Anatomy & Physiology I and II

Anatomy & Physiology Study Guide

2.4 Chapter Two Review Levels of organization progress from molecules to a complete organism: • The 11 organ systems of the body are the integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, and reproductive systems. • Anatomical structures and physiological mechanisms occur in a series of interacting levels of organization. Homeostasis is the tendency toward internal balance: • Homeostasis is the existence of a stable environment within the body. • Physiological systems preserve homeostasis through homeostatic regulation. • Autoregulation occurs when a cell, tissue, organ, or organ system changes its activities automatically as its environmental changes. Extrinsic regulation involves responses from the nervous system or endocrine system. • Homeostatic regulation mechanisms usually involve a receptor that is sensitive to a particular stimulus, a control center that receives and processes the information supplied by the receptor and sends out commands, and an effector that responds to the commands of the control center and whose activity either opposes or enhances the stimulus. Negative feedback opposes change, whereas positive feedback exaggerates it: • Negative feedback is a corrective mechanism involving an action that directly opposes a variation from normal limits. • No one organ system has total control over the body’s internal environment; all organ systems work in concert. • In positive feedback, an initial stimulus produces a response that enhances the change in the original conditions and creates a positive feedback loop.

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