreeze agents. Some moths and bumblebee warm up prior to flight by shivering contraction of their thoracic flight muscles. Most large, flying insects have evolved a mechanism to prevent overheating during flight, blood circulatory through the flight muscles carries heat from the thorax to the abdomen which gets rid of the heat.

8. Behavioral mechanism : Body posture & orientation of the wings to the sun c an markedly affect the body temperature of basking insects. Example- Perching dragonflies or butterflies can regulate their radiation heat gain by postural adjustment. To prevent overheating, many grounds- dwelling arthropods raise their bodies as high off the ground as possible to minimize heat gain from the ground. Many black beetles may be more active earlier in the day because they absorb more radiation and heat faster. Conversely, white beetles are more active in the hotter parts of the day because they absorb less heat. Maximum heat gain Minimum heat gain

9. Temperature regulation in Vertebrates : IN FISHES : The temperature of the surrounding water determines the body temperature of most fishes. Antifreeze agents: Fishes that live in extremely cold water have (antifreeze) materials in their blood.(Polyalcohol – eg Sorbitol, Glycerol or water soluble peptides and glycopeptides) These fishes also have proteins and protein-sugar compounds that helps to stay flexible and swim freely in a supercooled state. Rete Mirabile : Some active fishes maintain a core temperature significantly above the temperature of the water. ( Example- Bluefin tuna, White Shark) Branches deliver blood to the deeper , powerful, red swimming muscles, where smaller vessels are arranged in a countercurrent heat exchanger called the rete mirabile .

10. Rete Mirabile

11. In Amphibians: Most amphibians have difficulty in controlling body heat because they produce little of it metabolically and rapidly lose most of the it from their body surfaces. Amphibians have an additional thermoregulatory problem because they must exchange oxygen and carbon dioxide across their skin surfaces and this moisture layer as a natural evaporative cooling system. This problem of heat loss through evaporation limits the habitats and activities of amphibians to warm, moist areas. Some amphibians, such as bullfrogs , can vary the amount of mucus they secrete from their body surface a physiological response that helps regulate evaporative cooling.

12. Normal frog Bull frog

13. In reptiles: Reptiles have dry rather than moist skin, which reduces loss of body heat through evaporation cooling of the skin. They have low metabolic rate and warm themselves by behavioral adaptations. Diving reptiles ( such as sea turtle, sea snake) conserve body heat by routing blood through circulatory shunts into the center of the body. These animals can also increase heat production in response to the hormones thyroxine and epinephrine . In addition tortoises and land turtle can cool themselves through salivating and frothing the mouth, moistening the eyes, and panting.

14. Vasoconstriction Vasodilation

15. In birds: They can maintain body temperature between 35 and 45°C with metabolic heat. Cooling Mechanism: Because they have no sweat glands, birds pant to lose heat through evaporative cooling. Some species have highly vascularised pouch ( gular pouch) in their throat that they flutter (a process called gular flutter) to increase evaporation from the respiratory system. Prevention of heat loss: Feathers are excellent insulators for the body especially down feathers that trap a layer of air next the body reduce heat loss from the skin. Aquatic species, who lose heat from their legs and feet have peripheral countercurrent heat exchange vessels called a rete mirabile in their to reduce heat loss.

16. Countercurrent heat exchange in birds

17. In mammals: Mammals that live in cold regions, such as the arctic fox and barren-ground caribou also have these exchange vessels in their extremities (eg- legs, tails, ears and nose). Thick pelts and a thick layer of insulating fat called blubber just under the skin help marine animals, such as seals and whales to maintain a body temperature of around 36 to 38°C. In the tail and flippers which have no blubber, a countercurrent system of arteries and veins helps minimize heat loss. Animals in hot climates, such as jackrabbit have mechanism(large ear) to rid the body of excess heat.

18. Birds and mammals also use behavioral mechanism to cope with external temperature changes such as they sun themselves and seek shade as the temperature fluctuates. Many animals huddle to keep warm; other share burrows for protection from temperature extremities. Migration to warm climates and hibernation many birds and mammals to survives the harsh winters. Basking by cat Hibernation by Bat

19. Heat production in birds and mammals Birds and mammals can generate heat ( thermogenesis) by many methods such as muscles contraction, ATPase pump enzyme and other metabolic processes. Muscles contraction: Every time a muscle cell contracts, the actin and myosin filament sliding over each other and hydrolysis of ATP molecules generates heat. Both voluntary muscular work and involuntary muscular work ( eg- shivering)generates heat. Heat generation by shivering is called shivering thermogenesis. ATPase pump enzyme: When the body cools, the thyroid gland release thyroxine hormone. Thyroxine increases the permeability of many cells to Na ions which leak into the cell. The ATPase pump quickly pump to these ions out. In the process, ATP is hydrolyzed, releasing heat energy. This type of heat generation is called non-shivering thermogenesis.

20. Control of thermogenesis : From amphibians to mammals thermogenesis is controlled by hypothalamus region of the brain. It has two regulatory areas i.e. Heating centre and cooling centre . Warm neuronal receptors excite cooling centre and inhibit heating centre while cool neuronal receptors excite heating centre and inhibit cooling centre . Heating centre : The heating centre controls- Vasoconstriction of superficial blood vessels Erection of fur and hair Shivering and non-shivering thermogenesis. Cooling centre : The cooling centre controls- Vasodilation of superficial blood vessels Panting Sweating

21. Adaptive Hypothermia : Hibernation Low metabolic rates Fat reserve Having brown fat Example- Bat, woodchucks, ground squirrel etc Aestivation For longer periods Slow metabolic rates Diminished water supplies Example- Pigmy mice, Columbian ground squirrel Winter sleep Prolonged sleep in winter Example- Bear, Badgers etc.

22. Conclusion Thermoregulation is the ability of an endothermic organism to maintain constant body temperature. Despite fluctuation in temperature of external environment. Piokilotherms depends on environment for their body temperature while homeotherms maintain their body temperature by itself. Hence by these various animals maintain their body temperature by behavior adjustments.