BSC 116 Test Number Three Study Guide
BSC 116 Test Number Three Study Guide BSC 116
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This 39 page Study Guide was uploaded by Ashley Bartolomeo on Thursday April 7, 2016. The Study Guide belongs to BSC 116 at University of Alabama - Tuscaloosa taught by Professor Harris in Spring 2016. Since its upload, it has received 68 views. For similar materials see Principles Biology II in Biological Sciences at University of Alabama - Tuscaloosa.
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Test Number Three Study Guide Chapter 42 Vocabulary Alveolus One of the deadend air sacs where gas exchange occurs in a mammalian lung Arteriole A vessel that conveys blood between an artery and a capillary bed Artery A vessel that carries blood away from the heart to organs throughout the body Atherosclerosis A cardiovascular disease in which fatty deposits called plaques develop in the inner walls of the arteries, obstructing the arteries and causing them to harden Atrioventricular (AV) Node A region of specialized heart muscle tissue between the left and right atria where electrical impulses are delayed for about 0.1 second before spreading to both ventricles and causing them to contract Atrioventricular (AV) Valve A heart valve located between each atrium and ventricle that prevents a backflow of blood when the ventricle contracts Atrium A chamber of the vertebrate heart that receives blood from the veins and transfers blood to a ventricle Blood A connective tissue with a fluid matrix called plasma in which red blood cells, white blood cells and cell fragments called platelets are suspended Bohr Shift A lowering of the affinity of hemoglobin for oxygen, caused by a drop in pH. It facilitates the release of oxygen from hemoglobin in the vicinity of active tissues Breathing Ventilation of the lungs through alternating inhalation and exhalation Bronchiole A fine branch of the bronchi that transports air to alveoli Bronchus One of a pair of breathing tubes that branch from the trachea into the lungs Capillary A microscopic blood vessel that penetrates the tissues and consists of a single layer of endothelial cells that allows exchange between the blood and interstitial fluid Capillary Bed A network of capillaries in a tissue or organ Cardiac Cycle The alternating contractions and relaxations of the heart Cardiac Output The volume of blood pumped per minute by each ventricle of the heart Cardiovascular System A closed circulatory system with a heart and branching network of arteries, capillaries and veins. The system is characteristic of vertebrates Closed Circulatory System A circulatory system in which blood is confined to vessels and is kept separate from the interstitial fluid Countercurrent Exchange The exchange of a substance or heat between two fluids flowing in opposite direction. For example, blood in a fish gill flows in the opposite direction of water passing over the gill, maximizing diffusion of oxygen into and carbon dioxide out of the blood Diaphragm A sheet of muscle that forms the bottom wall of the thoracic cavity in mammals. Contraction of the diaphragm pulls air into the lungs Diastole The stage of the cardiac cycle in which a heart chamber is relaxed and fills with blood Diastolic Pressure Blood pressure in the arteries when the ventricles are relaxed Double Circulation A circulatory system consisting of separate pulmonary and systemic circuits, in which blood passes through the heart after completing each circuit Electrocardiogram A record of the electrical impulses that travel through heart muscle during the cardiac cycle Endothelium The simple squamous layer of cells lining the lumen of blood vessels Erythrocyte A blood cell that contains hemoglobin, which transports oxygen; also called a red blood cell Erythropoietin A hormone that stimulates the production of erythrocytes. It is secreted by the kidney when body tissues do not receive enough oxygen Gas Exchange The uptake of molecular oxygen from the environment and the discharge of carbon dioxide to the environment Heart A muscular pump that uses metabolic energy to elevate the hydrostatic pressure of the circulatory fluid (blood or hemolymp). The fluid then flows down a pressure gradient through the body and eventually returns to the heart Heart Attack The damage or death of cardiac muscle tissue resulting from prolonged blockage of one or more coronary arteries Heart Murmur A hissing sound that most often results from blood squirting backward through a leaky valve in the heart Heart Rate The frequency of heart contraction (in beats per minute) Hemoglobin An iron containing protein in red blood cells that reversibly binds oxygen Hemolymph In invertebrates with an open circulatory system, the body fluid that bathes tissues High Density Lipoprotein (HDL) A particle in the blood made up of thousands of cholesterol molecules and other lipids bound to protein. HDL scavenges excess cholesterol Hypertension A disorder in which blood pressure remains abnormally high Larynx The portion of the respiratory tract containing the vocal cords; also called the voice box Leukocyte A blood cell that functions in fighting infections; also called a white blood cell Low Density Lipoprotein (LDL) A particle in the blood made up of thousands of cholesterol molecules and other lipids bound to a protein. LDL transports cholesterol from the liver for incorporation into cell membranes Lung An infolded respiratory surface of a terrestrial vertebrate, land snail, or spider that connects to the atmosphere by narrow tubes Lymph The colorless fluid, derived from interstitial fluid, in the lymphatic system of vertebrates Lymph Node An organ located along a lymph vessel. Lymph nodes filter lymph and contain cells that attack viruses and bacteria Lymphatic System A system of vessels and nodes, separate from the circulatory system, that returns fluid, protein and cells to the blood Myoglobin An oxygen storing, pigmented protein in muscle cells Open Circulatory System A circulatory system in which fluid called hemolymph bathes the tissues and organs directly and there is no distinction between the circulating fluid and the interstitial fluid Plasma The liquid matrix of blood in which the blood cells are suspended Positive Pressure Breathing – A breathing system in which air is forced into the lungs Pulse The rhythmic bulging of the artery walls with each heartbeat Residual Volume The amount of air that remains in the lungs after forceful exhalation Respiratory Pigment A protein that transports oxygen in blood of hemolymph Semilunar Valve A valve located at each exit of the heart, where the aorta leaves the ventricle and the pulmonary artery leaves the right ventricle Single Circulation A circulatory system consisting of a single pump and circuit, in which blood passes from the sites of gas exchange to the rest of the body before returning to the heart Sinoatrial (SA) node Stem Cell Any relatively unspecialized cell that can produce, during a single division, one identical daughter cell and one more specialized daughter cell that can undergo further differentiation Stroke The death of nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the head Stroke Volume The volume of blood pumped by heart ventricle in a single contraction Surfactant A substance secreted by alveoli that decreases surface tension in the fluid that coats the alveoli Systematic Circuit The branch of the circulatory system that supplies oxygenated blood to and carries deoxygenated blood away from organs and tissues throughout the body Systole The stage of the cardiac cycle in which a heart chamber contracts and pumps blood Systolic Pressure Blood pressure in the arteries during contraction of the ventricles Thrombus A fibrin containing clot that forms in a blood vessel and blocks the flow of blood Tidal Volume The volume of air a mammal inhales and exhales with each breath Trachea The portion of the respiratory tract that passes from the larynx to the bronchi; also called the windpipe Tracheal System In insects, a system of branched, air filled tubes that extends throughout the body and carries oxygen directly to cells Vasoconstriction A decrease in the diameter of blood vessels caused by contraction of smooth muscles in the vessel walls Vasodilation An increase in the diameter of blood vessels caused by relaxation of smooth muscles in the vessel walls Ventilation The flow of air or water over a respiratory surface Ventricle A heart chamber that pumps blood out of the heart Venule A vessel that conveys blood between a capillary bed and a vein Vital Capacity The maximum volume of air that a mammal can inhale and exhale with each breath Key Facts Circulatory systems link exchange surfaces with cells throughout the body In animals with simple body plans, a gastrovascular cavity mediates exchange between the environment and cells that can be reached by diffusion. Because diffusion is slow over long distances, most complex animals have a circulatory system that moves fluid between cells and the organs that carry out exchange with the environment. Arthropods and most molluscs have an open circulatory system, in which hemolymph bathes organs directly. Vertebrates have a closed circulatory system, in which blood circulates in a closed network of pumps and vessels The closed circulatory system of vertebrates consists of blood, blood vessels and a two to four chambered heart. Blood pumped by a heart ventricle passes to arteries and then to the capillaries, sites of chemical exchange between blood and interstitial fluid. Veins return blood from capillaries to an atrium, which passes blood to a ventricle. Fishes, rays and sharks have a single pump in their circulation. Airbreathing vertebrates have two pumps combined in a single heart. Variations in ventricle number and separation reflect adaptations to different environments and metabolic needs Coordinated cycles of heart contraction drive double circulation in mammals The right ventricle pumps blood to the lungs, where it loads O2 and unloads CO2. Oxygen rich blood from the lungs enters the heart at the left atrium and is pumped to the body tissues by the left ventricle. Blood returns to the heart through the right atrium The cardiac cycle, a complete sequence of the heart’s pumping and filling, consists of a period of contraction, called systole, and a period of relaxation, called diastole. Heart function can be assessed by measuring the pulse (number of times the heart beats each minute) and cardiac output (volume of blood pumped by each ventricle per minute). The heartbeat originates with impulses at the sinoatrial (SA) node (pacemaker) of the right atrium. They trigger atrial contraction, are delayed at the atrioventricular (AV) node, and are then conducted along the bundle branches and Purkinje fibers, triggering ventricular contraction. The nervous system, hormones, and body temperature affect pacemaker activity Patterns of blood pressure and flow reflect the structure and arrangement of blood vessels Blood vessels have structures well adapted to function. Capillaries have narrow diameters and thin walls that facilitate exchange. The velocity of blood flow is lowest in the capillary beds as a result of their large total crosssectional area. Arteries contain thickelastic walls that maintain blood pressure. Veins contain oneway valves that contribute to the return of blood to the heart. Blood pressure is altered by changes in cardiac output and by variable constriction of arterioles Fluid leaks out of capillaries and is returned to blood by the lymphatic system, which also defends against infection Blood components function in exchange, transport, and defense Whole blood consists of cells and cell fragments (platelets) suspended in a liquid matrix called plasma. Plasma proteins influence blood pH, osmotic pressure, and viscosity, and they function in lipid transport, immunity (antibodies), and blood clotting (fibrinogen). Red blood cells, or erythrocytes, transport )2. Five types of white blood cells, or leukocytes, function in defense against microorganisms and foreign substances in the blood. Platelets function in blood clotting, a cascade of reactions that converts plasma fibrinogen to fibrin. A variety of diseases impair function of the circulatory system. In sicklecell disease, an aberrant form of hemoglobin disrupts erythrocyte shape and function, leading to blockage of small blood vessels and a decrease in the oxygencarrying capacity of the blood. In cardiovascular disease, inflammation of the arterial lining enhances deposition of lipids and cells, resulting in the potential for lifethreatening damage to the heart or brain. Gas exchange occurs across specialized respiratory surfaces At all sites of gas exchange, a gas undergoes net diffusion from where its partial pressure is higher to where it is lower. Air is more conductive to gas exchange than water because air has a higher O2 content, lower density, and lower viscosity. The structure and organization of respiratory surfaces differ among animal species. Gills are outfoldings of the body surface specialized for gas exchange in water. The effectiveness of gas exchange in some gills, including those of fishes, is increased by ventilation and countercurrent exchange between blood and water. Gas exchange in insects relies on a tracheal system, a branched network of tubes that bring O2 directly to cells. Spiders, land snails, and most terrestrial vertebrates have internal lungs. In mammals, air inhaled through the nostrils passes through the pharynx into the trachea, bronchi, bronchioles, and deadend alveoli, where gas exchange occurs Breathing ventilates the lungs Breathing mechanisms vary substantially among vertebrates. An amphibian ventilates its lungs by positive pressure breathing, which forces air down the trachea. Birds use a system of air sacs as bellows to keep air flowing through the lungs in one direction only, preventing the mixing of incoming and outgoing air. Mammals ventilate their lungs by negative pressure breathing, which pulls air into the lungs when the rib muscles and diaphragm contract. Incoming and outgoing air mix, decreasing the efficiency of ventilation. Sensors detect the pH of cerebrospinal fluid (reflecting CO2 concentration in the blood), and a control center in the medulla oblongata adjusts breathing rate and depth to match metabolic demands. Additional input to the control center is provided by sensors in the aorta and carotid arteries that monitor blood levels of O2 as well as CO2 (via blood pH) Adaptations for gas exchange include pigments that bind and transport gases In the lungs, gradients of partial pressure favor the net diffusion of O2, into the blood and CO2 out of the blood. The opposite situation exists in the rest of the body. Respiratory pigments such as hemocyanin and hemoglobin bind O2, greatly increasing the amount of O2 transported by the circulatory system Evolutionary adaptations enable some animals to satisfy extraordinary O2 demands. Deepdiving mammals stockpile O2 in blood and other tissues and deplete it slowly Chapter 43 Vocabulary Acquired Immunodeficiency Syndrome (AIDS) The symptoms and g present during the late stages of HIV infection, defined by a specified reduction in the number of T cells and the appearance of characteristic secondary infections Active Immunity Longlasting immunity conferred by the action of B cells and T cells and the resulting B and T memory cells specific for a pathogen. Active immunity can develop as a result of natural infection or immunization Adaptive Immunity A vertebratespecific defense that is mediated by B lymphocytes (B cells) and T lymphocytes (T cells) and that exhibits specificity, memory and selfnonself recognition; also called acquired immunity Antibody A protein secreted by plasma cells (differentiated B cells) that binds to a particular antigen; also called immunoglobulin. All antibodies have the same Yshaped structure and in their monomer form consist of two identical heavy chains and two identical light chains Antigen A substance that elicits an immune response by binding to receptors of B or T cells Antigen Presentation The process by which an MHC molecule binds to a fragment of an intracellular protein antigen and carries it to the cell surface, where it is displayed and can be recognized by a T cell Antigen Receptor The general term for a surface protein, located on B cells and T cells, that binds to antigens, initiating adaptive immune responses. The antigen receptors on B cells are called B cell receptors, and the antigen receptors on T cells are called T cell receptors Antigen Presenting Cell A cell that upon ingesting pathogens or internalizing pathogen proteins generates peptide fragments that are bound by class II MHC molecules and subsequently displayed on the cell surface to T cells. Macrophages, dendritic cells, and B cells are the primary antigen presenting cells Autoimmune Disease An immunological disorder in which the immune system turns against itself B Cells The lymphocytes that complete their development in the bone marrow and become effector cells for the humoral immune response Cell Mediated Immune Response The branch of adaptive immunity that involves the activation of cytotoxic T cells, which defend against infected cells Clonal Selection The process by which an antigen selectively binds to and activates only those lymphocytes bearing receptors specific for the antigen. The selected lymphocytes proliferate and differentiate into a clone of effector cells and a clone of memory cells specific for the stimulating antigen Complement System A group of about 30 blood proteins that may amplify the inflammatory response, enhance phagocytosis or directly lyse extracellular pathogens Cytotoxic T Cell A type of lymphocyte that, when activated, kills infected cells as well as certain cancer cells and transplanted cells Dendritic Cell An antigen presenting cell, located mainly in lymphatic tissues and skin, that is particularly efficient in presenting antigens to helper T cells, thereby initiating a primary immune response Effector Cell A lymphocyte that has undergone clonal selection and is capable of mediating an adaptive immune response Epitope A small, accessible region of an antigen to which an antigen receptor or antibody binds Heavy Chain One of the two types of polypeptide chains that make up an antibody molecule and B cell receptor; consists of a variable region, which contributes to the antigen binding site and a constant region Helper T Cell A type of T cell that, when activated, secretes cytokines that promote the response of B cells (humoral response) and cytotoxic T cells (cell mediated response) to antigens Histamine A substance released by mast cells that causes blood vessels to dilate and become more permeable in inflammatory and allergic responses HIV (Human Immunodeficiency Virus) The infectious agent that causes AIDS. HIV is a retrovirus Humoral Immune Response The branch of adaptive immunity that involves the activation of B cells and that leads to the production of antibodies, which defend against bacteria and viruses in body fluids Immune System An organism’s system of defenses against agents that cause disease Immunization The process of generating a state of immunity by artificial means. In vaccination, an inactive or weakened form of a pathogen is administered, inducing B and T cell responses and immunological memory. In passive immunization, antibodies specific for a particular pathogen are administered, conferring immediate but temporary protection Inflammatory Response An innate immune defense triggered by physical injury or infection of tissue involving the release of substances that promote swelling, enhance the infiltration of white blood cells, and aid in tissue repair and destruction of invading pathogens Innate Immunity A form of defense common to all animals that is active immediately upon exposure to a pathogen and that is the same whether or not the pathogen has been encountered previously Interferon A protein that has antiviral or immune regulatory functions. Interferona and interferonb, secreted by virusinfected cells, help nearby cells resist viral infection; interferony, secreted by T cells, helps activate macrophages Light Chain One of the two types of polypeptide chains that make up an antibody molecule and B cell receptor; consists of a variable region, which contributes to the antigen binding site and a constant region Lymphocyte A type of white blood cell that mediates immune responses. The two main classes are B cells and T cells Lysozyme An enzyme that destroys bacterial cell walls; in mammals, it is found in sweat, tears and saliva Macrophage A phagocytic cell present in many tissues that functions in innate immunity by destroying microbes and in acquired immunity as an antigen presenting cell Major Histocompatibility Complex (MHC) Molecule A host protein that functions in antigen presentation. Foreign MHC molecules on transplanted tissue can trigger T cell responses that may lead on rejection of the transplant Mast Cell A vertebrate body cell that produces histamine and other molecules that trigger inflammation in response to infection and in allergic reactions Memory Cell One of a clone of longlived lymphocytes, formed during the primary immune response, that remains in a lymphoid organ until activated by exposure to the same antigen that triggered its formation. Activated memory cells mount the secondary immune response Monoclonal Antibody Any of a preparation of antibodies that have been produced by a single clone of cultured cells and thus are all specific for the same epitope Natural Killer Cell A type of white blood cell that can kill tumor cells and virusinfected cells as part of innate immunity Neutrophil The most abundant type of white blood cell. Neutrophil are phagocytic and tend to selfdestruct as they destroy foreign invaders, limiting their life span to a few days Passive Immunity Short term immunity conferred by the transfer of antibodies, as occurs in the transfer of maternal antibodies to a fetus or nursing infant Pathogen An organism or virus that causes disease Phagocytosis A type of endocytosis in which large particulate substances or small organisms are taken up by a cell. It is carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophils, and dendritic cells) Plasma Cell The antibody secreting effector cell of humoral immunity. Plasma cells arise from antigen stimulated B cells Primary Immune Response The initial adaptive immune response to an antigen which appears after a lag of about 1017 days Secondary Immune Response The adaptive immune response elicited on second or subsequent exposures to a particular antigen. The secondary immune response is more rapid, of greater magnitude, and of longer duration than the primary immune response T Cells The class of lymphocytes that mature in the thymus; they include both effector cells for the cell mediated immune response and helper cells required for both branches of adaptive immunity Thymus A small organ in the thoracic cavity of vertebrates where maturation of T cells is completed Toll Like Receptor (TLR) A membrane receptor on a phagocytic white blood cell that recognized fragments of molecules common to a set of pathogens Key Facts In Innate Immunity, Recognition and Response Rely on Traits Common to Groups of Pathogens In both invertebrates and vertebrates, innate immunity is mediated by physical and chemical barriers as well as cellbased defenses. Activation of innate immune responses relies on recognition proteins specific for broad classes of pathogen. Microbes that penetrate barrier defenses are ingested by phagocytic cells, which in vertebrates include macrophages and dendritic cells. Additional cellular defenses include natural killer cells, which can induce the death of virusinfected cells. Complement system proteins, interferons, and other antimicrobial peptides also act against pathogens. In the inflammatory response, histamine and other chemicals that are released at the injury site promote changes in blood vessels that enhance immune cell access. Pathogens sometimes evade innate immune defenses. For example, some bacteria have an outer capsule that prevents recognition, while others are resistant to breakdown within lysosomes. In Adaptive Immunity, Receptors Provide PathogenSpecific Recognition Adaptive immunity relies on two types of lymphocytes that arise from stem cells in the bone marrow: B cells and T cells. Lymphocytes have cellsurface antigen receptors for foreign molecules (antigens). All receptor proteins on a single B or T cell are the same, but there are millions of B and T cells in the body that differ in the foreign molecules that their receptors recognize. Upon infection, B and T cells specific for the pathogen are activated. Some T cells help other lymphocytes; others kill infected host cells. B cells called plasma cells produce soluble proteins called antibodies, which bind to foreign molecules and cells. Activated B and T cells called memory cells defend against future infections by the same pathogen. Recognition of foreign molecules by B cells and T cells involves the binding of variable regions of receptors to an epitope, a small region of an antigen. B cells and antibodies recognize epitopes on the surface of antigens circulating in the blood or lymph. T cells recognize epitopes in small antigen fragments (peptides) that are presented on the surface of host cells by proteins called major histocompatibility complex (MHC) molecules. This interaction activates a T cell, enabling it to participate in adaptive immunity. The four major characteristics of B and T cell development are the generation of cell diversity, selftolerance, proliferation, and immunological memory. Proliferation and memory are both based on clonal selection Adaptive Immunity Defends Against Infection of Body Fluids and Body Cells Helper T cells interact with antigen fragments displayed by class II MHC molecules on the surface of antigenpresenting cells: dendritic cells, macrophages, and B cells. Activated helper T cells secrete cytokines that stimulate other lymphocytes. In the cell mediated immune response, activated cytotoxic T cells trigger destruction of infected cells. In the humoral immune response, antibodies help eliminate antigens by promoting phagocytosis and complement mediated lysis Active immunity develops in response to infection of to immunization. The transfer of antibodies in passive immunity provides immediate, shortterm protection Tissues or cells transferred from one person to another are subject to immune rejection. In tissue grafts and organ transplants, MHC molecules stimulate rejection. Lymphocytes in bone marrow transplants may cause a graftversushost reaction Disruptions in Immune System Function Can Elicit or Exacerbate Disease In allergies, such as hay fever, the interaction of antibodies and allergens triggers immune cells to release histamine and other mediators that cause vascular changes and allergic symptoms. Loss of selftolerance can lead to autoimmune diseases, such as multiple sclerosis. Inborn immunodeficiency’s result from defects that interfere with innate, humoral, or cellmediated defenses. AIDS is an acquired immunodeficiency caused by HIV. Antigenic variation, latency, and direct assault on the immune system allow some pathogens to thwart immune responses. HIV infection destroys helper T cells, leaving the patient prone to disease. Immune defense against cancer appears to primarily involve action against viruses that can cause cancer and cancer cells that harbor viruses. Chapter 44 Vocabulary Aldosterone A steroid hormone that acts on tubules of the kidney to regulate the transport of sodium ions (Na+) and potassium ions (K+) Ammonia A small, toxic molecule (NH3) produced by nitrogen fixation or as a metabolic waste product of protein and nucleic acid metabolism Angiotensin II A peptide hormone that stimulates constriction of precapillary arterioles and increases reabsorption of NaCl and water by the proximal tubules of the kidney, increasing blood pressure and volume Anhydrobiosis A dormant state involving loss of almost all body water Aquaporin A channel protein in a cellular membrane that specifically facilitates osmosis, the diffusion of free water across the membrane Atrial Natriuretic Peptide A peptide hormone secreted by cells of the atria of the heart in response to high blood pressure. ANP’s effects on the kidney alter ion and water movement and reduce blood pressure Bowman’s Capsule A cupshaped receptacle in the vertebrate kidney that is the initial, expanded segment of the nephron, where filtrate enters from the blood Collecting Duct The location in the kidney where processed filtrate, called urine, is collected from the renal tubules Cortical Nephron In mammals and birds, a nephron with a loop of Henle located almost entirely in the renal cortex Countercurrent Multiplier System A countercurrent system in which energy is expended in active transport to facilitate exchange of materials and generate concentration gradients Distal Tubule In the vertebrate kidney, the portion of a nephron that helps refine filtrate and empties it into a collecting duct Excretion The disposal of nitrogencontaining metabolites and other waste products Filtrate Cellfree fluid extracted from the body fluid by the excretory system Filtration In excretory systems, the extraction of water and small solutes, including metabolic wastes, from the body fluid Glomerulus A ball of capillaries surrounded by Bowman’s capsule in the nephron and serving as the site of filtration in the vertebrate kidney Juxtaglomerular Apparatus A specialized tissue in nephrons that releases the enzyme renin in response to a drop in blood pressure or volume Kidney In vertebrates, one of a pair of excretory organs where blood filtrate is formed and processed into urine Loop of Henle The hairpin turn, with a descending and ascending limb, between the proximal and distal tubules of the vertebrate kidney; functions in water and salt reabsorption Malpighian Tubule A unique excretory organ of insects that empties into the digestive tract, removes nitrogenous wastes from the hemolymph, and functions in osmoregulation Metanephridium An excretory organ found in many invertebrates that typically consists of tubules connecting ciliated internal openings to external openings Nephron The tubular excretory unit of the vertebrate kidney Osmoconformer An animal that is isosmotic with its environment Osmoregulator An animal that controls its internal osmolarity independent of the external environment Peritubular Capillary One of the tiny blood vessels that form a network surrounding the proximal and distal tubules in the kidney Protonephridium An excretory system, such as the flame bulb system of flatworms, consisting of a network of tubules lacking internal openings Reabsorption In excretory systems, the recovery of solutes and water from filtrate Renal Cortex The outer portion of the vertebrate kidney Renal Medulla The inner portion of the vertebrate kidney, beneath the renal cortex Renal Pelvis The funnelshaped chamber that receives processed filtrate from the vertebrate kidney’s collecting ducts and is drained by the ureter ReninAngiotensinAldosterone System (RAAS) A hormone cascade pathway that helps regulate blood pressure and blood volume Secretion (1) The discharge of molecules synthesized by a cell (2) The active transport of wastes and certain other solutes from the body fluid into the filtrate in an excretory system Transport Epithelium One or more layers of specialized epithelial cells that carry out and regulate solute movement Urea A soluble nitrogenous waste produced in the liver by a metabolic cycle that combines ammonia with carbon dioxide Ureter A duct leading from the kidney to the urinary bladder Urethra A tube that releases urine from the mammalian body near the vagina in females and through the penis in males; also serves in males as the exit tube for the reproductive system Uric Acid A product of protein and purine metabolism and the major nitrogenous waste product of insects, land snails, and many reptiles. Uric acid is relatively nontoxic and largely insoluble in water Urinary Bladder The pouch where urine is stored prior to elimination Vasa Recta The capillary system in the kidney that serves the loop of Henle Vein A vessel that carries blood toward the heart Key Facts Osmoregulation Balances the Uptake and Loss of Water and Solutes Freshwater fish live in water less concentrated than body fluids; fish tends to gain water, lose salt. Does not drink water. Salt in (active transport by gills), water in but only salt out. Has large volume of urine but urine is less concentrated than body fluids Marine bony fish live in water more concentrated than body fluids; fish tends to lose water, gain salt. Drinks water. Salt in (active transport by gills) but salt and water out. Has small volume of urine and urine is slightly less concentrated than body fluids. Terrestrial vertebrates live in terrestrial environment; tends to lose body water to air. Drinks water. Salt in (by mouth) but salt and water out. Has moderate volume of urine and urine is more concentrated than body fluids. Cells balance water gain and loss through osmoregulation, a process based on the controlled movement of solutes between internal fluids and the external environment and on the movement of water, which follows by osmosis Osmoconformers are isosmotic with their marine environment and do not regulate their osmolarity. In contrast, osmoregulators control water uptake and loss in a hypoosmotic or hyperosmotic environment, respectively. Waterconserving excretory organs help terrestrial animals avoid desiccation, which can be lifethreatening. Animals that live in temporary waters may enter a dormant state called anhydrobiosis when their habitats dry up. Transport epithelia contain specialized epithelial cells that control the solute movements required for waste disposal and osmoregulation. An Animal’s Nitrogenous Wastes Reflect Its Phylogeny and Habitat Protein and nucleic acid metabolism generates ammonia. Most aquatic animals excrete ammonia. Mammals and most adult amphibians convert ammonia to the less toxic urea, which is excreted with a minimal loss of water. Insects and many reptiles, including birds, convert ammonia to uric acid, a mostly insoluble waste excreted in a pastelike urine The kind of nitrogenous waste excreted depends on an animal’s evolutionary history and habitat. The amount excreted is coupled to the animal’s energy budget and dietary protein uptake. Diverse Excretory Systems Are Variations on a Tubular Theme Most excretory systems carry out filtration, reabsorption, secretion and excretion. Invertebrate excretory systems include the protonephridia of flatworms, the metanephridia or earthworms, and the Malpighian tubules of insects. Kidneys function in both excretion and osmoregulation in vertebrates Excretory tubules (consisting of nephrons and collecting ducts) and blood vessels pack the mammalian kidney. Blood pressure forces fluid from blood in the glomerulus into the lumen on Bowman’s capsule. Following reabsorption and secretion, filtrate flows into a collecting duct. The ureter conveys urine from the renal pelvis to the urinary bladder. The Nephron is Organized for Stepwise Processing of Blood Filtrate Within the nephron, selective secretion and reabsorption in the proximal tubule alter filtrate volume and composition. The descending limb of the loop of Henle is permeable to water but not salt; water moves by osmosis into the interstitial fluid. The ascending limb is permeable to salt but not water; salt leaves by diffusion and by active transport. The distal tubule and collecting duct regulate K+ and NaCl levels in body fluids. In mammals, a countercurrent multiplier system involving the loop of Henle maintains the gradient of salt concentration in the kidney interior. Urea exiting the collecting duct contributes to the osmotic gradient of the kidney Natural selection has shaped the form and function of nephrons in various vertebrates to the osmoregulatory challenges of the animals’ habitats. For example, desert mammals, which excrete the most hyperosmotic urine, have loops of Henle that extend deep into the renal medulla, whereas mammals in moist habitats have shorter loops and excrete more dilute urine. Hormonal Circuits Link Kidney Function, Water balance, and Blood Pressure The posterior pituitary gland releases antidiuretic hormone (ADH) when blood osmolarity rises above a set point, such as when water intake is inadequate. ADH increases the permeability to water of the collecting ducts by increasing the number of epithelial aquaporin channels. When blood pressure or blood volume in the afferent arteriole drops, the juxtaglomerular apparatus releases renin. Angiotensin II formed in response to renin constricts arterioles and triggers releases of the hormone aldosterone, raising blood pressure and reducing the release of renin. This reninangiotensinaldosterone system has function that overlap with those of ADH and are opposed by atrial natriuretic peptide. Chapter 45 Vocabulary Adrenal Gland One of two endocrine glands located adjacent to the kidneys in mammals. Endocrine cells in the outer portion (cortex) respond to adrenocorticotropic hormone (ACTH) by secreting steroid hormones that help maintain homeostasis during longterm stress. Neurosecretory cells in the central portion (medulla) secrete epinephrine and norepinephrine in response to nerve signals triggered by shortterm stress Androgen Any steroid hormone, such as testosterone, that stimulates the development and maintenance of the male reproductive system and secondary sex characteristics Anterior Pituitary A portion of the pituitary gland that develops from nonneural tissue; consists of endocrine cells that synthesize and secrete several tropic and nontropic hormones Antidiuretic Hormone (ADH) A peptide hormone, also called vasopressin, that promotes water retention by the kidneys. Produced in the hypothalamus and released from the posterior pituitary, ADH also functions in the brain Autocrine Referring to a secreted molecule that acts on the cell that secreted it Calcitonin A hormone secreted by the thyroid gland that lowers blood calcium levels by promoting calcium deposition in bone and calcium excretion from the kidneys; nonessential in adult humans Catecholamine Any of a class of neurotransmitters and hormones, including the hormones epinephrine and norepinephrine, that are synthesized from the amino acid tyrosine Endocrine Gland A ductless gland that secrets hormones directly into the interstitial fluid, from which they diffuse into the bloodstream Endocrine System In animals, the internal system of communication involving hormones, the ductless glands that secrete hormones, and the molecular receptors on or in target cells that respond to hormones; functions in concert with the nervous system to effect internal regulation and maintain homeostasis Epinephrine A catecholamine that, when secreted as a hormone by the adrenal medulla, mediates “fightorflight” responses to shortterm stresses; also released by some neurons as a neurotransmitter; also called adrenaline Estradiol A steroid hormone that stimulates the development and maintenance of the female reproductive system and secondary sex characteristics; the major estrogen in mammals Estrogen Any steroid hormone, such as estradiol, that stimulates the development and maintenance of the female reproductive system and secondary sex characteristics Glucocorticoid A steroid hormone that is secreted by the adrenal cortex and that influences glucose metabolism and immune function Growth Hormone (GH) A hormone that is produced and secreted by the anterior pituitary and that has both direct (nontropic) and tropic effects on a wide variety of tissues Hypothalamus The ventral part of the vertebrate forebrain; functions in maintaining homeostasis especially in coordinating the endocrine and nervous systems; secreted hormones of the posterior pituitary and releasing factors that regulate the anterior pituitary Local Regulator A secreted molecule that influences cells near where it is secreted Mechanoreceptor A sensory receptor that detects physical deformation in the body’s environment associated with pressure, touch, stretch, motion, or sound MelanocyteStimulating Hormone (MSH) A hormone produced and secreted by the anterior pituitary with multiple activities, including regulating the behavior of pigment containing cells in the skin of some vertebrates Melatonin A hormone that is secreted by the pineal gland and that is involved in the regulation of biological rhythms and sleep Mineralocorticoid A steroid hormone secreted by the adrenal cortex that regulates salt and water homeostasis Negative Feedback A form of regulation in which accumulation of an end product of a process slows the process; in physiology, a primary mechanism of homeostasis, whereby a change in a variable triggers a response that counteracts the initial change Negative Pressure Breathing A breathing system in which air is pulled into the lungs Nervous System In animals, the fastacting internal system of communication involving sensory receptors, networks of nerve cells, and connections to muscles and glands that respond to nerve signals; functions in concert with the endocrine system to effect internal regulation and maintain homeostasis Neurohormone A molecule that is secreted by a neuron, travels in body fluids, and acts on specific target cells, changing their functioning Neurotransmitter A molecule that is released from the synaptic terminal of a neuron at a chemical synapse, diffuses across the synaptic cleft, and binds to the postsynaptic cell, triggering a response Nitric Oxide (NO) A gas produced by many types of cells that functions as a local regulator and as a neurotransmitter Norepinephrine A catecholamine that is chemically and functionally similar to epinephrine and acts as a hormone or neurotransmitter; also called noradrenaline Oxytocin A hormone produced by the hypothalamus and released from the posterior pituitary. It induces contractions of the uterine muscles during labor and causes mammary glands to eject milk during nursing Paracrine Referring to a secreted molecule that acts on a neighboring cell Parathyroid Gland One of four small endocrine glands, embedded in the surface of the thyroid gland, that secretes parathyroid hormone Parathyroid Hormone (PTH) A hormone secreted by the parathyroid glands that raises blood calcium level by promoting calcium release from bone and calcium retention by the kidneys Pheromone In animals and fungi, a small molecule released into the environment that functions in communication between members of the same species. In animals, it acts much like a hormone in influencing physiology and behavior. Pineal Gland A small gland on the dorsal surface of the vertebrate forebrain that secretes the hormone melatonin Pituitary Gland An endocrine gland at the base of the hypothalamus; consists of a posterior lobe, which stores and releases two hormones produced by the hypothalamus, and an anterior lobe, which produces and secretes many hormones that regulate diverse body functions. Pons A portion of the brain that participates in certain automatic, homeostatic functions, such as regulating the breathing centers in the medulla Positive Feedback A form of regulation in which an end product of a process speeds up that process; in physiology, a control mechanism in which a change in a variable triggers a response that reinforces or amplifies the change Posterior Pertaining to the rear, or tail end, of a bilaterally symmetrical animal Posterior Pituitary An extension of the hypothalamus composed of nervous tissue that secretes oxytocin and antidiuretic hormone made in the hypothalamus; a temporary storage site for these hormones Progesterone A steroid hormone that prepares the uterus for pregnancy; the major progestin in mammals Progestin Any steroid hormone with progesteronelike activity Prolactin A hormone produced and secreted by the anterior pituitary with a great diversity of effects in different vertebrate species. In mammals, it stimulates growth of and milk production by the mammary glands Prostaglandin One of a group of modified fatty acids that are secreted by virtually all tissues and that perform a wide variety of functions as local regulators Proximal Tubule In the vertebrate kidney, the portion of a nephron immediately downstream from Bowman’s capsule that conveys and helps refine filtrate Signal Transduction The linkage of a mechanical, chemical or electromagnetic stimulus to a specific cellular response Testosterone A steroid hormone required for development of the male reproductive system, spermatogenesis, and male secondary sex characteristics; the major androgen in mammals Thyroid Gland An endocrine gland, located on the ventral surface of the trachea, that secretes two iodinecontaining hormones, triiodothyronin (T3) and thryoxine (T4), as well as calcitonin Thyroid Hormone Either of two iodinecontaining hormones (triiosothyronine and thyroxine) that are secreted by the thyroid gland and that help regulate metabolism development and maturation in vertebrates Thyroxine (T4) One of two iodinecontaining hormones that are secreted by the thyroid gland and that help regulate metabolism, development and maturation in vertebrates Tropic Hormone A hormone that has an endocrine gland or endocrine cells as a target Utricle In the vertebrate ear, a chamber in the vestibule behind the oval window that opens into the three semicircular canals Key Facts Hormones and other signaling molecules bind to target receptors, triggering specific response pathways The forms of signaling between animal cells differ in the type of secreting cell and the route taken by the signal to its target. Endocrine signals, or hormones, are secreted into the extracellular fluid by endocrine cells or ductless glands and reach target cells via circulatory fluids. Paracrine signals act on neighboring cells, whereas autocrine signals act on the secreting cell itself. Neurotransmitters also act locally, but neurohormones can act throughout the body. Pheromones are released into the environment for communication between animals of the same species. Local regulators, which carry out paracrine and autocrine signaling, include cytokines and growth factors (polypeptides), prostaglandins (modified fatty acids), and nitric oxide (a gas). Polypeptides, steroids and amines comprise the major classes of animal hormones. Depending on whether they are water soluble or lipid soluble, hormones activate different response pathways. Feedback regulation and coordination with the nervous system are common in endocrine signaling Hormone pathways may be regulated by negative feedback, which dampens the stimulus, or positive feedback, which amplifies the stimulus and drives the response to completion In insects, molting and development are controlled by three hormones: PTTH; ecdysteroid, whose release is triggered by PTTH; and juvenile hormone. Coordination of signals from the nervous and endocrine systems and modulation of one hormone activity by another bring about the sequence of developmental stages that lead to an adult form In vertebrates, neurosecretory cells in the hypothalamus produce two hormones that are secreted by the posterior pituitary and that act directly on nonendocrine tissues: oxytocin, which induces uterine contractions and release of milk from mammary glands, and antidiuretic hormone (ADH), which enhances water reabsorption in the kidneys. Other hypothalamic cells produce hormones that are transported to the anterior pituitary, where they stimulate or inhibit the release of particular hormones, Often, anterior pituitary hormones act in a cascade. For example, the secretion of thyroidstimulating hormone (TSH) is regulated by thyrotropinstimulating hormone (TRH). TSH in turn induces the thyroid gland to secrete thyroid hormone, a combination of the iodinecontaining hormones T3 and T4. Thyroid hormone stimulates metabolism and influences development and maturation. Most anterior pituitary hormones are tropic hormones, acting on endocrine tissues or glands to regulate hormone secretion. Tropic hormones of the anterior pituitary include TSH, follicle stimulating hormone (FSH), luteinizing hormone (LH), and adrenocorticotropic hormone (ACTH). Growth hormone (GH) has both tropic and nontropic effects. It promotes growth directly, affects metabolism and stimulates the production of growth factors by other tissues. Endocrine glands respond to diverse stimuli in regulating homeostasis, development and behavior Parathyroid hormone (PTH), secreted by the parathyroid glands, causes bone to release Ca2+ into the blood and stimulates reabsorption of Ca2+ in the kidneys. PTH also stimulates the kidneys to activate vitamin D, which promotes intestinal uptake of Ca2+ from food. Calcitonin, secreted by the thyroid, has the opposite effects in bones and kidneys as PTH. Calcitonin is important for calcium homeostasis in adults of some vertebrates, but not humans. In response to stress, neurosecretory cells in the adrenal medulla release epinephrine and norepinephrine, which mediate various fightorflight responses. The adrenal cortex releases glucocorticoids, such as cortisol, which influence glucose metabolism and the immune system. It also releases mineralocorticoids, primarily aldosterone, which help regulate salt and water balance. Sex hormones regulate growth, development, reproduction and sexual behavior. Although the adrenal cortex produces small amounts of these hormones, the gonads (testes and ovaries) serve as the major source. All three types – androgens, estrogens and progestins – are produced in males and females, but in different proportions The pineal gland, located within the brain, secretes melatonin, which functions in biological rhythms related to reproduction and sleep. Release of melatonin is controlled by the SCN, the region of the brain that functions as a biological clock. Hormones have acquired distinct roles in different species over the course of evolution. Prolactin stimulates milk production in mammals but has diverse effects in other vertebrates. Melanocyte stimulating hormone (MSH) influences fat metabolism in mammals and skin pigmentation in other vertebrates. Chapter 46 Vocabulary Abortion The termination of a pregnancy in progress Acrosome A vesicle in the tip of a sperm containing hydrolytic enzymes and other proteins that help sperm reach the egg Asexual Reproduction The generation of offspring from a single parent that occurs without the fusion of gametes (by budding, division of a single cell, or division of the entire organism into two or more parts). In most cases, the offspring are genetically identical to the parent Astrocyte A glial cell with diverse functions, including providing structural support for neurons, regulating the interstitial environment, facilitating synaptic transmission, and assisting in regulating the blood supply to the brain Birth Control Pills A hormonal contraceptive that inhibits ovulation, retards follicular development, or alters a woman’s cervical mucus to prevent sperm from entering the uterus Blastocyst The blastula stage of mammalian embryonic development, consisting of an inner cell mass, a cavity, and an outer layer, the trophoblast. In humans, the blastocyst forms 1 week after fertilization Cervix The neck of the uterus, which opens into the vagina Clitoris An organ at the upper intersection of the labia minora that engorges with blood and becomes erect during sexual arousal Cloaca A common opening for the digestive, urinary and reproductive tracts found in many nonmammalian vertebrates but in few mammals Conception The fertilization of an egg by a sperm in humans Contraception The deliberate prevention of pregnancy Corpus Luteum A secreting tissue in the ovary that forms from the collapsed follicle after ovulation and produces progesterone Ectopic Occurring in an abnormal location Egg The female gamete Ejaculation The propulsion of sperm from the epididymis through the muscular vas deferens, ejaculatory duct, and urethra Endometriosis The condition resulting from the presence of endometrial tissue outside the uterus Endometrium The inner lining of the uterus, which is richly supplied with blood vessels Epididymis A coiled tubule located adjacent to the mammalian testis where sperm are stored Estradiol A steroid hormone that stimulates the development and maintenance of the female reproductive system and secondary sex characteristics; the major estrogen in mammals Estrous Cycle A reproductive cycle characteristic of female mammals except humans and certain other primates, in which the nonpregnant endometrium is reabsorbed rather than shed, and sexual response occurs only during midcycle at estrus Fetus A developing mammal that has all the major structures of an adult. In humans, the fetal stage lasts from the 9 week of gestation until birth Follicle A microscopic structure in the ovary that contains the developing oocyte and secretes estrogens Follicle Stimulating Hormone (FSH) A tropic hormone that is produced and secreted by the anterior pituitary and that stimulates the production of eggs by the ovaries and sperm by the testes Gametogenesis The process by which gametes are produced Glans The rounded structure at the tip of the clitoris or penis that is involved in sexual arousal Gonad A male or female gamete producing organ Hermaphroditism A condition in which an individual has both female and male gonads and functions as both a male and a female in sexual production by producing both sperm and eggs In Vitro Fertilization Fertilization of oocytes in laboratory containers followed by artificial implantation of the early embryo in the mother’s uterus Labia Majora A pair of thi
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