Ch. 19 Cardiovascular System: Heart
Identify the two processes within the heart that occur due to pressure changes associated with the cardiac cycle.
A cardiac cycle is the inclusive period of time from initiation of one heartbeat to the start of the next. 1. Systole: contraction of a chamber 2. Diastole: relaxation of a chamber
Mnemonic: Aorta vs. Vena Cava- which one is on the right and which one is on the left?
Aorta and right each have 5 letters, so aorta is on the right. Vena and cava and left each have 4 letters, so the vena cava is on the left.
Describe the general structure of cardiac muscle.
Cardiac muscle cells are small, have one or two centrally located nuclei, and are branched.
Define autorhythmicity.
SA nodal cells are unique in that they exhibit autorhythmicity, meaning that they are capable of depolarizing and firing an action potential spontaneously without external influence.
Explain the significance of coronary arteries as functional end arteries.
Some arteries may share connections, called arterial anastomoses. Other arteries terminate in capillary beds only, and are called end arteries. The left and right coronary arteries are considered functional end arteries because, although there coronary arteries have anastomoses, if one of the arteries becomes blocked these anastomoses are too tiny to shunt sufficient blood from one artery to the other. As a result, the part of the heart wall that was supplied by one coronary artery branch will die due to lack of blood flow to the tissue.
Identify and locate the components of the heart's conduction system.
Stimulation of the heart involves the initiation of an action potential at the SA node and its transmission through the conduction system. The conducting system includes sinoatrial (SA) node, atrioventricular (AV) node, AV bundle, and Purkinje fibers, which are composed of specialized cardiac cells that initiate and conduct action potentials resulting in a heartbeat.
List the three variable that may influence stroke volume.
Stroke volume is influenced by venous return, inotropic agents, and afterload.
Define each of the three variables, and describe the factors that influence each one and how it affects stroke volume.
Venous return is directly correlated with store volume. Positive inotropic agents increase stroke volume, negative inotropic agents decrease stroke volume. Afterload is inversely related to stroke volume.
Identify the coronary veins and describe the specific areas of the heart drained by their major branches.
Venous return is through the cardiac veins (great, middle, and small) into the coronary sinus, which collects venous blood and drains deoxygenated blood from the heart wall directly into the right atrium of the heart.
Differentiate between the three primary types of blood vessels.
1. Arteries: carry blood away from the heart 2. Veins: carry blood back to the heart 3. Capillaries: exchange sites between either the blood and the air sacs (alveoli) of the lungs or the blood and the body cells.
List the five events of the cardiac cycle.
1. Atrial systole 2. Early ventricular systole 3. Late ventricular systole 4. Early ventricular diastole 5. Late ventricular diastole
List and describe what occurs during the five events of the cardiac cycle.
1. Atrial systole is the contraction of atria to finish filling the ventricles, which are in diastole. 2. Early ventricular systole is a time of isovolumetric contraction: Ventricles begin to contract, AV valves are pushed closed, and no blood leaves the ventricles yet. 3. Late ventricular systole is the time of ventricular ejection: Semilunar valves are pushed open, and blood is forced through the semilunar valves into the arterial trunk. 4. Early ventricular diastole is the beginning of ventricular relaxation: AV valves remain closed, and semilunar valves close. 5. Late ventricular diastole is a time to begin ventricular filling as AV valves open and passive filling of the ventricle begins.
Name the three layers of the heart wall and the tissue components of each.
1. Epicardium: outermost layer that is also called the visceral layer of serous pericardium. 2. Myocardium: the middle and thickest layer. Contraction of the cardiac muscle in the myocardium generates the force necessary to pump blood. 3. Endocardium: covers the internal surface of the heart and the external surfaces of the heart valves. It is continuous with the inner lining of blood vessels.
Describe the steps for SA nodal cells to spontaneously depolarize and serve as the pacemaker cells.
1. Reaching threshold as Na+ enters the nodal cells through open voltage-gated Na+ channels 2. depolarization as Ca2+ enters the nodal cells through open voltage-gated Ca2+ channels 3. Repolarization as K+ exits the nodal cells through voltage-gated K+ channels At rest, the parasympathetic nervous system decreases the inherent rhythm of nodal cells from a firing rate of 100 per minute to 75 per minute.
Describe the structure and function of the heart.
1. Two pumps: Each pump has a receiving chamber (atrium) and a pumping chamber (ventricle). - Right side: pumps deoxygenated blood to the lungs. - Left side: pumps oxygenated blood to the body. 2. Great vessels: Arteries (arterial trunks) transport blood away from the heart. - Pulmonary trunk transports from right side. - Aorta transports from left side. Veins transport blood toward the heart. - Vena cavae (SVC and IVC) drain into the right side. - Pulmonary veins drain into left side. 3. Valves: Heart valves prevent back flow to ensure one-way blood flow. - Atrioventricular (AV) valves (i.e., right AV valve and left AV valve) are between the atrium and ventricle. - Semilunar valves (i.e., pulmonary semilunar valve and aortic semilunar valve) are between ventricle and arterial trunk.
Identify the components of an ECG recording.
An electrocardiogram (ECG) is a graphic recording of the electrical changes in the heart and is used in the diagnosis and treatment of abnormal heart function.
Describe blood flow through the coronary arteries.
Blood flow to the heart wall is not a steady stream; it is impeded and then flows, as the heart rhythmically contracts and relaxes.
Discuss how cardiac muscle meets it energy needs.
Cardiac muscle cells rely almost exclusively on aerobic cellular respiration for supplying ATP. - It is also versatile in being able to use different types of fuel molecules, including fatty acids, glucose, lactic acid, amino acids, and ketone bodies.
Define the refractory period.
Cardiac muscle exhibits a longer refractory period than skeletal muscle fibers to allow time for contraction and relaxation of the muscle cells before they are stimulated again- a necessary requirement for the "pumping action" of the heart.
Define cardiac output.
Cardiac output is a measure of how effective the cardiovascular system is in transporting substances through the body. It is defined as the amount of blood pumped by a single ventricle in 1 minute. Cardiac output is the heart rate multiplied by the stroke volume.
Explain what is meant by cardiac reserve.
Cardiac reserve is a measure of the ability of the heart to increase pumping capacity beyond the normal resting cardiac output (CO).
Coronary circulation
Circulation of blood to and from the heart wall.
Identify the coronary arteries, and describe the specific areas of the heart supplied by their major branches.
Coronary arteries supply oxygenated blood to the heart wall and include the left and right coronary arteries that branch off the aorta. - three major coronary arteries off the right side of the heart (RMP): the right coronary artery splits into the right marginal artery and posterior inter ventricular artery - three major coronary arteries off the left side of the heart (LAC): the left coronary artery, the anterior inter ventricular artery, and circumflex artery.
Compare and contrast the structure and function of the two types of heart valves.
Each valve consists of endothelium-lined fibrous connective tissue flaps called cusps, or leaflets. 1. Atrioventricular valves - the right AV valve covers the right atrioventricular opening, and it has three cusps; the left AV valve covers the left atrioventricular opening, but it only has two cusps. - When open, the cusps of the valve extend into the ventricles, allowing blood to move from an atrium into the opening of a ventricle. This causes the AV valves to close. - The papillary muscles secure the thin chordae tendineae that attach to the lower surface of each AV valve cusp, preventing blood flow back into the atrium. 2. Semilunar valves - the pulmonary semilunar valve is located between the right ventricle and the pulmonary trunk, and the aortic semilunar valve is located between the left ventricle and the aorta. - each valve is composed of three cusps - neither papillary muscles nor chord tendineae are associated with these valves. - The semilunar valves open when the ventricles contract and the force of the blood pushes the AV valves open and blood enters the arterial trunks. - The valves close when the ventricles relax and the pressure in the ventricle becomes less than the pressure in a great arterial trunk. - Blood in the arteries begins to fall backward toward the ventricle and is caught in the cusps of the semilunar valves, and they close, preventing the back flow of blood into the ventricle.
Summarize the variables that influence cardiac output.
Heart rate is altered by stimulating the conducting system, and stroke volume is usually altered by changes in the myocardium. Both heart rate and stroke volume are directly related to cardiac output.
Define chronotropic agents, and describe how they affect heart rate.
Heart rate is altered through chronotropic agents, which change SA node and AV node activity. Positive chronotropic agents increase the heart rate and the negative chronotropic agents decrease the heart rate.
Explain the intercellular structures of the cardiac muscle.
Intercalated discs tightly link the cardiac muscle cells together and permit the passage of action potentials. - Desmosomes act as mechanical junctions to prevent cardiac muscle cells from pulling apart. - Gap junctions provide a low-resistance pathway for the flow of ions between cardiac cells. They allow an action potential to move continuously along the sarcolemma of cardiac muscle cells, resulting in synchronous contraction of that chamber.
Atrioventricular valve mnemonic
LAB RAT: Left Atrium: Bicuspid Right Atrium: Tricuspid
Compare and contrast parasympathetic and sympathetic innervation to the heart.
Parasympathetic innervation comes from the cardioinhibitory center to decrease the heart rate.. Sympathetic innervation comes from the cardioacceleratory center to increase the heart rate and increase force of contraction.
Describe the spread of the action potential through the heart's conduction system.
The action potential travels through the conduction system as follows: 1. SA node 2. AV node 3. AV bundle 4. bundle branches 5. Purkinje fibers Following stimulation by the conduction system, there is a propagation of the action potential at the sarcolemma and contraction of sarcomeres within the cardiac muscle cells.
Describe the general function of the cardiovascular system.
The general function of the cardiovascular system is to transport blood throughout the body to allow the exchange of substances (e.g., respiratory gases, nutrients, and waste products) between the blood of capillaries and the body's cells. The "goal" of the cardiovascular system is to provide adequate perfusion to all body tissues.
Perfusion
The delivery of blood per time per gram of tissue; typically expressed in mL/min/g. Adequate perfusion involves delivering sufficient blood to maintain the health of all body cells.
List the electrical events of an action potential that occur at the sarcolemma.
The electrical events of cardiac muscle include depolarization, plateau, and depolarization at the sarcolemma.
Describe the location and function of the fibrous skeleton.
The fibrous skeleton provides an attachment site for heart valves and cardiac muscle, and prevents action potentials from spreading between the atria and ventricles except through the AV node.
Describe the location and position of the heart in the thoracic cavity.
The heart is located posterior to the sternum left of the body midline between the lungs in the mediastinum. The posterosuperior surface of the heart is called the base. The inferior, conical end of the heart is called the apex. *Think of the heart's position like an "upside down" pyramid with the apex below the base.
Briefly summarize the mechanical events of muscle contraction.
The mechanical events are similar to those of skeletal muscle fibers and involve cross bridge cycling and the shortening of sarcomeres within cardiac muscle cells.
Describe the function of the pericardium and the purpose of the serous fluid within the pericardial cavity.
The pericardial cavity is a potential space between the layers of the serous pericardium that contain serous fluid, which is produced by the serous membranes and lubricates the surfaces to reduce friction.
List the structural components of the pericardium.
The pericardium that encloses the heart includes the pericardial sac, which has an outer fibrous pericardium and an inner parietal layer of serious pericardium, and a visceral layer of serous pericardium (epicardium) that forms the outer layer of the heart wall.
Compare and contrast pulmonary circulation and systemic circulation of the cardiovascular system. Trace blood flow through both circuits.
The pulmonary circulation convert deoxygenated blood from the right side of the heart through blood vessels to the lungs for the pickup of oxygen and the release of carbon dioxide, and then back through blood vessels to the left side of the heart. The systemic circulation moves oxygenated blood from the left side of the heart. The blood vessels to the systemic cells such as those of the liver, skin, muscle, and brain for the exchange of nutrients, respiratory gases, and wastes before returning the blood in vessels that enter the right side of the heart. Thus, the basic pattern of blood flow is the right side of the heart--->lungs--->the left side of the heart--->systemic tissues of the body --->back to the right side
Describe the pumps and channels associated with cardiac nodal cells.
The pumps and channels associated with neurons are also in the plasma membrane of nodal cells. A type of channel unique to nodal cells is the slow voltage-gated Na+ channel that allows the nodal cells to spontaneously depolarize.
Describe the pumps and channels within cardiac muscle cells.
The pumps and channels associated with skeletal muscle fibers are also in the plasma membrane of cardiac muscle cells. A type of channel unique to the function of cardiac muscle cells in transmitting an action potential is the voltage-gated Ca2+ channel.
Compare the superficial features of the anterior and posterior aspects of the heart.
The right side of the heart is more visible from the anterior view, and the left side of the heart is more visible from the posterior view.