Anatomy and Physiology I Final Exam Study Guide From Exam

Anatomy and Physiology I Final Exam Study Guide From Exam 1: Lesson 2 (slides 3-18, 21-31, 35-52) Introduction • 1665 Robert Hooke inspected thin slices of cork and found they consisted of millions of small, irregular units • This research produced the cell theory o Cells are building blocks of all plants and animals o All cells come from division of preexisting cells o Cells are smallest units that perform all vital physiological functions o Each cell maintains homeostasis at cellular level • Cytology- the study of cellular structure and function; part of cell biology- integrates aspects of biology, chemistry and physics • Two general classes of cells: o Sex cells (germ/reproductive cells)-are either the sperm of males or oocytes of females o Somatic cells- include all other cells in human body 3-1 • Plasma membrane- outer boundary of a cell, also called cell membrane o Physical isolation-physical barrier that separates inside of cell from surrounding extracellular fluid o Regulation of exchange with environment- plasma membrane controls entry of ions and nutrients, eliminations of wastes and release of secretions o Sensitivity to environment- first part of the cell affected by changes in the composition, concentration or pH of extracellular fluid ▪ Contain receptors that allow cell to recognize and respond to specific molecules in its environment o Structural support- specialized connections between plasma membrane, or between membranes and extracellular materials give tissues stability • Plasma membrane is extremely thin and contains lipids, proteins and carbohydrates • Membrane lipids-form most of the surface area of the plasma membrane but only make up 42% of its weight o Plasma membrane is called the Phospholipid bilayer-phospholipid molecules in it form two layers o Has hydrophilic end (phosphate portion) and hydrophobic end (lipid portion) o In each half of bilayer, lie with hydrophilic heads at membrane surface and hydrophobic tails in inside o Also contains cholesterol and small quantities of other lipids o Water and solutes cannot cross the lipid portion of the plasma membrane • Membrane proteins-account for about 55% of weight of plasma membrane o Integral proteins-part of membrane structure and cannot be removed with damaging/destroying the membrane ▪ Most span the width of the membrane one or more times, therefore known as transmembrane proteins ▪ Greatly o Peripheral proteins-bound to the inner or outer surface of the membrane and easily separated from it • Different types of functional proteins: o Anchoring proteins-attach plasma membrane to other structures and stabilize its position ▪ Inside cell, membrane proteins are bound to the cytoskeleton ▪ Outside the cell, other membrane proteins may attach cell to extracellular protein fibers or to another cell o Recognition proteins (identifiers)-cells of immune system recognize other cells as normal or abnormal based on presence or absence of characteristic recognition proteins o Enzymes-may be integral or peripheral; catalyze reactions in extracellular fluid or in cytosol, depending on location of the protein and its active site o Receptor proteins- sensitive to the presence of specific extracellular molecules called ligands ▪ Extracellular ligand will bind to appropriate receptor, causing changes in the activity of the cell o Carrier proteins-bind solutes and transport them across the plasma membrane ▪ May require ATP as energy source o Channels-some integral proteins contain a central pore or channel that forms a passageway across the plasma membrane ▪ Permits movement of water and small solutes across plasma membrane ▪ Many are highly specific and permit passage of only one ion 3-5 • Permeability- property of plasma membrane that determines precisely which substances can enter or leave the cytoplasm • Impermeable- membrane through which nothing can pass • Freely permeable-membrane through which any substance can pass without difficulty • The permeability of plasma membrane lies between these extremes, making it selectively permeable • Distinction may be based on size, electrical charge, molecular shape, lipid solubility • Passive processes move ions or molecules across the membrane with no expenditure of energy from the cell • Active processes require the cell to expend energy, in form of ATP (generally) • Types of transport include: diffusion (passive), carrier-mediated transport (passive or active), vesicular transport (active) • 1. Diffusion- when the net movement of a substance from an area of higher concentration to an area of lower concentration o Difference between high and low concentrations is called concentration gradient o Diffusion tends to eliminate this gradient o Described as proceeding down a concentration gradient or downhill o Factors that influence diffusion rates: ▪ Distance-the shorter the distance, the more quickly concentration gradients are eliminated ▪ Molecule size- the smaller the molecule size, the faster concentration gradients are eliminated ▪ Temperature- the higher the temperature, the faster the diffusion rate ▪ Concentration gradient- the larger the concentration gradient, the faster diffusion will proceed ▪ Electrical forces-opposite electrical chargers attract each other, and like charges repel • Interior of membrane has net negative charge due to high concentration of proteins; pulls positive ions from extracellular fluid into the cell, while opposing entry of negative ions • The net result of the chemical and electrical forces acting on any ion is called the electrochemical gradient o An ion or molecule can diffuse across plasma membrane only by crossing the lipid portion of the membrane or passing through a membrane channel o Simple diffusion- alcohol, fatty acids, steroids, lipid soluble drugs, dissolved gases; can enter cells easily because they can diffuse through lipid portions of membrane o Channel mediated diffusion- whether an ion can cross a membrane channel depends on: size and charge of ion, size of hydration sphere, interactions between ion and channel walls ▪ Leak channels- (passive channels), remain open and allow passage of ions across plasma membrane o Osmosis-special case of diffusion, net diffusion of water across a membrane (osmosis for movement of water, diffusion for movement of solutes) ▪ Each solute in a solution diffuses as though it were the only material in solution- concentration gradient of another ion has no effect on rate of another ion’s diffusion ▪ Water molecules tend to flow across a membrane toward the solution containing the higher solute concentration- because this movement is down the concentration gradient for water ▪ Osmosis is diffusion of water molecules across selectively permeable membrane ▪ Occurs across a selectively permeable membrane that is freely permeable to water but not to solutes ▪ Water flows across selectively permeable membrane toward solution with higher concentration of solutes, where concentration of water is lower o Osmolarity and tonicity ▪ Total solute concentration in an aqueous solution is it’s Osmolarity, or osmotic concentration ▪ When we describe effects of various osmotic solutions on cells we use term tonicity instead of Osmolarity because the nature of solutes is often as important as the total Osmolarity ▪ Isotonic- solution that does not cause an osmotic flow of water into or out of the cell ▪ Osmolarity refers to the solute concentration of the solution while tonicity is a description of how the solution affects a cell ▪ Hypotonic solution-water will flow into the cell, causing it so swell; may burst and release contents, known as hemolysis ▪ Hypertonic solution-causes cell to lose water by osmosis, causing the cell to shrivel known as crenation ▪ Normal saline- NaCl, given to patients to combat sever blood loss or dehydration; isotonic to the body cells ▪ Dextran-carbohydrate that cannot cross membrane, elevate the Osmolarity of the blood, and as osmosis draws water into the vessels from the extracellular fluid, blood volume increases 3-6 • 2. Carrier-mediated transport-integral proteins bind specific ions or organic substrates and carry them across the plasma membrane o Specificity- each carrier protein in plasma membrane will bind and transport only certain substances o Saturation limits- availability of substrate molecules and carrier proteins limits the rate of transport into or out of cell ▪ When all available carrier proteins operate at max speed, carriers are called saturated; rate of transport cannot increase regardless of size of concentration gradient o Regulation- hormones provide an important means of coordinating carrier protein activity ▪ Co transport (symport)- carrier transports two substances in same direction at same time, either into or out of the cell ▪ Counter transport (antiport)- one substance moves into cell and other moves out o Two examples: o 1. Facilitated diffusion-molecule to be transported first binds to a receptor site on carrier protein, shape of protein then changes, moving the molecule across the membrane and releasing it into the cytoplasm ▪ No ATP is expended, molecules move from area of higher to lower concentration (once carriers are saturated, rate of transport cannot increase, regardless of further increases in gradient) ▪ All cells move glucose by facilitated diffusion o 2. Active transport- high energy bond (ATP or another compound) provides energy needed to move ions or molecules across membrane ▪ Not dependent on concentration gradient- cell can import or export specific substrates, regardless of their intracellular or extracellular concentrations ▪ Carrier proteins called ion pumps actively transport cations sodium NA+, potassium K+, calcium Ca 2+ and magnesium Mg2+ across membranes ▪ Specialized cells transport additional ions, such as iodide I-, chloride Cl- and iron Fe2+ ▪ Sometimes one carrier protein will move more than one kind of ion at the same time; if counter transport occurs, the carrier protein is called an exchange pump ▪ Sodium-Potassium exchange pump: sodium and potassium are the principle cations in body fluids • Sodium concentrations are high in extracellular fluids but low in cytoplasm while potassium is low in the extracellular fluid and high in cytoplasm • Exchanges intracellular sodium for extracellular potassium- for each ATP consumed, three sodium ions are ejected and two potassium ions reclaimed • If ATP is available, rate of transport depends on concentration of sodium in cytoplasm ▪ Secondary active transport-transport itself doesn’t require energy from ATP but cell often needs to expend ATP at a later time to preserve homeostasis • Moves substrate down its concentration gradient but unlike proteins in facilitated transport, these carrier proteins can also move another substrate at the same time without regard to its concentration gradient • The gradient for one substance provides the driving force needed by the carrier protein, and the second substance gets a free ride o 3. Vesicular transport- materials move into or out of the cell in vesicles, small membranous sacs that form at, or fuse with, the plasma membrane ▪ Known as bulk transport • 1. Endocytosis-extracellular materials are packaged in vesicles at the cell surface and imported into the cell o Involve large volumes of extracellular material and requires energy in form of ATP o Vesicles known as endosomes- those formed by pinocytosis are called pinosomes and those by phagocytosis phagosomes o 1. Receptor mediated Endocytosis-highly selective and produces vesicles that contain a specific target molecule in high concentrations ▪ Materials in extracellular fluid bind to receptors on the membrane surface, most receptor molecules being glycoproteins ▪ Each receptor molecule binds a specific ligand or target, such as a transport protein or hormone ▪ Receptors bound to ligand cluster together and once area of membrane has become covered with ligands, it forms grooves or pockets that move to one area of the cell and then pinch off to form an endosome ▪ Endosomes produced in this process are called coated vesicles-protein fiber network that first carpeted inner membrane surface beneath receptor ligand clusters now surrounds them ▪ Coated vesicles fuse with primary lysosomes filled with digestive enzymes, create secondary lysosomes-lysosomal enzymes then free ligands from their receptors and the ligands enter the cytoplasm by diffusion or active transport o 2. Pinocytosis- (cell drinking) formation of endosomes filled with extracellular fluid ▪ Not as selective as receptor-mediated Endocytosis because no receptor proteins are involved ▪ A deep groove or pocket forms in the plasma membrane and then pinches off o 3. Phagocytosis- (cell eating) produces phagosomes containing solid objects that may be as large as the cell itself ▪ Cytoplasmic extensions called pseudopodia surround the object, and their membranes fuse to form a phagosome ▪ This vesicle then fuses with many lysosomes, which enzymes then digest its contents ▪ Performed only be specialized cells • 2. Exocytosis-vesicle created inside the cell fuses with and becomes part of the plasma membrane o Vesicle contents are released into extracellular environment From Exam 2: Lesson 8-9 (slides 5-7, 14-52, 62-75) : Five functions of skeletal system • Skeletal system- includes bones of the skeleton and the cartilages, ligaments and other connective tissues that stabilize or interconnect the bones • Support- provides structural support for entire body; provide framework for attachment of soft tissues and organs • Storage of minerals and lipids- calcium salts act as reserves that maintain normal concentrations of calcium and phosphate ions in body fluids; bones store energy reserves as lipids in areas filled with yellow bone marrow • Blood cell production- red blood cells, white blood cells and other blood elements produced in red bone marrow filling cavities of many bones • Protection-surround soft tissues and organs; ribs protect heart/lungs, skull the brain, vertebrae shield spinal cord, pelvis cradles digestive/reproductive organs • Leverage- function as levers that can change magnitude and direction of forces generated by muscles 6-2 • Bones are classified by o Shape, bone markings (surface features; marks), internal tissue organization (spongy, compact) • Bone structure (Internal tissue organization of bones) o Diaphysis- extended tubular shaft of the bone ▪ At each end is an expanded area known as the epiphysis ▪ Connected to each epiphysis at narrow zone known as the metaphysis ▪ Wall of diaphysis consists of a layer of compact bone or dense bone • Compact bone-solid, forms a sturdy protective layer that surrounds a central space called medullary cavity or marrow cavity ▪ Epiphysis consists largely of spongy bone called cancellous/trabecular bone • Spongy bone- consists of open network of struts and plates that resembles latticework with a thin covering or cortex of compact bone o Structure of a flat bone ▪ Resembles spongy bone sandwich with compact bone covering core of spongy bone ▪ In the cranium, layer of spongy bone between compact is called the diploe ▪ Red bone marrow is present within the spongy bone but no medullary cavity as in the long bone : Osteocytes, osteoblasts, osteoprogenitor cells, osteoclasts