EXCRETORY AND NERVOUS SYSTEMS. How do animals manage toxic nitrogenous waste? . Animals either eliminate ammonia from the body quickly or convert it into other nitrogenous compounds that are less toxic.
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Animals either eliminate ammonia from the body quickly or convert it into other nitrogenous compounds that are less toxic.
The breakdown of proteins by cells releases a nitrogen-containing, or nitrogenous, waste: ammonia.
Ammonia is poisonous. Even moderate concentrations of ammonia can kill most cells.
Animals that cannot dispose of ammonia continuously, as it is produced, have evolved ways to store nitrogenous wastes until they can be eliminated.
Insects, reptiles, and birds convert ammonia into a sticky white compound called uric acid, which is much less toxic than ammonia and is also less soluble in water.
Mammals and some amphibians convert ammonia to a different nitrogenous compound—urea. Urea is less toxic than ammonia, but unlike uric acid, it is highly soluble in water
Excretory systems are extremely important in maintaining the proper balance of water in blood and body tissues.
In some cases, excretory systems eliminate excess water along with nitrogenous wastes.
In other cases, excretory systems must eliminate nitrogenous wastes while conserving water.
Many animals use kidneys to separate wastes and excess water from blood to form a fluid called urine.
Kidneys separate water from waste products.
Kidney cells pump ions from salt to create osmotic gradients.
Water then “follows” those ions passively by osmosis.
Kidneys, however, usually cannot excrete excess salt.
The functions of the nervous system are accomplished by the peripheral nervous system and the central nervous system.
The peripheral nervous system, which consists of nerves and supporting cells, collects information about the body’s external and internal environment.
The central nervous system, which consists of the brain and spinal cord, processes that information and creates a response that is delivered to the appropriate part of the body through the peripheral nervous system.