Normal Cell Structure and Function Spr2024 Lecture Notes

Normal Cell: Structure & Function Dr. Stefany Primeaux [email protected] Lecture 01 Why are we interested in the structure and function of the “normal” cell? Cells are the fundamental units of life. Communication between cells/tissues/systems Understanding Pathophysiology begins with understanding t...

Normal Cell: Structure & Function Dr. Stefany Primeaux [email protected] Lecture 01 Why are we interested in the structure and function of the “normal” cell? Cells are the fundamental units of life. Communication between cells/tissues/systems Understanding Pathophysiology begins with understanding the cell! Outline These topics should mostly be a review Learning Objectives at end of PPT Begins with the Cell Understanding Pathophysiology begins with understanding the cell Injury to any cellular component can lead to disease Cell dysfunction and/or death Epithelial Cells: Crohn’s disease, skin carcinomas Connective Tissue cells: Marfan syndrome, Rheumatoid arthritis Muscle Cells: Sarcopenia, heart failure Neural Cells: Parkinson’s, Alzheimer's Epithelial Cells Apical surface Epithelial cells cover and line body surfaces. Epithelial cells are specialized for the selective secretion and absorption of ions and organic molecules, and for protection. Replicate often to replace damaged or dead cells Aid in the transportation of filtered material through the use active-transport systems Innervated and provide sensory information Avascular Basal surface Basement membrane What are some examples of epithelial cells? Epithelial Cells Examples of Diseases: Eczema, Psoriasis, Dermatitis, Carcinoma, Peptic ulcers Epithelial cells are the target. Lectures on skin disorders, GI disorders, genetic disorders, etc. Connective tissue cells Connective tissue cells connect, anchor, and support the structures of the body. Most abundant tissue in the body. These tissues form a framework for the body. Two major structural proteins: Collagen & Elastin Connective tissue diseases is any disease that has the connective tissue of the body as a primary target of pathology. Many feature abnormal immune activity with inflammation. Leukocytes (white blood cells) Leukocytes (WBC) & Fibroblasts are critical for Wound Healing Fibroblasts secrete Collagen, which is important for maintaining the structural framework of tissues and extracellular matrix (ECM). Play a Critical Role in Wound Healing. Picrosirius red stain: collagen stain Connective tissue cells Examples of Diseases: Rheumatoid Arthritis, Lupus, Scleroderma, Marfan Syndrome, Ehlers-Danlos Syndrome Connective tissue is the target! Lectures on Inflammation, Infection/Immunity, Diabetes, musculoskeletal disorders, skin disorders, etc. Muscle Cells There are 3 types of muscle cells in the human body: Skeletal Muscle: anchored by tendons to bone and is used to effect skeletal movement such as locomotion and in maintaining posture. Voluntary muscle Cardiac Muscle: is similar skeletal muscle, but only found in heart. Involuntary muscle Smooth Muscle: found within the walls of organs and structures such as the esophagus, stomach, intestines, bladder, blood vessels. Involuntary muscle Examples of Diseases: Lou Gehrig’s Disease, Atrophy, Muscular Dystrophy Myasthenia Gravis Cardiomyopathy Muscle cells are the target. Lectures on musculoskeletal disorders, cardiovascular disease, etc. Neurons A neuron is a cell of the nervous system that is specialized to initiate, integrate and conduct electrical signals to other cells. Neurons/nerve cells are the target. Dysfunction of neurons can affect these processes! Examples of Diseases: Multiple Sclerosis, Parkinson’s, Alzheimer’s, Stroke, Shingles, Depression Lectures on disorders of Brain Function, Pain, addiction, stress Functions of Cell Membrane Membranes form a major structural element in cells! Cell is surrounded by a phospholipid bilayer 1. Membranes separate or compartmentalize ions and molecules 1. Allow for the development of fluid compartments in body 2. Detecting chemical signals from other cells 3. Link adjacent cells together by membrane junction Fluid compartments in body Fluid compartments are separated by selectively permeable membranes that control movement of water and solutes TOTAL BODY WATER (TBW) = 42L, 60% BW INTRACELLULAR FLUID (ICF) volume = 28 L, 2/3 TBW INTRACELLULAR FLUID volume = 28 L, 2/3 TBW Na+ K+ Cl- 14 mM 140 mM 15 mM EXTRACELLULAR FLUID (ECF) volume = 14 L, 1/3 TBW INTERSTITIAL PLASMA Volume FLUID =3L volume = 11 L 20% 80% of ECF of ECF Na+ K+ Cl- 140 mM 4 mM 105 mM **Volume of body fluid compartment depends on amount of solute it contains. Movement of Water & Solutes across Cell Membrane Cell membranes act as barriers that considerably slow the diffusion of molecules across their surfaces. POLAR POLAR POLAR POLAR H2O H2O H2O Limiting factor is the hydrophobic interior of the cell membrane’s phosopholipid bilayer. Movement of Solutes Solutes want to move from area of high concentration to area of low concentration Proteins imbedded in cell membrane control diffusion across the membrane and set up concentration differences. Fluid Distribution: Sodium and Water Balance Amount of sodium in body is a prime determinant of ECF volume Solutes (NaCl) confined to ECF. Dietary salt overload (NaCl) adds NaCl and increases total [solute]ECF Dietary water overload decreases total [solute]ECF Water follows salt! [Na+]PLASMA indicates water balance - NOT Na+ balance [Na+]ECF controls ECF/ICF water distribution Movement of Water & Molecules Osmosis is the movement of water across a semipermeable membrane. Osmolarity is the total concentration of all solutes in a solution. Defined as the number of osmoles of solute per liter (L) of solution. Osmolarity takes into account the total concentration of penetrating solutes and non-penetrating solutes Tonicity is the ability of an extracellular solution to make water move into or out of a cell by osmosis. A solution’s tonicity is related to its osmolarity. Lecture on Fluid & Electrolyte Imbalances How does tonicity affect these red blood cells? Let’s add: 0.9% saline solution (normal saline) Isotonic, normal NaCl (~300mOsm) 0.4% saline solution Hypotonic , Low NaCl What can move across cell membrane? 1.9% saline solution Hypertonic, High NaCl Water moves to restore “normal” ECF: Na+ = 140 ICF: Na+ = 14 Cell Communication (chemical communication) Cell communication Autocrine, paracrine, endocrine, neuroendocrine Hydrophilic or lipophilic signal Cells regulate their responses to chemical messengers by increasing or decreasing the number of active receptors on their surface Signal Transduction Neurons/Nerves: Electrical Signals (electrical communication) Electrical Potential Electro-chemical gradient Inside of cell is negative compared to outside of cell Resting membrane potential Graded Potentials Hyperpolarize (IPSP) Depolarize (EPSP) Action Potentials Neurons communicate by chemical and electrical signals Outline These topics should mostly be a review Learning Objectives Understand the different cell types and their functions and roles in the body. Understand the functions of the cell membrane and how ions and molecules move across the cell membrane. Understand fluid compartments and the relationship between Na+ and water. Practice what would happen if you added excess salt or excess fluids/water to your diet. Think in terms of tonicity and water flow. Understand cell communication and receptor regulation. Understand action potentials and ion movement which can increase or decrease the likelihood of generating an action potential. Cell Adaptation Dr. Stefany Primeaux [email protected] Spring 2024 Lecture 02 Why do we care about Cell Adaptation? All diseases exert their effects on the smallest living unit of the body: The Cell Cells are able to adapt to changes in work demands or threats to survival. When injured, cells can: 1. 2. Develop adaptive, compensatory changes in an attempt to maintain homeostasis Develop maladaptive changes, which are derangements of structure or function Outline I. Cell Differentiation & Proliferation II. Adaptations of Growth & Differentiation III. Cell injury IV. Cell Death V. Wound Healing Cell Population Cell population is determined by a balance of cell proliferation, death by apoptosis and emergence of newly differentiated cells from stem cells Cell numbers increased by mitotic division Tissue size is directly related to changes in cell size and/or number! Cell becomes more specialized in structure & function Cell numbers decrease by programmed cell death Practice Question Mr. King has hypertension and his doctor told him that now his heart has to work harder. Cells often adapt in response to an injury or an increase in work demand. In general, tissue size will increase with: A. B. C. D. Increased proliferation and increased apoptosis Increased proliferation and decreased apoptosis Decreased proliferation and increased apoptosis Decreased proliferation and decreased apoptosis Answer: B Rationale: Proliferation, or cell division, increases the number of cells in a tissue. Apoptosis, or programmed cell death, decreases the number of cells in a tissue. If proliferation is increased, tissue size increases. If apoptosis decreases, cell death decreases; cell numbers and tissue size increase Cell Differentiation: Stem Cells Differentiation: when cells become more specialized in structure and function Depends on internal and external stimuli