KEY CONCEPT The human body has five levels of organization.
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
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
Epithelial: protection sheet of cells skin, stomach lining
Connective Tissue: Support the body Bone, fat, tendons
Muscle: contracting cells Skeletal, cardiac cells
Nerve Tissue: Transmit electric signals Brain & Spinal Cord
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.
There are 11 major organ systems in the human body.
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
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
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
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
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