Download Ch31-AnimalSystems

Animal Systems
Organization and Homeostasis
Organization in Living Things
• Cells are organized into tissues
• Tissues are organized into organs
• Organs are organized into systems
• Systems form an organism
Four tissue types
• Epithelial
• Connective
• Nervous
• Muscular
Epithelial tissue
• Epithelial cells form
the outer covering,
line the internal
cavities, and make
up the glands.
• Examples: Skin,
mucous
membranes.
Connective tissue
• Consists of living
cells in a secreted
matrix.
• Examples: bone,
cartilage, blood.
Muscular tissue
• Specialized protein
fibers allow these
cells to contract.
• Examples: skeletal
muscle, smooth
muscle, cardiac
muscle.
Nervous tissue
• Neurons have the
ability to pass an
“electrical” signal
from one cell to
another, or to target
cells (muscles,
glands, organs).
Tissues form organs
• The skin is an
example of an
organ made up of
multiple tissues:
epithelial, muscular,
nervous, and
connective tissues.
Homeostasis
• Homeostasis is the act of keeping the
internal environment of a living organism
within an acceptable range of conditions.
• Homeostasis controls temperature, pH,
blood volume, oxygen levels, blood sugar
levels, and other conditions.
• Negative feedback maintains
homeostasis.
Negative Feedback
• Negative feedback keeps
conditions within an ideal
range.
• As conditions exceed the
limits of the ideal range,
chemical signals
(hormones) regulate
conditions. Most often this
is controlled by the
hypothalamus in the brain.
Positive Feedback
• Positive feedback
takes a condition out of
the normal range,
often to some end
point.
• During labor, oxytocin
increases contractions,
which stimulate more
oxytocin production,
until birth occurs.
Maintaining Temperature
• Ectotherms are animals
that derive body heat from
the environment. Their
body temperature may
vary widely.
• Endotherms rely on
metabolic reactions and
physiological systems to
maintain a steady body
temperature.
Maintaining Temperature
Blood Glucose Regulation