Thermoregulation

Homeostasis: Thermoregulation

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

Multiple Choice

Homeostasis

• allows for a wildly fluctuating internal environment

• is impossible in vertebrates

• is the maintenance of a relatively stable internal environment and often incorporates a form of feedback regulation

• is the maintenance of a relatively stable external environment and often incorporates a form of feedback regulation

Multiple Choice

Sweats and pants to keep cool.

• endotherm
• ectotherm

Multiple Choice

Homeostatic cooling mechanisms include

• piloerection and panting

• panting and vasoconstriction

• sweating and piloerection

• sweating and vasodilation

Multiple Choice

Shivering heats up the muscles and warms the blood flowing through them.

• TRUE

• FALSE

Multiple Choice

Slows down and hibernates when its cold.

• endotherm
• ectotherm

Multiple Choice

Maintaining body temperature is an example of a:

• negative feedback loop

• positive feedback loop

Multiple Choice

What happens to the rate of an enzyme reaction when heated up?

• Increases

• Decreases

• Increase and then decreases

• decreases and then increases

Multiple Choice

Temperature regulation center in the brain of a human

• hypothalamus

• thermoregulation

• receptor

• negative feedback

Multiple Choice

Why is the bodies core temperature 37^oC?

• Optimum temperature for enzymes

• No specific reason

• To limit the enzymes rate of reaction

• Its not 37^oC

Multiple Choice

Ectothermic organisms include

• birds and mammals

• reptiles, fish, amphibians, and all invertebrates

Multiple Choice

An ectotherm's temperature is rapidly decreasing due to a sudden cold front and severe weather conditions. What is the organism most likely to do?

• Nothing, environmental conditions do not effect ectotherm's internal temperature.

• Nothing, the organism must learn how to survive the weather conditions anyway.

• Seek shelter from the storm in a cool place underground.

• Seek shelter that provides warmth to increase the organism's temperature.

Multiple Select

An endothermic organism is outside in the cold snow. What behavioral adaptations might they do to maintain their temperature? Select all that apply.

• Seek shelter because they cannot maintain their temperature.

• Shiver to generate body heat.

• Move around to increase blood flow.

• Bask in the sun.