Chapter 16 Cardiovascular Emergencies 1 study guide

Chapter 16 Cardiovascular Emergencies 1. Anatomy and Physiology  The heart is divided down the middle into two sides (left and right) by a wall called the septum. Each side of the heart has an atrium, or upper chamber, to receive incoming blood, and a ventricle, or lower chamber, to pump outgoing blood  Normal electrical impulses begin in the sinus node, which is in the upper part of the right atrium and is also known as the sinoatrial (SA) node. The impulses travel across both atria, stimulating them to contract.  Between the atria and the ventricles, the impulses cross a bridge of special electrical tissue called the atrioventricular (AV) node.  The impulses then exit the atrioventricular node and spread throughout both ventricles via the bundle of His, the right and left bundle branches, and the Purkinje fibers, causing the ventricular muscle cells to contract.  Cardiac muscle cells have a special characteristic called automaticity that is not found in any other type of muscle cells. Automaticity allows a cardiac muscle cell to contract spontaneously without a stimulus from a nerve source.  The stimulus that originates in the sinoatrial node is controlled by impulses from the brain, which arrive by way of the autonomic nervous system. The autonomic nervous system is the part of the brain that controls the functions of the body that do not require conscious thought, such as the heartbeat, respirations, dilation and constriction of blood vessels, and digestion of food.  The autonomic nervous system has two parts, the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system is also known as the “fight-or-flight” system and makes adjustments to the body to compensate for increased physical activity. The sympathetic nervous system speeds up the heart rate, increases respiratory rate and depth, dilates blood vessels in the muscles, and constricts blood vessels in the digestive system.  The parasympathetic nervous system directly opposes the sympathetic nervous system. The parasympathetic nervous system slows the heart and respiratory rates, constricts blood vessels in the muscles, and dilates blood vessels in the digestive system. Normally, these two systems balance each other, but in times of stress, the sympathetic nervous system gains primary control, whereas in times of relaxation, the parasympathetic system takes control. ~ Circulation  To carry out its function of pumping blood, the myocardium, or heart muscle, must have a continuous supply of oxygen and nutrients.  The stroke volume is the volume of blood ejected with each ventricular contraction. In the normal heart, increased oxygen demand of the myocardium itself is supplied by dilation, or widening, of the coronary arteries, which increases blood flow.  The coronary arteries are the blood vessels that supply blood to the heart muscle  They start at the first part of the aorta, just above the aortic valve. The right coronary artery supplies blood to the right atrium and right ventricle and, in most people, the bottom part, or inferior wall, of the left ventricle. The left coronary artery supplies blo