Transcript Slide 1

Nervous & Excretory Systems
• Regulation within animal systems requires maintaining
homeostasis- the ability of the body or a cell to seek
and maintain a stable internal environment when
dealing with external changes
• There are several organ systems that work together to
maintain an organism’s internal environment, despite
changes that occur in its external environment.
• The nervous system maintains homeostasis by
controlling and regulating the other parts of the body.
• The excretory system helps regulate the concentration
of water and other components of body fluids.
The Excretory System Maintains Homeostasis In 3 Steps:
1. Filtration- Filters substances from the blood
2. Reabsorption- Regulate the chemical composition
of body fluids by retaining the proper amounts of
water, salts, and nutrients
3. Secretion- Elimination of wastes in the form of
urine
Evolutionary Trends in Excretion
Complex
Simple
Animal
Aquatic
Worms and
Taxon
Invertebrates
Mollusks
Release
Wastes
By…
diffusion to remove
waste across their cell
membranes directly into
the water
Use of nephridia- tiny
pores along the body
excrete waste
Insects
Using malpighian
tubules to collect and
excrete wastes
Vertebrates
Use of kidneys,
ureters, and a
bladder to collect
and excrete waste
Picture of
system
Examples
Sponges, jellyfish,
Earthworm, clam,
Grasshopper, ants,
planaria
octopus
bees
mammals, birds,
reptiles, fish,
amphibians
Kidneys (renal = kidney) Paired organs that receive blood
via the renal artery
 Contain millions of filtering units
called nephrons that remove
wastes (excess salt and urea)
from the blood and produce
urine.
 Every 45 minutes kidneys filter
all the blood in your body
 Filtered blood leaves kidneys and returns to circulation carrying
nutrients, salts, and water via the renal vein
 Excess water and toxic waste in the form of urine leave the kidney
via the ureter
 Sometimes excess salts or minerals in the urine crystallize and form
kidney stones. When kidney stones block the ureters, they cause
great pain.
 Ureters—tubes that
carry urine from
kidneys to urinary
bladder
 Bladder—muscular
sac where urine is
stored temporarily
before being
excreted
 Urethra—tube that carries urine from bladder
to the outside
Levels of Organization
Nephrons
Kidneys, Bladder, Ureter, Urethra
Excretory
Interaction with other systems for Regulation
Lungs of the respiratory
system remove CO2 from
blood.
The circulatory system
brings wastes to the lungs,
kidneys, and skin for
excretion.
Skin of the integumentary
system excretes water, urea,
salts, and other wastes
through sweat.