Cellular Physiology - Week 1 Student Notes PDF

Cellular Physiology P T 8 2 0 2 , A P P L I E D P H Y S I O LO GY Objectives I. Review foundational concepts of cellular physiology II. Cellular Transport III. Application Guyton and Hall. Medical Physiology, 14 th...

Cellular Physiology P T 8 2 0 2 , A P P L I E D P H Y S I O LO GY Objectives I. Review foundational concepts of cellular physiology II. Cellular Transport III. Application Guyton and Hall. Medical Physiology, 14 th Ed. 2021. Objective I: Review Cell Structure and Function There are over 200 different Cells are the basic structural and function unit of types of human cells; the living tissue entire body contains about 35-40 trillion cells Each tissue or organ is an aggregate of many different cells held together by intercellular supporting structures Each cell is specially adapted to perform one or a few particular functions (form follows function) Cell types are often very different from one another, but also contain certain basic characteristics © 2013 Pearson Education Inc.  Cells Tissues Organs Systems © 2013 Pearson Education, Inc. Microorganisms Living in the Body Outnumber Human Cells Not only are there many human cells in our bodies – there are trillions of microbes on skin In mouth Gut Nose Can cause diseases, but most of the time they live in harmony with their human hosts and provide vital functions that are essential for survival of their hosts Cell Structure Major components: Nucleus, cytoplasm and plasma/cell membrane Substances that make up the cell: Water: make up 70-85% of cell (except in adipose cells) Ions: important for cellular reactions and some cellular control mechanisms (Sodium, Potassium, Calcium) Proteins: 10-20% of cell mass; divided into structural vs functional (enzymes) Lipids: group of substances that are soluble in a fat solvent Guyton and Hall. Medical Physiology, 14 th Carbohydrates: play a major role in cell nutrition and Ed. 2021. structural formation -Glycocalyx- carbohydrate coating of cell Plasma Membrane or Cell membrane Structure: Lipid bilayer Phospholipid: hydrophobic core and hydrophilic head; serves as a barrier to movement of most molecules into/out of cell Cholesterol- structure, rigidity Proteins: integral (protrude through membrane; channels) and peripheral (enzymes or controllers of transport through membrane) Functions: Separates (provides protection for) intracellular contents from extracellular environment Selective transport: transport nutrients into the cell, toxins out of the cell Cell recognition via surface antigens Cell communication Guyton and Hall. Medical Physiology, 14 th Ed. 2021. Tissue organization Review Cell Structure and Function Koeppen, B., & Stanton, B. (2018). Berne & Levy physiology (Seventh edition). Elsevier. Application Structure Function Application Provide energy through ATP hydrolysis for cellular Oxidative phosphorylation; Mitochondria processes such as muscle ATP synthesis contraction and nerve impulse propagation. Sarcoplasmic Reticulum Controls skeletal muscle (skeletal muscle endoplasmic Ca2+ storage, regulation contraction and relaxation reticulum) Proteins serve as structural support, biochemical catalysts, hormones, Ribosomes Translate RNA to proteins enzymes, and building blocks (eg actin and myosin skeletal muscle are proteins) Cellular Functions Barrier and Transport Migration plasma membrane acts a selective Capacity of cells to move within the barrier body more to come on cellular transport Eg. To form tissues (in embryo); immune response Digestion Metabolism digestion and removal of unwanted Sum of anabolic (formation and materials within the cell maintenance) and catabolic (breakdown) processes Signaling Communicate and response to signals Cell Division from their environment Formation of new cells Many are chemicals in the ECF secreted Mitosis and meiosis by endocrine (distant) glands, paracrine (nearby) glands, or autocrine (self) Cell Death Apoptosis- planned/programmed cellular death Digestion by the cell Cell lives and grows – needs nutrients and other substances to do this Most substances pass through cell process of diffusion or active transport - Endocytosis more on this later Lysosomes within the cell bind to vesicle release acid hydrolases and begin to breakdown or digest substances – glucose Residual bodies are then excreted through exocytosis Autophagy and recycling Lysosomes play big part in the recycling of used/old units of the cell Autophagy – eat ones self obsolete organelles, large proteins aggregates are degraded and recycled Key mechanism for tissue development, cell survival and maintenance of homeostasis Energy extraction form Nutrients Cellular Locomotion Outside of cardiac, skeletal, and smooth muscle movement there are 2 types of cellular locomotion 1. Ameboid movement: crawling type movement of an entire cell in relation to its surroundings (ex. WBC’s or leukocytes) 2. Ciliary movement : cilia perform whiplike movement on the surface of cells (respiratory airways) Guyton and Hall. Medical Physiology, 14 th Ed. 2021. Objective II. Cellular Transport Movement of substances across the cell membrane, either into or out of cell Critical for all components of cell function Helps maintain homeostasis Foundation for action potentials Transport of Substances Through Cellular Membranes intracellular fluid extracellular fluid most fluid is intracellular, though about 1/3 of body fluid is extracellular Extracellular fluid is in constant motion and contains the ions and nutrients needed by the cells to maintain life thus, ECF has been labeled the ‘internal environment’ of the body or ‘milieu interieur’ by Claud Bernard (19th century) transport is critical for maintaining homeostasis, providing cells with nutrients, removing wastes, and keeping cells Guyton and Hall. Medical Physiology, 14 th Ed. 2021. viable  Extracellular fluid Fluid is transported through the body in two stages movement of blood through the body in the blood vessels movement of fluid between the blood capillaries and the intercellular spaces between the tissue cells Cellular Transport Cellular Transport Active Passive Transport Transport (uses energy) (no energy) Primar Vesicles Diffusion Osmosis y Secondar Endocyto Exocytosi Facilitat Simple ed y sis s Channel Carrier Proteins Proteins Types of Cellular Transport Passive Molecules freely move Net movement determined by electrochemical gradient Active Cell “spends energy” to move molecules Molecules are typically moved against electrochemical gradient Review: Electrochemical Gradient Gradient of electrochemical potential, determines how/what moves across a membrane Chemical component: difference in solute concentration (image A) rate of diffusion inward is proportional to concentration of molecules on outside and vice versa flow from areas of high to low Electrical component: difference in charge across the membrane (image B) even with no difference in concentration, an electrical potential applied across a membrane causes ions to flow from one side of the membrane to another Guyton and Hall. Medical Physiology, 14 th Ed. 2021. These will eventually balance out = equilibrium potential Diffusion Spontaneous net movement of molecules from an area of high concentration to an area of lower concentration, driven by collision of molecules Driven by concentration gradient (how much of substance is on one side of the membrane vs the other) other factors that can influence diffusion: altering the channel or carrier protein structure (gating), electrical gradient, pressure Two types: Simple ahdictionary.com Guyton and Hall. Medical Physiology, 14 th Facilitated Ed. 2021. Diffusion Simple: movement of molecules down concentration gradient from area of high to low concentration Facilitated: movement of molecules across a membrane with help: Carrier mediated via protein carrier specific for one chemical; binding of substrate causes transport protein to change shape Channel mediated: through a channel protein; mostly ions selected on basis of size and charge ahdictionary.com Diffusion Carrier mediated facilitated diffusion: changing shape of protein ahdictionary.com Selective permeability of Protein channels Highly selective for transport of one or more specific ion or molecule Different selectivity for various ion channels are believed to determine the specificity of various channels for a particular ion Sodium, potassium  Rates of Diffusion The role of concentration of a substance on its rate of diffusion In general: increased concentration = increase rate of diffusion Facilitated diffusion reaches a maximal rate or “Vmax” Application: glucose crosses some cell Guyton and Hall. Medical Physiology, 14 th membranes by facilitated diffusion; insulin can Ed. 2021. increase rate of facilitated diffusion, increasing Cellular Transport Cellular Transport Active Passive Transport Transport (uses energy) (no energy) Primar Vesicles Diffusion Osmosis y Secondar Endocyto Exocytosi Facilitat Simple ed y sis s Channel Carrier Proteins Proteins Osmosis Movement, diffusion of water across a membrane; the most abundant substance that diffuses through the cell membrane Move through specific water channels called aquaporins Osmotic Pressure: the amount of pressure required to stop osmosis * Application: osmosis causes cells to swell and shrink; any change in the cell volume can disrupt function, especially in neurons Cellular Transport Cellular Transport Active Passive Transport Transport (uses energy) (no energy) Primar Vesicles Diffusion Osmosis y Secondar Endocyto Exocytosi Facilitat Simple ed y sis s Channel Carrier Proteins Proteins  Active Transport Primary: requires energy directly from ATP hydrolysis Energy from ATP changes shape of transport protein that ‘pumps’ solutes or ions across the membrane (eg. Na+-K+ pump); ATP-dependent transporters Active transport Secondary: requires energy indirectly from ionic gradients created by primary active transport; solute carriers Primary active transport dependent When sodium ions are transported out of cells by primary active transport, a large concentration gradient of sodium ions across the cell membrane develops  Vesicular Transport Endocytosis: transport into the cell (vital for cells to obtain nutrients and other substances to live and grow) phagocytosis: cellular internalization or ingestion of large particles pinocytosis: non-specific uptake of small molecules and water into the cell receptor-mediated endocytosis: allows for uptake of specific molecules, must have certain receptor Exocytosis: transport out of the cell Transcytosis: transport into, across, and out of cell Example: Phagocytosis Vesicular trafficking: transport from one area or organelle in a cell to another © 2013 Pearson Education, Inc. Membrane Transport Proteins Proteins involved in the movement of molecules across membranes I. Aquaporins (osmosis) Enable water movement Can be regulated by hormones II. Ion Channels Selective (most) vs. nonselective Gating Voltage gated channels: open/close in response to electrical membrane potential changes Chemical/Ligand gated channels: open and close in response to chemical binding Example: Guyton and Hall. Medical Physiology, 14 th Gating Ed. 2021. Membrane Transport Proteins III. Solute carriers (transporters) 2 types: Uniporter (facilitated transport): transports single molecule Cotransport: transports more than one molecule at a time (ex. secondary active transport) Symporter: transports two or more molecules in same direction Antiporter (exchange transporter): two ore more molecules transported in opposite direction IV. ATP-Dependent Transporters: Involved in primary active transport Example: P-type ATPases; phosphorylates ATP Na+/K+-ATPase: 1 ATP=3Na+ out, 2K+ in So Why do PTs Really Care?? Extracellular Edema Occurs when excess fluid accumulates in the extracellular spaces 1. abnormal leakage of fluid from the plasma to the interstitial spaces across the capillaries – osmosis or gradient change 2. Failure of the lymphatics to return fluid from the interstitium back into the blood, often called lymphedema  Health Condition Diabetes mellitus (DM2) metabolic disorder characterized by hyperglycemia (elevated blood glucose) mediated by insufficient pancreatic insulin secretion, insulin resistance in peripheral tissues (skeletal muscles!), and inadequate suppression of glucagon production Condition that impacts normal cellular transport! Spellman CW. Pathophysiology of Type 2 Diabetes: Targeting Islet Cell Dysfunction. :6.  Skeletal muscle plays a large role in maintaining blood glucose homeostasis Between 70-90% of glucose from blood is taken up by skeletal muscle in the post-prandial state (after a meal). Normal Glucose Uptake by Skeletal Muscle Ske Normal Insulin response Guyton & Hall 4Ed DM Type II - Insulin response  What role do we play? Regular aerobic training has been shown to increase GLUT4 transport to the skeletal muscle cell 20-70%. Counteract hyperglycemia by reducing blood glucose levels. Evans PL, McMillin SL, Weyrauch LA, Witczak CA. Regulation of Skeletal Muscle Glucose Transport and Glucose Metabolism by Exercise Training. Nutrients. 2019;11(10). doi: 10.3390/nu11102432 Thank you!