KEY CONCEPT The human body has five levels of organization.

Cells Tissue Organ Organ system Organism

Organisms are made up of specialized cells. Specialized cells develop from a single zygote (beginning cells when sperm and egg meet. Organisms are made up of specialized cells. red blood cell nerve cell

Zygotes (the cells created by fertilization) first divide into embryonic stem cells. Stem cells develop into specialized cells by: differentiation, or acquiring specialized structures and functions This means that some genes are turned on and off. *Remember all cells of an organism have the exact same DNA

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

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

There are 11 major organ systems in the human body.

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

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

Negative feedback loops are necessary for homeostasis. Feedback compares current conditions to set ranges. Negative feedback counteracts change and brings the body back to a SET POINT (example: breathing) Negative Feedback Loop O2 / CO2 level returns to normal Holding breath, CO2 levels rise, Control system forces exhale, inhale

Positive feedback increases change (intensifies a process) - Once a vessel is damaged, platelets start to cling to the injured site and release chemicals that attract more platelets. The platelets continue to pile up and release chemicals until a clot is formed. During labor, a hormone called oxytocin is released that intensifies and speeds up contractions. The increase in contractions causes more oxytocin to be released and the cycle goes on until the baby is born. The birth ends the release of oxytocin and ends the positive feedback mechanism platelets fibrin white blood cell red blood cell blood vessel clot

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.

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