The Human Body: An Orientation

1. The Human Body: An Orientation

2. Organ System Overview • Cardiovascular System • Transports materials in bodyvia blood pumped by heart • Oxygen • Carbon dioxide • Nutrients • Wastes Figure 1.2f

3. Organ System Overview • Lymphatic System • Returns fluids to blood vessels • Cleanses the blood • Involved in immunity Figure 1.2g

4. Organ System Overview • Respiratory System • Keeps blood supplied with oxygen • Removes carbon dioxide Figure 1.2h

5. Organ System Overview • Digestive System • Breaks down food • Allows for nutrient absorption into blood • Eliminates indigestible material Figure 1.2i

6. Organ System Overview • Urinary System • Eliminates nitrogenous wastes • Maintains acid-basebalance • Regulates water and electrolytes • Checkpoint: • At which level of structural organization is the stomach? Organ • Which organ system includes the Pineal, Thyroid, Thymus and Adrenal Glands? Endocrine Figure 1.2j

7. Organ System Overview • Reproductive System • Produces offspring Figure 1.2k–l

8. Necessary Life Functions • Maintain boundaries • Movement • Locomotion of body/body parts • Movement of substances • Responsiveness • Ability to sense changes and react • Digestion • Break-down and absorption of nutrients

9. Survival Needs • Nutrients • Chemicals for energy and cell building • Includes carbohydrates, proteins, lipids, vitamins, and minerals • Oxygen • Required for the chemical reactions of digestion & respiration (cellular metabolism)

10. Survival Needs • Water • 60–80% of body weight • Provides fluids for metabolic reactions • Stable body temperature • Metabolic reactions occur most efficiently within a specific temperature range (36.1-37.5 oC = 96.9-99.5 oF) • Atmospheric pressure • Must be appropriate for exchange of gases in lungs in a timely manner to maintain cellular respiration

11. Interrelationships Among Body Systems Organ systems work together to promote the well-being of the entire body by completing necessary life functions. Checkpoint:Why is O2 so vital to survival? Figure 1.3

12. Homeostasis • Homeostasis—maintenance of a stable internal environment • A dynamic state of equilibrium • Continuous changes (within limits) that maintain overall balance within the body • Homeostasis is necessary for normal body functioning and to sustain life • Homeostatic Imbalance • A disturbance in homeostasis resulting in disease • Increasing age results in less stable internal conditions, which leads to increased risk for illness

13. Controlling Homeostasis • The body uses electrical and hormonal control signals through the nervous and endocrine systems to constantly monitor and control homeostasis. • Three essential components of the control systems: 1. Receptor • Responds to changes in the environment (stimuli) • Sends information to control center

14. Maintaining Homeostasis 2. Control Center • Determines set point (optimum level) for variable • Analyzes information • Determines appropriate response 3. Effector • Provides a means for response to the stimulus

15. Maintaining Homeostasis 3 4 Output: Information sent along efferent pathway to effector. Input: Information sent along afferent pathway to control center. Control Center Efferent pathway Afferent pathway 5 Receptor detects change. Effector 2 Receptor Response of effector feeds back to reduce the effect of stimulus and returns variable to homeostatic level. Approaches Control Center Exits Control Center IMBALANCE 1 Stimulus produces change in variable. VARIABLE (in homeostasis) IMBALANCE Figure 1.4, step 5

16. Feedback Mechanisms • Negative Feedback • Includes most homeostatic control mechanisms • Shuts off the original stimulus, or reduces its intensity • Works like a household thermostat • Examples:heart rate, blood pressure, respiration rate, glucose levels

17. Feedback Mechanisms • Positive Feedback • Increases the original stimulus to push the variable farther away from original value • Reaction continues at a faster rate • Examples: blood clotting, childbirth • Checkpoint: When you are thirsty, you drink water. Is the thirst sensation part of a negative feedback or a positive feedback mechanism? Why?