1. KEY CONCEPT The human body has five levels of organization.

2. Specialized cells develop from a single zygote.
Zygotes first divide into embryonic stem cells.
Stem cells develop in two stages.
Determination: cells commit to become one cell type
Differentiation: cells acquire specialized structures and functions

3. Specialized cells perform specific tasks.
Specialized cells function together in tissues, organs, organ systems, and the whole organism.
Specialized cells perform specific tasks.
Tissues are groups of similar cells working together.
epithelial tissue
connective tissue
muscle tissue
nervous tissue
cell
tissue

4. Epithelial: protection sheet of cells
skin, stomach lining

5. Connective Tissue: Support the body
Bone, fat, tendons

6. Muscle: contracting cells
Skeletal, cardiac cells

7. Nerve Tissue: Transmit electric signals
Brain & Spinal Cord

8. Organs are different tissues working together.
Organ systems are two or more organs working together.
Organism is all organ systems working together.
ORGANS
ORGAN SYSTEM
ORGANISM
Each organ system affects other organ systems.
An organ system must do a specific job.
Organ systems must also work together to keep the organism healthy.

9. There are 11 major organ systems in the human body.

10. 28.2 Mechanisms of Homeostasis
Homeostasis is the regulation and maintenance of the internal environment
Conditions within the body must remain within a narrow range.
pore
sweat
glands
hair
follicle
muscle
goose
bump
Control systems help maintain homeostasis.
sensors gather data
control center receives data, sends messages
communication system delivers messages to target organs, tissues
targets respond to change

11. Negative feedback loops are necessary for homeostasis.
28.2 Mechanisms of Homeostasis
Negative feedback loops are necessary for homeostasis.
Feedback compares current conditions to set ranges.
Negative feedback counteracts change.
Negative Feedback Loop
O2 / CO2 level returns to normal
Holding breath, CO2 levels rise,
Control system forces exhale, inhale

12. 28.2 Mechanisms of Homeostasis
Positive feedback increases change.
Torn vessel stimulates release of clotting factors
platelets
fibrin
white blood cell
red blood cell
blood vessel
clot
growth hormones stimulate cell division

13. A disruption of homeostasis can be harmful.
28.3 Interactions among systems
A disruption of homeostasis can be harmful.
Homeostasis can be disrupted for several reasons.
sensors fail
targets do not receive messages
injury
illness

14. 28.3 Interactions among systems
Short-term disruption usually causes little or no harm.
Cold or flu
Long-term disruptions can cause more damage.
Diabetes is a serious long-term disruption of homeostasis. 1 2 3 4
Pancreas cells attacked;insulin declines
Blood glucose levels rise,
Body burns fat; blood more acidic,
Cells impaired; all organs damaged.
pancreas
fats
kidneys