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Structural Levels, continued…

Structural Levels, continued…. Organism – any living thing considered as a whole Unicellular, multicellular Human organism is a complex of organ systems that are mutually dependent on one another. Characteristics of Life. Six Essential Characteristics of Life

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Structural Levels, continued…

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  1. Structural Levels, continued… • Organism – any living thing considered as a whole • Unicellular, multicellular • Human organism is a complex of organ systems that are mutually dependent on one another

  2. Characteristics of Life • Six Essential Characteristics of Life • Organization – an organism’s parts are interrelated • All living things are composed of cells • Metabolism (Energy) – ability to use energy to perform vital functions such as growth, movement, and reproduction • Energy from sun (plants) or food (animals)

  3. Six Essential Characteristics of Life, continued… • Homeostasis – ability of an organism to sense changes in the environment and make the adjustment that help maintain its life • Growth – ability of an organism to increase in size (partially or totally) • Either by increasing cell number or cell size

  4. Six Essential Characteristics of Life, continued… • Cells – all organisms are made of one more cells • Reproduction – the formation of new cells or organisms a. Sexual or asexual reproduction

  5. Environmental Requirements of Organisms Organisms require certain factors in their environment or surroundings: • Water • Foods • Oxygen • Heat – energy from metabolic reactions • Pressure • Atmospheric  breathing • Hydrostatic  blood pressure

  6. Homeostasis – Maintenance of Life • The existence and maintenance of a relatively constant environment within the body • Narrow range of conditions (variables) • Temperature, volume, chemical content • Set point = ideal normal value • Normal range = range of values in which an organism can operate normally

  7. Examples: Cold = shiver Hot = sweat

  8. Negative Feedback • Maintains homeostasis by resisting deviation from the set point • Three components: • Receptor – monitors the value of a variable • Control center – establishes the set point around which the variable is maintained • Effector – can change the variable

  9. Hole’s Essentials of Human Anatomy and Physiology, 8th ed., Shier, et al, 2003, McGraw-Hill Higher Education Negative Feedback, continued… • Example: • Stimulus/Response: exercise increases HR and blood pressure increases • Receptor: blood vessels near heart • Control center: brain receives message and sends message to decrease HR • Effector: heart decreases HR • Response: blood pressure decreases

  10. Negative Feedback, continued…

  11. Positive Feedback • Mechanism by which any deviation from an ideal normal value or set point is made greater • Does not maintain homeostasis

  12. Positive Feedback, continued… Example

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