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Physiology notes- Body Fluids.doc

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PHGY 209
Anne Weschler

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Physiology Reading Notes: Body Fluids 24-27 , 360-362, 500-501, 593 - physiological genomics: integration of molecular biology with physiology - pathophysiology: disease states can be viewed as physiology “gone wrong” - cells: simplest structural units into which a complex multicellular organism can be divided and still keep the functions characteristic of life - cell differentiation: process of transforming an unspecialized cell into a specialized cell - to form multicellular structures cells migrate to other cells and form adhesions - differentiated cells with the same characteristics form tissues (nerve, muscle), tissues together form organs (heart, lung), organs together form organ system (urinary system) - 4 types of cells based on functions ( are tissues): 1. muscle cells - generate the mechanical forces that produce movement 2. nerve cells - initiate and conduct electrical signals 3. epithelial cells - selective secretion and absorption of ions and organic molecules, and for protection. -- basement membrane- (some) cells which rest on an extracellular protein layer called the basement membrane, it forms the boundaries between compartments and function as barrier substances from external environment 4. connective tissue cells - connect, and support structures of body (some found in loose meshwork of cells and fibers under epithelial layers) - ex. adipose cells, bone cells, red blood cells, white blood cells - 3 type of muscle cells 1. skeletal 2. cardiac 3. smoth (all different shape, and contractile activity) - extracellular matrix- fluid is in the matrix of it, it surrounds cell, consists proteins, minerals functions: 1. provides support to cellular attachments 2. transmit info through chemical messengers to cells ( regulate migration, growth, differentiation) the proteins of the matrix consist ropelike collagen fibers and rubberband- like elastic fibers -nephron - a tube in the kidneys that filters and excretes waste materials from the blood and produces urine - fluid surrounding cells- extracellular fluid -20–25 percent is in the fluid portion of blood, the plasma -75–80 percent of the extracellular fl uid, which lies around and between cells, is known as the interstitial fluid. - extracellular fluid are pretty much homogenous, intracellular is not -Water accounts for about 55–60 percent of normal body weight in an adult male, and slightly less in a female. (Females generally have more body fat than do males, and fat has a low water content.) -*Two-thirds of the water is intracellular fl uid. The remaining one-third is extracellular. As described previously, 75–80 percent of this extracellular fl uid is interstitial fl uid, and 20–25 percent is plasma. -two components of extracellular fl uid—the interstitial fl uid and the blood plasma—are separated by the cellular wall of the smallest blood vessels, the capillaries. -homeostasis is a dynamic, not a static, process. dynamic constancy- In such a state, a given variable like blood glucose may vary in the short term, but is fairly constant when averaged over the long term. -decreased room temperature “leads to” increased heat loss from the body -The activities of cells, tissues, and organs must be regulated and integrated with each other so that any change in the extracellular fl uid initiates a reaction to correct the change. The compensating mechanisms that mediate such responses are performed by homeostatic control systems. -negative feedback system, in which an increase or decrease in the variable being regulated brings about responses that tend to move the variable in the direction opposite (“negative” to) the direction of the original change. ex. When there is no cell energy, glucose molecules are enzymatically broken down to provide chemical energy thatis stored in adenosine triphosphate (ATP). As ATP accumulates in the cell, it inhibits the activity of some of the enzymes involved in the breakdown of glucose. -positive feedback: accelerates a process, leading to an “explosive” system ex. parturition (birth) - changes in the external environment can displace a variable from its set point ex. set point for body temperature is higher during the day than at night. -feedforward regulation anticipates changes in regulated variables such as internal body temperature or energy availability, improves the speed of the body’s homeostatic responses, and minimizes fl uctuations in the level of the variable being regulated—that is, it reduces the amount of deviation from the set point. ex. produces a certain acid when smelling food, prepares stomach for the job - afferent- direction towards brain, efferent- is the other way to muscles... muscles are the effectors - muscle and gland are major effectors -with glands, effector may be a hormone secreted into the blood. A hormone is a type of chemical messenger secreted into the blood by cells of the endocrine system -depending on the specifi c nature of the refl ex, the integrating center may reside either in the nervous system or in an endocrine gland -refl ex is a specifi c involuntary, unpremeditated, unlearned “built-in” response to a particular stimulus-local homeostatic responses- initiated by a change in the external or internal environment -refl ex, therefore, a local response is the result of a sequence of events proceeding from a stimulus. Unlike a refl ex, however, the entire sequence occurs only in the area of the stimulus.- individual areas of the body with mechanisms for local self-regulation. - intercellular communication— is performed by chemical messengers. -messengers: ( all messengers act between cells—that is, intercellularly, except autocrine)- involves secretion to extracellular region 1)hormones--a hormone functions as a chemical messenger that enables the hormone-secreting cell to communicate with cells acted upon by the hormone—its target cells 2) neurotransmitters- the way nerve cells communicate with each other, or other effectors such as muscles 3) paracrine/autocrine agents- local communication between cells - neurotransmittes subgroup of paracrine -paracrine - other cells autocrine- acts on its own cell -norepinephrine- neurotransmitter, there is also negative feedback, so it doesnt increase too much -A nerve cell, endocrine gland cell, and other cell type may all secrete the same chemical messenger. Thus, a particular messenger may sometimes function as a neurotransmitter, as a hormone, or as a paracrine/autocrine agent. ex. norepinephrine - there are two types that do not require any secretion 1) gap junctions:- up via the membrane-bound messenger -justacrine -adaptation denotes a characteristic that favors survival in specifi c environments -the improved functioning of an already existing homeostatic system—is known as acclimatization. - developmental acclimatization - ifan acclimatization is induced very early in life, however, at a critical period for development of a structure or response, may be irreversible - circadian rhythm, which cycles approximately, environment provides some cues (light/dark cycle) free running rhythm- absence of environmental cues -hypothalamus, a specifi c collection of nerve cells (the suprachiasmatic nucleus) functions as the principal pacemaker, or time clock, for circadian rhythms. -One output of the pacemaker goes to the pineal gland, a gland within the brain that secretes the hormone melatonin. (melatonin secreted in the darkness) - hydrolysis- large molecules are broken down to small with the help of enzymes R1—R 2+ H—O—H 34 R 1—OH + H—R 2 dehydration: one net water molecule is removed to combine two small molecules into one larger one. -osmosis: water moves from regions of low solute concentrations to regions of high solute concentrations -Molecules having a number of polar bonds and/or ionized groups will dissolve in water. Such molecules are said to be hyd
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