1. Metabolism and Survival
Key Area 4d & e
Importance of Thermoregulation

2. By the end of this topic you should be able to:
Explain how thermoregulation takes place in mammals in terms of hypothalamus, nerves, effectors and skin
State that organisms must have adaptations to survive environmental change

3. Negative Feedback
When a factor affecting the body’s internal environment deviates from its norm (or set-point) the body responds to correct the change.
The change is detected by receptors and a decision sent by nerve impulse or hormones to effectors which bring about the change to return to the norm

4. Thermoregulation
An example of homeostasis is the body’s regulation of body temperature no matter what the external temperature is.
The hypothalamus is the temperature monitoring centre of the body. It does this in 2 ways:
it contains thermoreceptors which are sensitive to temperature changes in the blood, allowing detection of the body’s core temperature
it detects nerve impulses from thermoreceptors in the skin

5. Thermoregulation
Information is then communicated by electrical impulses through nerves to the effectors (muscles, sweat glands, blood vessels…) which bring about the corrective responses to return the body temperature to normal

6. Body Temperature

7. Increased body temp - Sweating
When the bodies temperature increases electrical impulses are sent along neurones to the sweat glands.
The water in the sweat released is evaporated off using the bodies heat which causes the skin to cool

8. Increased body temp - Vasodilation
When we get too hot arterioles leading to the skin become dilated, which allows lots of blood to flow near the skins surface and a loss of heat from the blood by radiation.

9. Decreased Metabolic Rate
Increased body temp –
Decreased Metabolic Rate
When we get too hot our metabolic rate decreases. This results in less heat being produced and causes a decrease in body temp back to the norm

10. Decreased Body Temperature - Shivering
When the bodies temperature starts to decrease one response is shivering. The muscles contract quickly which generates heat to bring the temp back to the norm

11. Decreased Body Temperature - Vasoconstriction
When we are cold arterioles leading to the skin become constricted, which reduces the flow of blood to the skins surface so only a little heat is lost from the blood by radiation.

12. Decreased Body Temperature - Skin
The skin acts as both a receptor and an effector and is able to regulate the temperature of the body.
The hair erector muscles contract causing the hair to stand up and trap a layer of insulating air.
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13. Increased Metabolic Rate
Decreased body temp –
Increased Metabolic Rate
When we get too cold our metabolic rate increases. This results in more heat being produced and causes a increase in body temp back to the norm

14. Advantage of Temperature Regulation
Organisms need to maintain an optimum body temperature for a number of reasons including:
Enzyme activity – enzymes involved in maintaining a high metabolic rate
Diffusion – temperature can affect diffusion rate (warmer temperatures increase the rate of diffusion of molecules such as oxygen and carbon dioxide that are involved in metabolism)

15. Thermoregulation - Endotherms
An animal (eg bird, mammals) that is able to regulate its own body temperature by homeostasis, independent of the temperature of the external environment
Their high metabolic rate generates heat energy helping to maintain a constant body temperature.

16. Thermoregulation - Ectotherms
An animal (eg fish, reptiles) that is unable to regulate its own body temperature and whose temperature varies directly with the temperature of the external environment.
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