Introduction

• Why do lizards sunbathe? Why do jackrabbits have huge ears? Why do dogs pant when they're hot? Animals have quite a few different ways to regulate body temperature!

• These thermoregulatory strategies let them live in different environments, including some that are pretty extreme.

Introduction

• Polar bears and penguins, for instance, maintain a high body temperature in their chilly homes at the poles, while kangaroo rats, iguanas, and rattlesnakes thrive in Death Valley, where summertime highs are over 38^∘C.

• consists of a ‘heat loss centre’ and a ‘heat gain centre’

• temperature-sensitive nerve cells (neurones) detect changes in the temperature of the blood flowing through the brain (internal stimuli)

• thermoregulation centre of the hypothalamus also receives information via sensory nerves from temperature-sensitive receptors located in the skin (external stimuli), and in many internal organs​

​The Hypothalamus as the Control Centre​

• Thyroxin is an iodine-containing hormone produced in the thyroid gland.

• On secretion it stimulates oxygen consumption and basal metabolic rate of the body organs.

• Variation in secretion of thyroxin helps to control body temperature.

​Another mechanism in thermoregulation

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Mechanisms of thermoregulation

• Endotherms, such as birds and mammals, use metabolic heat to maintain a stable internal temperature, often one different from the environment.

• Ectotherms, like lizards and snakes, do not use metabolic heat to maintain their body temperature but take on the temperature of the environment.

Mechanisms of thermoregulation

• Both endotherms and ectotherms have adaptations—features that arose by natural selection—that help them maintain a healthy body temperature. These adaptations can be behavioral, anatomical, or physiological.

Mechanisms of thermoregulation

• Some adaptations increase heat production in endotherms when it’s cold. Others, in both endotherms and ectotherms, increase or decrease exchange of heat with the environment.

Categories of thermoregulatory mechanisms

• Changing behavior

• Increasing metabolic heat production

• Controlling the exchange of heat with the environment