Human Phys Chapter 1
List the organ systems of the body and give one-sentence descriptions of their functions. -Circulatory -Digestive -Endocrine -Immune -Integumentary -Lymphatic -Musculoskeletal -Nervous -Reproductive -Respiratory -Urinary
-Circulatory: Transports blood throughout the body. -Digestive: Digests and absorbs nutrients and water; eliminates wastes. -Endocrine: Regulates and coordinates many activities in the body. -Immune: Defends the body against pathogens, returns interstitial fluid to the blood, and forms white blood cells. -Integumentary: Protects the body against injury, dehydration, and pathogens; helps regulate body temperature. -Lymphatic: Collects extracellular fluid for return to circulation. Participates in immune defenses. -Musculoskeletal: Supports and protects the body and allows for body movement. Produces blood cells. -Nervous: Regulates and coordinates many activities of the body; detects and responds to changes in the internal and external environments; allows for states of consciousness, learning, memory, emotions, etc. -Reproductive: Produces germ cells (eggs in females, sperm in males). In females, provides nutritive environment for the developing embryo and fetus, and nutrition for the infant after birth. -Respiratory: Exchanges oxygen from the air with carbon dioxide to and from the cells of the body by means of the blood and helps to regulate hydrogen ion concentration in the body fluids. -Urinary: Regulates the plasma concentration of minerals and water and excretes organic wastes.
Make a list of the General Principles of Physiology, without the paragraphs that accompany each one. See if you can explain what is meant by each Principle. To really see how well you've learned physiology at the end of your course, remember to return to the list you've made and try this exercise again at that time
1. Homeostasis is essential for health and survival. The ability to maintain physiological variables such as body temperature and blood sugar concentrations within normal ranges is the underlying principle upon which all physiology is based. Keys to this principle are the processes of feedback and feedforward. Challenges to homeostasis may result from disease or from environmental factors such as famine or exposure to extremes of temperature. 2. The functions of organ systems are coordinated with each other. Physiological mechanisms operate and interact at the level of cells, tissues, organs, and organ systems. Furthermore, organ systems often interact with each other to control a homeostatic variable, such as blood pressure (urinary and circulatory systems). 3. Most physiological functions are controlled by multiple regulatory systems, often working in opposition. Typically, control systems in the human body operate such that a given variable, such as heart rate, receives both stimulatory and inhibitory signals. A great example is the autonomic nervous system. 4. Information flow between cells, tissues, and organs is an essential feature of homeostasis and allows for integration of physiological processes. Cells can communicate with nearby cells via locally secreted chemical signals; a good example of this is the signaling between cells of the stomach that results in acid production. Cells can also communicate long distances using electrical signals or chemical messengers such as hormones. 5. There is controlled exchange of materials between compartments and across cellular membranes. The movement of water and solutes—such as ions, sugars, and other molecules—between the extracellular and intracellular fluid is critical for the survival of all cells, tissues, and organs. In this way, important biological molecules are delivered to cells and wastes are removed and eliminated from the body. In addition, regulation of ion movements creates the electrical properties that are crucial to the function of many cell types. 6. Physiological processes are dictated by the laws of chemistry and physics. Examples of chemistry in physiology include the law of mass action that governs common reactions like that of hemoglobin and oxygen. Physical laws and properties such as gravity, electromagnetism, and resistance help explain how blood flows through vessels, how we perceive light, how air moves through bronchioles and so on. 7. Physiological processes require the transfer and balance of matter and energy. Growth and the maintenance of homeostasis require regulation of the movement and transformation of energy-yielding nutrients and molecular building blocks between the body and the environment and between different regions of the body. Organic nutrients are ingested, stored in various forms, and metabolized to provide energy. The concentrations of many inorganic molecules must also be regulated to maintain body structure and function, for example, the calcium found in bones. One of the most important functions of the body is to respond to changing demands, such as the increased requirement for nutrients and oxygen in exercising muscle. This requires a coordinated allocation of resources to regions that most require them at a particular time. 8. Structure is a determinant of—and has coevolved with—function. The form and composition of cells, tissues, organs, and organ systems determine how they interact with each other and with the physical world. There are many examples of how different body parts converge in their structure to accomplish similar functions. For example, enormous elaborations of surface areas to facilitate membrane transport and diffusion can be observed in the cardiovascular, respiratory, urinary, digestive, and reproductive systems.
Describe the conditions under which acclimatization occurs. In what period of life might an acclimatization be irreversible? Are acclimatizations passed on to a person's offspring?
Acclimatization is an improved ability to respond to an environmental stress and is induced by prolonged exposure to the stress. If it occurs early in life, it may be irreversible, and thus is known as a developmental acclimatization. Acclimatizations are not inheritable
Under what conditions do circadian rhythms become free-running?
Brain pacemakers internally drive circadian rhythms but they are entrained by environmental cues. In the absence of such cues they become free-running. For example, circadian rhythms run free when a person is maintained in constant darkness or constant light.
Describe the levels of cellular organization and state the four types of specialized cells and tissues.
Cells divide and differentiate into four specialized types―muscle cells, neurons, epithelial cells, and connective tissue cells. Corresponding to the four general categories of differentiated cells, there are four general types of tissues: muscle tissue, nervous tissue, epithelial tissue, and connective tissue. The differentiated cells with similar properties aggregate form tissues; tissues in combination form organs, many with discreet functional units. Organ systems consist of groups of organs that in combination perform a specific function in the body.
Contrast feedforward and negative feedback.
Feedforward regulation initiates an adaptive response in the body in anticipation of a change in the environment. Feedforward regulation happens before homeostasis has been disrupted and helps to minimize fluctuations and speed up the response. Negative feedback occurs only after there has been a change in the environment. Negative feedback mechanisms come into play to restore the variable toward its original set point.
Describe several important generalizations about homeostatic control systems
Homeostatic control systems perform regulatory responses to preserve relatively stable conditions of the internal environment. Important generalizations include: (1) Stability of an internal environmental variable is achieved by the balancing of inputs and outputs. It is not the absolute magnitudes of the inputs and outputs that matter but the balance between them. (2) In negative feedback, a change in the variable being regulated brings about responses that tend to move the variable in the direction opposite the original change—i.e., back toward the initial value or set point. (3) Homeostatic control systems cannot maintain constancy of any given feature of the internal environment in the face of continued change in the external environment, but can only minimize changes. Therefore, any regulated variable will have a more-or-less narrow range of normal values depending upon environmental conditions. (4) The set point of some variables regulated by homeostatic control systems can be reset—i.e., physiologically raised or lowered. (5) It is not always possible for everything to be maintained within a narrow normal range by homeostatic control systems. There is a hierarchy of importance, such that certain variables may be altered markedly to maintain others within their normal range.
What is the basic difference between a local homeostatic response and a reflex?
In a reflex, nerves or hormones act as the afferent and efferent pathways. These long-distance communication mechanisms are unnecessary for local homeostatic responses.
Name the two fluids that constitute the extracellular fluid. What are their relative proportions in the body, and how do they differ from each other in composition?
Interstitial fluid and blood plasma constitute the extracellular fluid, which accounts for one-third of the total-body water. The ICF is nearly four times greater in volume than the plasma (75-80% of ECF (11 L) vs. 20-25% of ECF (3 L), respectively). Except for protein concentration and red blood cells in the plasma, the two fluids are identical in composition.
State the relative volumes of water in the body fluid compartments.
Intracellular fluid (ICF) volume is twice as large as extracellular fluid (ECF) volume and accounts for about 40% of the body's weight. In other words, two-thirds of total-body water is ICF and one-third is ECF. In an average 70-kg person, ICF is 28 L, plasma is 3 L, and interstitial fluid is 11 L.
List the general categories of intercellular messengers.
Neurotransmitters, hormones, and autocrine/paracrine substances (local)
How do phase-shifts occur?
Phase-shifts are brought about by changes in environmental cues, such as experiencing a change in light-dark cycles because of a jet flight across to a different time zone.
List the components of a reflex arc.
Stimulus, receptor, afferent pathway, integrating center (compare to set point), efferent pathway, effectors
What is the most important environmental cue for entrainment of body rhythms?
the light-dark cycle
