3. Zygote: fertilized cell created by the union of the egg and sperm >200 types of human cells Embryonic stem cells –Created during earliest divisions –Potential to become any type of cell

4. Determination –Stem cells commit to a specific type –Few weeks into development –Irreversible

5. Stem cell programmed to become a muscle cell Stem cell programmed to become a nerve cell ON Genes (switches) exist in both cells, but are activated in one type and deactivated in the other.

6. Differentiation –Cells acquire the structures & functions of a specialized cell –Specific genes activated

8. Programmed cell death (apoptosis) between the fingers

9. Webbed Toes

10. Cell: Basic unit Tissue: Group of cells –4 types Organ: Groups of tissue –Ex: lung contains each tissue Organ System: Group of organs working together –Digestive System Organism: all organ systems working together

11. Muscle: contracting cells –Skeletal, cardiac cells

12. Connective Tissue: Support the body –Bone, fat, tendons

13. Epithelial: protection sheet of cells –skin, stomach lining

14. Nerve Tissue: Transmit electric signals –Brain & Spinal Cord

15. Homeostasis Process where the body maintains a constant internal environment Reactions & enzymes work best in specific conditions Control systems adjust to internal/external changes –pH, temp, fluids

16. Control Systems Sensors (aka: receptors) –Gather information about the body and environment –Ex: skin senses pressure Communication Center –Messages sent throughout the body to respond –Ex: Impulse travel through your nerves Control Center –Receives information from the sensors –Ex: Brain interprets the impulse Targets –Body part that changes its activity –Ex: Muscles in foot stretch/contract abruptly !*%!?%&#

17. Negative Feedback Loops Regulates most of the body Counters changes in the body that move conditions away from a set point –Reverses the change Keeps internal environment stable

19. Positive Feedback Loop Increases the changes away from set points Important when rapid changes needed Ex: Oxytocin released –W–When uterus contractions begin, oxytocin released to speed up the contractions (not stop them)

20. Working Together Thermoregulation: Maintenance of body temperature –Skin: sensors provide feedback to brain –Nervous & Endocrine system: send messages to/from brain –Muscles: Start to shiver

21. Homeostasis disruption Sensors fail Wrong messages sent Message doesn’t reach target Serious injury Microorganism infection Short Term –Temporary discomfort (usually)

22. Long Term: Diabetes Normal –Insulin controls glucose level –High: cells intake more glucose –Low: pancreas creates more glucose Type 1 –Immune system destroys cells to produce insulin –Pancreas fails –Blood pH decreases (more acidic) Type 2 –Insulin production decreases –Glucose level in blood rises –Cells starve