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

2. Specialized cells develop from a single zygote.
Organisms are made up of specialized cells.
red blood cell
nerve cell

3. Zygotes first divide into embryonic stem cells.
Stem cells develop in two stages.
determination, or committing to become one cell type
differentiation, or acquiring specialized structures and functions

4. 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

5. 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

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

7. KEY CONCEPT 28.2 Homeostasis is the regulation and maintenance of the internal environment.

8. Conditions within the body must remain within a narrow range.
Homeostasis involves keeping the internal environment within set ranges.

9. 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
pore
sweat
glands
hair
follicle
muscle
goose
bump

10. 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

11. 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

12. KEY CONCEPT 28.3 Systems interact to maintain homeostasis.

13. 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.

14. Organ systems must also work together to keep the organism healthy.
Organ systems work together to produce Vitamin D.
Thermoregulation maintains a steady body temperature. 1 2 3 4
Skin absorbs UV light
Liver produces inactive vitamin D
Kidneys produce active vitamin D
Active vitamin D used in bones
UV light

15. A disruption of homeostasis can be harmful.
Homeostasis can be disrupted for several reasons.
sensors fail
targets do not receive messages
injury
illness

16. Short-term disruption usually causes little or no harm.
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