Physiology Semester 1 Past Paper PDF

Cell and transport mechanism, Homeostasis Dr.Rasha Eldeeb Associate Professor of Physiology www.gmu.ac.ae COLLEGE OF HEALTH SCIENCES  Cell and transport mechanism,...

Cell and transport mechanism, Homeostasis Dr.Rasha Eldeeb Associate Professor of Physiology www.gmu.ac.ae COLLEGE OF HEALTH SCIENCES  Cell and transport mechanism, Homeostasis Learning Objectives: Describe the general characteristics of cells Describe the structure of the plasma membrane (Fluid Mosaic Model) Describe the structure and function of the different cell organelles. Enlist the different types of transport mechanisms existing across the cell membrane and explain the mechanism of each Define Homeostasis and explain its mechanism  What Is Physiology? It is the branch of biology that studies the functions and vital processes of living organisms. It explains the physical and chemical factors responsible for life's origin, development, and progression.  Why Do We Study Physiology? To understand the physiologic principle that underlies normal function to cure impairments Distinguish between Process & Function Physiology Integrate both to complete the picture!  What You Should Know is… The Human body is organized from cells to organs The organ systems operate as integrated units The human body needs a constant internal environment to perform its function properly Physiology deals with the mechanisms that maintain a stable internal environment despite the changes in the external environment (Homeostasis) What is the structural and Functional Unit of life? The Cell The Cell  The Cell Membrane The cell membrane (plasma membrane) is a thin, elastic, and semipermeable barrier between the cell and its surroundings. Its Lipid bilayer consists of phospholipids and cholesterol, only 2 molecules thick, and continuous over the entire cell surface. Each molecule has : – Head: is the phosphate portion of phospholipids that are charged ( polarized) and soluble in water (hydrophilic). – Tail: is the lipid portion of phospholipids, that is uncharged (non-polarized) and relatively insoluble in water (hydrophobic) The hydrophilic ends are exposed to H2O present outside [extracellular fluid (ECF)] and inside [intracellular fluid (ICF)] the cell, while the hydrophobic ends meet in the water-poor interior of the membrane.  The Cell Membrane Proteins: 55% They do not form a continuous layer as lipids but, they exist as globular units that may be either : – Integral proteins: that extend through the whole thickness of the membrane. – Peripheral proteins: They are attached to the surface of the cell membrane either from inside or from outside i.e. they do not penetrate the whole thickness of the membrane. The functions of cell membrane proteins ▪ Structural proteins (lipoproteins and glycoproteins) ▪ Pumps (Na+/K+ pump) ▪ Receptors (for hormones, chemical transmitters,….) ▪ Carriers (glucose transporters) ▪ Enzymes (adenyl cyclase enzyme) ▪ Ion channels (Na +, K+, and Ca2+ channels) ▪ Tissue typing, and antibody processing (immunity) Carbohydrates: 3%: They are either combined with proteins (glycoproteins) or with lipids (glycolipids). When they cover the whole membrane, they are called glycocalyx.  The Cell Membrane The functions of the Cell Membrane Regulate the passage of substance into and out of cells Detect chemical messengers arriving at the cell surface Link adjacent cells together by membrane junctions Anchor a variety of proteins, including intracellular and extracellular protein filaments involved in the generation and transmission of force, to the cell surface  The Nucleus Usually, it is the largest organelles It is bounded by a nuclear membrane (envelope) with pores It controls the normal cell function Contains the DNA in chromosomes Each cell has a fixed number of chromosomes that carry genes The genes control cell characteristics What is inside the nucleus? It is the largest structure present inside the boundaries of the nucleus It is the dark staining zone in the center of the nucleus It is the place where intensive synthesis of ribosomal RNA takes place Its main components are ribonucleic acid (RNA), deoxyribonucleic acid (DNA) and proteins What is inside the nucleus? The genetic material (DNA) is found which is the hereditary material of the cell DNA is spread out and appears as Chromatin in non-dividing cells DNA is condensed and wrapped around proteins forming as Chromosomes in dividing cells  Cell Organelles Mitochondria Endoplasmic reticulum Ribosomes It contains its DNA; It is Two types: It contains two sub-units mDNA, RNA, and 1. Smooth- ribosome free It is the site of protein ribosomes. synthesis; therefore, it is It produces high- - detoxify drugs and pesticides. considered ad the Protein energy compound -absorb, synthesize, and transport fat factory of the cell ATP -break down glycogen to form glucose. It is either free-floating or It is the Powerhouse attached to the of the cell. 2. Rough - contains ribosomes: it manufactures proteins. Endoplasmic Reticulum.  Cell Organelles Golgi Apparatus Lysosomes Cytoskeleton It is a membrane-bound organelle It is the framework of the cell It is a series of flattened sacs containing a variety of enzymes. It contains small microfilaments and that modifies, packages, It contains digestive enzymes larger microtubules. stores, and transports They support the cell, giving it its materials out of the cell. It helps digest food particles inside or outside the cell. shape and helping with the Works with the ribosomes movement of its organelles. and Endoplasmic Reticulum. They are called suicide bags  The Cytoskeleton MICROTUBULES It is a hollow tube present in all cell types except RBCs It is responsible for the intracellular movement of cytoplasmic Organelles It forms Cilia and Flagella MICROFILAMENTS It is attached to the cytoplasmic side of the Plasma Membrane It strengthens the cell surface INTERMEDIATE FILAMENTS It is tough, insoluble protein fiber with strength It resists pulling forces on the cell  The Cellular Extensions Microvilli: Tubular extensions of the plasma membrane which contain actin filaments Stereocilia: Modified Microvilli seen on the cells in the Epididymis Cilia are shorter and more numerous in cells; they move in a single direction across the cell pair Flagella are longer and fewer (usually 1-3) on cells What is the difference between Cytosol and Cytoplasm? https://www.menti.com/alueetusxe5p  TRANSPORT MECHANISMS Solutes (e.g. ions, glucose, gases …… etc) can cross the cell membrane by: ▪ Diffusion: either simple or facilitated ▪ Active transport: either primary or secondary ▪ Endocytosis and exocytosis Solvents (e.g. H2O) can pass across the cell membrane by: ▪ Filtration ▪ Osmosis  Transport of Solutes Diffusion It is a passive process substance in a solution (or in a gas) that expands to occupy all the available volume. It is produced by the kinetic motion of the molecules, and it occurs in the direction of their concentration gradient. This occurs through either the lipid bilayer or the proteins embedded in it (transport proteins), depending on the: molecular size, lipid solubility, and charge of the substance. Generally, diffusion across cell membranes can be divided into 2 main types: Simple diffusion It occurs through the lipid bilayer. The following substances can diffuse through the lipid bilayer of cell membranes: Lipid-soluble substances (e.g. O2, N2, and alcohols), Water, Small uncharged water-soluble molecules (which cross the lipid bilayer along with water molecules) e.g. CO2 (which is also lipid soluble). Diffusion is directly related to Lipid solubility, Concentration gradient, Surface area, Temperature. Diffusion is inversely related to the thickness of the membrane and the Molecular weight. Facilitated diffusion This mechanism moves substances passively in the direction of their chemical (concentration) gradient, but it requires a type of transport protein The molecules of substances that diffuse by this mechanism (e.g. glucose and most amino acids) The facilitated diffusion is regulated by hormones  Different types of Carriers If the carrier transports only If the carrier transports two If the carrier transports two one molecule, it is called molecules (Cotransport) in the molecules (Cotransport) in uniport [e. g. glucose same direction it is called opposite directions, it is called transporters (GLUT1, symport e.g. Na-dependent antiport (Counter transport) GLUT2,….) glucose transport e.g. Cl-/HCO3- exchange. Transport of Solutes Active Transport Primary active transport It is the transport of substances against their electrical or concentration gradients (i.e. from a lower to a higher concentration. It requires: Specific carrier proteins and Energy (provided only by hydrolysis of ATP) Examples: Na+ - K+ pump (Na+/K+ ATPase),Ca2+ pump ,H+ pump (proton pump). Secondary active transport It is the cotransport of Na+ down its electrochemical gradient (created by the primary active transport) and another substance (e.g. glucose or amino acids) by a carrier protein (symport). Example: Sodium-dependent glucose transport (glucose absorption in the intestine and glucose reabsorption in the kidney).  Remember -Na+ - K+ pump In the cell membrane, there are carrier proteins that have: – Three receptor sites for Na+ from inside – Two receptor sites K+ from outside. – The inside part (near mitochondria) has ATPase activity. So, three Na+ ions will bind to the carrier from inside, while two K+ ions will bind from outside. This will activate the ATPase carrier leading to hydrolysis of ATP liberating the energy. This energy causes configuration change in the carriers pushing Na+ to outside and K+ to inside the cell [i.e. it has a coupling ratio of 3/2]. Function of Na+ - K+ pump: – Electrogenic pump; creates more positivity outside the cell (and more negativity inside). – Controls the cell volume.  Endocytosis and Exocytosis Both pinocytosis and phagocytosis are called Endocytosis. Pinocytosis (Cell Drinking): This is a transport mechanism by which large particles. The particle at first contacts the cell membrane, then, the latter is depressed, and, on each side, it rises and folds over the particle (which will thus become a vacuole inside the cytoplasm, the wall of which is made of a part of the cell membrane). Phagocytosis (Cell Eating) It is a process by which bacteria and dead tissue are engulfed by cells, and ingested. Exocytosis (Cell Vomiting): This is the reverse of endocytosis. The membrane of the granule or vesicle fuses with the cell membrane, then the area of fusion breaks down and its contents are expelled outside the cell while the cell membrane remains intact.  Filtration Filtration is the passive movement of water through a porous membrane due to a difference in hydrostatic pressure on the two sides of the membrane [e.g. formation of interstitial (tissue) fluid through the capillary membrane and glomerular filtrate in nephrons]. The amount of fluid filtered per time unit is directly proportional to the: ▪ Pressure gradient ▪ Surface area of the membrane ▪ Membrane permeability ▪ Dissolved molecules (solutes) with smaller diameters than the pores pass with the filtered fluid.  Osmosis Osmosis is the passive movement of water through a semipermeable membrane from an area containing pure water or a diluted solution of a solute (NaCl or glucose) to an area in which there is a higher concentration of solute (the membrane is impermeable to the solute and permeable to the solvent). The pressure required to apply the concentrated solution to prevent water movement from the diluted solution is called the osmotic pressure. The amount of osmotic pressure is directly proportional to the number of particles per unit volume of solution. So, ionizing solutes (e.g. NaCl) are more osmotically active (because each ion is active by itself) than non-ionizable solutes (e.g. glucose). The osmotic pressure is expressed in osmoles or milliosmoles which can be converted to mmHg, since one milliosmole = about 19.3 mmHg.  The osmolarity of a certain solution is the number of osmoles per liter of this solution, while its osmolality is the number of osmoles per kilogram of solvent. In the body, the osmotically-active substances are dissolved in water (= solvent), and are usually measured and are expressed in milliosmoles per liter of water (since water density is 1). All body fluids have the same osmolality =290 milliosmoles/liter. Solutions that have an osmolality equal to that of the plasma are called isotonic solutions, while those having a higher osmolality are hypertonic, and those having a lower osmolality are hypotonic. A 0.9% NaCl solution is isotonic with the plasma and is known as the isotonic (or physiological) saline solution. Remember Transport aims to maintain homeostasis https://www.menti.com/als6szng19sg  What is Homeostasis? Is to maintain the physical and chemical composition of the internal environment (Extracellular Fluid) constant despite the changes in the external environment It is a vital concept in human physiology Normal Physiological ranges in fasting blood : ▪ Arterial pH 7.35-7.45 ▪ O2 content 17.2-22.0 ml/100 ml ▪ Glucose75-110 mg/100 ml  Regulation of the Body Functions Regulation- the ability of an organism to maintain a stable internal condition in a constantly changing environment, done by: ▪ Chemical (hormonal) Regulation: a regulatory process performed by hormone or active chemical substance in blood or tissue. It responds slowly, acts extensively, and lasts for a long time ▪ Nervous Regulation process in which body functions are controlled by the nervous system. It responds fast; acts exactly or locally, lasts for a short time ▪ Auto-regulation: a tissue or an organ can directly respond to environmental changes that are independent of nervous and hormonal control. The Amplitude of the regulation and the Extension of the effects are smaller than the other two types.  When the internal environment is disturbed by a stimulus either a successful compensation occurs, and homeostasis is reestablished, or homeostasis Fail to compensate, and the pathology appears (illness, death)  Feedback Homeostasis is maintained through the regulatory process called “feedback” A feedback loop is a cycle of events in which a body condition (such as temperature) is continually monitored and adjusted to be within specific limits The basic components of the feedback loop are: o Receptor : detects changes (stimuli) in the body o Control center : determines a set point for a normal range, receives input from the receptor, and sends output when changes are needed o Effectors': causes the response determined by the control center  There are two types of feedback loops: Positive loops where the response enhances the condition as it increases the action of the control system; examples: blood clotting, contraction of the uterus during childbirth (parturition) Negative loops where the response counteracts or antagonizes the condition Most feedback loops in the body are negative feedback loops Negative Feedback Positive Feedback Learning Resources: 1. Marieb EN. Human Anatomy and Physiology, 9th Edition, Pearson International Edition; 2014. ISBN-13: 978-1-2920-2649-7 2. Guyton, Arthur C. Textbook of medical physiology / Arthur C. Guyton, John E. Hall.—11th ed. 3. Ganong's Review of Medical Physiology/Kim E. Barrett, Susan M. Barman, Scott Boitano and Heddwen L.Brooks,23rd ed. 4. Instructional Web site 5. Lectures PDF on Moodle 6. https://www.clinicalkey.com/#!/content/book/3-s2.0-B9780702031144000026  DISCLAMER The contents of this presentation, can be used only for the purpose of a Lecture, Scientific meeting or Research presentation at Gulf Medical University, Ajman. www.gmu.ac.ae  RBC and Anemia Dr.Rasha Eldeeb Associate Professor of Physiology www.gmu.ac.ae COLLEGE OF HEALTH SCIENCES  RBC and Anemia Learning Objectives: Define blood and its cellular and noncellular components. Explain the functions of blood Describe the plasma and its content Explain the functions of plasma proteins State the difference between the plasma and the serum Describe the RBC and relate its structure to the function. Define anemia and describe its different types according to the etiology and the morphology. State the Fate of Anemia. To Start with … What is Blood?  Blood Is the only fluid tissue in the body It is a specialized type of connective tissue in which living blood cells ( Red Blood cells, White blood cells and platelets) , are suspended in a nonliving fluid matrix called plasma It appears to be a thick, homogeneous liquid, the microscope reveals that it has both cellular and liquid components  Composition of the Blood Cellular component: 40-45% Cells (or corpuscles) Red blood corpuscles (R.B.Cs) or erythrocytes: about 5 millions/mm3. When decreased in number, the condition is called anemia, and when increased, it is called polycythemia White blood cells (W.B.Cs) or leukocytes: 4000-11000/mm3. When decreased in number, the condition is called leukopenia, and when increased, it is called leukocytosis Platelets or thrombocytes: 100000-400000/mm3. When decreased in number, the condition is called thrombocytopenia, and when increased, it is called thrombocytosis Liquid component: 55-60% (Plasma) Water (90%) Plasma proteins (7.1%) Lipids, hormones, enzymes, nutrients and waste products (2%) Various electrolytes e.g. Na+, K+, Cl-, HCO3-, Ca2+ and PO43- (0.9 %)  Plasma Proteins Types of plasma proteins: Albumin ranges from 3.5-5 g/dL (the average is 4 g/dL). Globulins [alpha (α), beta (β), and gamma (У)] range from 2.3-3.5 g/dL (the average is 2.7 g/dL). Fibrinogen is about 0.3 g/dL. Site of synthesis: All plasma proteins are synthesized in the liver except У globulins, which are synthesized by the B-lymphocytes and plasma cells Source of plasma proteins: The plasma proteins are normally formed from food proteins, and in starvation, they can also be formed from tissue proteins (reserve type) 100000-400000/mm3 4-5 millions/mm3 4000-11000/mm3 7 Serum= Plasma – Clotting Factors Now… What is RBC?  RBCs= Red Blood Corpuscles= Erythrocytes The RBCs is non nucleated , biconcave disc and formed of cytoplasm that has no mitochondria or cell organelles and is enclosed by a cell membrane. The biconcave shape is produced by 2 proteins in their membranes called ankyrin and spectrin. The cytoplasm is formed mainly (34%) of hemoglobin (Hb) as each RBC contains about 30 pg of hemoglobin (Hb). It also contains electrolytes (especially K+ & HCO3-) and several enzymes e.g. carbonic anhydrase & glucose-6-phosphate dehydrogenase (G-6-PD). What is the importance of the Biconcave shape in RBCs? oIt increases the surface area for diffusion of gases and decreases the distance that gases diffuse through it. oIt allows flexibility and shape change while squeezing through capillaries. oIt allows variations in the shape and dimensions of RBCs which is useful in the differential diagnosis of anemias.  RBCs The life span of RBCs is 120 days then destroyed and removed by the spleen. Red blood corpuscles (R.B.Cs) or erythrocytes: about 5 million/uL. Its Diameter is about 7 and its Volume is 90 3 Male: 4.7 to 6.1 million /uL Female: 4.2 to 5.4 million /uL. Why there is difference in Male and female in RBCs count? This is mainly due to difference in hormonal profile between the two genders , as male sex hormones, androgens, stimulate hemopoiesis) What are the Functions of RBCs? o The main function of RBCs is to transport hemoglobin, which in turn carries respiratory gases. o The hemoglobin in the RBCs is an excellent acid-base buffer , and responsible for most of the acid-base buffering power of whole blood. o The carbonic anhydrase, enzyme inside the RBCs catalyzes the reversible reaction between CO2 and water to form carbonic acid (H2CO3). o Essential for maintenance of diastolic arterial blood pressure. o The thin cell membrane allows free diffusion of O2 and CO2 in both directions, and the biconcave shape of the red cells provides the largest possible surface area for this purpose. o It plays an important role in producing blood viscosity, which is essential for maintenance of the diastolic arterial blood pressure. o Its membrane glycoprotein layer contains the specific agglutinogens that determine the blood group. What do we mean by Blood Group?  Two antigens (agglutinogen)—type A and type B—occur on the surfaces of the red blood cells in a large proportion of human beings Blood is normally classified into four major O-A-B blood types, depending on the presence or absence of the two agglutinogens, the A and B agglutinogens When neither A nor B agglutinogen is present, the blood is type O (Universal Donner). When only type A agglutinogen is present, the blood is type A. When only type B agglutinogen is present, the blood is type B. When both A and B agglutinogens are present, the blood is type AB (Universal Recipient). There are 6 common types of Rh antigens, each of which is called an Rh factor. These types are designated C, D, E, c, d, and e. If the person has Rh factor on his RBC cell membrane his blood type is Rh positive. What is the Importance of blood group?  In blood transfusion (to avoid incompatibility reactions) In marriage (to avoid erythroblastosis fetalis) http://t3.gstatic.com/images?q=tbn:pRVPq_xdAbMWUM:http://www.theodora.com/drugs/images/176.jpg Medicolegal importance; in cases of disputed paternity, blood grouping tests can only exclude paternity but can not prove it. http://t3.gstatic.com/images?q=tbn:r2uj8Zw7-n9r3M:http://divorcelawyers.co.za/wp-content/uploads/2010/08/paternity-test.jpg http://t3.gstatic.com/images?q=tbn:v7g7G9AtShMfnM:http://www.labworksfla.com/dna%2520strand.jpg How is RBCs Formed?  By Erythropoiesis It is the process of formation of RBCs. Where is the site of Erythropoiesis?  During Intrauterine Life: o 0-2 months (yolk sac), o 2-7 months ( liver, spleen), o 5-9 months (bone marrow) During the late months of Gestation and after birth: o Infants: bone marrow (practically all bones) o Adults: confined to the axial skeleton, proximal ends of the femur, and humerus- Extramedullary hemopoiesis can resume in the liver and spleen in diseases where the bone marrow is destroyed or affected by fibrosis. Active cellular marrow is called red marrow; inactive marrow that is infiltrated with fat is called yellow marrow What do we need for Erythropoiesis to occur?  The Bone Marrow: A healthy red bone marrow is essential for normal hemopoiesis Hormones Diet Diet containing: ▪ Proteins of high biological value. ▪ Minerals especially copper and cobalt ▪ Vitamins: Almost all vitamins are required Hypoxia particularly vitamin B12 and folic acid. (Maturation factors) Erythropoietin The liver: forms the globin part of Hb, stores vitamin B12 & iron, and secretes erythropoietin. Hormones: as androgens and thyroxin. Blood O2 Tension: Decreased O2 tension (hypoxia) stimulates erythropoiesis indirectly by stimulating the release of Erythropoietin What is the Fate of RBCs?  Life span of the RBCs in the bloodstream is 120 days. Old RBCs become rigid and fragile, and their hemoglobin begins to degenerate Dying erythrocytes are engulfed by macrophages and / or lysed mainly extravascularly in the reticuloendothelial system (Liver, Spleen, and Bone marrow)  The Variation In RBCs Count And Shape Anemia: the condition of decreased RBCs count Polycythemia: the condition of abnormally high hematocrit (High RBCs count in circulation) o Primary o Secondary Hereditary Spherocytosis: RBCs are spherocytic in normal plasma and hemolyze more readily than normal cells in hypotonic NaCl solutions. (Cell fragility), it is caused by abnormalities of the protein network that maintains the shape and flexibility of the red cell membrane So, Now… What Is Anemia?  Anemia means deficiency of hemoglobin in the blood which can be caused by either too few red blood cells or too little hemoglobin in the cells leading to decreased O2 carrying capacity of the blood and, thus, tissue hypoxia.  It is classified into A. Etiological Classification (B) Morphological Classification (According to the cause) (According to RBCs size and HB concentration) 1. Hemorrhagic anemia 1. Normocytic (blood loss) normochromic anemia 2. Decreased production of 2. Microcytic hypochromic RBCs anemia 3. Hemolytic anemia 3. Macrocytic normochromic anemia  Etiological Classification (1) Hemorrhagic anemia (blood loss) Caused by acute or chronic blood loss (e.g. epistaxis, bleeding esophageal varices or peptic ulcer, piles or bilharziasis) (2) Decreased production of RBCs A. Aplastic anemia: Bone marrow aplasia means lack of functioning bone marrow (bone marrow destruction) caused by radiation, chemotherapy, infection, malignancy (leukemia), and intoxication with drugs. B. Nutritional (deficiency ) anemia: iron deficiency anemia, vitamin B12 deficiency anemia ( megaloblastic anemia), Folic acid deficiency anemia  Etiological Classification (3) Hemolytic anemia:(excessive hemolysis (breakdown) of the RBCs) A. Corpuscular cause (congenital): Abnormalities in the red cell membranes e.g. congenital spherocytosis), Hemoglobinopathies e.g. sickle cell anemia and thalassemia), Deficiency of the G-6-PD enzyme B. Extracorpuscular causes (Acquired) Immune causes: Incompatible blood transfusion, Autoimmune hemolytic http://www.google.ae/images?q=tbn:Z6cypxnzUa8cXM::www.cartage.org.lb/en/themes/sciences/lifescience/generalbiology/physiology/LymphaticSystem/Antibody anemia (i.e. formation of abnormal antibodies that attack the RBCs) Nonimmune causes: Infections e.g. malaria, Toxins e.g. snake venoms, Certain http://t3.gstatic.com/images?q=tbn:2bn7EwMasVqR6M:http://www.majidkareem.info/wp-content/uploads/2008/10/spleen.bmp drugs & chemicals, Hypersplenism  Morphological Classification It is classified according to the main 3 blood indices: Morphological Classification Morphological Classification  Morphological Classification 1- Normocytic normochromic anemia: Normal MCV (size of RBCs) and normal MCH and MCHC (amount of Hb in each RBC), but total RBC count is decreased. This is due to Acute blood loss (hemorrhage), Bone marrow depression, and Excessive hemolysis (destruction) of RBCs. 2- Microcytic hypochromic anemia: It is a type of anemia with small size of RBCs (MCV Capillaries—> (In capillary bed)—>Venules—> small veins—>large veins—> Heart called Resistance vessels So, … What Is The Function of CVS?  Transport and distribute essential substances to the tissue Remove metabolic byproducts Adjustment of oxygen and nutrient supply in different physiological states Regulation of body temperature Humoral communication Now, … How Does The Heart Function?  The parts of the heart normally beat in orderly sequence: Contraction of the atria (atrial systole) is followed by contraction of the ventricles (ventricular systole), and during diastole all four chambers are relaxed. Contraction of the heart is preceded by electrical stimulation (action Potential) The heartbeat originates in a specialized cardiac conduction system and spreads to all parts of the myocardium. To Understand How Does The Heart Function As a Pump You Should Know :  The Properties of Cardiac Muscle Excitability Rhythmicity Conductivity Contractility  Excitability: The cardiac muscle can respond to an adequate stimulus by generating an action potential. Rhythmicity ( automaticity) : The cardiac muscle can initiate its beats regularly and continuously. Cardiac rhythm is myogenic in origin independent of nerve supply. The peacemaker of the heart is the SAN. Conductivity: it’s the ability to spread the cardiac electrical impulse through the conductive system all over the cardiac tissue. Contractility: it is the ability to translate the electrical stimulation (Action potential) into mechanical work ( muscle contraction in the form of systole and diastole) So, … What Is Pumped Out Of The Heart?  Stroke Volume: (SV): It is the volume of blood pumped by each ventricle per beat. Usually it equals 70-80 ml/beat during rest. ▪ SV = EDV –ESV ▪ EDV: Volume of blood remaining in the ventricle at end of diastole = 135 ml. ▪ ESV: Volume of blood remaining in the ventricle at end of systole = 65-70 ml during rest.  Cont.,. Cardiac Output: (CO) : It is the volume of blood pumped by each ventricle per minute. Normally it equals the venous return, and this is called the steady state 5-5.5 L/ min during rest. ▪ CO = Heart Rate (HR) X stroke volume (SV) Cardiac Index = CO/surface area Ejection Fraction: % of EDV that is ejected by the left ventricle per beat = SV / EDV. ▪ Normally lies between 55-80% (average 67 %)  Important Terms Preload: Load acting on the ventricle before its contraction. Venous return or End diastolic Volume (EDV) represents preload to the heart. Afterload: Load acting on the ventricle during its contraction. Arterial resistance or TPR represents afterload to the heart Now, … What Is ECG?  Electrocardiography (ECG) It is the algebraic summation of the electrical activity occurring in the cardiac muscle during the cardiac cycle. It is a recording of the electrical activity (depolarization & repolarization) generated by the cardiac muscle during the cardiac cycle The Electrical activity is either Depolarization (due to Na+ influx) or Repolarization (due to K+ efflux) The Electrical activity precedes cardiac contraction The parts of the heart normally beat in an orderly sequence: Contraction of the atria (atrial systole) is followed by contraction of the ventricles (ventricular systole) and during diastole all four chambers are relaxed  ECG Recording Because the body fluids are good conductors (volume conductors), fluctuations in the potential that represent the algebraic sum of the action potentials of myocardial fibers can be recorded extracellularly The signals are detected using metal electrodes attached to the extremities and chest wall and are then amplified and recorded by the electrocardiograph The ECG may be recorded by using an active (exploring electrode) connected to an indifferent electrode at zero potential (unipolar recording) or by using two active electrodes (bipolar recording)  Einthoven's Triangle EINTHOVEN (a Deutch scientist born in 1860 and died in 1927) stated that In a volume conductor, the sum of the potentials at the points of an equilateral triangle with a current source in the center is zero at all times. This triangle was named after him Einthoven Triangle (putting the heart in the middle) Einthoven's triangle can be approximated by placing electrodes on both arms and the left leg. These are the three standard limb leads used in electrocardiography The center of the triangle offers a reference point for the unipolar ECG leads Lead II = Lead I + Lead III  Leads used in ECG Recording (1) STANDARD BIPOLAR LIMB LEADS (using 2 active electrodes) LEAD I : records the potential difference between the LEFT ARM and the RIGHT ARM (LA – RA) LEAD II: records the potential difference between the LEFT LEG and the RIGHT ARM (L.L. – R.A.) LEAD III: records the potential difference between the LEFT LEG and the LEFT ARM (L.L – L.A.) (2) Unipolar Leads (a) Unipolar Limb Leads (aVR, aVL & aVF) aV.R. = When the exploring electrode is put on the right arm aV.L. = When the exploring electrode is put on the left arm aV.F. = When the exploring electrode is put on the left leg  (b) Unipolar Chest Leads There are six unipolar chest leads: V 1 = when the exploring electrode is put in the fourth intercostal space at the right sternal border V2 = When the exploring electrode is put in the fourth intercostal space at the left sternal border V3 = When the exploring electrode is equidistant (in midpoint) between V2 and V4 V4 = When the exploring electrode is at the apex beat in the fifth intercostals space in the left mid-clavicular line V5 = When the exploring electrode is in the left fifth intercostals space in the anterior axillary line V6 = when the exploring electrode is in the left fifth intercostals space in the mid- axillary line ECG Leads Now, … What Is The Importance of The Different ECG Leads?  The value of different ECG leads The leads I, and aVL look at the left lateral surface of the heart. The leads II, III, & aVF look at the inferior surface of the heart. Lead aVR looks at the atria. V1 and V2 look at the right ventricle. V3 and V4 look at the anterior and lateral walls of the left ventricle Now …Everything is ready!! What Do We Have???!!! Normal ECG Now, … What Does It Mean? Now, … How to Interpret An ECG?  Interpretation of ECG Commonly followed sequence of analysis 1. Check voltage calibration 2. Heart rhythm 3. Heart rate 4. Intervals( PR, QRS, QT) 5. Mean QRS axis 6. Abnormalities of the P wave 7. Abnormalities of QRS 8. ST segment and T wave abnormalities  RR interval to determine heart rate Heart rate = 1500 (bpm) number of small boxes between two consecutive beats Heart rate = 300 (bpm) number of Large boxes between two consecutive beats The standard ECG paper speed is 25mm/sec  Cont.,. Determination of voltage and duration in ECG A normal ECG recording shows: o P wave: It is a positive wave. It is caused by atrial depolarization. Its duration is about 0.1 sec. Its amplitude is 0.1 (up to 0.25) mV o QRS : R is positive, and Q and S are negative waves. QRS is due to ventricular depolarization. Its duration is 0.06-0.08 sec, and its amplitude is about 1mV. Q wave is due to depolarization of the interventricular septum and its duration is about 0.02 sec. R wave is due to depolarization of most of the ventricular muscle fibers and its duration equals 0.04 sec. S wave is a small negative wave due to depolarization of the remaining parts of the base of ventricles and its duration equals 0.02 sec. o T wave: It is a positive wave. It is caused by ventricular Repolarization. Its duration is about 0.25 sec, and its amplitude is 0.2 (up to 0.4) mV. o Atrial repolarization is not recorded as it is submerged in QRS complex o U wave: Sometimes a positive U wave is recorded due to the slow repolarization of the papillary muscle or Purkinje fibers  PR interval o It is the duration between the beginning of P wave to the beginning of R wave o Normal duration is 0.16 sec. (0.12-0.2 sec.) It should not exceed 0.2 sec. o PR interval indicates conduction time from atria to the ventricle. Any delayed conduction in the AV node or bundle of His will prolong PR interval and it is seen in I degree heart block. o It is prolonged in cases of : Partial heart block, increased vagal tone, Atrial hypertrophy. o It is shortened in cases of : AV nodal rhythm, increased sympathetic stimulation and Wolf- Parkinson – White syndrome.  Applications of The ECG Study the function of the heart (rate, rhythm, axis) Diagnosis of cardiac dysfunctions as: Arrhythmias Disorders in the activation sequence ―Atrioventricular conduction defects (blocks) ―Bundle-branch block Increase in wall thickness or size of the atria and ventricles (hypertrophy) Myocardial ischemia and infarction Drug effect (Digitalis ,Quinidine ) Electrolyte imbalance (Potassium , Calcium ) Carditis (Pericarditis ,Myocarditis) Pacemaker monitoring Learning Resources: 1. Marieb EN. Human Anatomy and Physiology, 9th Edition, Pearson International Edition; 2014. ISBN-13: 978-1-2920-2649-7 2. Guyton, Arthur C. Textbook of medical physiology / Arthur C. Guyton, John E. Hall.—11th ed. 3. Ganong's Review of Medical Physiology/Kim E. Barrett, Susan M. Barman, Scott Boitano and Heddwen L.Brooks,23rd ed. 4. Instructional Web site 5. Lectures PDF on Moodle 6. https://www.clinicalkey.com/#!/content/book/3-s2.0-B9780702031144000026  DISCLAMER The contents of this presentation, can be used only for the purpose of a Lecture, Scientific meeting or Research presentation at Gulf Medical University, Ajman. www.gmu.ac.ae  Cardiac Cycle Dr. Sovan Bagchi, PhD Professor of Physiology www.gmu.ac.ae COLLEGE OF MEDICINE  Learning Objectives Describe pressure volume loop of a cardiac cycle Define stroke volume, end-diastolic ventricular volume, end-systolic ventricular volume, ejection fraction, and give the normal values under resting conditions Describe heart sounds Describe cardiac murmurs Events of the Cardiac Cycle Left ventricular pressure- volume loop  End diastolic ventricular volume is the volume of blood in each ventricle at the end of diastole. (End diastolic volume= 130 ml ) End systolic ventricular volume is the volume of blood that remains in each ventricle at the end of systole. (End systolic volume= 50 ml) Stroke Volume is the amount of blood ejected by each ventricle per stroke( or contraction). (Stroke volume = 70 - 90 ml) Ejection fraction is the percentage of the ventricular volume ejected with each stroke. (Ejection fraction = 55 to 65%) A relatively good index of ventricular function  Heart Sounds The heart sounds are produced by vibrations caused by the sudden closure of valves or due to myocardial contraction or due to vibration caused by rushing of blood into the chambers of the heart. Four heart sounds can be recorded via phonocardiography, but normally only two, the first and the second heart sounds, are audible through a stethoscope.  First Heart Sound Caused by the vibrations set up by the sudden closure of AV valves. Occurs at the beginning of ventricular systole. Low pitched( 25 – 45 Hz) Longer duration( 0.14 Sec) Can be heard in the mitral and tricuspid area, but better heard in mitral area.  Second Heart Sound Caused by the closure of Semilunar valves (Aortic and pulmonary valves) Occurs at the end of ventricular systole. High pitched( 50 Hz) Shorter duration( 0.11 sec) Auscultated in aortic and pulmonary areas.