NURS 5315 Advanced Pathophysiology

NURS 5315 Advanced Pathophysiology Clinical implication for Beta blockers? (book) Atrial fibrillation, chronic left heart failure or reduced ejection fraction Beta Blockers (book) reduce myocardial demand. By blocking beta receptors. Myocardial contractility is a change in developed tension at a given resting fiber length, which is simply the ability of the heart muscle to shorten. At the molecular level, thin filaments of actin slide over thick filaments of myosin called the cross-bridge cycle of muscle contraction. (video) Calcium interacts with troponin C which causes tropomyosin to move thus allowing actin and myosin to work together to cause contraction. Explain the difference between cardiac hemodynamic measures Video Lecture: Cardiac Output Cardiac output is the amount of blood pushed from the left ventricle in 1 minute. It is calculated by multiplying the heart rate in beats per minute by the stroke volume. Right Heart (book) pumps blood through the lungs Left Heart (book) sends blood throughout the systemic circulation, which supplies all of the body except the lungs. Arteries (hint A for away) (Book) carry blood (away) from the heart to all parts of the body, where they branch into arterioles and even smaller vessels until they become a fine meshwork of capillaries. Capillaries (Book) allow the closest contact and exchange between the blood and the interstitial space, or interstitium—the environment in which the cells live Venules and the veins (Book) carry blood from capillaries back to the heart. Lymph (Book) is returned to the cardiovascular system by vessels of the lymphatic system. Blood flow through the heart chambers/valves (Book) The right heart pumps de-oxygenated blood through to the right atriumthrough the tricuspid valve right ventriclepulmonary semilunar valvepulmonary arteryLungs (now oxygenated blood)Pulmonary veinsLeft AtriumBicuspid or Mitral valveLeft VentricleAortic Semilunar ValveAorta The coronary arteries provide blood to which part of the heart. (Book) The myocardium and other heart structures are supplied with oxygen and nutrients by the coronary circulation What are the two major coronary arteries? (Book) The major coronary arteries are the right coronary artery (RCA) and the left coronary artery (LCA) The transmission of electrical impulses, termed cardiac action potentials move throughout the myocardium. Analyze the process of action potentials. (Book) As an electrical impulse passes from cell to cell (fiber to fiber) in the myocardium, it stimulates an intracellular process that results in fiber shortening—that is, muscular contraction or systole. Between action potentials, the fibers relax and return to their resting length, causing diastole. The various phases of the cardiac action potential are related to changes in the permeability of the cell membrane to sodium, potassium, chloride, and calcium(Book) Threshold is the point at which the cell membrane's selective permeability to these ions is temporarily disrupted, leading to depolarization. If the resting membrane potential becomes more negative as a result of a decrease in extracellular potassium concentration (hypokalemia), it is termed hyperpolarization. How potassium affects myocardial action potentials, contraction, and clinical manifestations. Hypokalemia When the resting membrane potential becomes more negative as a result of a decrease in extracellular potassium concentration (Book) it is termed hyper-polarization. Calcium and Excitation-contraction coupling is the process by which an action potential arriving at the plasma membrane of the muscle fiber triggers the cycle leading to cross-bridge activity and contraction. (Book) It enters the myocardial cell from the interstitial fluid after electrical excitation, which increases the membrane permeability to calcium. Two types of calcium channels (L-type and T-type) are identified in cardiac tissues. Calcium interacts with troponin C which causes tropomyosin to move thus allowing actin and myosin to work together to cause contraction. (Lecture) The greater the amount of intracellular calcium the stronger the contraction. Hypercalcemia Because serum calcium levels are increased, a greater amount of calcium is also contained inside the cells. The threshold potential becomes more positive (hyperpolarized) (e.g., moves from −60 to −50 millivolts) and the cell membrane becomes refractory to depolarization (decreased excitability). Hypocalcemia manifestations there is an increase in neuromuscular excitability Hypocalemia manifestations Two clinical signs are Chvostek sign and Trousseau sign. Chvostek sign is elicited by tapping on the facial nerve just below the temple. A positive sign is a twitch of the nose or lip. Trousseau sign is contraction of the hand and fingers when the arterial blood flow in the arm is occluded for 5 minutes with the use of a blood pressure cuff. More severe forms manifest tetany. Myocardial relaxation (Lecture) intracellular calcium levels decrease. Magnesium is required for (Book) the binding of ATP to the myosin site. Hypomagnesaemia: (Book) clinical manifestations include behavioral changes, irritability, increased reflexes, muscle cramps, ataxia, nystagmus, tetany, convulsions, tachycardia, hypotension. Because magnesium inhibits potassium channels, loss of magnesium results in movement of potassium out of the cell, with renal excretion resulting in hypokalemia. Hypermagnesemia clinical manifestations(Book) clinical manifestations include lethargy, drowsiness; loss of deep tendon reflexes; nausea and vomiting; muscle weakness; hypotension; bradycardia; respiratory distress; heart block, cardiac arrest. Excess magnesium concentration depresses skeletal muscle contraction and nerve function. 1. Explain the difference between cardiac hemodynamic measures Video Lecture: Cardiac output Cardiac output is the amount of blood pushed from the left ventricle in 1 minute. It is calculated by multiplying the heart rate in beats per minute by the stroke volume.