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Unformatted text preview: Circulatory Systems Purpose of Circulatory System • transport nutrients, respiratory gases, hormones, metabolic products, etc. throughout the body • temperature control • Structural elements of circulatory systems: • pump (heart) • conduits (vessels) • transport medium (blood) • open vs. closed organization Vertebrate Circulatory Systems • Deoxygenated blood Fows to gas exchange organ (gills or lungs), oxygenated blood Fows to rest of body (systemic) • Increased number of heart chambers permits increased separation of blood Fow to the gas exchange organs and to the rest of the body • The human heart: two pumps in one • 4 chambers: 2 atria and 2 ventricles • blood enters atrium, pumped out of ventricle • right heart -> lungs • left heart -> systemic • valves prevent backFow • The cardiac system has two phases: • “ systole ” = contraction phase • “ diastole ” = relaxation phase • heart sounds are made by valve opening and closing • Blood pressure can be measured using a sphygmomanometer and a stethoscope • Effective pumping requires: • sequential contraction of chambers • coordinated contraction of muscle cells within chamber • depends on special features of cardiac muscle • mechanisms for regulation are speci¡c electrical events (reFected in EKG) • Three types of muscles: • cardiac (striated) • smooth • skeletal (striated) • striations in skeletal and cardiac muscle due to regular alignment of actin and myosin ¡laments (myo¡brils) • muscle contraction depends on actin and myosin ¡laments sliding past each other • types of muscle differ in: • connections between adjacent cells • regulation of contractions • Sequential contraction of chambers depends on specialized cells that initiate action potential and contraction: • sinoatrial node : pacemaker activity, no stimulus required • atrioventricular node : delays (~0.1 sec) start of ventricular contraction • bundle of His and Purkinje ¡bers : transmit action potential to ventricle walls • Action potentials in cardiac cells differ from those in neurons or skeletal muscles in terms of: • kinetics • ion channels involved • How are contractions of muscle cells coordinated within chambers? MCDB 1B: Plant Physiology Outline MCDB 1B: Intro to Plant Physiology 1 • cardiac muscle cells connected by gap junctions • electrical continuity allows rapid spread of action potential • no gap junctions between atria and ventricles • EKG waves reFect speci¡c electrical events: • P corresponds to depolarization and contraction of atria • Q,R, and S correspond to depolarization of ventricles • T corresponds to relaxation and repolarization of ventricles • Nervous system control of heart rate: • sympathetic nerves -> release epinephrine (adrenaline) -> increase heart rate (¡ght or Fight) • parasympathetic nerves -> release acetylcholine -> decrease pacemaker activity, slow heart rate • The nervous system controls heart rate by inFuencing resting potential...
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This note was uploaded on 09/01/2009 for the course MCDB MCDB 1B taught by Professor Weimbs,finklestein during the Winter '09 term at UCSB.
- Winter '09