University:
Kentucky State University
Course:
BIO 303 | Human Physiology
Academic year:

2024
Views:

499

Pages:

54
Author:

Arielle Armstrong

INTRODUCTION TO PHYSIOLOGY AND TRANSPORT Anatomy and Physiology Defined • Two branches of science that deal with body’s parts and function • Anatomy • The science of body structures and relationships • First studies by dissection (cutting apart) • Imaging techniques • Physiology • The science of body functions Levels of Structural Organization Levels of structural organization ▪ Chemical level: Atoms (C, H, O, N, P, Ca, S), Molecules (DNA, H2O, Glucose) ▪ Cellular level: Cells are the basic structural and functional unit of any organism ▪ Tissue level: Groups of cells and surrounding materials that perform a certain function. ▪ Organ level: composed of different types of tissues that have a recognizable shape and specific functions. ▪ System level (organ-system level): consists of related organs with a common function. ▪ Organismal level: All parts of the body The Eleven Systems of The Human Body The Eleven Systems of The Human Body Basic Life Processes Metabolism: Sum of all chemical processes in the body • Catabolism: Breakdown • Anabolism: build up • Responsiveness: ability to detect and respond to changes • Movement • Growth: hypertrophy(size) and proliferation(no.) • Differentiation: development of a cell from unspecialized (precursor,stem)to a specialized state. • Basic Life Processes • Reproduction: Formation of new cells for growth, repair or replacement or formation of a new individual Homeostasis • A condition of equilibrium (balance) in the body’s internal environment. • Dynamic condition • Shift occur in a narrow range that is compatible with maintaining life. • Example • Blood glucose levels range between 70 and 110 mg of glucose/dL of blood • Whole body contributes to maintain the internal environment within normal limits Homeostasis and Body Fluids • Maintaining the volume and composition of body fluids is important • Body fluids are defined as dilute, watery solutions containing dissolved chemicals inside or outside of the cell • Intracellular Fluid (ICF) • Fluid within cells • Extracellular Fluid (ECF) • Fluid outside cells • Interstitial fluid is ECF between cells and tissues Interstitial Fluid and Body Function • Cellular function depends on the regulation of composition of interstitial fluid (Body’s internal environment) • Composition of interstitial fluid changes as substances move across capillary walls to: • provide nutrients (glucose, oxygen, ions) to tissue cells • remove waste (carbon dioxide) from tissue cells Control of Homeostasis • Homeostasis is constantly being disrupted • Physical insults • Intense heat or lack of oxygen • Changes in the internal environment • Drop in blood glucose due to lack of food • Physiological stress • Demands of work or school • Disruptions • Mild and temporary (balance is quickly restored) • Intense and Prolonged (poisoning or severe infections) • REGULATING SYSTEMS: mainly nervous system and endocrine system Feedback System (Loop) • Cycle of events • Body status is monitored and re-monitored • Each monitored variable is termed a controlled condition • Any change is called a stimulus • Three Basic components • Receptor, ex; nerve endings • Control center, ex; brain • Effector, ex; muscle Feedback Systems • Receptor • Body structure that monitors changes in a controlled condition • Sends input to the control center • Nerve ending of the skin in response to temperature change Feedback Systems • Control Center • Brain • Sets the range of values to be maintained • Evaluates input received from receptors and generates output command • Nerve impulses, hormones • Brain acts as a control center receiving nerve impulses from skin temperature receptors Feedback Systems • Effector • Receives output from the control center • Produces a response or effect that changes the controlled condition • Found in nearly every organ or tissue • Body temperature drops the brain sends and impulse to the skeletal muscles to contract • Shivering to generate heat Negative and Positive Feedback systems • The response feeds back information to the control center to change controlled condition: • Negative Feedback systems • Reverses a change in a controlled condition (Occurs more often) • Regulation of blood pressure (force exerted by blood as it presses again the walls of the blood vessels) • Positive Feedback systems • Strengthen or reinforce a change in one of the body’s controlled conditions (not very often) • Normal child birth Negative Feedback: Regulation of Blood Pressure Good • External or internal stimulus increase BP • Baroreceptors (pressure sensitive receptors) • Detect higher BP • Send nerve impulses to brain for interpretation • Response sent via nerve impulse sent to heart and blood vessels • BP drops and homeostasis is restored • Drop in BP negates the original stimulus thing Positive Feedback Systems: Normal Childbirth • Uterine contractions pushes baby to cervix • Stretch-sensitive receptors in cervix send impulse to brain • Oxytocin is released into the blood • Contractions are enhanced and so Oxytocin release and baby pushes farther down the uterus • Cycle continues to the birth of the baby (no stretching) Good thing Positive Feedback: Blood Loss • Normal conditions, heart pumps blood under pressure to body cells (oxygen and nutrients) • Severe blood loss • Blood pressure drops • Cells receive less oxygen and function less efficiently • If blood loss continues • Heart cells become weaker • Heart pumping decrease • BP continues to fall more • May lead to death Bad thing Homeostatic Imbalances • Normal equilibrium of body processes are disrupted • Moderate imbalance • Disorder: any abnormality of structure and function • Disease: specific term for an illness with recognizable signs and symptoms • Signs are objective changes such as a fever, swelling or high blood pressure • Symptoms are subjective changes such as headache • Severe imbalance • Death Cells and homeostasis Cell structure: 1. Plasma membrane • forms the cell’s outer boundary • separates the cell’s internal environment from the outside environment • lipid bilayer: Glycerol head (hydrophilic backbone) and fatty acid (hydrophobic tail) • is a selective barrier: • lipid soluble substances cross the lipid bilayer • water soluble substances only cross through channels • plays a role in cellular communication Cell structure: 2. Cytoplasm - all the cellular contents between the plasma membrane and the nucleus - cytosol - the fluid portion, mostly water - organelles - subcellular structures having characteristic shapes and specific functions Fig. 3.1 Generalized Body Cell Cell Structure 3. Nucleus - large organelle that contains DNA - contains chromosomes, each of which consists of a single molecule of DNA and associated proteins - a chromosome contains thousands of hereditary units called genes Plasma Membrane • Flexible yet sturdy barrier • The fluid mosaic model - the arrangement of molecules within the membrane resembles a sea of lipids containing many types of proteins • The lipids act as a barrier to certain substances • The proteins act as “gatekeepers” to certain molecules and ions Structure of a Membrane • Consists of a lipid bilayer - made up of phospholipids, cholesterol and glycolipids • Integral proteins – firmly embedded and extended into or through the lipid bilayer • Transmembrane proteins - most integral proteins, span the entire lipid bilayer • Peripheral proteins – more loosely attached to the inner or outer surface of the membrane, do not extend through it Structure of the Plasma Membrane Structure of a Membrane • Glycoproteins - membrane proteins with a carbohydrate group attached that protrudes into the extracellular fluid • Glycocalyx - the “sugary coating” surrounding the membrane made up of the carbohydrate portions of the glycolipids and glycoproteins; functions: • Signature • Adherence • protection • attracts fluid Functions of Membrane Proteins • Integral proteins are Ion channels Transporters - selectively move polar or ionic substances through the membrane Receptors - for cellular recognition; a ligand is a molecule that binds with a receptor Enzymes - catalyze chemical reactions Linkers Mechanical activities and division • Membrane glycoprotein and glycolipids often are: Cell-identity markers, ex. ABO blood type • Peripheral proteins: support the plasma membrane Fig 3.03 Membrane Permeability • The cell is either permeable or impermeable to certain substances • The lipid bilayer is permeable to oxygen, carbon dioxide and steroids, slightly permeable to water and urea (small uncharged), but impermeable to glucose ( large polar uncharged). • Transmembrane proteins act as channels and transporters to assist the entrance of certain substances, for example, glucose and ions. Very selective • Macromolecules such as proteins only pass by endocytosis and exocytosis. Gradients Across Plasma Membrane • Concentration gradient: Difference in the concentration of a chemical from one place to another ( Na and O2 outside, K and CO2 inside) • Electrical gradient: Difference in electrical charges between two compartments. (Membrane Potential) • Both help substances move across the plasma membrane down their Chemical or electrical gradient to reach equilibrium. (Electrochemical gradient) Diffusion • Passive process due to particles kinetic energy • Move down the concentration gradient( high to low) • Factors affecting Diffusion rate: ✓Steepness of conc. Gradient (directly) ✓Temperature (directly) ✓Mass of diffusing substance (indirectly) ✓Surface area (directly) ✓Diffusion distance (indirectly) Diffusion Simple Diffusion • Through the lipid bilayer: fast • O2, CO2, N • Fatty acids • Steroids • Fat soluble vitamins (A,E,D,K) • Small alcohol and ammonia • H2O and Urea (slightly) Facilitated Diffusion • Through membrane ion channels: slower due to surface area. • mostly; K+, Cl• Na+, Ca+2 • gated channels: open/close • Has a maximum velocity Simple vs. Facilitated Diffusion Simple Diffusion vs. Facilitated Diffusion simple diffusion rate of diffusion  (Co-Ci) Rate of diffusion Vmax • Vmax=Maximum velocity • In Facilitated:Transp ort rate increases as the concentration of the solute increases until the carriers are saturated facilitated diffusion Concentration gradient (Co-Ci) Passive vs. Active Transport • Passive processes - substances move across cell membranes without the input of any energy; use the kinetic energy of individual molecules or ion. • Active processes - a cell uses energy, primarily from the breakdown of ATP, to move a substance across the membrane, i.e., against a concentration gradient Passive vs. Active Transport Passive: Simple Diffusion, Channelmediated Facilitated Diffusion, and Carriermediated Facilitated Diffusion High Low Transport maximumsaturation Channel-mediated Facilitated Diffusion of Potassium ions through a Gated K + Channel Extracellular fluid Glucose 1 Plasma membrane Cytosol Glucose transporter Glucose gradient 2 3 Glucose Carrier-mediated Facilitated Diffusion of Glucose across a Plasma Membrane Active Transport Primary Na+ gradient Extracellular fluid Na+/K+ ATPase Cytosol K+ gradient 3 Na+ expelled P 3 Na+ 1 2K+ ATP 2 ADP 3 P + 4 2K imported Solutes are transported across plasma membranes with the use of energy, from an area of lower concentration to an area of higher Concentration Sodiumpotassium pump Active Transport • Primary Active ex; Na+/K+ ATPase Pump, the most prevalent Work non stop to maintain low intracellular Na+ and high intracellular K+. (Direct use of energy) • Secondary active The energy stored (Kinetic) in a Na+ or H+ conc. gradient is used to drive other substances against their gradient. ( indirectly uses ATP by a primary active pump). Symporters (same direction) and antiporters (different direction) Secondary active transport Osmosis • Net movement of water through a selectively permeable membrane from an area of high concentration of water (lower concentration of solutes) to one of lower concentration of water • Water can pass through plasma membrane in 2 ways: through lipid bilayer by simple diffusion through water channels called aquaporins (integral membrane proteins) 1. 2. Osmolarity • The concentration of osmotically active particles in a solution. • Osmolarity= conc.(mol/L) * number of particles • Number of particles (E.g., NaCl=2, glucose=1) • Not: Molarity is the number of molecules per liter. mol/L Fig 3.6 This Membrane is impermeable to the solute Osmosis, Hydrostatic pressure and Osmotic pressure • Hydrostatic pressure: Pressure exerted by a liquid • Osmotic pressure: Due to impermeable solute particles concentration(high conc.) Colloidosmotic pressure or oncotic pressure: Osmotic pressure created by proteins. • Tonicity and its effect on RBCS Lysis, explode Shrink Clinical Application on solutions tonicity • Intravenous solutions: • Normally: Isotonic ( Saline 0.9% NaCl) and (Dextrose 5%) • Cerebral edema: hypertonic solution are useful • Severe dehydration: hypotonic solutions Transport in Vesicles • Vesicle - a small spherical sac formed by budding off from a membrane to transport macromolecules. • Endocytosis - materials move into a cell in a vesicle formed from the plasma membrane; types: 1. receptor-mediated endocytosis (specific) 2. phagocytosis 3. bulk-phase endocytosis (pinocytosis) • Exocytosis - vesicles fuse with the plasma membrane, releasing their contents into the extracellular fluid ( cells e.g., endocrine cells and nerve cells) • Transcytosis - a combination of endocytosis and exocytosis. E.g., Intestine cells, endothelial cells. • All of the above mechanisms require energy from ATP 1 Binding Receptor-LDL complex Receptor-Mediated Endocytosis Plasma membrane LDL particle Receptor Invaginated plasma membrane Clathrin-coated pit 2 Vesicle formation Clathrin-coated vesicle 3 Uncoating Transport vesicle Uncoated vesicle 4 Fusion with endosome 5 Recycling of receptors to plasma membrane Endosome Transport vesicle Digestive enzymes Lysosome 6 Degradation in lysosome Phagocytosis Phagocytosis: • Endocytosis where the cell engulfs large solid particles(dead cell, microorganism) • Cells carry out endocytosis; e.g., Neutrophils and macrophages • Binding of the particle to a plasma membrane protein causes pseudopods extension around the particle. • Phagosome formation • Fusion with lysosome for digestion Bulk-phase Endocytosis • In which a droplet of extracellular fluid, no receptor needed. • Most body cells carry out bulk phase endocytosis esp. kidney and intestine • Also known as Pinocytosis

Introduction to Physiology and Transport

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