BIOL 3 Chapter 32 Circulation 04 30 2014 4 chambered hearts consist of two separate pumps 1 pump consisting of right atrium right ventricle deals with deoxygenated blood Superior inferior vena cava where oxygen depleted blood enters right atrium through o o o o o o o o o o 2 large veins After filling with blood right atrium contracts forcing blood into right ventricle Contraction of right ventricle sends oxygen depleted blood to lungs through pulmonary arteries vessels that carry blood away from heart and to lungs Other pump consisting of left atrium left ventricle deals with oxygenated blood Oxygen rich blood from lungs enters left atrium through pulmonary veins is squeezed into left ventricle Contraction of left ventricle sends oxygenated blood through aorta to rest of body Valves maintain direction of blood flow o When ventricles contract blood must be prevented from flowing back into atria Blood entering pulmonary artery aorta must also be prevented from flowing back into ventricles as heart relaxes Directionality of blood flow is maintained by 1 way valves Pressure in 1 direction opens them but reverse pressure forces them closed Atrioventricular valves allow blood to flow from atria into ventricles but not the reverse Semilunar valves allow blood to enter pulmonary artery aorta when ventricles contract but prevent blood from returning as ventricles relax Cardiac muscle is present only in the heart Cardiac muscle cells are small branched striated Cells connected by intercalated discs contain desmosomes that link cells together prevent strong heart contractions from pulling muscle cells apart Cells contain gap junctions allowing electrical signals to spread from 1 muscle cell to another producing synchronous heart muscle contractions Coordinated contractions of atria ventricles produce cardiac cycle Heart beats in coordinated fashion Both atria contract pump blood into ventricles Both ventricles contract pump blood into arteries that exit heart All chambers relax briefly before cycle repeats This cardiac cycle lasts less than 1 second Cardiac cycle generates forces that are measured when blood pressure is taken Systolic pressure higher of the two readings is measured during ventricular contraction contractions Diastolic pressure minimum pressure in arteries as heart rests between Blood pressure reading of less than 120 80 is considered healthy pressure of 140 90 or higher is high blood pressure High blood pressure hypertension is caused by constriction of small arteries which causes resistance to blood flow strain on heart Some people have genetic tendency toward hypertension It s also associated with smoking obesity lack of exercise high alcohol consumption stress aging Electrical impulses coordinate sequence of heart chamber contractions Contraction of heart is initiated coordinated by pacemaker cluster of specialized heart muscle cells that produce spontaneous electrical signals at a regular rate Heart s pacemaker is sinoatrial SA node located in upper wall of right atrium Electrical signals from SA node pass freely into connecting cardiac muscle cells then Electrical signal then passes from right atrium to specialized group of muscle cells between right atrium right ventricle atrioventricular AV node From AV node signal to contract spreads along specialized tracts of rapidly conducting muscle fibers atrioventricular bundle AV bundle which sends branches to lower portion Here bundles branch further forming Purkinje fibers transmit electrical signal throughout o o o o o o throughout atria of both ventricles ventricle Variety of disorders can interfere with complex series of events that produce normal cardiac cycle o When pacemaker fails rapid uncoordinated weak contractions fibrillation may occur o Fibrillation may be treated with defibrillating machine which applies jolt of electricity to heart synchronizing contractions of ventricular muscle cells pacemaker resumes its normal coordinating function What is blood Blood has 2 major components o Liquid plasma comprises about 55 of total blood volume Plasma is primarily water where proteins salts nutrients wastes are dissolved Proteins are most abundant dissolved molecules by weight include Albumin helps to maintain blood s osmotic strength Globulins antibodies that play an important part in immune response Fibrinogen important in blood clotting Cell based portion which is about 40 45 of total blood volume consists of red blood o o cells white blood cells platelets Cell based components of blood are formed in bone marrow Blood contains 3 cell based components red blood cells white blood cells and platelets but only the white blood cells are complete functional cells Mature red blood cells are not actual cells because they lack a nucleus which is lost during development Platelets are small fragments of cells All 3 cell components originate from blood stem cells that reside in bone marrow Stem cells unspecialized cells that can divide to produce offspring capable of maturing into 1 or more types of specialized cells o Red blood cells carry oxygen from lungs to tissues About 99 of all blood cells about 45 of total blood volume are oxygen carrying red blood cells erythrocytes Red color of erythrocytes is caused by protein hemoglobin which transports What is blood again oxygen in blood Each hemoglobin has 4 iron containing heme groups that can bind 4 oxygen molecules o Oxygenated hemoglobin takes on bright red color o o o o o o Neutrophils Eosinophils Basophils Lymphocytes Monocytes against disease cellular debris Hemoglobin becomes bluish as it releases O2 picks up CO2 at tissues Red blood cells have life span of 4 months are replaced by new ones from bone marrow o White blood cells break down old red blood cells Iron from erythrocytes is returned to bone marrow where it s recycled into new red blood cells White blood cells defend body against disease There are 5 types of white blood cells also called leukocytes o White blood cells make up less than 1 of cellular portion of blood help to protect body o Monocytes for example enter tissues transform into macrophages that engulf bacteria Platelets cell fragments that aid in blood clotting Platelets pieces of megakaryocytes that reside in bone marrow Blood clotting complex process that plugs damaged blood vessels protects animals from Blood leaving the heart travels from arteries to arterioles to capillaries then into venules finally to excessive blood loss What are the types
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