Medical brain notes 36

  PHYSIOLOGY Physiology  (fiz- ē -ol′ ō -j ē ; the study of nature) is the scientific dis-cipline that deals with the processes or functions of living things. It is important in physiology to recognize structures as dynamic rather than fixed and unchanging. The major goals of physiology are (1) to understand and predict the body’s responses to stimuli and (2) to understand how the body maintains conditions within a narrow range of values in the presence of continually changing internal and external environments.  Human physiology  is the study of a specific organism, the human, whereas  cellular physiology  and  systemic physiology  are subdivisions that emphasize specific organizational levels.

  STRUCTURAL AND FUNCTIONAL ORGANIZATION OF THE HUMAN BODY A. Describe the six levels of organization of the body, anddescribe the major characteristics of each level. B. List the eleven organ systems, identify their components,and describe the major functions of each system. The body can be studied at six structural levels: chemical, cell, tissue, organ, organ system, and organism (figure 1.1). Chemical Level   The structural and functional characteristics of all organisms are determined by their chemical makeup. The  chemical  level of organization involves how atoms, such as hydrogen and carbon, interact and combine into molecules. The function of a molecule is intimately related to its structure. For example, collagen mol-ecules are strong, ropelike fibers that give skin structural strength and flexibility. With old age, the structure of collagen changes, and the skin becomes fragile and more easily torn. Cell Level Cells  are the basic structural and functi...

  CHARACTERISTICS OF LIFE Humans are organisms sharing characteristics with other organ-isms. The most important common feature of all organisms is life. This text recognizes six essential characteristics of life: 1.                         Organization  refers to the specific interrelationshipsamong the parts of an organism and how those parts interact to perform specific functions. Living things are highly organized. All organisms are composed of one or more cells. Some cells, in turn, are composed of highly specialized organelles, which depend on the precise functions of large molecules. Disruption of this organized state can result in loss of function and death.   2.      Metabolism  (m̆e-tab′̄o-lizm) is the ability to use energyto perform vital functions, such as growth, movement, and reproduction. Plants capture energy from sunl...

  MICROBESIN YOUR BODY Did you know that you have more microbial cells than human cells in your body? astoundingly, for every cell in your body, there are ten microbial cells. That’s as many as 100 trillion microbial cells, which can collectively account for anywhere between 2 and 6 pounds of your body weight! a microbe is any living thing that cannot be seen with the naked eye (for example, bacteria, viruses, fungi, and protozoa). The total population of micro-bial cells on the human body is referred to as the microbiota, while the combination of these microbial cells and their genes is known as the microbiome. The micro-biota includes so-called “good” bacteria that do not cause disease and may even help us. it also includes pathogenic, or “bad” bacteria.             With that many microbes in and on our bodies, you might wonder how they affect our health. To answer that question, in October 2007 the national institute of heal...

  HOMEOSTASIS   A.   Define homeostasis, and explain why it is important for proper body function. B.   Describe a negative-feedback mechanism and give an example. C.   Describe a positive-feedback mechanism and give an example. Homeostasis  (h̄o′m̄e-̄o-st̄a′sis; homeo-, the same) is the existenceand maintenance of a relatively constant environment within the body despite fluctuations in either the external environment or the internal environment. Most body cells are surrounded by a small amount of fluid, and normal cell functions depend on the mainte-nance of the cells’ fluid environment within a narrow range of con-ditions, including temperature, volume, and chemical content. These conditions are called  variables  because their values can change. For example, body temperature is a variable that can increase in a hot environment or decrease in a cold environment. Homeostasis is the maintenance of a variable, such as body temperature, around an i...

  When you begin to study anatomy and physiology, the number of new words may seem overwhelming. Learning is easier and more interesting if you pay attention to the origin, or  etymology  (et′ ĕ -mol′o-j ē ), of new words. Most of the terms are derived from Latin or Greek. For example,  anterior  in Latin means “to go before.” Therefore, the anterior surface of the body is the one that goes before when we are walking.             Words are often modified by adding a prefix or suffix. For example, the suffix  -itis  means an inflammation, so  appendicitis  is an inflammation of the appendix. As new terms are introduced in this text, their meanings are often explained. The glossary and the list of word roots, prefixes, and suffixes on the inside back cover of the textbook also provide additional information about the new terms. Body Positions The  anatomical position  refers to ...