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The Study of Body Function • Physiology CHAPTER 1 – fundamentally represents the study of how living organisms work • Molecules cell tissue organ organ system • how organisms accomplish tasks essential for life – function & integration • body parts work together at various levels of organization (cellular and tissue organization) & whole organism – mechanisms & their effects • sequence of events – Parts of larger stories (workings of human organism itself) – Nothing works in isolation – Integrated entity 1 History of Physiology Father of Physiology speculated on fx of human body applied physical laws to study of human body good health assoc’d with balance of humours Studied cardiovascular and nervous systems Aristotle http://www.awakenyourwarrior.com/pages/philosophercoach.html Erasistratus http://www.health.gov.mt/impaedcard/issue/issue1/ipc0012206.jpg Father of Modern Physiology observed the milieu interieur remained remarkably constant despite constantly changing environment 1st to study biology quantitatively William Harvey http://www.nndb.com/people/033/000100730/ Claude Bernard 2 http://www.answers.com/topic/william-harvey?cat=health Father of American Physiology • Early 19th century in US – physiology treated as an aspect of theory & practice of physics – 1824, Thomas Jefferson, Univ of VA • Robley Dunglison www.healthsystem.virginia.edu – English physician – Professor of Anatomy, Physiology, Surgery, Materia Medica, Pharmacy & History of Medicine, 1825 – teaching was an explanation of “successive theories” – published several books & articles » Human Physiology 3 Homeostasis & Feedback Control coined the term homeostasis in his book, The Wisdom of the Body • Homeostasis – maintenance of a relatively stable internal environment • basically represented by the state of equilibrium of the body’s internal environment by dynamic processes of feedback and regulation – reason for regulatory mechanisms – not an easy accomplishment • every organ system is involved with the maintenance and necessitates integrated function – major foundation for medical diagnostic procedures Walter Cannon 1871-1945 http://www.harvardsquarelibrary.org/unitarians/cannon_walter.html How is the maintenance of homeostasis accomplished? 4 Feedback mechanism • Set point – normal range of measurements & values – factor or event being regulated is called the variable • Control systems that promote homeostasis are characterized by 3 interdependent components: – receptor – control or integration center – effector Why referred to as a “loop”? “loop” emphasizes feedback mechanism because it is a continuous cycle to maintain homeostasis 5 QUESTION • Is our internal environment absolutely constant? • Are we always in a state of balance? 6 Negative Feedback Mechanism • Most common homeostatic control mechanism • Reverse direction control mechanism – works by output of system causes a decrease or shuts off the original stimulus – continuous, ongoing processes • All negative feedback mechanisms have the same goal Preventing sudden severe changes in the body ANTAGONISTIC EFFECTORS effectors have antagonistic (opposite) actions allows for finer degree of control 7 Positive Feedback Mechanism • Same direction control system – enhance or exaggerate the response over the original stimulus, thus the output is increased • Usually control episodic or infrequent events that do not require continuous adjustments – examples? • Limited – Proceed with very little control – Human body doesn’t use PFM alot 8 Homeostatic Imbalance Goiter Homeostatic imbalance places an individual at higher risk of disease, which typically are a result of certain pathological conditions & aging MRI, T1 weighted 9 Homeostatic Regulation • Regulatory mechanisms for homeostasis – intrinsic • within organ – extrinsic • “outside” organ – nervous & endocrine systems » innervation by nerve fibers » hormones Advantages/Disadvantages? • Intrinsic mechanisms need to focus the effect – More specific for organ Can also be a disadvantage because have mechanisms that automatically turn on – Bleeding out, but increase heart rate because of decreased heart rate so causes you to bleed out MORE. 10 tissues (cells with similar functions ) primary tissue types Cells basic unit of structure & function organ primary tissues grouped into anatomical & functional units Activities & interactions of tissues determine the physiology of organ http://www.dundee.ac.uk/biocentre/SLSBDIV4ebl.htm simplest structural unit that complex, multicellular organism can be divided into retaining functional characteristics of life smallest unit of life 11 Muscle Tissue • Specialized for contraction • Three types of muscle tissue: Skeletal – skeletal - SkM • generally attached to bone via tendon; exceptions (tongue & diaphragm) – myofibers • 4th wk of development, myoblasts • arranged in bundles (variation in strength) • graded contractions – Cardiac – controlled individually cardiac - CM • wall of heart, myocardial cells • form continuous sheet • intercalated discs – – couple cells mechanically & electrically smooth - SmM • nonstriated, fusiform (spindled) shape • forms sheet, circularly &/or longitudinally arranged Smooth – peristalsis (wave-like contractions; lumen) Which muscle type is termed voluntary muscle? involuntary muscle? 12 Nervous Tissue • Consists of: – neurons • highly specialized to generate & conduct nerve impulses – an electrical event • constructed of cell body (soma), dendrites & axon – each has structural attributes & function – supporting cells • also known as neuroglial, or glial cells • nonconducting cells that support, insulate & protect neuron • more abundant • limited ability to divide http://www.mhhe.com/biosci/ap/histology_mh/neurons.jpg 13 Epithelial Tissue Pseudo-stratified squamous epithelium Simple squamous epithelium cover body surfaces & line body cavities Simple stratified transitional classified according to number of layers & shape perform a variety of functions - boundary 14 ET forms boundaries & thus serves as a barrier to be effective Site of regulation for substances entering/leaving the body a | Schematic drawing of intestinal epithelial cells. The junctional complex, which is located at the most apical region of lateral membranes, is circled. b | Electron micrograph of the junctional complex in mouse intestinal epithelial cells. The tight junction is circled. (Mv, microvilli; TJ, tight junction; AJ, adherens junction; DS, desmosome.) http://www.nature.com/nrm/journal/v2/n4/fig_tab/nrm0401_285a_F1.html Glands Exocrine duct 16 Exocrine Glands classification • Components: – duct – secretory unit • acinus • myoepithelial cells http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Epithelia/Epithel.htm 17 Connective Tissue • Characterized by: – large amt of extracellular material in the spaces between connective tissue cells • extracellular matrix, or ECM – fibers & ground substance – vary in composition & arrangement between tissue types – comprised of varied cell types • Categorized into – CT proper – supportive CT – liquid CT areolar CT 18 Adipose tissue BONE BLOOD Dense irregular CT 19 Organs & Organ Systems architecture of most organs are similar organ described as a structure composed of 2 or more tissue types 20 Stem cells • tissues of an organ are comprised of differentiated cells produce ALL specialized cells types of body – highly specialized capable of forming unrelated cell types • differentiation begins during embryonic development – zygote/embryo • totipotent stem cells – blastocyst • pluripotent stem cells – trilaminar embryo • ectoderm, mesoderm & endoderm – give rise to 4 primary tissue types http://www.scq.ubc.ca/stem-cell-bioengineering/ • adult stem cells – multipotent • form related cell types 21 Hierarchical system to structural organization levels of cellular organization human body is a complex society of differentiated cells, which combine structurally & functionally to carry out lifesustaining processes Cells are the basic units of the society & almost all exhibit fundamental activities common to all forms of life. 22 Body Fluid Compartments • Extracellular fluid - ECF – fluid in blood & spaces that surround cells • Plasma – found in blood • interstitial, or tissue fluid – found between cells • Intracellular fluid – ICF – fluid within cells • Mainly comprised of water – aqueous compartments • Composition varies between compartments – ECF considered more “homogenous” than ICF • What organ plays impt role in ECF composition/volume? – KIDNEYS • Compartmentalization Properties of these barriers determine what moves between compartments – who serves as the “barriers”? • Plasma membranes of cells and Epithelial cells and blood vessel 23 walls