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The Study of Body Function CHAPTER 1
Physiology 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 How you work is all directed by the molecules in the organism Everything is all related to each other Function and Integration Cellular level and tissue organization too MISCONCEPTION that all is known (we know some, but there is A LOT still left to learn)
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History of Physiology Father of Physiology
applied physical laws to study of human body Studied cardiovascular and nervous systems speculated on fx of human body good health assoc’d with balance of humours Aristotle Erasistratus Father of Modern Physiology observed the milieu interieur remained remarkably constant despite constantly changing environment Aristotle Claim to fame: he stated that an individual who is in good health (function properly) is associated with balances of humours (which are blood (spring), phlegm, yellow bile (summer) and black bile) Erasistratus Greek anatomist and royal physician He applied the physical laws of that time to study of human body, so made it more scientific rather than just an observation Found info on 2 organ systems and found: Nervous: Was able to distinguish between motor and sensory for the nervous system, and knew they were linked to the brain Cardio: looked at heart rhythms (arthymologist) and able to distinguish arteries and veins William Harvey English Physician Collected data and numbers Looked at not just that we have vessels that carry blood away from heart, but that we have arteries, capillaries and veins that have specific functions. Claude Bernard Homeostasis 1st to study biology quantitatively William Harvey Claude Bernard
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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 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 Actually a British man 26 year old practicing physician Was made an offer of 1500 year salary, room and board and supplies for his students. Took the job because of the paycheck which allowed him to marry the young lady he was interested in. Great talker, made stories of everything that was there so you could follow one event to the next
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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 Human body in a state of EQUILIBRIUM Actually a dynamic process that requires us to have information of what is going on Feedback mechanisms along with regulation Walter Cannon How is the maintenance of homeostasis accomplished?
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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 HOW is the maintenance of homeostasis accomplished? By control mechanisms such as FEEDBACK Variable: event/factor that is being regulated Has a set point, which is the normal range of values, that it should fall within Receptor: senses the variable that we are looking at If it senses an increase it sends info to a CONTROL/INTEGRATION CENTER (flows alongs afferent pathways, so TOWARDS the central nervous system) Control or Integration Center: decides what to do and sends info through a efferent pathway Effector: element that brings the variable back to homeostatic range, so back to it’s set point. Why referred to as a “loop”? Why referred to as a “loop”? “loop” emphasizes feedback mechanism because it is a continuous cycle to maintain homeostasis
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QUESTION Is our internal environment absolutely constant?
Are we always in a state of balance? Absolutely constant? NO We have a dynamic balance or consistency Not just one value but conditioned around a set point Always in a state of balance? Not true yes or no 6
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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 Reverse control: if we increase it we are going to decrease it, and vice versa Output of the system causes it to go into the opposite direction Continuous because sometimes we overshoot and have to go into another direction EX: glucose levels Have an event that causes a rise in blood/glucose level Respond by stimulate cells to release insulin to get blood-glucose level back to set point ANTAGONISTIC EFFECTORS effectors have antagonistic (opposite) actions allows for finer degree of control
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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 Output is ALWAYS increased Example? Blood clotting, want to stop leakage of blood by initiating a sequence of events that forms a blood clot to stop the leakage Are parameters that help limit blood clotting Childbirth, can’t stop it. Lactation, release of milk from breast.
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Homeostatic Imbalance
Goiter Breakdown of some element of homeostasis Goiter – enlarged thyroid gland Homeostatic imbalance places an individual at higher risk of disease, which typically are a result of certain pathological conditions & aging MRI, T1 weighted
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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. By standing up, causes blood pressure to fall which causes the heart rate to increase. Have receptors in vascular system that picks up on changes of the system which causes a response to get you back to homeostasis.
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tissues (cells with similar functions )
organ primary tissues grouped into anatomical & functional units tissues (cells with similar functions ) primary tissue types Activities & interactions of tissues determine the physiology of organ Cells basic unit of structure & function 4 Primary Tissue Types Epithelial Connective Muscle Nervous The activities and actions of the tissues determine the physiology of tissues d simplest structural unit that complex, multicellular organism can be divided into retaining functional characteristics of life smallest unit of life
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Which muscle type is termed voluntary muscle? involuntary muscle?
Muscle Tissue Skeletal Specialized for contraction Three types of muscle tissue: 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 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 peristalsis (wave-like contractions; lumen) Cardiac Involved with MOVEMENT Skeletal – cells are controlled individually or as groups. So if you activate a muscle like your bicep, you don’t necessarily activate all of the fibers there. Voluntary? – skeletal: because you have control Involuntary? – cardiac and smooth; don’t have to tell your heart to beat. Smooth Which muscle type is termed voluntary muscle? involuntary muscle?
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Nervous Tissue Consists of: neurons supporting cells
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 Highly modified cells for communication. Conduct a nerve impulse (action potential: an electrical event) Support cells (non conducting cells): cannot generate nerve impulse may be able to communicate in other ways More neuroglial than neurons Neurons cannot divide (as of now) referred to amiotic
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Epithelial Tissue cover body surfaces & line body cavities
Pseudo-stratified squamous epithelium Simple squamous epithelium cover body surfaces & line body cavities Ex: skin, respiratory tract, urinary.. Serves as a boundary. Police of what can enter and exit tissues and organs Classified according to the number of layers One (simple) more than one (stratified) Flat (squamous), cube (cuboidal) and rectangular (columnar) Always classify TOP layer Simple stratified classified according to number of layers & shape transitional perform a variety of functions - boundary
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ET forms boundaries & thus serves as a barrier to be effective
Site of regulation for substances entering/leaving the body Boundaries are not exclusive to epithelial tissues Find junctional complexes: usually found on apical (top) surface and has a tight junction, adherens junction, and desmosome. 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.)
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Glands Exocrine duct Predominantly an epithelial tissue type
Retain port of cells that forms a duct Exocrine gland: gland that makes a product that secretes it to lumen, has a duct that goes to surface Epithelial cord degenerates and you end up with clusters of epithelial cells forming an endocrine gland: secretion does not go into duct (DUCTLESS glands = Endocrine gland) Exocrine duct
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Exocrine Glands Components: duct secretory unit acinus
classification Components: duct secretory unit acinus myoepithelial cells Duct: helps move the product to be expressed on the surface – ALWAYS simple cuboidal epithelial Secretory unit: Acinus: actually make and secrete a product Myoepithelial cells: lie around the outside of the secretory portion, epithelial cells that have contractile proteins that squeeze secretory portion to help move it to be expressed on the surface of the duct. Simple tubular: one duct and tubular secretory portion Simple acinar: one duct and circle secretory portion Compound: more than one duct
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Connective Tissue Characterized by: Categorized into
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 PANTYHOSE: binds and supports Wide diversity of tissues that fall underneath the category Fiber types: collagen, reticular and elastic Bone compared to areolar CT: both have ground substances, fibers and cell types. But how it all comes together is different Liquid CT: BLOOD areolar CT
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Adipose tissue BONE Dense irregular CT BLOOD
Bone and Cartilage = Supportive Connective Tissue Liquid: Blood CT Proper: (two categories: loose and dense) Dense irregular CT BLOOD
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Organs & Organ Systems architecture of most organs are similar
Most organs have all four tissue types. Integument organ: Epithelial on top, CT, nerve tissue (innervated), muscle tissue (arrector pili muscle) 11 Organ systems in human body. Not circulatory: USE CARDIOVASCULAR, lymphatic vessels are not part of cardiovascular system Not Immune: USE LYMPHATIC SYSTEM, add lymphatic vessels to here. architecture of most organs are similar organ described as a structure composed of 2 or more tissue types
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Stem cells tissues of an organ are comprised of differentiated cells
highly specialized 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 adult stem cells multipotent form related cell types produce ALL specialized cells types of body capable of forming unrelated cell types Stem cells allow for possibilities to treat diseases and aging Now can be specialized for certain functions. Can give diabetic pancreatic islets instead of insulin injections Stem cells come from two different sources (adult and embryonic) Sperm and egg fuse together become diploid and divides to form cleavage stage embryos (called totipotent stem cells) Totipotent – can produce all types of stem cells in the body. EVERYTHING, can make four identical individuals As you go through cleavage stage development, see embryo start to take the form of a blastocyst (starting to differentiate) Pluripotent – capable of forming UNRELATED cell types, limited, can’t make anything we want Then form trilaminar embryo with three germ layers that gives rise to 4 primary tissue types Multipotent stem cells- forms related cell types, further restricted. There are instances that you can take neuroglial cells and can make them into a neuron.
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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 life-sustaining processes Hiccups in the system are seen in TISSUES Everything that is dysfunctional ^^ Cells are the basic units of the society & almost all exhibit fundamental activities common to all forms of life.
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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 who serves as the “barriers”? Plasma membranes of cells and Epithelial cells and blood vessel walls We are aqueous critters, so mainly composed of water. ** Primary solvent is WATER Why is ECF considered more homogenous than ICF fluid? ** ASKED/SITUATION ON TEST. Have a wide variety of different cell types that are gonna be much more individualistic than the ECF fluid compartment. Interstitial fluid and plasma can exchange with each other so they tend to be more similar to each other in their composition Properties of these barriers determine what moves between compartments
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