Ch.25 Control of Body Temperature and Water Balance

WHAT ARE REABSORPTION AND SECRETION?
Blood filtrate is refined to urine through reabsorption and secretion. High NaCl concentration in the medulla promotes reabsorption of water. Antidiuretic hormone regulates the amount of water excreted by the kidneys. Kidney dialysis can be a lifesaver by compensating.

WHAT IS THE RELATIONSHIP BETWEEN BEAR AND ITS CONCENTRATION?
Bears sleep a lot during winter, but bears do not hibernate. Instead, they become dormant. Their body temperature drops from 37C to about 31 to 34C. True hibernators may cool to 30C. Dormant bears are easily awakened and true hibernators are slower to awaken. That is the biggest difference between bears and true hibernators.

WHAT ARE EXAMPLES OF HOMEOSTASIS?
- Thermoregulation: the maintenance of internal temperature within narrow limits
The process by which animals maintain an internal temperature within a tolerable range. Ectothermic and endothermic animals are connected to them.

- Osmoregulation: the control of the gain and loss of water and solutes

Osmoconformers have the same internal solute concentration as seawater, and many marine invertebrates are osmoconformers. They control their solute concentrations.

- Excretion: the disposal of nitrogen-containing wastes

SUMMARY:
Heat exchange with the environment may occur by conduction, convection, radiation, and evaporation. Five general categories of adaptations promote thermoregulation. Increased metabolic heat production, humoral changes boost metabolic rate in birds and mammals, shivering, increased physical activity, and honeybees cluster and shiver. Circulatory adaptations increased or decreased blood flow to skin, large ears in elephants, and countercurrent heat exchange. Land animals gain water by drinking and eating, lose water by evaporation and waste disposal. and conserve water using. Nitrogenous wastes are toxic breakdown products of protein. Animals dispose of nitrogenous wastes in different ways. The excretory system expels wastes, regulates water balance and regulates ion balance. The key processes of the urinary system are filtration, reabsorption, secretion, and excretion. Filtration is when blood forces water and many small solutes into the nephron. Reabsorption is when valuable solutes are reclaimed from the filtrate. Secretion is excess H+ and toxins are added to the filtrate. Excretion is the final product, urine, is excreted. Reabsorption in the proximal and distal tubules removes nutrients, salt and water. pH is regulated by reabsorption of HCO3-, and secretion of H+.

KEY TERMS:
- Homeostasis: maintenance of steady internal conditions despite fluctuations in the external environment
- Thermoregulation: the maintenance of internal temperature within narrow limits
- Osmoregulation: the control of the gain and loss of water and solutes
- Excretion: the disposal of nitrogen-containing wastes
- Ectothermic: absorb heat from their surroundings
- Endothermic: derive body heat mainly from their metabolism
- Osmoconformers: have the same internal solute concentration as seawater
- Osmoregulators: control their solute concentrations
- Ammonia: poisonous, solube in water, easily disposed of by aquatic animals
- Nephrons: functional units of the kidneys, and extract a filtrate from the blood


http://www.youtube.com/watch?v=aQZaNXNroVY
This video talks about the urinary system and connection between the urinary system and the nephron.

5 FACTS:
1) An animal's regulation of body temperature helps maintain homeostasis.
2) Thermoregulation involves adaptations that balance heat gain and loss.
3) A variety of ways to dispose of nitrogenous wastes have evolved in animals.
4) The urinary system plays several major roles in homeostasis.
5) The key processes of the urinary system are filtration, reabsorption, secretion, and excretion.