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Chapter 1 The Study of Body Function Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-1 Human Physiology Physiology: study of how body works to maintain life Pathophysiology: how physiological processes are altered in disease or injury Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-3 Using Scientific Method to Develop New Drugs If effective and safe, clinical trials performed Phase I Trials: Toxicity and metabolism tested in healthy human volunteers Phase II Trials: Effectiveness and toxicity tested in target population Phase III Trials: Widespread test of drug in diverse population Phase IV Trials: Drug is tested for other potential uses Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-8 Homeostasis Is maintenance of a state of dynamic constancy In which conditions are stabilized above and below a physiological set point By negative feedback loops Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-10 Negative Feedback Loops Sensor: Detects deviation from set point Integrating center: Determines response Effector: Produces response Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-11 Homeostasis continued Regulatory mechanisms: Positive feedback is rare because it amplifies changes It is involved in producing blood clots In females it is used to create the LH surge that causes ovulation Positive feedback between the uterus and oxytocin secretion occurs during labor Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-15 Homeostasis continued Regulatory mechanisms: Negative feedback loops control blood pressure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-16 Organs Are anatomical and functional units made of two or more primary tissues Systems are groups of organs working together to maintain homeostasis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-41 Skin—The Largest Organ Has an outer layer of protective cornified epidermis Next layer is dermis, which contains connective tissue, glands, blood vessels, nerves Inner layer is hypodermis, which contains fat Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-42 Stem Cells Most cells in organs are highly specialized or differentiated Many organs retain small populations of adult stem cells These are less differentiated; can become many cell types E.g. bone marrow stem cells can give rise to all of the different blood cell types Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1-43