ch. 25 questions
The linear velocity of blood flow in the circulatory system varies widely. What is the linear velocity in the aorta?
30 to 35 cm/second The linear velocity of blood flow in the circulatory system varies from 30 to 35 cm/second in the aorta.
The cardiac reserve refers to the maximum percentage of increase in cardiac output that can be achieved above the normal resting level. What is the normal young adult's percentage cardiac reserve?
300% - 400% The normal adult has a cardiac reserve of approximately 300 percent to 400 percent.
The semilunar valves of the heart open at the onset of the ejection period. Approximately what percentage of the stroke volume is ejected during the first quarter of systole?
60% Approximately 60 percent of the stroke volume is ejected during the first quarter of systole.
Which client is most likely to be experiencing vasodilation?
A 51-year-old man with a history of hypertension who is taking a medication that blocks the effect of the renin-angiotensin-aldosterone system Angiotensin is a potent vasoconstrictor, and medications that block this induce vasodilation. Epinephrine is also a vasoconstrictor. Histamine is a vasodilator, so antihistamine medications are likely to induce vasoconstriction. Serotonin is a vasoconstrictor, so medications that block its reuptake and increase free levels are apt to promote vasoconstriction.
Which neurotransmitter is associated with the parasympathetic nervous system?
Acetylcholine The actions of the autonomic nervous system are mediated by chemical neurotransmitters. Acetylcholine is the postganglionic neurotransmitter for parasympathetic neurons and norepinephrine is the main neurotransmitter for postganglionic sympathetic neurons. Sympathetic neurons also respond to epinephrine, which is released into the bloodstream by the adrenal medulla. The neurotransmitter dopamine can also act as a neurotransmitter for some sympathetic neurons.
A client is diagnosed with an abdominal aortic aneurysm that the physician just wants to "watch" for now. When teaching the client about signs/symptoms to watch for, the nurse will base the teaching on which physiologic principle?
As the aneurysm grows, more tension is placed on the vessel wall, which increases the risk for rupture. Because the pressure is equal throughout, the tension in the part of the balloon with the smaller radius is less than the tension in the section with the larger radius. The same holds true for an arterial aneurysm in which the tension and risk of rupture increase as the aneurysm grows in size. Wall tension is inversely related to wall thickness, such that the thicker the vessel wall, the lower the tension, and vice versa. Although arteries have a thicker muscular wall than veins, their distensibility allows them to store some of the blood that is ejected from the heart during systole, providing for continuous flow through the capillaries as the heart relaxes during diastole.
A client took a weight loss drug that activated the alpha-adrenergic receptors in the sympathetic nervous system. Which manifestations would the nurse expect to occur? Select all that apply.
Increased blood pressure of cardiac contraction Increased cardiac cycle speed Sympathetic nervous system control of vascular smooth muscle tone occurs through receptor-activated opening and closing of the calcium channels. In general, alpha adrenergic receptors are excitatory in that they cause the channels to open and produce vasoconstriction. Increased sympathetic activity produces an increase in the heart rate, BP and the velocity and force of cardiac contraction.
Which factor represents the amount of blood that the heart must pump with each beat and is determined by the stretch of the cardiac muscle fibers and the actions of the heart prior to cardiac contraction?
Preload Preload is the distending force that stretches the heart muscle just prior to the work of the onset of ventricular contraction. It represents the volume of blood stretching the ventricular muscle fibers at the end of diastole (i.e., end-diastolic volume) and is the sum of the blood remaining in the heart at the end of systole (end-systolic volume) and the venous return to the heart.
A nurse is teaching a client the correct technique for taking an arterial pulse. The nurse explains that the pulsations are:
Pressure pulses The arterial pressure pulse represents the energy that is transmitted from molecule to molecule along the length of the vessel. When taking a pulse, it is the pressure pulses that are felt. Pressure pulses have no direct relation to the blood flow. It is the pressure pulses that produce the Korotkoff sounds heard during blood pressure measurement. Pressure pulses would be felt even if there was no blood flow at all.
In the circulatory system, pressure is inversely related to which factor?
Volume In the circulatory system, pressure is inversely related to volume. Arterial circulation contains a lower percentage of total blood volume and has higher pressure than the venous circulation, which contains the majority of circulating blood. Flow is related to viscosity and radius is related to wall tension. Velocity is inversely proportional to the cross-sectional area of the vessel.