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Lipids A person with high cholesterol has more Total cholesterol < 200 mg/dl than twice the risk of coronary heart Borderline high 200–239 mg/dl disease as someone whose cholesterol is High 240–above below 200 mg/dL order generic trihexyphenidyl line pain management for dog in heat. Triglycerides >150 mg/dl High > 200 mg/dl and above Normal triglyceride levels vary by age and sex purchase trihexyphenidyl 2mg overnight delivery advanced pain institute treatment center. Reduced specific gravity can indicate diabetes insipidus purchase discount trihexyphenidyl on line knee joint pain treatment, certain renal diseases, excess fluid intake, or diabe- tes mellitus. Raised specific gravity can indicate dehydration, adrenal insufficiency, nephrosis, congestive cardiac failure, or liver disease. This page intentionally left blank Appendix C Interactive Exercises Chapter 1: Introduction Multiple Choice to Disease 1. Their hearts can handle the slightly increased viscosity of the True or False blood and thus higher red blood cell levels may 1. False simple history can determine if she ate recently or if she is under stress, depressed, or anxious, 4. The physician can consult a blood test to determine anemia Fill-Ins or other blood disorders. By applying the Chapter 2: Immunity and Disease science of epidemiology to accidents, perhaps prevention can reduce mortality from accidents Answers to Cases for Critical Thinking as well. Obesity is the result of an energy imbalance; antibodies against the rubella virus so his eating too many calories and not getting enough immune system has seen the rubella virus. Body weight may be the result contracted measles recently because he has of genetics, metabolism, behavior, environment, IgM against the rubella virus; IgM is the frst culture, and socioeconomic status. The bites happened after the women died because trauma is a trigger for infammation 5. In low-income countries research and by plasma cells, increase phagocytosis, and resources should be directed toward infectious stimulate cytotoxic T cells and natural killer disease. A-29 A-30 L Appendix C Interactive Exercises Multiple Choice they sneeze or cough would also help decrease transmission. Infuenza is transmitted in respiratory drop lets generated by coughing and sneezing. True or False Isolation of fu patients would help decrease the transmission of the disease. At frst a patient might donate two to three times per week and later once every and Disorders of the 2–3 months. Chelation therapy is also available Cardiovascular System for those who cannot donate blood. The heart or vascular diseases that should be considered for this patient include atherosclerosis, 1. Smoking increases risk of atherosclerosis, chronic venous insuffciency, and cardiac arrhy 6. Thrombocytopenia, impaired synthesis of clot- Chapter 8: Diseases ting factors, and vitamin K defciency are to be and Disorders of the considered. A physical Multiple Choice examination, medical history, and allergy test- ing are helpful is diagnosing allergic rhinitis. If bile flow to the small intestine is blocked, dietary fat remains undigested and is 10. Following a high-fat True or False meal the gallbladder secretes bile into the small intestine. False hemoglobin that comes from dying erythrocytes and the orange- and yellow-colored breakdown 6. False drates and proteins and manufactures bile, which is used for fat absorption and the absorption of 9. Finally, as blood flow through the liver is restricted by cirrhosis, abdomi- Fill-Ins nal and esophageal venous pressure increases, which leads to the distortion of the esophageal 1. This could be an infec- Fill-Ins tion of the urethra or the urinary bladder, which would cause painful urination with blood in the 1. If a tumor, surgery, radiation, and Disorders of the and chemotherapy are the treatments. This patient has a renal tumor, and hematuria results from damage to the renal tissue. Surgery, Answers to Cases for Critical Thinking radiation, and chemotherapy are the treatments. Taking antiviral medication on a regular basis may decrease transmission of the virus. Because prostate cancer often grows very slowly, some men (especially those who are older or who Chapter 12: Diseases have other major health problems) may never and Disorders of the need treatment for their cancer. Cryptorchidism is the name of the disease, Endocrine System and complications can include infertility and testicular cancer. Hormone therapy and surgery Answers to Cases for Critical Thinking are possible treatments. Diabetes type 1 is consistent with age of onset, high urine production, and weight loss when Multiple Choice the boy should be growing. Treatment Chapter 14: Diseases requires intravenous antibiotics, analgesics, and anti-infammatories. A common cause of Eye and Ear dementia is Alzheimer’s disease, which is progres- sive and eventually fatal. To distinguish between Answers to Cases for Critical Thinking the types of dementia, J. Diabetes can damage the blood vessels in the back of the eye and result in impaired vision. The doctor examines the ear drum externally using an otoscope to observe the Chapter 15: Mental Illness tension on the tympanic membrane and notice any drainage. A warm heating pad gives some and Cognitive Disorders comfort and Tylenol (especially for children) is used to reduce pain and fever. Antibiotics kill Answers to Cases for Critical Thinking bacteria and stop bacterial growth, and this 1. Bone infection would be Integumentary System accompanied by fever and systemic symptoms such as weakness. A tumor would also cause Answers to Cases for Critical Thinking pain and weakness. Impetigo is the diagnosis; Staphylococcus aureus tumors and bloodwork can rule out infections. Tinea pedis Appendix D Prevention Plus Suggested Answers Chapter 1: Introduction Chapter 3: Infectious Diseases to Disease Advice for Travelers Four Modifiable Risk Factors 1. The immune response takes from 10 days to 2 weeks to reach its peak because after initial for Chronic Disease exposure to the antigen, lymphocytes need to 1. Four modifiable risk factors for chronic disease become activated, reproduce, and develop.
Diseases
Arterioles are the infow valves that control the rate of nutritive blood fow through organs and individual regions within them best order trihexyphenidyl treatment pain between shoulder blades. Veins do quality trihexyphenidyl 2 mg stomach pain treatment home, however order trihexyphenidyl overnight knee pain treatment uk, collectively regu late the distribution of available blood volume between the peripheral and central venous compartments. Recall that central blood volume (and therefore pressure) has a marked infuence on stroke volume and cardiac output. Consequently, when one considers what periheral veins are doing, one should be thinking primarily about what the effects will be on central venous pressure and cardiac output. Constriction of the veins (venoconstriction) is largely medi ated through activity of the sympathetic nerves that innervate them. As in arterioles, these sympathetic nerves release norepinephrine, which interacts with a1-receptors and produces an increase in venous tone and a decrease in vessel diameter. There are, however, several functionally important diferences between veins and arterioles. One important consequence of the lack of basal venous tone is that vasodilator metabolites that may accumulate in the tissue have little efect on veins. Because of their thin walls, veins are much more susceptible to physical infu ences than are arterioles. The large effect of internal venous pressure on venous diameter was discussed in Chapter 6 and is evident in the pooling of blood in the veins of the lower extremities that occurs during prolonged standing (as discussed further in Chapter 10). Often external compressional forces are an important determinant of venous volume. Very high pres sures are developed inside skeletal muscle tissue during contraction and cause venous vessels to collapse. Because veins and venules have one-way valves, the blood displaced from veins during skeletal muscle contraction is forced in the for ward direction toward the right side of the heart. In fact, rhythmic skeletal muscle contractions may produce a considerable pumping action, often called the skeletal musce pump, which helps return blood to the heart during exercise. Certain general factors, however, dominate the primary control of the peripheral vasculature when it is viewed from the standpoint of overall cardio vascular system function; these infuences are summarized in Figure 7-5. Basal tone, local metabolic vasodilator factors, and sympathetic vasoconstrictor nerves acting through a1-receptors are the major factors controlling arteriolar tone and therefore the blood fow rate through peripheral organs. Sympathetic vasocon strictor nerves, internal pressure, and external compressional forces are the most important infuences on venous diameter and therefore on peripheral-central dis tribution of blood volume. However, with regard to fow control, most organs can be placed somewhere in a spectrum that ranges from almost total dominance by local metabolic mechanisms to almost total dominance by sympathetic vasoconstrictor nerves. The fow in organs such as the brain, heart muscle, and skeletal muscle is very strongly controlled by local metabolic control, whereas the fow in the kidneys, skin, and splanchnic organs is very strongly controlled by sympathetic nerve activ ity. Consequently, some organs are automatically forced to participate in overall cardiovascular reflex responses to a greater extent than are other organs. The over all plan seems to be that, in cardiovascular emergency, fow to the brain and heart will be preserved at the expense of everything else if need be. In the following sections, we consider how blood fow control differs between some major organs. But it is well to keep in perspective that all organs are part of the overall, hydraulically interconnected cardiovascular system. What happens in any single organ ultimately has ramifcations throughout the entire system. In the following summary of fow control in specific organs, we attempt to address both local and global issues by listing the important and sometimes unique factors that control fow in major organs or organ systems. The major right and left coronary arteries that serve the heart tissue are the first vessels to branch of the aorta. Thus, the drivingfrcefr myocardial blood fow is the sstemic arterial pressure, jut as it isfr other systemic organs. Most of the blood that flows through the myocardial tissue returns to the right atrium by way of a large cardiac vein called the coronar sinus. In a resting individual, the myocardium extracts 70% to 75% of the oxygen in the blood that passes through it. Because of this high extraction rate, coronary sinus blood normally has a lower oxygen content than blood at any other place in the cardiovascular system. Because myocardial oxygen extraction cannot increase significantly from its high resting value, increases in myocardial oxgen consumption must be accompa nied by appropriate increases in coronar blood fow. The issue of which metabolic vasodilator factors play the dominant role in modulating the tone of coronary arterioles is unresolved at present. Many suspect that adenosine, released from myocardial muscle cells in response to increased metabolic rate, may be an important local coronary metabolic vaso dilator infuence. Regardless of the specific details, myocardial oxgen consump tion is the most important infuence on coronar blood fow. Large frces and/or pressures are generated within the myocardial tissue during cardiac musce contraction. Such intramyocardial forces press on the outside of coronary vessels and cause them to collapse during systole. Because of this sstolic compression and the associated collapse of coronary vessels, coro nary vascular resistance is greatly increased during systole. The result, at least for much of the left ventricular myocardium, is that coronary fow is lower during systole than during diastole, even though systemic arterial pressure (ie, coronary perfusion pressure) is highest during systole. Systolic com pression has much less efect on fow through the right ventricular myocar dium, as is evident from the right coronary artery fow trace in Figure 7-6. This is because the peak systolic intraventricular pressure is much lower for the right heart than for the left heart, and the systolic compressional forces in the right ventricular wall are correspondingly less than those in the left ventricular wall. Phasic flows in the left and right coronary arteries in relation to aortic and left ventricular pressures. Systolic compressional frces on coronar vessel are greater in the endocardial (nside)lyers ofthe le ventrculr wal than in the epicardiallyers. Normally, the endocar dial region of the myocardium can make up for the lack of fow during systole by a high fow in the diastolic interval. However, when coronary blood fow is limited-for example, by coronary disease and stenosis-the endocardial lay ers of the left ventricle are often the first regions of the heart to have difculty maintaining a fow sufcient for their metabolic needs. Myocardial infrcts (areas of tissue killed by lack of blood fow) occur most frequently in the endo cardial layers of the left ventricle. Coronar arterioles are densel innervated with sympathetic vasoconstrictor fbers, yet when the actvit ofthe sympathetic nervou s system increases, the coro nar arteroles normall vasodilate rather than vasoconstict. This is because an increase in sympathetic tone increases myocardial oxygen consumption by increasing the heart rate and contractility. The increased local metabolic 4 Consider that the endocardial surface of the left ventricle is exposed to intraventricular pressure (=120 mmHg during systole), whereas the epicardial surface is exposed only to intrathoracic pressure (=OmmHg).
In Figure 7-1 order trihexyphenidyl 2mg amex pain medication for little dogs, the spe cifc receptor for a chemical vasoconstrictor agent is shown linked by a specifc G protein to phospholipase C trihexyphenidyl 2mg otc pain treatment back. The overall result is stimulation of Ca2+ efux order cheapest trihexyphenidyl allied pain treatment center ohio, membrane hyperpolarization, and decreased contractile machinery sensitivity to Ca2+-all of which act synergistically to cause vasodilation. Nitric oxide can be produced by endothelial cells and also by nitrates, a clinically important class of vasodilator drugs. The "vascular tone" of a region can be taken as an indication of the "level of activation" of the individual smooth muscle cells in that region. As described in Chapter 6, the blood flow through any organ is determined largely by its vascular resistance, which is depen dent primarily on the diameter of its arterioles. Basal Tone Arterioles remain in a state of partial constriction even when all external influ ences on them are removed; hence, they are said to have a degree of basal tone (sometimes referred to as intrimic tone). The understanding of the mechanism is incomplete, but basal arteriolar tone may be a refection of the fact that smooth muscle cells inherently and actively resist being stretched as they continually are in pressurized arterioles. Another hypothesis is that the basal tone of arterioles is the result of a tonic production of local vasoconstrictor substances by the endo thelial cells that line their inner surface. In any case, this basal tone establishes a baseline of partial arteriolar constriction from which the external influences on arterioles exert their dilating or constricting effects. These influences can be separated into three categories: local infuences, neural influences, and hormonal infuences. The interstitial concentrations of many substances reflect the balance between the metabolic activity of the tissue and its blood supply. Interstitial oxygen levels, for example, fall whenever the tissue cells are using oxy gen faster than it is being supplied to the tissue by blood flow. Conversely, inter stitial oxygen levels rise whenever excess oxygen is being delivered to a tissue from the blood. Many substances in addition to oxygen are present within tissues and can affect the tone of the vascular smooth muscle. When the metabolic rate of skel etal muscle is increased by exercise, tissue levels of oxygen decrease, but those of carbon dioxide, H+, and K+ increase. In addition, with increased metabolic activity or oxygen deprivation, cells in many tissues may release adenosine, which is an extremely potent vasodilator agent. At present, it is not known which of these (and possibly other) metabolically related chemical alterations within tissues are most important in the local meta bolic control of blood fow. It appears likely that arteriolar tone depends on the combined action of many factors. For conceptual purposes, Figure 7-2 summarizes current understanding of local metabolic control. Vasodilator factors enter the interstitial space from the tissue cells at a rate proportional to tissue metabolism. These vasodilator fac tors are removed from the tissue at a rate proportional to blood fow. Whenever tissue metabolism is proceeding at a rate for which the blood fow is inade quate, the interstitial vasodilator factor concentrations automatically build up and cause the arterioles to dilate. The process continues until blood flow has risen sufciently to appropriately match the tissue metabolic rate and prevent further accumulation of vasodilator 3 An important exception to this rule occurs in the pulmonary circulation and is discussed later in this chapter. Local metabolic mechanisms represent byfr the most important meam oflocal fow control. By these mechanisms, individual organs are able to regulate their own fow in accordance with their specifc metabolic needs. As indicated below, several other types of local infuences on blood vessels have been identifed. However, many of these represent fne-tuning mechanisms and many are important only in certain, usually pathological, situations. A large number of studies have shown that blood vessels respond very differently to certain vascular infuences when their endothelial lining is missing. Acetylcholine, for example, causes vasodilation of intact vessels but causes vasoconstriction of vessels stripped of their endothelial lining. This and similar results led to the realization that endothelial cells can actively participate in the control of arterio lar diameter by producing local chemicals that affect the tone of the surrounding smooth muscle cells. In the case of the vasodilator effect of infusing acetylcholine through intact vessels, the vasodilator infuence produced by endothelial cells has been identifed as nitric oxide. Nitric oxide is produced within endothelial cells from the amino acid, L-arginine, by the action of an enzyme, nitric oxide syn thase. Nitric oxide synthase is activated by a rise in the intracellular level of the Ca2+. Acetylcholine and several other agents (including bradykinin, vasoactive intes tinal peptide, and substance P) stimulate endothelial cell nitric oxide production because their receptors on endothelial cells are linked to receptor-operated Ca2+ channels. Probably more importantly from a physiological standpoint, fow related shear stresses on endothelial cells stimulate their nitric oxide production presumably because stretch-sensitive channels for Ca2+ are activated. Such fow related endothelial cell nitric oxide production may explain why, for example, exercise and increased blood fow through muscles of the lower leg can cause dila tion of the blood-supplying femoral artery at points far upstream of the exercising muscle itsel£ Agents that block nitric oxide production by inhibiting nitric oxide synthase cause signifcant increases in the vascular resistances of most organs. For this reason, it is believed that endothelial cells are normally always producing some nitric oxide that is importantly involved, along with other factors, in reducing the normal resting tone of arterioles throughout the body. Endothelial cells have also been shown to produce several other locally acting vasoactive agents including the vasodilators "endothelial-derived hyperpolarizing factor", prostacyclin and the vasoconstrictor endothelin. Much recent evidence suggests that endothelin may play important roles in such important overall process such as bodily salt handling and blood pressure regulation. One general unresolved issue with the concept that arteriolar tone (and there fore local nutrient blood fow) is regulated by factors produced by arteriolr endothelial cells is how these cells could know what the metabolic needs of the downstream tissue are. This is because the endothelial cells lining arterioles are exposed to arterial blood whose composition is constant regardless of flow rate or what is happening downstream. One hypothesis is that there exists some sort of communication system between vascular endothelial cells. That way, endothelial cells in capillaries or venules could telegraph upstream information about whether the blood fow is indeed adequate. In most cases, however, definite information about the relative importance of these substances in cardiovascular regulation is lacking. Prostaglandins and thromboxane are a group of several chemically related prod ucts of the cyclooxygenase pathway of arachidonic acid metabolism. Certain prostaglandins are potent vasodilators, whereas others are potent vasoconstric tors. Despite the vasoactive potency of the prostaglandins and the fact that most tissues (including endothelial cells and vascular smooth muscle cells) are capable of synthesizing prostaglandins, it has not been demonstrated convincingly that prostaglandins play a crucial role in normal vascular control. It is clear, how ever, that vasodilator prostaglandins are involved in inflammatory responses.
The central blood volume includes the blood in the superior vena cava and the intrathoracic portions of the inferior vena cava order trihexyphenidyl with amex treatment pain ball of foot, right atrium and ventricle order trihexyphenidyl 2mg on-line postoperative pain treatment guidelines, pulmonary circulation buy trihexyphenidyl 2mg otc treatment for joint pain for dogs, and left atrium; this constitutes ~25% of the total blood volume. The central blood volume can be decreased or increased by shifts in blood to and from the extrathoracic blood volume. From a functional standpoint, the most important components of the extrathoracic blood volume are the veins of the extremities and abdominal cavity. Blood shifts readily between these veins and the vessels of the central blood volume. Blood in the central and extrathoracic arteries can be ignored in these shifts because of their low compliance. Furthermore, the extrathoracic blood volume in the neck and head is of little importance because there is far less blood in these regions and blood volume inside the cranium cannot change much because the skull is rigid. The volume of blood in the veins of the abdomen and extremities is about equal to the central blood volume; therefore, about half of the total blood volume is involved in shifts in distribution that affect the filling of the heart. Under normal conditions, changes in central venous pressure are a good reflection of central blood volume because the compliance of the intrathoracic vessels tends to be constant. Central venous pressure can be measured by placing the tip of a catheter in the right atrium. In general, the use of central venous pressure to assess changes in central blood volume depends on the assumption that the right heart is capable of pumping normally. In certain situations, however, the physiologic meaning of central venous pressure is changed. Also, central venous pressure does not necessarily reflect left atrial or left ventricular filling pressure. Abnormalities in right or left heart function or in pulmonary vascular resistance can make it difficult to predict left atrial pressure from central venous pressure. Unfortunately, measurements of the peripheral venous pressure, such as the pressure in an arm or leg vein, are subject to too many influences to be helpful in most clinical situations (e. Consider what happens if blood is steadily infused into the inferior vena cava of a healthy person. This difference between the input and output of blood produces an increase in central blood volume. It will occur first in the right atrium, where the accompanying increase in pressure enhances right ventricular filling, end-diastolic fiber length (preload), and stroke volume. Increased flow into the lungs increases pulmonary blood volume and filling of the left atrium. The output of the left ventricle will increase according to Starling’s law of the heart so that the output of the two ventricles exactly matches. It can be surmised from the discussion above that central blood volume is altered by two events: changes in total blood volume and changes in the distribution of total blood volume between central and extrathoracic regions. An increase in total blood volume can occur as a result of an infusion of fluid, the retention of salt and water by the kidneys, or a shift in fluid from the interstitial space to plasma (see Chapter 15). A decrease in blood volume can occur as a result of hemorrhage; fluid losses through sweat, vomiting, or diarrhea; or the transfer of fluid from plasma into the interstitial space. In the absence of compensatory events, changes in total blood volume result in proportional changes in both central and extrathoracic blood volume. For example, a moderate hemorrhage (10% of blood volume) with no distribution shift would cause a 10% decrease in central blood volume. Central blood volume can be altered by a shift in blood volume to or away from the extrathoracic circulation. Shifts in the distribution of blood volume occur for two reasons: a change in transmural pressure or a change in venous compliance. Changes in the transmural pressure of vessels in the chest or periphery can either enlarge (increased P ) or diminish (decreased P ) their size. Because total bloodT T volume is finite, volume shifts in response to changes in transmural pressure in one region affect the volume of the other region. If it is slowly turned vertically on its long axis, the lower end of the balloon has the greatest transmural pressure because of the weight of the water pressing from above. Consequently, the lower end of the balloon will bulge and the upper end will shrink; volume increases in the lower end at the expense of a loss at the upper end. The best physiologic example of a change in regional transmural pressure occurs when a person stands up. Standing increases the transmural pressure in the blood vessels of the legs because it creates a vertical column of blood between the heart and those vessels. The arterial and venous pressures at the ankles during standing can easily be increased almost 100 mm Hg higher than those in the individual in the recumbent position. The increased transmural pressure (outside pressure is still atmospheric) results in little distention of arteries because of their low compliance but results in considerable distention of veins because of their high compliance. In fact, ~550 mL of blood is needed to fill the stretched veins of the legs and feet when an average person stands up. Filling of the veins of the buttocks and pelvis also increases but to a lesser extent than the lower extremities, because the increase in transmural pressure is less. When a person stands, blood continues to be pumped by the heart at the same rate and stroke volume for one or two beats. However, much of the blood reaching the legs remains in the veins as they become passively stretched to their new size by the increased venous transmural pressure. For example, upon standing, sympathetic nerves to peripheral veins are activated causing them to contract. The resulting decrease in venous compliance results in a redistribution of blood volume toward the central blood volume. However, because the cardiovascular system is a true “circulatory” system, it is equally true that the output of the heart alters vascular volumes and pressures. One of the more important consequences of the elastic nature of large arteries is that it reduces cardiac work and myocardial oxygen demand. Consider the example in which the heart pumps blood for 4 seconds at a constant flow of 100 mL/s (6 L/min) into rigid arteries with a resistance of 16. This would then generate a constant pressure of 100 mm Hg, and cardiac work over the 4 seconds would be simply pressure (P) × total volume (V) or 100 mm Hg × 400 mL = 40,000 mm Hg mL. If the heart pumped intermittently and ejected blood at 100 mL/s into noncompliant arteries during the first half-second of the cycle only (i. However, pressure would rise to 200 mm Hg during each ejection and drop to 0 mm Hg during relaxation. Although no work would be done during relaxation, work done during the contraction would be 80,000 mm Hg mL (200 mm Hg × 400 mL). In this situation, the oxygen demand on the heart would be substantially increased even though the output of the heart over 4 seconds was no better than that in the steady flow example. In contrast, if this same intermittent flow was ejected into arteries with infinite compliance (i. The same 400 mL would be ejected over 4 seconds in this situation but, against a constant pressure of 100 mm Hg, the work done would again equal to 40,000 mm Hg mL. Of course, arteries in the human body are neither totally rigid nor infinitely compliant. This example serves to demonstrate that decreased arterial compliance increases cardiac work and oxygen demand.
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