Chapter #31
Animal Systems and
Homeostasis
Structure and Function
Pg. 636 - 644
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
• Nerves
• Lymph Glands
• Vessels
• Lungs
• Small Intestine
• Skin
Tissues Form Organs
• The skin is an
example of an
organ made up of
multiple tissues:
epithelial,
muscular, nervous,
and connective
tissues.
Organs To Organ Systems
•Nervous System
•Endocrine System
•Musculo-skeletal System
•Circulatory System
•Respiratory System
•Digestive System
•Immune System
Organ Systems to Organisms
•Mammals
•Birds
•Amphibians
•Reptiles
•Fish
•Insects
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.
Maintaining Temperature
Blood Glucose Regulation
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.
Thinking Questions
1. Why is positive feedback not a good way
to maintain homeostasis?
2. What are some other examples of
positive feedback loops in the human
body?
3. Why do young animals often have more
body fat than adults? How does this
maintain homeostasis?