BODY ORGANIZATION
AND HOMEOSTASIS
Key Concepts:
1.
What are the levels of organization
in the body?
2.
What is homeostasis?
Key Terms
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Cell
Cell membrane
Nucleus
Cytoplasm
Tissue
Muscle tissue
Nervous tissue
Connective tissue
Epithelial tissue
Organ
Organ System
Homeostasis
Stress
Cells
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Basic unit of structure and function in a living
thing
Human body contains about 100 trillion cells
Structure of cells – all animal cells contain
cell membrane, nucleus and cytoplasm
Function of cells – release energy from food,
grow and reproduce and get rid of wastes
Tissues
Group of similar cells that perform the same
function
Four types:
 Muscle – can contract or shorten, make body
move
 Nervous – carry electrical signals between
brain and other body parts
 Connective – provides support for body and
connects all parts
 Epithelial – covers surfaces of body both
inside and out
Organs and Organ Systems
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Organs - structures composed of different
types of tissues – performs a specific job,
more complex than tissue
Organ Systems – group of organs that work
together to perform a major function
Major Organ Systems of the Human Body
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Circulatory
Digestive
Nervous
Skeletal
Endocrine
Muscular
Excretory
Respiratory
Homeostasis
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Process by which an organism’s internal
environment is kept stable in spite of changes
in the external environment
All systems of the body work together to
maintain homeostasis
Examples
– body temperature – stays close to 37°C whatever
the outside temperature
- Sweating to cool off and shivering to get warm
Stress and Homeostasis
Stress - The reaction of your body to potentially
threatening, challenging or disturbing events.
Throws off homeostasis
Example – Bike Race – heart beats faster,
breathing increases, adrenaline is pumped
into your bloodstream.
At the end of the race – all quickly return to
normal