T1 Phys - Topic 1 - Cells, Tissues, Homeostasis - Apr 2021 PDF

Physiology Module #1: Basic Chemistry Review, Cells & Tissues Levels of Structure Atoms    ultramicroscopic building blocks of matter contain a nucleus (protons and neutrons) and surrounding electrons the number of protons and electrons are equal (Tortora) Molecule: when two or more atoms bond to...

Physiology Module #1: Basic Chemistry Review, Cells & Tissues Levels of Structure Atoms    ultramicroscopic building blocks of matter contain a nucleus (protons and neutrons) and surrounding electrons the number of protons and electrons are equal (Tortora) Molecule: when two or more atoms bond to form a stable structure (Tortora) Compound: a substance made of different atoms (e.g., H2S, CH4) p. 2 Element: a substance made entirely of the same atoms (e.g., oxygen)  4 elements: oxygen, hydrogen, carbon, nitrogen make up 96% of the body’s mass (Tortora) Ion: an atom with an unequal number of protons and electrons (it therefore has a positive or negative charge) (Tortora) Free radical: an atom or molecule with an unpaired electron www.science/howstuffworks.com p. 3 Chemical Reactions   there is energy stored in the bonds between atoms and molecules a chemical reaction occurs when these bonds are formed or are broken Metabolism: the sum of all chemical reactions occurring in the body  anabolism: the building phase of metabolism  simple molecules are combined to make more complex ones  this requires/uses energy  catabolism: the breaking phase of metabolism  complex molecules are broken down into simpler ones  this produces/releases energy ATP (adenosine triphosphate): the ‘energy currency’ of the body    ATP provides a form of energy that is usable by all cells the energy stored in ATP is ‘spent’ to perform many (very important) body functions including:  muscle contraction  cell division  movement of some substances across cell membranes  making large molecules out of smaller ones the energy needed to reform ATP is ‘gained’ by breaking down (i.e. catabolizing) food Consuming/’Spending’ ATP  to get the energy needed to perform various functions, ATP is broken which releases energy (Tortora) Reforming/’Gaining’ ATP    to reform ATP (attach P back on to ADP), you need energy cells get the energy from carbohydrates, fats, and proteins substances used to make energy (i.e. reform ATP) are collectively called energy substrates (Tortora) p. 4 Cellular Preference: depending on the cell, the demand for energy, and the energy substrate available, different substrates will be used Cellular Respiration:     a series of reactions that transfer energy from food to ATP processes can be either anaerobic or aerobic anaerobic: cellular respiration happens without oxygen present/being used aerobic: cellular respiration happens with oxygen present/being used (Tortora) p. 5 Carbohydrate (Glucose) Metabolism      the preferred energy substrate cells use stored glucose (glycogen) or blood glucose the energy released in breaking down glucose is used to reform ADP + Pi into ATP the process of making ATP from glucose occurs in the cell cytoplasm and is called glycolysis through glycolysis, a molecule of glucose is broken into 2 molecules of pyruvic acid and 2 ATP In the Presence of Oxygen (i.e. aerobic)   pyruvic acid enters the mitochondria a series of reactions yield 26‐28 more ATP In the Absence of Oxygen (i.e. anaerobic)   pyruvic acid does not go into the mitochondria – it is converted into lactic acid which quickly converts to lactate lactic acid/lactate diffuses out of the cell into the blood (used by other cells) Fat Metabolism     fat can be used to generate ATP but only in the presence of oxygen (i.e. aerobically) lipolysis: breakdown of stored fat (use the glycerol and fatty acids to make ATP) the # of ATP generated depends on the size of the fat (e.g., palmitic acid  129 ATP) liver cells (hepatocytes) make ketone bodies which are used by other cells (esp. heart, nervous system, kidneys) to make ATP Protein Metabolism    proteins are broken down into amino acids using amino acids to generate ATP takes longer and produces extra wastes only small amounts of proteins/amino acids are used to generate ATP p. 6 Key Cellular Substances Nutrients: substances needed for body structure and function Oxygen (O2): cells need oxygen to function Inorganic Compounds   no carbon water, many salts, acids, bases Water (H2O)    accounts for ~ 65% of body weight nearly all chemical reactions in the body occur in water in a solution, a substance (the solvent) dissolves another substance (the solute) Acids, Bases, and Salts  when inorganic acids, bases, or salts dissolve in water, they separate (dissociate) into ions and become surrounded by water molecules  acid: a substance that dissociates into one or more hydrogen ions (H+)  base: a substance that dissociates into one or more hydroxide ions (OH‐)  salt: a substance that dissociates into positive and negative ions (no H+ or OH‐) pH      the more hydrogen ions (H+) dissolved in a solution, the more acidic it is the more hydroxide ions (OH‐) dissolved in solution, the more basic (alkaline) it is acidity or alkalinity is expressed on the pH scale (values range from 0‐14) 7.0 is neutral the body doesn’t tolerate significant changes in pH (Tortora) p. 7 (Tortora) p. 8 Organic Compounds   contain carbon ATP, proteins, lipids, carbohydrates, nucleic acids Adenosine Triphosphate (ATP): refer to previous notes Proteins        large, complex molecules structures made up of amino acids structural proteins: framework of body parts regulatory proteins: hormones contractile proteins: shorten muscle cells catalytic proteins: regulate biochemical reactions transport proteins: carry substances in the body immunological proteins: help fight off invading pathogens Lipids     fats and other fat‐like substances necessary for many different body functions fatty acids – energy substrates Wikipedia triglycerides are the storage form of excess calories Carbohydrates     function primarily as an energy substrate sugars (e.g., glucose, fructose, sucrose, lactose) starches (major carb source in our diets) glycogen is the storage form of glucose Nucleic Acids  DNA – your genetic material – controls most cell activities  RNA – relays genetic instructions to guide protein synthesis (Tortora) p. 9 The Cell  the smallest functional unit that can retain the necessary characteristics for life (Tortora) Tissue   a group of similar cells that perform a similar function there are 4 major groups of tissue: 1. epithelial 2. connective 3. muscular 4. nervous p. 10 Organ   part of the body composed of at least 2 different kinds of tissue all the tissues involved contribute to a specific function/activity (Netter) Organ System   a group of organs related to each other that perform functions together organ systems operating together form the organism Organism (Tortora) p. 11 Homeostasis       “The condition of balance in the body’s internal environment due to the constant interaction of the body’s many internal regulatory processes.” the body is dynamic – it’s constantly changing the different parts of the body operate within specific parameters – homeostatic mechanisms keep the internal environment within those limits all structures contribute to maintaining homeostasis when something disrupts homeostasis, there are mechanisms that will have the opposite effect most disruptions are mild and temporary and the return to homeostasis is relatively quick Feedback Systems (Loops)  a cycle of events in which the internal environment is:  monitored  evaluated  changed  re‐monitored  re‐evaluated… Terminology   controlled condition: the variable being monitored stimulus: whatever disrupts/changes the controlled condition (disruptions can be external or internal) Components of a Feedback System/Loop  each system/loop will have:  a sensor/receptor  transmission pathways  a control center  an effector(s) Sensor/Receptor    a structure that monitors changes in a controlled condition they detect chemical, electrical, mechanical changes it sends information to the control centre (via a transmission pathway) Transmission Pathway   the nervous and blood vessel pathways relays messages between (1) the sensor/receptor and the control centre and (2) the control centre and the effector (Tortora) p. 12 Control Centre      comprises the nervous and endocrine systems sets the range of values within which the controlled condition should be maintained evaluates and compares the input received from the sensor/receptor against the set range determines the body’s responses to the change in the controlled condition sends the commands (when needed) to the effector (via transmission pathways) Effector    the structure(s) that ultimately produces the response to a given stimulus receives the commands from the control centre produces the response that will change the controlled condition The Lack of Internal Uniformity   the inside of the body is not uniform homeostatic mechanisms also function to maintain key differences in the body Negative and Positive Feedback Systems/Loops  physiological feedback systems/loops are either negative or positive Negative Systems/Loops    reverse changes in the internal environment very stable predominant system/loop Positive Systems/Loops     strengthen changes in the internal environment there must be a mechanism that shuts down the response inherently unstable uncommon (Tortora) p. 13 The Implications of Homeostatic Imbalances/Dysfunctions          if all controlled conditions remain within established limits, homeostasis is maintained and the body stays healthy the body can change the parameters within which it is acceptable to function adaptation: the adjustment of an organism to its environment compensation: the adjustment of an organism to counterbalance a defect if part(s) of the body is dysfunctional (i.e. it can’t or is less able to contribute to maintaining homeostasis), homeostasis will be harder to maintain or may not be maintained there are limits to how much the body can compensate in the short term and the long term…  if homeostasis is mildly affected, you may not notice it (symptoms may be mild)  if homeostasis is moderately affected, disease states can occur  if homeostasis is severely affected, death is possible the body’s fuel is ATP as we age, the ability to maintain and efficiently return to homeostasis decreases p. 14 The Cell Cell Structures Plasma (Cell) Membrane  a flexible, sturdy barrier surrounding the cell contents  separates the cell from the external environment  it contains membrane proteins that identify the cell, strengthen the membrane, and move substances in and out of the cell  it is selectively permeable (it allows some substances to pass through (in or out) and not others)  it is involved in communication (between cells, between cells and their environment) Intracellular fluid (a.k.a. cytosol): fluid inside the cell Extracellular fluid: fluid outside the cell This includes:  fluid between cells (interstitial fluid)  fluid in blood vessels (plasma)  fluid surrounding the brain & spinal cord (cerebrospinal fluid)  contains lots of substances; cells must extract what they need when they need it p. 15 Membrane proteins: proteins embedded within the membrane or attached to one side of the membrane (inside or outside) They function as:  selective channels that allow and/or move molecules from one side of the membrane to the other  receptors that recognize specific molecules  identify the cell  strengthen and support cell membranes and connect adjacent cell membranes Microvilli: finger‐like projections of the plasma membrane that increase surface area (no movement) Cytoplasm: the contents of a cell (everything inside the plasma membrane but outside the nucleus)   2 components intracellular fluid/cytosol (water, dissolved substances) and organelles cell metabolism, storage (Tortora) p. 16 Cytoskeleton: a network of protein filaments within the cytosol It has multiple functions including:  structural framework for cell shape  a scaffold for the organization/placement and movement of cell contents (organelles)  force transmission  aiding in cell movement (Marieb) p. 17 (Porth) (creativebiomart.net) p. 18 Organelles Nucleus (pl. nuclei): rounded or elongated structure usually located near the centre of the cell   the control center for cell ‐ it is responsible for the cell’s metabolism, growth, and reproduction (it contains the genetic material (DNA)) present in all human cells except for red blood cells (RBCs) Ribosomes: site of protein synthesis Endoplasmic Reticulum (rER): site of protein synthesis (ribosomes are attached) Smooth Endoplasmic Reticulum (sER): makes lipid molecules, regulates calcium within the cell and regulates metabolism Golgi Complex (a.k.a. apparatus, body): processes, sorts, packages, and delivers molecules to the plasma membrane or around the cell Lysosomes: break down substances that the cell has taken in or normal parts of the cell that are damaged Mitochondria (sing. mitochondrium): power plants of the cell (they transform organic compounds into energy (ATP) that is easily accessible to the cell) Cilia (sing. cilium): short, hair‐like projections extending from the surface of the cell – their movement causes steady movement of fluid/particles along the cell surface Flagella (sing. flagellum): similar to cilia but longer, they move the cell p. 19 (Tortora) p. 20 Membrane Transport  cells must be able to transport material across the plasma membrane (both in and out)  membrane transport is either passive or active (depending on whether it requires energy)  passive transport (diffusion, osmosis) – no energy is needed to move the substance  active transport (active transport, transport in vesicles) – energy is needed to move the substance Concentration Gradient   a difference in the concentration of a chemical from one place to another (e.g., from the inside to the outside of the plasma membrane) in moving substances in and out and in being selectively permeable, concentration gradients can be formed (and maintained) Passive Processes Diffusion    movement of molecules across the plasma membrane down their concentration gradient both the solvent and the solutes undergo diffusion (they move down their concentration gradients) across the plasma membrane, molecules can either move straight through or go through membrane proteins (Tortora) (Tortora) p. 21 Osmosis  passive movement of water across a selectively permeable plasma membrane from an area of high water concentration to an area of low water concentration  osmosis only occurs when a membrane is permeable to water and not to certain solutes (Tortora) Active Processes Active Transport    the movement of a substance across a membrane against its concentration gradient energy is used/needed to ‘pump’ it in or out of the cell movement is through membrane‐bound proteins (Tortora) p. 22 Transport in Vesicles  vesicle: a small spherical sac  endocytosis: extracellular materials are brought into a cell in a vesicle formed by the plasma membrane  phagocytosis: a form of endocytosis in which the cell engulfs large solid particles like bacteria, viruses, worn‐out cells  exocytosis: vesicles formed in a cell fuse with the plasma membrane and release materials out of the cell Endocytosis (ThoughtCo.com) Exocytosis (ThoughtCo.com) (Tortora) p. 23 Cell Junctions 1. tight junctions: prevent the passage of substances between cells 2. anchoring junctions (anchor cells to one another) 3. gap junctions provide channels to allow substances to pass between cells (Tortora) p. 24 Tissue: a group of similar cells that function together to perform specialized activities  4 types: 1) epithelial 2) connective 3) muscle 4) nervous Epithelial Tissues    cover body surfaces, line hollow organs, body cavities, and ducts, and form glands function as selective barriers, secretory surfaces, and protective surfaces common locations: skin, gastrointestinal tract, respiratory tract, lining of blood vessels and the heart Structure  ‘free’ (a.k.a. ‘apical’) surface  lateral surfaces  basal surface Blood Supply  epithelial tissue is avascular  epithelial tissue has a nerve supply Basement membrane  a thin layer that anchors the epithelial cells to the underlying connective tissue  provides a surface for cell migration during growth or wound healing (Tortora) p. 25 Classification of Epithelial Tissue 1) Layering    simple: one layer, good for the passage of substances pseudostratified: a single layer (not all cells reach the free surface), some have cilia, goblet cells secrete mucous stratified: more than one layer, good for protection 2) Shape    squamous: flat and thin, rapid movement of substances (simple), protection (stratified) cuboidal: cube (or hexagon) shaped, free surface may have microvilli, good for secretion or absorption columnar: taller than wide, free surface may have cilia or microvilli, good for secretion or absorption (Tortora) Glandular Epithelium   gland: one or more cells that make and secrete a particular product 2 kinds: exocrine and endocrine Exocrine glands   secrete their products into ducts (tubes) that empty onto the epithelial surface examples: sweat, salivary, oil Endocrine glands   secrete their products into the interstitial fluid and diffuse directly into the bloodstream without flowing through a duct examples: pituitary, thyroid, adrenals p. 26 (Porth) (Tortora) p. 27 Connective Tissue (CT) Structure    made of extracellular matrix (ECM ‐ the material between the cells) and cells most CTs have a good blood supply most CTs have a nerve supply Functions       protection support/definition binding transportation energy immunity Extracellular matrix  contains:  protein fibres  ground substance Protein Fibres    collagen: white, very strong, resist tensile (pulling) forces (fibre arrangement is determined by the forces acting on the fibres) – Wolff’s Law elastin: yellow, smaller than collagen, strong but stretchy reticular: thin, fine collagen fibres that form branching networks Ground Substance   may be fluid, gel‐like or calcified it supports the cells and through it, substances are exchanged between the blood and the cells p. 28 Connective Tissue Cells  ‐blasts, macrophages, plasma cells, mast cells, adipocytes ‐blasts     each major type of CT contains cells with a name ending in –blast fibroblasts in loose and dense CT osteoblasts in bone chondroblasts in cartilage Fibroblasts: present in all general CT, they produce the protein fibres and the ground substance Macrophages: eat bacteria and cellular debris Plasma cells: part of the immune response (secrete antibodies) Mast cells: make histamine (part of the inflammatory response) Adipocytes: cells that store fat Types of Connective Tissue (5 types) 1) 2) 3) 4) 5) Loose (areolar, adipose, reticular) Dense (regular, irregular, elastic) Bone Cartilage (hyaline, fibrocartilage, elastic) Liquid (blood, lymph) Loose Connective Tissue   more cells and fewer fibres, fibres are loosely intertwined 3 types: a) areolar b) adipose c) reticular a) areolar  most widely distributed CT in the body (the universal packing tissue/glue)  found in and around nearly every body structure (beneath the skin, around blood vessels, nerves, and body organs)  function: strength, elasticity, support p. 29 b) adipose    areolar tissue that contains a lot of adipocytes locations: beneath the skin, around some organs (kidneys, heart, behind eyeball) function: thermoregulation, energy, support, protection (Tortora) c) reticular   locations: liver, spleen, lymph nodes, basement membrane, around blood vessels and muscles function: forms the supporting framework of organs, binds smooth muscle cells, filters and removes old blood cells and microbes (Tortora) p. 30 Dense Connective Tissue   more fibres (mostly collagen), fewer cells 3 types: a) regular b) irregular c) elastic a) regular    collagen is arranged in parallel patterns locations: tendons (muscle to bone) and most ligaments (bone to bone) function: very strong but somewhat pliable structural connections (Tortora) b) irregular    collagen is arranged in random/irregular patterns locations: structure, support function: tensile (pulling strength in many directions (Tortora) p. 31 c) elastic    high elastin content locations: lung tissue, arteries, ligaments between vertebrae function: stretch and recoil (Tortora) Bone     a.k.a. osseous tissue fewer cells with large amounts of collagen fibres the matrix is filled with calcium phosphate salts which make it very hard function: protection and support, movement (Tortora) p. 32 Cartilage      strong and resilient cells are called chondrocytes ground substance has large amounts of collagen, also contains elastin fibres avascular, aneural 3 types: a) hyaline cartilage b) fibrocartilage c) elastic cartilage a) hyaline Cartilage     most common cartilage in the body blue‐white appearance locations: ends of bones, parts of ribs, tip of nose, parts of the throat and lungs, fetal skeleton function: flexibility, support, friction reduction, shock absorption (Tortora) b) fibrocartilage   locations: between vertebrae (intervertebral discs), pubic symphysis, menisci function: support (Tortora) p. 33 c) Elastic Cartilage    has elastin fibres locations: epiglottis, part of the external ear function: support and flexibility while maintaining shape (Tortora) Liquid   blood: cells surrounded by a fluid ECM called plasma  cells: red blood cells, white blood cells, platelets  function: transport system lymph: a plasma‐like fluid in lymphatic vessels – functions in immunity, transportation, fluid regulation (Tortora) p. 34 Muscle Tissue   specialized cells that use ATP in the generation of force 3 types: a) skeletal b) smooth c) cardiac (a) skeletal      a.k.a. striated muscle compartmentalized by CT, they are attached to the skeleton (some attach to the skin) cell structure: cells are cylindrical and can be quite long function: movement and heat production conscious/voluntary control (Tortora) p. 35 (b) smooth     found in the walls of hollow tubes (e.g. lungs, blood vessels, stomach, intestines) involuntary control cell structure: spindle shaped function: constriction of tubes, movement of substances through the tubes (Tortora) (c) cardiac     cell structure: branched striated fibres that fit tightly together function: blood flow/propulsion found only in the heart involuntary control (Tortora) Muscle Tissue Striated Cell Shape Control p. 36 Nervous Tissue   designed for communication 2 types of cells: a) neuroglia b) neurons Neuroglia  they support, nourish, and protect the nervous system (Porth) Neurons   nerve cells 3 parts: dendrite, cell body, axon Dendrite   structure: multiple or single extensions off the cell body function: it is the input portion of the neuron Cell Body (a.k.a. soma, perikaryon)   structure: contains the nucleus and other organelles function: cell processes (e.g. protein synthesis) Axon   a thin cylindrical process off the cell body function: it is the output portion of the neuron p. 37 (Tortora) p. 38