38. Animal Form and Function

Thermoregulation

CounterCurrent Exchange | CounterCurrent Multipliers | LOH and Vasa Recta | Renal Physiology |

Countercurrent Exchange

An ectotherm such as a lizard does not maintain a fairly constant body temperature.

No. A lizard maintains a fairly constant body temperature by moving between warm and cool places as needed to regulate heat absorption and loss.

Endotherms must always maintain a fairly constant body temperature to survive.

No. Many endotherms' temperatures drop significantly for hibernation and in daily or nightly torpor.

In furry animals, raised hairs keep the animal cooler than lowered hairs.

No. The raised hairs trap more heat in the additional calm air space created.

A dilated blood vessel conserves more heat than a constricted one.

No. A dilated blood vessel radiates more heat than a constricted one.

Ectotherms generally do not conserve body heat as effectively as do marine mammals.

Contrast endothermy with ectothermy.

Which statement is true regarding thermoregulation?

Temperature Regulation Of The Human Body | Physiology | Biology | FuseSchool

Thermoregulation 5, Body temperature

Counter current exchanger

Explain why it would be impossible for a gorilla the size of King Kong to have fur. (Your answer should explain how the surface area to volume ratio of a normal-sized gorilla would compare to Kong’s; relate this to the role of surface area and volume in heat generation and heat transfer, and consider the function of fur.)

You are studying a large tropical reptile that has a high and relatively stable body temperature. How do you determine whether this animal is an endotherm or an ectotherm?
a. You know from its high and stable body temperature that it must be an endotherm.
b. You subject this reptile to various temperatures in the lab and find that its body temperature and metabolic rate change with the ambient temperature. You conclude that it is an ectotherm.
c. You note that its environment has a high and stable temperature. Because its body temperature matches the environmental temperature, you conclude that it is an ectotherm.
d. You measure the metabolic rate of the reptile, and because it is higher than that of a related species that lives in temperate forests, you conclude that this reptile is an endotherm and its relative is an ectotherm.

Less surface area is exposed to the environment.

No. This advantage is true. Because much of the bat's surface is pressed against other bats, less surface area is exposed to the colder environmental temperature.

In this configuration, less heat is needed for each bat, and therefore each bat requires less food.

No. This advantage is true. Any heat given off by any bat is shared with the rest. That, coupled with the lowered body temperature of the hibernating bats, means they need much less fuel.

Any heat generated by any bat is shared by other bats.

No. This is a major advantage of huddling.

Huddling behavior decreases the amount of food needed for bats to stay warm.

No. This advantage is true. The inactivity and lowered body temperature of hibernation allow these animals to survive on stored energy supplies and fewer calories.

Huddling behavior helps bats stay warm while they feed.

What does huddling prevent?

In the late fall, bats hibernate in clusters with many bats pressed together and holding on to one another. Which of the following statements does not represent an advantage of this behavior?

LOOP OF HENLE explained!!

Vasa Recta Counter Current Exchange

Consider three spheres with radii of 1 cm, 5 cm, and 10 cm. Calculate the surface area and the volume of each sphere, and plot the results on a graph with radius on the x-axis and surface area and volume on the y-axis. (Surface area of a sphere = 4πr2; volume of a sphere = (4/3)πr3.) Explain how the graph shows the relationship between size and surface area to volume ratio.

When your body temperature is too high, sweating helps to correct the situation because it lowers the metabolic rate by dumping toxic ions.

No. Sweating does lower the temperature, but it neither lowers the metabolic rate nor dumps toxic ions.

When your body temperature is too low, vasodilation in the skin helps to correct the situation because it conserves heat in the body core.

No. Vasodilation in the skin leads to heat loss.

When your body temperature is too low, shivering helps to correct the situation because it lowers the metabolic rate and conserves blood sugar.

When your body temperature is too high, vasodilation in the skin helps to correct the situation because it redirects heat from the body core to the outside.

Think of what your body does to lose and gain heat.

Which of the following statements is true?

No. Body heat would be conducted into the solid rock.

heat escaped his open mouth by conduction

No. He would lose heat through the evaporation of saliva from his open mouth.

receiving heat by conduction from the sun

No. He would receive heat from the sun by radiation.

heat evaporated away on the gentle breeze

No. Heat was carried away by convection on the breeze.

Contrast convection, conduction, radiation, and evaporation.

The wolf, his coat glowing in the early spring sunshine, sat atop a cold boulder after unsuccessfully pursuing a plump jackrabbit. He continued to pant while __________.

Explain why most endotherms are homeothermic and most ectotherms are poikilothermic.

No. Radiation does not involve a direct transfer of heat.

It is a cold day in the lecture hall. When you rest your arm on the cool laminated desktop at your seat, heat is transferred __________.

No. The thyroid gland releases hormones that can influence body temperature. However, the thyroid gland is not the main thermostat in the body. Also, a fever is associated with a higher temperature set point.

No. It is true that the hypothalamus is the main thermostat in the body, but fever is associated with a higher temperature set point, not a lower set point.

No. The circulatory system is involved in temperature regulation through vasoconstriction and vasodilation, but it does not control the body's temperature set point.

No. The integumentary system is involved in temperature regulation through vasoconstriction, vasodilation, and sweating, but it does not control the body's temperature set point. Also, a fever is associated with a higher temperature set point.

The cells that control thermoregulation are found in a special location in the brain.

During a fever, the __________ readjusts the set point of the body to a __________ temperature.

No. The term ectotherm is used to describe the source of heat for an organism.

can generate enough metabolic heat to keep its body temperature above that of its surroundings

No. This is the description of an endotherm.

has a body temperature that varies considerably

No. Although the body temperature of some ectotherms may vary with external temperatures, many ectotherms live in environments where the external temperature is remarkably constant. There is a better answer.

obtains most of its heat from its environment

A trout is an ectotherm.

By definition, an ectotherm __________.

Can ectotherms have stable body temperatures? Explain.

In 1847, the German biologist Christian Bergmann noted that mammals and birds living at higher latitudes (farther from the equator) are on average larger and bulkier than related species living at lower latitudes. Suggest an evolutionary hypothesis to explain this observation.

An elephant rolls in the mud and sprays water over its back.

No. This provides the animal with evaporative cooling as well as portable shade.

A man gets "goose bumps" after walking outside in the winter without a jacket.

No. Goose bumps result from the body's attempts to raise hairs for improved insulation. Our sparse body hair makes this mechanism ineffective. In any case, it is a physiological response to decreased body temperature.

A woman puts on a wide-brimmed hat while laboring in the sunshine.

No. The woman is providing herself with portable shade to cool the body.

Sweat oozes from the hide of a thirsty antelope in the drought-stricken Serengeti plains.

No. This is neither behavioral nor warming. It is a physiological method of cooling. Drinking water would be a cooling behavior.

A falcon migrates from San Francisco to Brazil for the winter.

Consider which of these involves behavior and environmental changes.

Which of the following is a description of a behavior that helps warm the body?

Which of the following is an advantage that ectotherms have over endotherms of the same size?
a. They require much less food.
b. They are less vulnerable to predation during cold weather.
c. They can remain active in cold weather or on cold nights.
d. They have higher metabolic rates and grow more quickly.

Reabsorption 8- Countercurrent exchange

The dinosaur Apatosaurus (Brontosaurus) is one of the largest terrestrial animals that ever lived—over 20 m in length and weighing over 20 metric tons. Is it more likely that Apatosaurus was homeothermic or poikilothermic? Explain.

Some diuretics are on a list of substances that the International Olympic Committee has banned for use by athletes. What do diuretics do? Propose an explanation for how diuretic use could be an unfair advantage for a competitor in a sport like wrestling, in which weight classes are part of the competition.

Which of the following is not an adaptation for reducing the rate of heat loss to the environment?
a. feathers or fur
b. increasing blood flow to surface blood vessels
c. huddling behavior of penguins
d. countercurrent heat exchange

The metabolic rate of a frog in summer (at 35°C) is about eight times higher than in winter (at 5°C). Compare and contrast the frog’s ability to move, exchange gases, and digest food at the two temperatures. During which season will the frog require more food energy, and why?

You are studying a large tropical reptile that has a high and relatively stable body temperature. How would you determine whether this animal is an endotherm or an ectotherm?

Countercurrent Multiplication in the Loop of Henle

Which of the following would increase the rate of heat exchange between an animal and its environment?
a. feathers or fur
b. vasoconstriction
c. wind blowing across the body surface
d.countercurrent heat exchanger

dilate, allowing blood to keep the skin warm

No. Dilation causes the diameter of blood vessels to increase, increasing blood flow to the skin. This would not be helpful, however, because heat in the skin would be lost to the environment.

constrict, forcing blood to flow through vessels in the skin

No. Vasoconstriction reduces blood flow through a vessel.

dilate, causing blood to pass through the cold skin more quickly

No. If the vessels were to dilate, blood flow would increase to the skin, resulting in heat loss to the environment.

dilate, preventing blood flow to the surface

No. Vasodilation increases blood flow, which would increase heat loss.

constrict, reducing heat loss from blood at the surface

Consider that on a cold day the goal is to conserve body heat.

On a cold day, blood vessels in the skin __________.

Dolphins have an insulating layer of blubber that protects them from cold water, but their flippers are not insulated. Propose a hypothesis to explain why dolphin flippers do not freeze. Describe an experiment you could do to test your hypothesis. (You may assume you have equipment for measuring temperatures in dolphin flippers.) What results would you expect if your hypothesis is correct?

After a long, hot run together, your friend tells you that you should dunk your head into a cooler of water to lower your body temperature more rapidly, rather than sitting and waiting to cool down. What do you think? Form a hypothesis about how the ice-cold water might affect the rate at which your body temperature returns to normal. How could you test your hypothesis?

can be prevented by drinking adequate amounts of water

No. Dehydration reduces sweating; thus, dehydration can cause the body to overheat dangerously. Drinking water makes sweating easier when it is necessary to cool the body.

No. It happens any time an individual is overheated. Sweating can also occur in the winter.

is a major thermoregulatory mechanism in dogs

No. Although dogs have sweat glands on their footpads, their major thermoregulatory mechanism is evaporative cooling through panting.

No. As long as water intake balances water loss, sweating can continue indefinitely without dehydration.

Consider when and why you sweat.

Sweating __________.

You are in a room of empty chairs. As the chairs fill with people, you become hotter and hotter. A ceiling fan is turned on, and you feel cooler. You gained heat by _________ and lost heat to the environment by _________ .
a. conduction … convection
b. radiation … convection
c. radiation … conduction
d. convection … radiation

No. Temperature of the blood is not the defining feature of endotherms.

No. Most endotherms have blood warmer than their environment, but temperature of the blood is not the defining feature of endotherms.

an animal that temporarily abandons warm-bloodedness

No. This is an animal involved in some kind of torpor to conserve energy.

an animal that regulates its body temperature by its behavior

No. This is generally an ectotherm's method of heat regulation, although some endotherms do also exhibit behavioral practices that supplement endothermy.

an animal that gets most of its body heat from its metabolism

A cat is an endotherm.

The term endotherm refers specifically to __________.

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