McKenna's Pharmacology for Nursing, 2e

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Introduction to the cardiovascular system

Learning objectives Upon completion of this chapter, you should be able to: 1. Label a diagram of the heart, including all chambers, valves, great vessels, coronary vessels and the conduction system. 2. Describe the flow of blood during the cardiac cycle, including flow to the cardiac muscle. 3. Outline the conduction system of the heart, correlating the normal ECG pattern with the underlying electrical activity in the heart. 4. Discuss four normal controls of blood pressure. 5. Describe the capillary fluid shift, including factors that influence the movement of fluid in clinical situations.

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Glossary of key terms actin: thin filament, a component of a sarcomere or muscle unit arrhythmia: a disruption in cardiac rate or rhythm arteries: vessels that take blood away from the heart; muscular, resistance vessels atrium: top chamber of the heart, receives blood from veins

auricle: appendage on the atria of the heart, holds blood to be pumped out with atrial contraction automaticity: property of heart cells to generate an action potential without an external stimulus capacitance system: the venous system; distensible, flexible veins that are capable of holding large amounts of blood capillary: small vessel made up of loosely connected endothelial cells that connect arteries to veins cardiac cycle: a period of cardiac muscle relaxation (diastole) followed by a period of contraction (systole) in the heart conductivity: property of heart cells to rapidly conduct an action potential of electrical impulse diastole: resting phase of the heart; blood is returned to the heart during this phase dysrhythmia: a disruption in cardiac rate or rhythm, also called an arrhythmia ectopic focus: a shift in the pacemaker of the heart from the sinoatrial node to some other site electrocardiogram (ECG): an electrical tracing reflecting the conduction of an electrical impulse through the heart muscle; does not reflect mechanical activity myocardium: the muscle of the heart myosin: thick filament with projections, a component of a sarcomere or muscle unit oncotic pressure: the pulling pressure of the plasma proteins, responsible for returning fluid to the vascular system at the capillary level pulse pressure: the systolic blood pressure minus the diastolic blood pressure; reflects the filling pressure of the coronary arteries resistance system: the arteries; the muscles of the arteries provide resistance to the flow of blood, leading to control of blood pressure sarcomere: functional unit of a muscle cell, composed of actin and myosin molecules arranged in layers to give the unit a striped or striated appearance sinoatrial (SA) node: the normal pacemaker of the heart; composed of primitive cells that constantly generate an action potential Starling’s law of the heart: addresses the contractile properties of the heart; the more the muscle is stretched, the stronger it will react, until it is stretched to a point at which it will not react at all syncytia: intertwining networks of muscle fibres that make up the atria and the ventricles of the heart; allow for a coordinated pumping contraction systole: contracting phase of the heart, during which blood is pumped out of the heart