1. Human Physiology Dr M Hassanpour Basic Science School Biology Department PBS course

2. Chapter 1 The Study of Body Function

3. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Objectives Define homeostasis and explain how this concept is used in physiology and medicine. Describe the nature of negative feedback loops and explain how these mechanisms act to maintain homeostasis. Describe the nature of positive feedback loops and explain now these mechanisms function in the body.

4. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Physiology Study of how the human body functions. How organisms accomplish tasks essential for life. Pathophysiology: How physiological processes are altered in disease or injury.

5. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Scientific Method Confidence in rational ability, honesty and humility. Specific steps in scientific method: Formulate hypothesis: Observations. Testing the hypothesis: Quantitative measurements. Analyze results: Select valid statistical tests. Draw conclusion.

6. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Homeostasis Maintaining constancy of internal environment. Dynamic constancy. Within a certain normal range. Maintained by negative feedback loops. Regulatory mechanisms: Intrinsic: Within organ being regulated. Extrinsic: Outside of organ, such as nervous or hormonal systems. Negative feedback inhibition.

7. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Feedback Loops Sensor: Detects deviation from set point. Integrating center: Determines the response. Effector: Produces the response. Figure 1.1

8. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Negative Feedback Defends the set point. Reverses the deviation. Produces change in opposite direction. Examples: Insulin decreases plasma [glucose]. Thermostat. Body temperature. Figure 1.3

9. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Negative Feedback (continued) Figure 1.4 Figure 1.6

10. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Positive Feedback Action of effectors amplifies the changes. Is in same direction as change. Examples: Oxytocin (parturition). Voltage gated Na + channels (depolarization).