1. Levels of Organization

2. Cell Specialization • 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

3. Determination • Determination • Stem cells commit to a specific type • Few weeks into development • Irreversible

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

5. Differentiation • Differentiation • Cells acquire the structures & functions of a specialized cell • Specific genes activated

7. Programmed cell death (apoptosis) between the fingers

8. Webbed Toes

9. Organization • 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

10. Muscle: contracting cells Skeletal, cardiac cells Body Tissues

11. Connective Tissue: Support the body Bone, fat, tendons Body Tissues

12. Epithelial: protection sheet of cells skin, stomach lining Body Tissues

13. Nerve Tissue: Transmit electric signals Brain & Spinal Cord Body Tissues

14. 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

15. !*%!?%&# 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

16. 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

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

19. 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

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

21. 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