Chapter 1: The Study of Body Function
Chapter 1: The Study of Body Function BIOL 3160
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This 7 page Class Notes was uploaded by Olivia Addis on Sunday January 17, 2016. The Class Notes belongs to BIOL 3160 at Clemson University taught by Dr. Tamara McNutt-Scott in Fall 2015. Since its upload, it has received 83 views. For similar materials see Human Physiology in Biological Sciences at Clemson University.
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Date Created: 01/17/16
Chapter 1: The Study of Body Function Physiology: the study of how the body works and the different mechanisms that function to meet the needs of the body. Body parts work together at different levels of organization (cells tissues organs organ system.) No “part” works in isolation. Mechanisms have a sequence of events so that they are parts to a larger story. Their effects are only a small party of what is going on in the body as a whole. A misconception of physiology is all is known, but there is much to still be learned in the field. History of Physiology Aristotle – speculated on the function of human body; good health was associated with a balance of humours (fluid) o Black bile, yellow bile, phlegm, and blood Erasistratus – Father of Physiology; dissected live criminals, which allowed him to study the cardiovascular and nervous systems o Also, applied physical laws to the body. William Harvey – Accurately described system circulation that the heart was the pump to move blood through the vessels. o First to study biology quantitatively Claude Bernard – Father of Modern Physiology; o observed the milieu interieur: internal environment remained remarkably constant despite changing external environment term Homeostasis later coined by Cannon to describe this Father of American Physiology th Physiology in the early 19 century was treated as an aspect of theory and practice. o Robey Dunglison brought this to UVA where he taught by explaining successive theories wrote Human Physiology books and was well recognized for his teaching methods Homeostasis & Feedback Control Homeostasis: Maintaining a relatively stable internal environment of equilibrium, by dynamic processes of feedback and regulation o Accomplished by feedback loops as regulatory mechanisms o Every system of the body helps to maintain the body’s equilibrium o Used for medical diagnostic procedures Feedback Mechanism The normal range of values (of a particular variable) is a set point. Changes beyond the set point are picked up by receptors that respond to specific stimuli and send a message along sensory nerve pathways to the integrating center (normally CNS) that makes a decision. The decision goes out from the integrating center through a motor neuron to an effector, which is generally muscles or glands, that responds to bring the variable back within the set point. o Why are feedback mechanisms referred to as a “loop”? “Loop,” emphasizes that the feedback mechanism is a continuous cycle to maintain homeostasis. o EX: A household thermostat that maintains temperature. When the room temperature gets too high, the air conditioning will cut on until the temperature is back within the set point, then the air conditioning is cut off. Questions From Lecture Is our internal environment absolutely constant? o No, the set point is a range and not absolute. Homeostasis is a state of dynamic constancy. Are we always in a state of balance? o The body works really hard so that conditions are stabilized around the set point, but the body may not always be in a state of balance. Negative Feedback Mechanism Most common homeostatic control Reverse direction control mechanism because it moves things in the opposite direction. o Output shuts off the original stimulus. o Continuous and ongoing to maintain the variable in the set point All negative feedback loops prevent sudden change in the body because if this were to happen in the body, it would cause shock and it would not be able to control anything. Antagonistic Effectors: Effectors have antagonistic actions that allow for finer degree of control. Ex: blood concentrations of glucose, calcium, and other substances; heart rate o The blood glucose levels rise, and this is detected by insulinsecreting cells of the pancreas, which acts as the sensor and integration center. Insulinsecreting cells (beta cells) release insulin into the blood. Then, most cells take up more glucose to store as fat and the liver stores it as glycogen. The blood glucose level declines to the set point and the insulinreleasing stimulus decreases as the body returns to homeostasis. The opposite can be achieved if insulin levels were to rise because insulin and glucose are antagonistic effectors. Positive Feedback Mechanism Samedirection control system so that an enhanced response occurs, and the output continues to increase. Episodic and does not occur all of the time so that it does not require continuous adjustments like a negative feedback mechanism does. o Ex: Blood clotting, milk production in breastfeeding, and parturition (childbirth) These mechanisms are limited because the body cannot control them very much. Homeostatic Imbalance puts one at risk for a disease, which are results of conditions and aging o Aristotle’s thoughts of a balance of humours are in line with the understanding that an imbalance in the body fluids would be harmful. Homeostatic Regulation Intrinsic – built into the organ being regulated Extrinsic – outside of the organ regulation by the nervous and endocrine systems o Endocrine system regulates by the secretion of chemicals called hormones into the blood that their target organs respond to. o Nerve fibers innervate the organs so that nerve impulses are conducted to the target organs. EX: Stand up suddenly and the heart rate increases to make up for the drop in blood pressure. Advantages: These mechanisms are selfregulatory and automatic. Disadvantages: They are selfregulatory and automatic. If they are not doing the right thing, it is hard to keep it in check and to fix the problem because they take care of themselves. Levels of Organization Cells: simplest structural unit Tissues: cells with similar functions Organ: primary tissues grouped into anatomical and functional units activities and interactions of tissues determine physiology of organ THE PRIMARY TISSUES 1. Muscle Tissue – Contraction Skeletal Muscle: striated, peripheral nucleus, “Lincoln logs” o attach to bone except for the diaphragm and tongue o made up of myofibers (skeletal muscle cells) o show up in the fourth week of development and fuse together to become multinucleate o bundle arrangement allow for a variation in strength o graded contractions for a spectrum of usage; allows for a specific degree of contraction for finer movements Cardiac Muscle: ybranch shape, uninucleate, striated o found in the wall of the heart and made up of myocardial cells o form a continuous sheet o intercalated discs couple cells mechanically and electrically so they can function as a whole Smooth Muscle: nonstriated (actin and myosin work differently than SkM and CM), fusiform o forms sheet, circularly and/or longitudinally o involved in peristalsis, which are wavelike contractions of a muscle to move something Lecture Question: Which muscle type is termed voluntary muscle? involuntary muscle? Skeletal muscle is voluntary because the organism has conscious control over it, but cardiac and smooth muscle are under involuntary control by the Autonomic Nervous System. 2. Nervous Tissue Neurons: specialized to generate conduct electrical nerve impulse o cell body (soma), dendrites (1+), and axon (only 1) Glial Cells: “nonconducting” cells that support, insulate and protect neuron o more abundant than the neurons o may have a limited ability to divide 3. Epithelial Tissue – cells that form membranes, which cover and line the body surfaces, and of glands, which are derived from these membranes. It performs a variety of functions such as being a boundary, but also absorption and secretion. Classified by the number of their layers and their shape. o Layers: Simple (1 layer), Stratified (2+ layers) o Shape: Squamous (flattened shape), Cuboidal (square), Columnar (taller than it is wide) Epithelial tissue forms barriers via junctional complexes that are a sit of regulation for substances. o Tight junction – seal; Gap junction – allow passage between cells; Desmosome – helps anchor the cells to the basement membrane and distribute stress Glands are made out of epithelial tissue and can be endocrine (ductless) or exocrine (contains a duct). o Exocrine glands are made up of a duct and a secretory unit of acini cells and myoepithelial cells, which have contractile abilities that squeeze acini so that its product will come out. o Exocrine glands are classified by the shape and number of its secretory portions. 4. Connective Tissue – large amount of extracellular material between cells Extracellular Matrix: fibers and ground substance that vary in composition and arrangement between types of connective tissue o ECM made up of interstitial fluid (IF), proteoglycans, and cell adhesion to maintain a fluid and adhesive matrix. o Also, made up of various cell types. Categorized into: CT proper (loose or dense), supportive CT (bone & cartilage), and liquid CT (blood) Organs and Organ Systems Architecture of most organs are similar. An organ is describes as a structure composed of 2+ tissue types. Stem Cells Tissues of an organ are comprised of highly specialized cells that are differentiated for their specific function Differentiation begins during embryonic development o Zygote/embryo – totipotent because it can produce ALL specialized cell types of the body o Blastulation occurs o Blastocyst/implantation – pluripotent stem cells are capable of forming unrelated cell types o trilaminar embryo (ectoderm, mesoderm, and endoderm) gives rise to the 4 primary tissue types Adult stem cells are multipotent, which form related cell types. They make the same tissue that they come from. Hierarchical System to Structural Organization Human body is a complex society of differentiated cells, which combine structurally and functionally to carry out lifesustaining processes. o Cells are the basic unit and exhibit the fundamental activities of all forms of life. Body Fluid Compartments Extracellular Fluid (ECF) – in blood and spaces that surround cells plasma and interstitial fluid Intracellular Fluid (ICF) – fluid within cells Mainly comprised of water – aqueous compartments o properties of water effect the functionality of compartments Composition varies between compartments. ECF is considered more “homogenous” than ICF because there is variability between cells and their function; therefore, their cellular contents. What organ plays an important role in ECF composition/volume? o Kidneys filter blood and eliminate water so they will have the most impact on ECF. Compartmentalization – who serves as the “barriers”? o Epithelial tissue and a plasma membrane o Properties of barriers determine what moves between compartments Compartmentalization gives us optimization of conditions for efficiency and to cost less energy to the body.
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