Chapter 46 Digestion Part 2

Question 1

Homeotherms

Answer 1

Maintain body temperature within a narrow range.

Question 2

Countercurrent exchange

Answer 2

Endotherms and ectotherms regulate heat loss to the environment, in which heat s transferred between fluids flowing in opposite directions.

Question 3

Radiation

Answer 3

The emission of electromagnetic waves by the surfaces of objects. The rate is determined by the temperature of the radiating surface.

Question 4

Evaporation

Answer 4

The conversion of water from the liquid to the gaseous state.

Question 5

Ketones

Answer 5

The liver processes fatty acids into these during the postabsorptive state.These are released into the blood during prolonged fasting and provide an important energy source for the many tissues (brain) which are capable of oxidizing these in the citric acid cycle.

Question 6

Endotherms

Answer 6

Organisms use their own metabolically generated heat to warm themselves.

Question 7

Ectotherms

Answer 7

Depend on external heat sources to warm their bodies.

Question 8

Heterotherm

Answer 8

Have body temperatures that vary with the environment.

Question 9

Acclimatization

Answer 9

Long-term exposure to a challenging environment, either very hot or very cold results in a fine-tuning of the adaptive mechanisms that persist for as long as the animal lives in that environment.

Question 10

Describe the four ways animals exchange heat the the environment.

Answer 10

Radiation—The emission of electromagnetic waves by the surface of objects. The colder it is ouside the body, the faster the body will lose heat.
Evaporation—The conversion of water from the liquid to the gaseous state. Body heat can be lost by the evaoporation of water from the skin, the respiratory tract, and the tongue. The heat required to drive the process is conducted from the surface, thereby cooling the animal.
Convection—The transfer of heat by the movement of air or fluid next to the body. Warm air from the body of the animal leaves and is replaced by cooler air. (i.e. sitting in front of a fan.)
Conduction—The body surface loses or gains heat through direct contact with cooler or warmer substances. (sitting in cool water)

Question 11

Describe the absorptive and post-absorptive states.

Answer 11

Absorptive State—1. Excess glucose is stored as glycogen in liver and muscle and as triglycerides in adipose cells. 2. Triglycerides are stored in adipose cells. 3. Amino acids are transported into all cells, including muscle, where they form proteins. Excess amino acids are converted to triglycerides in the liver, from where they are secreted into the blood and stored in adipose cells. 4. Absorption of nutrients occurs along the length of the small intestine. 5. A portion of absorbed glucose and fats is used to supply energy needs.
Postabsorptive State—1. Glycogen in broken down into glucose in the liver and secreted into the blood—glycogenolysis. 2. Triglycerides stored in adipose tissue are broken down to glycerol and fatty acids. The glycerol is used by the liver to make glucose. 3. Proteins are broken down into amino acids, some of which are used by the liver to make glucose, which is then secreted into the blood.—gluconeogenesis. 4. All cells use glucose as an energy source to make ATP. Fatty acids are used for energy by most cells, except those of the nervous system.

Question 12

What are the three disadvantages of endotherms?

Answer 12

1. The body has to use energy and eat a lot of food in order to maintain a constant internal temperature due to radiating heat loss.
2. There is a greater risk of hypothermia or over heating.
3. Because of the evaporation of bodily fluids to maintain temperature, the endotherm is restricted to environments near water.