The structures and functions of body parts maintain the life of the organism. 1. Requirements of organisms a. Water is used in many metabolic processes, provides the environment for metabolic reactions, and transports substances.
b. Nutrients supply energy, raw materials for building substances, and chemicals necessary in vital reactions.
c. Oxygen is used in releasing energy from nutrients; this energy drives metabolic reactions.
d. Heat is a product of metabolic reactions and helps control rates of these reactions.
e. Pressure is an application of force; in humans, atmospheric and hydrostatic pressures help breathing and blood movements, respectively.
2. Homeostasis a. If an organism is to survive, the conditions within its body fluids must remain relatively stable.
b. The tendency to maintain a stable internal environment is called homeostasis.
c. Homeostatic mechanisms include those that regulate body temperature, blood pressure, and blood glucose concentration.
d. Homeostatic mechanisms employ negative feedback.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.