NGR 5141 - Module 7 QUESTIONS AND ANSWERS. Questions and Answers () (Verified Answers).

1. Using Laplace’s law, show how an aneurysm develops. Think of the hemodynamics involved In Laplace’s law, the wall tension is directly related to the product of intraventricular pressure and internal radius and inversely to the wall thickness. The relationship can be calculated by Laplace’s equation which is T = (p x r)/ µm. T is wall tension, p is intraventricular pressure, r is the internal radius of the sphere, and µm is the wall thickness. This is interpreted as the amount of tension generated in the wall of the ventricle to produce a given intraventricular pressure which is dependent on the size of the ventricle. An aneurysm is a localized dilatation or outpouching of a vessel wall or cardiac chamber and are usually found in the thoracic or abdominal aorta. When the ventricles dilate, the myocardial fibers in the wall develop a greater tension which produces pressure within the ventricles. This higher tension in the myocardial fibers causes a decrease in the rate of fiber shortening which also decreases the potential of the ventricle to eject blood. 2. Pharmacologic agents such as beta- adrenergic blockers are used in the management of hypertension and heart failure. Explain the physiological rationale for the agent in relation to the autonomic innervation of the cardiovascular system Beta-adrenergic blockers help to reestablish the balance between oxygen supply and myocardial demands. They also decrease catecholamine-induced elevations of heart rate such as epinephrine and norepinephrine, myocardial contractility, and blood pressure. When the heart rate is lowered, there is additional diastolic filling time available for coronary perfusion. This reduction leads to improved oxygen delivery to the heart. They are useful in hypertension due to the reduction of blood pressure and heart rate. They are also useful in heart failure since they help to decrease the workload of the heart. 3. Explain the hormonal control of blood pressure. Hormones play a role in the control of blood pressure by contracting or relaxing the arteriolar smooth muscle. Hormones have the ability to increase the blood supply to organs causing more flow in certain times like stress, redistribute blood volume in cases of hemorrhage or shock, and regulate heat loss. Epinephrine causes vasoconstriction in the most of the vascular beds. Norepinephrine has more vasoconstrictive effects than epinephrine. Antidiuretic hormone (ADH) is a vasoconstrictor which increases peripheral resistance. It causes reabsorption of water by the kidneys. When it’s reabsorbed, the blood plasma volume increases c