Chapter 25
Control of Body Temperature and Water Balance
I.
Thermoregulation
1.
Thermoregulation is the
maintenance of internal temperature within a range that allows cells to function
efficiently.
2. The
regulation of body temperature (thermoregulation) of animals helps maintain
homeostasis.
(1) Endotherms are animals that they are warmed mostly by heat generated by metabolism (anabolism and catabolism), i.e., thermoregulators.
(2)
Ectotherms are animals that they gain most of their heat from external
sources, i.e., thermoconformers.
II.
Osmoregulation and
Excretion
1.
Animals balance their
levels of water and solutes through osmoregulation.
2.
Osmoconformers are
organisms whose body fluids have a solute concentration equal to that of their
surroundings.
Osmoregulators are
organisms whose body fluids have a solute concentration different from that of
their environment, and that must use energy in controlling water loss or gain.
3.
Most aquatic animals
dispose of their nitrogenous wastes as ammonia (NH3). Mammals, most
adult amphibians, sharks, and some bony fishes excrete urea as the major waste
product. To avoid water loss, insects, land snails, and many reptiles convert
ammonia to uric acid.
4.
The kidney has 2 main
regions, an outer renal cortex and an inner renal medulla. Each kidney contains
about a million nephrons.
A nephron contains a renal
corpuscle and tubule (and
(6)
capillary network).
The (1) glomerulus and (2) Bowmanꞌs capsule make up
the blood-filtering unit
(renal corpuscle) of the nephron. The nephron tubule has 3 sections:
(3) The proximal tubule
(4) The loop of Henle
(5)
The distal tubule
5. Four
major processes of the urinary system:
(1)
Filtration: (in the
glomerulus and Bowmanꞌs capsule)
(2)
Reabsorption: the reclaiming of water and valuable solutes, including
glucose, amino acids, ions, and vitamins from the filtrate in kidney.
(3)
Secretion: the elimination of excess ions, drugs, and toxic substances
from the blood.
(4)
Excretion: the disposal of nitrogen-containing
metabolic wastes.
6. Kidney dialysis is a medical treatment for kidney disease, and blood is filtrated by a machine that mimics the action of a nephron.