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Cardiovascular Summary.doc

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PHGY 210
Ann Wechsler

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SUMMARY CARDIOVASCULAR PHYSIOLOGY Functions of the cardiovascular system: - Bringing fuel to cells - Bringing oxygen to cells - Removal of waste products - Circulation of hormones - Ciriculation of immune cells and antibodies - Regulation of electrolytes - Regulation of pH - Water balance, osmoregulation, thermoregulation - Different types of cardiovascular system: Insects Piscine Amphibians Mammals and and reptiles birds Type of Open circulation Closed, single- Closed , double- Closed, double- circulation The blood is not loop circulation loop circulation loop circulation always in the 2 types of vessels circulation: pulmonary and systemic Number of - 1 1 new and old 2 ventricles blood mix in the ventricle Number of - 1 2 2 atria Total number - 2 3 4 (2 hearts of chambers separated by septa) Series and parallels: - The systemic and pulmonary circulations are in series with one another. - Within the systemic circulation there is a parallel system that brings blood to all organs in the body. Where is the blood? - Veins and venules: 61% - Pulmonary circulation: 12% - Arteries: 11% - Heart: 9% - Arterioles and capillaries: 7% Note: arterial system = resistance; venous system = capitance Stephen Hales (1733): - First measurement of arterial blood pressure - He stuck a glass tube in the artery of a horse and measured blood pressure according to the height of the blood column. - Blood stops going up when it gets to equilibrium with atmospheric pressure. - Results: 1 o 2m of blood = 200cm of H2O = 14,2cmHg = 142mmHg - We now measure central VENOUS pressure with a catheter that we insert in one of the two jugular veins so that it gets in the right atrium. - We can also use the observation of the jugular vein to figure out the central venous pressure. Anatomy of the heart: Be able to locate The four chambers: - Left atrium - Right atrium - Left ventricle - Right ventricle The walls: - Left ventricular free wall ( thick) - Right ventricular free wall - Interventricular septum - Interatrial septum The great vessels: - Right and left pulmonary arteries - Right and left pulmonary veins - Superior and inferior vena cava - Pulmonary trunk - Aorta Cardiac valves (see table): - Mitral (bicuspid) valve - Aortic valve - Tricuspid valve - Pulmonic valve Cardiac tissues: - Chordae tendinae: o Fibrous tissue - Papillary muscle: o Pulls down on the chordae tendinae to prevent blood to flow from ventricles to atria. - Endocardium (endothelium): o Smooth layer of cells similar to those in blood vessels - Myocardium: o Muscle cells responsible for contraction of the heart - Epicardium: - Pericardial fluid (space): o Lubricates to allow movement - Pericardium: 2 o Sac that surrounds the heart. Summary of the cardiovascular system and circulation Electrical system of the heart: SA (sinoatrial) node: - Only area in the heart capable of spontaneous activity - A single cell from the SA node can still beat. AV (atrioventricular) node: - Only bit of muscle that connects atria and ventricles 3 - Slow conduction in the AV nodes gives time to atria to complete contraction before the ventricles start to contract. Bundle of His: - Quick - Bifurcates to left and right bundle branches - Note that the ventricular septum is activated before the rest of the ventricles. Purkinje fibers: - The earliest branch of the Purkinje fibers to be activated is on the left side. Activation sequence: - SA node - Right atrium, then left atrium - AV node - Bundle of His - Both bundle branches (simultaneous) - In the ventricles the action potential propagates: o First, on the interventricular septum, from top to apex of the heart o Then, on the ventricular free walls: From apex to top From interior to exterior Note that electrical current in the heart travels through gap junctions (nexus) Local circuit current is necessary since it is the mechanism by which propagation occurs everywhere you have action potentials. The electrocardiogram (ECG or EKG): - Recording of the electrical activity of the heart - The ECG set-up: o Extracellular recording o Voltage = potential difference o Reference measure = RL (right leg). It is always connected o 4 additional leads (cables): Chest lead RA lead LA lead LL lead - 2 senses of lead: o Wire that comes from the machine o Combination of wires used to record electrical activity P-wave: usually small and positive QRS complex: much sharper T wave: smaller in amplitude, but longer Amplitude is around 1mV Amplitude = height of the QRS complex - Bipolar limb leads (Einthovens triangle): o I: 4
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