By D. Fadi. University of Southern Mississippi. 2018.
The patient should be able to indicate the particular type of coin purchase 60 mg alli visa, such as a dime versus a penny purchase alli 60mg free shipping, or a nickel versus a quarter cheap alli 60mg otc, on the basis of the sensory cues involved. For example, the size, thickness, or weight of the coin may be an indication, or to differentiate the pairs of coins suggested here, the smooth or corrugated edge of the coin will correspond to the particular denomination. The second task, graphesthesia, is to recognize numbers or letters written on the palm of the hand with a dull pointer, such as a pen cap. Praxis and gnosis are related to the conscious perception and cortical processing of sensory information. Being able to transform verbal commands into a sequence of motor responses, or to manipulate and recognize a common object and associate it with a name for that object. The relationship between the words that describe actions, or the nouns that represent objects, and the cerebral location of these concepts is suggested to be localized to particular cortical areas. Certain aphasias can be characterized by a deficit of verbs or nouns, known as V impairment or N impairment, or may be classified as V–N dissociation. To describe what is happening in a photograph as part of the expressive language subtest, a patient will use active- or image-based language. The lack of one or the other of these components of language can relate to the ability to use verbs or nouns. Damage to the region at which the frontal and temporal lobes meet, including the region known as the insula, is associated with V impairment; damage to the middle and inferior temporal lobe is associated with N impairment. Judgment and Abstract Reasoning Planning and producing responses requires an ability to make sense of the world around us. Making judgments and reasoning in the abstract are necessary to produce movements as part of larger responses. Will hitting the snooze button multiple times lead to feeling more rested or result in a panic as you run late? In the mental status exam, the subtest that assesses judgment and reasoning is directed at three aspects of frontal lobe function. First, the examiner asks questions about problem solving, such as “If you see a house on fire, what would you do? The prefrontal cortex is composed of the regions of the frontal lobe that are not directly related to specific motor functions. Anterior to that are the premotor cortex, Broca’s area, and the frontal eye fields, which are all related to planning certain types of movements. Anterior to what could be described as motor association areas are the regions of the prefrontal cortex. The antecedents to planning certain movements are judging whether those movements should be made, as in the example of deciding whether to hit the snooze button. The neurological exam does not necessarily assess personality, but it can be within the realm of neurology or psychiatry. A clinical situation that suggests this link between the prefrontal cortex and personality comes from the story of Phineas Gage, the railroad worker from the mid-1800s who had a metal spike impale his prefrontal cortex. Later anecdotal evidence from his life suggests that he was able to support himself, although he had to relocate and take on a different career as a stagecoach driver. The disorders associated with this procedure included some aspects of what are now referred to as personality disorders, but also included mood disorders and psychoses. Depictions of lobotomies in popular media suggest a link between cutting the white matter of the prefrontal cortex and changes in a patient’s mood and personality, though this correlation is not well understood. As an extreme measure to deal with a debilitating condition, the corpus callosum may be sectioned to overcome intractable epilepsy. When the connections between the two cerebral hemispheres are cut, interesting effects can be observed. If a person with an intact corpus callosum is asked to put their hands in their pockets and describe what is there on the basis of what their hands feel, they might say that they have keys in their right pocket and loose change in the left. They may even be able to count the coins in their pocket and say if they can afford to buy a candy bar from the vending machine. If a person with a sectioned corpus callosum is given the same instructions, they will do something quite peculiar. They will not even move their left hand, much less report that there is loose change in the left pocket. The reason for this is that the language functions of the cerebral cortex are localized to the left hemisphere in 95 percent of the population. Additionally, the left hemisphere is connected to the right side of the body through the corticospinal tract and the ascending tracts of the spinal cord. Motor commands from the precentral gyrus control the opposite side of the body, whereas sensory information processed by the postcentral gyrus is received from the opposite side of the body. For a verbal command to initiate movement of the right arm and hand, the left side of the brain needs to be connected by the corpus callosum. Language is processed in the left side of the brain and directly influences the left brain and right arm motor functions, but is sent to influence the right brain and left arm motor functions through the corpus callosum. Likewise, the left-handed sensory perception of what is in the left pocket travels across the corpus callosum from the right brain, so no verbal report on those contents would be possible if the hand happened to be in the pocket. Unlike normal people, this patient can perform two independent tasks at the same time because the lines of communication between the right and left sides of his brain have been removed. Whereas a person with an intact corpus callosum cannot overcome the dominance of one hemisphere over the other, this patient can. If the left cerebral hemisphere is dominant in the majority of people, why would right-handedness be most common? The Mental Status Exam The cerebrum, particularly the cerebral cortex, is the location of important cognitive functions that are the focus of the mental status exam. The regionalization of the cortex, initially described on the basis of anatomical evidence of cytoarchitecture, reveals the distribution of functionally distinct areas. Cortical regions can be described as primary sensory or motor areas, association areas, or multimodal integration areas. The functions attributed to these regions include attention, memory, language, speech, sensation, judgment, and abstract reasoning. The mental status exam addresses these cognitive abilities through a series of subtests designed to elicit particular behaviors ascribed to these functions. Losses of language and speech functions, known as aphasias, are associated with damage to the important integration areas in the left hemisphere known as Broca’s or Wernicke’s areas, as well as the connections in the white matter between them. The subtests related to these functions depend on multimodal integration, as well as language-dependent processing. The prefrontal cortex contains structures important for planning, judgment, reasoning, and working memory. The famous case of Phineas Gage suggests a role for this cortex in personality, as does the outdated practice of prefrontal lobectomy.
This extended period is critical buy alli 60 mg without a prescription, since the heart muscle must contract to pump blood effectively and the contraction must follow the electrical events buy 60 mg alli with amex. Without extended refractory periods buy 60 mg alli visa, premature contractions would occur in the heart and would not be compatible with life. The extended refractory period allows the cell to fully contract before another electrical event can occur. Their influx through slow calcium channels accounts for the prolonged plateau phase and absolute refractory period that enable cardiac muscle to function properly. Calcium ions also combine with the regulatory protein troponin in the troponin-tropomyosin complex; this complex removes the inhibition that prevents the heads of the myosin molecules from forming cross bridges with the active sites on actin that provide the power stroke of contraction. The bundle branches would have an inherent rate of 20–30 impulses per minute, and the Purkinje fibers would fire at 15–20 impulses per minute. While a few exceptionally trained aerobic athletes demonstrate resting heart rates in the range of 30–40 beats per minute (the lowest recorded figure is 28 beats per minute for Miguel Indurain, a cyclist), for most individuals, rates lower than 50 beats per minute would indicate a condition called bradycardia. Depending upon the specific individual, as rates fall much below this level, the heart would be unable to maintain adequate flow of blood to vital tissues, initially resulting in decreasing loss of function across the systems, unconsciousness, and ultimately death. Electrocardiogram By careful placement of surface electrodes on the body, it is possible to record the complex, compound electrical signal of the heart. The term “lead” may be used to refer to the cable from the electrode to the electrical recorder, but it typically describes the voltage difference between two of the electrodes. The 12-lead electrocardiograph uses 10 electrodes placed in standard locations on the patient’s skin (Figure 19. In continuous ambulatory electrocardiographs, the patient wears a small, portable, battery-operated device known as a Holter monitor, or simply a Holter, that continuously monitors heart electrical activity, typically for a period of 24 hours during the patient’s normal routine. Each component, segment, and interval is labeled and corresponds to important electrical events, demonstrating the relationship between these events and contraction in the heart. Since the Q wave may be difficult to view in some tracings, the measurement is often extended to the R that is more easily visible. Such an area, which may actually be a component of the conduction system or some other contractile cells, is known as an ectopic focus or ectopic pacemaker. An ectopic focus may be stimulated by localized ischemia; exposure to certain drugs, including caffeine, digitalis, or acetylcholine; elevated stimulation by both sympathetic or parasympathetic divisions of the autonomic nervous system; or a number of disease or pathological conditions. Occasional occurances are generally transitory and nonlife threatening, but if the condition becomes chronic, it may lead to either an arrhythmia, a deviation from the normal pattern of impulse conduction and contraction, or to fibrillation, an uncoordinated beating of the heart. In general, the size of the electrical variations, the duration of the events, and detailed vector analysis provide the most comprehensive picture of cardiac function. Additionally, it will not reveal the effectiveness of the pumping, which requires further testing, such as an ultrasound test called an echocardiogram or nuclear medicine imaging. External Automated Defibrillators In the event that the electrical activity of the heart is severely disrupted, cessation of electrical activity or fibrillation may occur. In fibrillation, the heart beats in a wild, uncontrolled manner, which prevents it from being able to pump effectively. The most common treatment is defibrillation, which uses special paddles to apply a charge to the heart from an external electrical source in an attempt to establish a normal sinus rhythm (Figure 19. These devices contain simple and direct verbal instructions that can be followed by nonmedical personnel in an attempt to save a life. In order to speed up the heart rate and restore full sinus rhythm, a cardiologist can implant an artificial pacemaker, which delivers electrical impulses to the heart muscle to ensure that the heart continues to contract and pump blood effectively. These artificial pacemakers are programmable by the cardiologists and can either provide stimulation temporarily upon demand or on a continuous basis. Oxygen from the lungs is brought to the heart, and every other organ, attached to the hemoglobin molecules within the erythrocytes. Normally, these two mechanisms, circulating oxygen and oxygen attached to myoglobin, can supply sufficient oxygen to the heart, even during peak performance. Both fatty acid droplets and glycogen are stored within the sarcoplasm and provide additional nutrient supply. The period of contraction that the heart undergoes while it pumps blood into circulation is called systole. Both the atria and ventricles undergo systole and diastole, and it is essential that these components be carefully regulated and coordinated to ensure blood is pumped efficiently to the body. Pressures and Flow Fluids, whether gases or liquids, are materials that flow according to pressure gradients—that is, they move from regions that are higher in pressure to regions that are lower in pressure. Accordingly, when the heart chambers are relaxed (diastole), blood will flow into the atria from the veins, which are higher in pressure. As blood flows into the atria, the pressure will rise, so the blood will initially move passively from the atria into the ventricles. When the action potential triggers the muscles in the atria to contract (atrial systole), the pressure within the atria rises further, pumping blood into the ventricles. During ventricular systole, pressure rises in the ventricles, pumping blood into the pulmonary trunk from the right ventricle and into the aorta from the left ventricle. Again, as you consider this flow and relate it to the conduction pathway, the elegance of the system should become apparent. Phases of the Cardiac Cycle At the beginning of the cardiac cycle, both the atria and ventricles are relaxed (diastole). Blood is flowing into the right atrium from the superior and inferior venae cavae and the coronary sinus. The two atrioventricular valves, the tricuspid and mitral valves, are both open, so blood flows unimpeded from the atria and into the ventricles. The two semilunar valves, the pulmonary and aortic valves, are closed, preventing backflow of blood into the right and left ventricles from the pulmonary trunk on the right and the aorta on the left. As the atrial muscles contract from the superior portion of the atria toward the atrioventricular septum, pressure rises within the atria and blood is pumped into the ventricles through the open atrioventricular (tricuspid, and mitral or bicuspid) valves. At the start of atrial systole, 862 Chapter 19 | The Cardiovascular System: The Heart the ventricles are normally filled with approximately 70–80 percent of their capacity due to inflow during diastole. Atrial contraction, also referred to as the “atrial kick,” contributes the remaining 20–30 percent of filling (see Figure 19. Atrial systole lasts approximately 100 ms and ends prior to ventricular systole, as the atrial muscle returns to diastole. At the end of atrial systole and just prior to atrial contraction, the ventricles contain approximately 130 mL blood in a resting adult in a standing position. Initially, as the muscles in the ventricle contract, the pressure of the blood within the chamber rises, but it is not yet high enough to open the semilunar (pulmonary and aortic) valves and be ejected from the heart. This increase in pressure causes blood to flow back toward the atria, closing the tricuspid and mitral valves. Since blood is not being ejected from the ventricles at this early stage, the volume of blood within the chamber remains constant. Consequently, this initial phase of ventricular systole is known as isovolumic contraction, also called isovolumetric contraction (see Figure 19.
Reduction in systemic vascular resistance leads to a considerable rise in cardiac out put order alli 60 mg visa. Sodium nitroprusside is a mixed venous and arteriolar dilator used also for acute reduction of blood pressure buy alli 60 mg line. These drugs reduce after load by reducing peripheral resistance and also reduce preload by reducing salt and water retention by way of reduction in aldosterone secretion generic alli 60mg with visa. They are nowadays considered a head of cardiac glycosides in the treatment of chronic heart failure. The following are essential for long-term management of chronic heart failure: Modify cardiovascular risk factor profile, e. When the increase in coronary blood flow is unable to match the increased oxygen demand, angina develops. It has become apparent that spasm of the coronary arteries is important in the production of angina. Organic nitrates: organic nitrates are potent vasodilators and successfully used in therapy of angina pectoris for over 100 years. The effects of nitrates are mediated through the direct relaxant action on smooth muscles. Vasodilating organic nitrates are reduced to organic nitrites, which is then converted to nitric oxide. The action of nitrates begins after 2-3 minutes when chewed or held under tongue and action lasts for 2 hours. The onset of action and duration of action differs for different nitrates and varying pharmaceutical preparations. Adverse effects include flushing, weakness, dizziness, tachycardia, palpitation, vertigo, sweating, syncope localized burning with sublingual preparation and contact dermatitis with ointment. Adrenergic blocking agents Exercise and emotional excitement induce angina in susceptible subject by the increase in heart rate, blood pressure and myocardial contractility through increased sympathetic activity. In most patients the net effect is a beneficial reduction in cardiac workload and myocardial oxygen consumption e. Adverse effects: Lethargy, fatigue, rash, cold hands and feet, nausea, breathlessness, nightmares and bronchospasm. Therapeutic uses other than angina include hypertension, Cardiac arrhythmias, post myocardial infarction and pheochromocytoma. Calcium channel blockers: calcium is necessary for the excitation contraction coupling in both the cardiac and smooth muscles. Calcium channel blockers appear to involve their interference with the calcium entry into the myocardial and vascular smooth muscle, thus decreasing the availability of the intracellular calcium e. Other therapeutic uses: hypertension, acute coronary insufficiency, tachycardia, Adverse effects: flushing nausea/vomiting, headache, Ankle swelling, dizziness, constipation, etc. Acetylsalicylic acid Acetylsalicylic acid (aspirin) at low doses given intermittently decreases the synthesis of thromboxne A2 without drastically reducing prostacylin synthesis. Thus, at the doses of 75 mg per day it can produce antiplatelet activity and reduce the risk of myocardial infarction in anginal patients. However, it is generally accepted that cardiac arrhythmias arise as the result of either of a) Disorders of impulse formation and/ or b) Disorders of impulse conduction. Pharmacotherapy of cardiac arrhythmias Antiarrhythmic drugs are used to prevent or correct cardiac arrhythmias (tachyarrhythmias). Drugs used in the treatment of cardiac arrhythmias are traditionally classified into: Class (I): Sodium channel blockers which include quinidine, lidocaine, phenytion, flecainide, etc. Lidocaine, which is used commonly as a local anaesthetic blocks both open and inactivated sodium channel and decreases automaticity. Adverse effects: excessive dose cause massive cardiac arrest, dizziness, drowsiness, seizures, etc. It is used in ventricular ectopic beats in patients with normal left ventricular function. Beta blockers may potentiate the negative inotropic action of other antiarrhythmics. Therapeutic uses: This is useful in tachyarrhythmias, in pheochromocytoma and in thyrotoxicosis crisis. It is also useful in patients with atrial fibrillation and flutter refractory to digitalis. The main adverse effects of this drug are anorexia, nausea, abdominal pain, tremor, hallucinations, peripheral neuropathy, A. It is absolutely contraindicated in patients on beta blockers, quinidine or disopyramide. Class - V drugs: Digoxin causes shortening of the atrial refractory period with small doses (vagal action) and a prolongation with the larger doses (direct action). This action is of major importance in slowing the rapid ventricular rate in patients with atrial fibrillation Diuretics Diuretics are drugs, which increase renal excretion of salt and water: are principally used to remove excessive extracellular fluid from the body. In order to understand the action of diuretics it is important to have some knowledge of the basic processes that take place in the nephron (unit structure of kidney. Approximately 180 liters of fluid is filtered from the glomerulus into the nephron per day. There are three mechanisms involved in urine formation 64 a) glomerular filtration b) tubular reabsorption c) Tubular secretion. Classification of diuretics:- Most of the diuretics used therapeutically act by interfering with sodium reabsorption by the tubules. Thiazide diuretics act by inhibiting NaCl symport at the distal convoluted tubule. Adverse effects: epigastric distress, nausea, vomiting, weakness, fatigue, dizziness, impotence, jaundice, skin rash, hypokalemia, hyperuricemia, hyperglycaemia and visual disturbance. Loop diuretics: Loop diuretics like frusemde inhibit Na - K – 2Cl symporter in the ascending limb. Adverse effects: Hypokalemia, nausea, anorexia, vomiting epigastric distress, fatigue weakness muscle cramps, drowsiness. Therapeutic uses: acute pulmonary edema, edema of cardiac, hepatic and renal disease. Hypertension, cerebral edema, in drug overdose it can be used to produce forced diuresis to facilitate more rapid elimination of drug. Potassium sparing diuretics mechanism of action: Potassium sparing diuretics (spironolactone, triamterene, amiloride) are mild diuretics causing diuresis by increasing the excretion of sodium, calcium and bicarbonate but decrease the excretion of potassium. Hyponatraemia 65 Therapeutic uses: used with conjunction with thiazides or loop diuretics in edema due to, cardiac failure nephrotic syndrome and hepatic disease. Carbonic anhydrase inhibitors: these drugs like acetazolamide inhibit the enzyme carbonic anhydrase in renal tubular cells and lead to increased excretion of bicarbonate, sodium and potassium ions in urine. Main adverse effects of these agents are drowsiness, hypokalemia, metabolic acidosis and epigastric distress. Osmotic diuretics: these drugs like mannitol and glycerine (glycerol) are freely filtered at the glomerulus and are relatively inert pharmacologically and undergo limited reabsorption by renal tubule. These are administered to increase significantly the osmolality of plasma and tubular fluid.
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Nuestras La voluntad de mantener los progresos registrados en el iniciativas de prevención han provocado cambios reales en la terreno del paludismo no solo debe provenir de los líderes transmisión del paludismo generic alli 60 mg mastercard, y la mayoría de los casos de febre mundiales en el ámbito de la salud y de los políticos purchase 60mg alli fast delivery, sino ya no se deben a éste discount alli 60 mg overnight delivery, incluso en África. Si estas pueden indicativo claro de progreso, y una señal de cómo se depuran conocer la verdadera carga del paludismo y pueden ver los constantemente las estrategias de control. Disponemos de resultados de las labores de prevención y control, la voluntad pruebas de diagnóstico económicas, rápidas y de calidad para eliminar y erradicar el paludismo nunca desaparecerá. También destaca la continuación de los dar lugar a una resurgencia de los casos de paludismo y las progresos realizados en pos del cumplimiento de los objetivos muertes debidas a esta enfermedad. Los métodos actuales de control del vector del paludismo La fnanciación internacional para el control de la enfermedad dependen en gran medida de un único tipo de insecticidas, ha crecido marcadamente durante la última década. Los países con poblaciones en riesgo de menor resistencia contra éste, lo que podría dar lugar rápidamente a tamaño continúan recibiendo más fnanciación por persona un problema de salud pública de gran envergadura. A medida que la incidencia del habrán distribuido aproximadamente 289 millones de redes paludismo disminuye en gran parte del África subsahariana, mosquiteras tratadas con insecticida en el África subsahariana, la necesidad de diferenciar esta enfermedad de otras febres sufcientes para cubrir el 76% de los 765 millones de personas no palúdicas se hace más urgente. Se estima que el 42% de los notifcados en África que han sido confrmados por una prueba hogares de África dispusieron a mediados de 2010 de al menos de diagnóstico ha aumentado de modo sustancial, desde menos una red mosquitera tratada con insecticida, y que el 35% de los del 5% a principios de la década hasta aproximadamente el 35% niños durmieron protegidos por uno. El porcentaje de niños que en 2009, pero en la mayoría de los países africanos y en una utilizan estas redes mosquiteras continúa hallándose por debajo minoría de países de otras regiones esta tasa continúa siendo de la meta del 80% fjada por la Asamblea Mundial de la Salud, baja. Unos pocos países han mostrado que es posible ampliar en parte porque, en algunos de los mayores países africanos, el rápidamente a escala nacional la disponibilidad de pruebas porcentaje de hogares provistos de al menos una red mosquitera de diagnóstico para el paludismo, siempre y cuando se preste continuó siendo bajo hasta fnales de 2009. Las bajas tasas atención a la adecuada preparación, formación, seguimiento, de uso reveladas por algunos estudios se deben a la falta de supervisión y control de calidad. Dichas experiencias se han sufcientes redes mosquiteras para cubrir a todos los miembros asociado a grandes reducciones del uso de terapias combinadas del hogar; los resultados de las encuestas domiciliarias sugieren basadas en la artemisinina y a una mejor vigilancia del que la mayoría (el 80%) de las redes mosquiteras tratadas con paludismo. La información facilitada por fabricantes indica que la Si bien la rápida ampliación de la distribución de redes cantidad de terapias combinadas basadas en la artemisinina mosquiteras tratadas con insecticida en África constituye un que se han administrado ha aumentado cada año desde 2005. La vida útil de una red mosquitera tratada con paludismo observados en el sector público, mientras que otros insecticida de larga duración se estima actualmente en tres años. Estas cifras representan ponen de relieve la fragilidad de la lucha antipalúdica y la un incremento sustancial desde 2005, cuando solamente cinco necesidad de mantener programas de control aun si el número países administraban sufcientes terapias combinadas basadas de casos se ha reducido de forma sustancial. Las experiencias de en la artemisinina para cubrir a más del 50% de los pacientes Rwanda y Zambia indican también que el seguimiento mensual tratados en el sector público. Sin embargo, la información sobre el de los datos de vigilancia de la enfermedad, tanto a nivel acceso al tratamiento es, en general, incompleta, especialmente nacional como subnacional, es esencial. Dado que los datos en lo referente al porcentaje de pacientes tratados en el sector epidemiológicos de muchos países del África subsahariana privado. Es necesario evitar constituye una amenaza para la vida terapéutica de las terapias que ocurran importantes acontecimientos epidemiológicos en combinadas basadas en este principio activo, ya que fomentan la países sin que éstos sean detectados e investigados. En noviembre de 2010, 25 países todavía permitían la comercialización de estos productos y 39 empresas farmacéuticas continuaban fabricándolos. La mayoría de los países que siguen permitiendo la comercialización de monoterapias se encuentra en la región de África, y la mayoría de los fabricantes se halla en la India. La propagación de la resistencia a los fármacos antipalúdicos durante las últimas décadas ha dado lugar a la intensifcación del seguimiento de la efcacia para hacer posible la detección precoz de la resistencia. A pesar de los cambios observados en la sensibilidad del parásito a las artemisininas, la efcacia clínica y parasitológica de las terapias combinadas basadas en este principio activo todavía no se ha visto comprometida, incluso en la subregión del Gran Mekong. No obstante, ambos componentes de la combinación farmacológica se hallan a riesgo actualmente, y el empleo de una terapia combinada basada en la artemisinina asociada a un medicamento inefcaz puede aumentar el riesgo de desarrollo o propagación de la resistencia a la artemisinina. Se detectó un descenso superior al 50% del número de casos confrmados de esta enfermedad entre 2000 y 2009 en 31 de los 56 países con paludismo endémico no africanos, y en otros ocho países se observaron reducciones de entre el 25% y el 50%. Se estima que el número de casos de paludismo aumentó desde 233 millones en 2000 a 244 millones en 2005, pero descendió a 225 millones en 2009, y que el número de muertes debidas al paludismo disminuyó desde 985000 en 2000 a 781000 en 2009. El progreso en la reducción de la carga del paludismo ha sido destacable, pero hay pruebas de que en 2009 aumentaron los casos de paludismo en tres países (Rwanda, Santo Tomé y Príncipe, y Zambia). En el Día Mundial de la Malaria 2008, el Secretario General para los grupos de población que viven en áreas de alta de las Naciones Unidas hizo un llamamiento para garantizar transmisión y son especialmente vulnerables a contraer una cobertura universal de los programas de prevención y paludismo o a sufrir sus consecuencias, en particular mujeres tratamiento del paludismo para fnales de 2010. Papúa Nueva Guinea, en la 50% a fnales de 2010 y en un 75% en 2015 las cifras de casos Región del Pacífco Occidental, adoptó también esta política de paludismo y muertes por esta enfermedad registradas en en 2009. En 2008, 33 de los 43 países de la Región de África con paludismo endémico z Políticas y estrategias de y 45 de los 63 países de otras regiones declararon la reali- lucha antipalúdica zación de pruebas de confrmación parasitológica en todos Para cumplir las metas propuestas para 2010 y 2015, los los casos presuntivos de paludismo, con independencia de países deben llegar a todas las personas a riesgo de la edad del paciente, y 77 de 86 países con Plasmodium falci- contraer paludismo facilitándoles una red mosquitera parum endémico informaron de que mantenían una política tratada con insecticida o fumigación intradomiciliaria con de tratamiento combinado basado en la artemisinina para insecticidas de acción residual, así como proporcionar paludismo P. En en la Región de África, distribuyen las redes mosquiteras de noviembre de 2010, 25 países todavía permitían la comercia- forma gratuita. La proporción mediana de niños menores de 5 años de edad por donantes no se ha debido a una reducción general del que dormían protegidos por una red de este tipo en estos países nivel de fnanciación nacional, aunque los países que han era del 45%. Las bajas tasas de utilización reveladas por algunos reducido su gasto recibieron más fnanciación externa que estudios se deben principalmente a la carencia de redes mosquit- los que ampliaron su gasto doméstico en el paludismo. Las personas de entre 5 y 19 de edad son las que menos tienden produciéndose en los países con menores poblaciones en a utilizar las redes mosquiteras tratadas con insecticida, en riesgo. La fnanciación externa se ha concentrado en activi- comparación con las pertenecientes a los grupos de edad dades de programas, en particular la distribución de redes superior e inferior. Las mujeres tienen una tendencia ligeramente mosquiteras tratadas con insecticida, medicamentos antipa- mayor que los hombres a dormir protegidas por una red tratada lúdicos y fumigación intradomiciliaria con insecticidas resi- (proporción mujeres:hombres = 1,1); ello se debe en parte a que las mujeres embarazadas tienden más a dormir protegidas por duales. No existe diferencia de los gobiernos nacionales a los recursos humanos, aunque alguna de uso entre niños y niñas (ratio niñas:niños = 0,99). El número de personas protegidas por fumigación intradomi- ciliaria con insecticidas residuales creció en el África subsahari- 12. Los países que se encuentran en las fases de preeliminación ana desde 13 millones en 2005 hasta 75 millones en 2009, una y de eliminación tienden a gastar más por persona a riesgo cantidad que corresponde a una protección del 10% de la de contraer paludismo que los países que se hallan en la fase población a riesgo en 2009. Si bien el aumento del gasto se debe en parte a la mayor fnanciación externa, la fnanciación gubernamental 18. La aplicación de la fumigación intradomiciliaria con insecticidas residuales se mantiene en general en los niveles z Progresos en la prevención del paludismo históricos, con 98 millones de personas protegidas en 2009 (69 millones en la India). Con la excepción de la India, el porcen- La cobertura con redes mosquiteras tratadas con taje de la población protegida por fumigación intradomiciliaria insecticida está creciendo rápidamente en algunos países tiende a ser menor que en los países africanos que emplean esta de África; el porcentaje de hogares que poseen al menos técnica, posiblemente debido a la naturaleza más focal que tiene una red mosquitera aumentó hasta el 42% a mediados de la enfermedad fuera de África. En menos de tres años, entre 2008 y 2010, se distribuyó en el manera de una sola clase de insecticidas, los piretroides, que son África subsahariana un total de 254 millones de redes mosquit- los compuestos más utilizados para la fumigación de interiores eras tratadas con insecticida, sufcientes para cubrir al 66% y constituyen la única clase de insecticida utilizado para tratar de los 765 millones de personas a riesgo. El uso generalizado de un solo tipo de distribución de otros 35 millones de redes mosquiteras tratadas insecticida incrementa el riesgo de que los mosquitos desarrol- antes de que termine 2010, sufcientes para cubrir un 10% más de len resistencia contra éste, lo que podría dar lugar rápidamente la población a riesgo. No obstante, todavía es preciso un trabajo a un importante problema de salud pública, especialmente en considerable para que lleguen redes mosquiteras tratadas con África, donde se está desplegando el control químico del vector insecticida a todos los hogares que las necesitan, y para que las con unos niveles de cobertura jamás vistos y donde es mayor la carga del paludismo. Al combinar los datos de encuestas domiciliarias con los datos millones de personas, permaneció en un nivel bajo, el 12%, provenientes de los centros sanitarios puede estimarse que, en debido principalmente a las bajas tasas de cobertura en Nigeria. El uso de monoterapias orales basadas en la artemisinina y el tratamiento del paludismo constituye una amenaza para la vida terapéutica de las terapias El número de pruebas de diagnóstico rápido y tratamientos combinadas basadas en este fármaco, ya que fomentan la propa- combinados basados en la artemisinina que se administran gación de la resistencia a éstos. En noviembre de 2010, 25 países está creciendo, y el porcentaje de casos presuntivos de todavía permitían la comercialización de estos productos y 39 paludismo que son objeto de una prueba parasitológica ha empresas farmacéuticas los fabricaban. La mayoría de los países aumentado del 67% en 2005 en todo el mundo al 73% en que todavía permiten la comercialización de monoterapias se 2009.
Reflexes This chapter began by introducing reflexes as an example of the basic elements of the somatic nervous system alli 60mg with amex. Simple somatic reflexes do not include the higher centers discussed for conscious or voluntary aspects of movement alli 60 mg sale. The example described at the beginning of the chapter involved heat and pain sensations from a hot stove causing withdrawal of the arm through a connection in the spinal cord that leads to contraction of the biceps brachii alli 60mg without prescription. The description of this withdrawal reflex was simplified, for the sake of the introduction, to emphasize the parts of the somatic nervous system. Because the neuromuscular junction is strictly excitatory, the biceps will contract when the motor nerve is active. The interneuron receives a synapse from the axon of the sensory neuron that detects that the hand is being burned. In response to this stimulation from the sensory neuron, the interneuron then inhibits the motor neuron that controls the triceps brachii. This is done by releasing a neurotransmitter or other signal that hyperpolarizes the motor neuron connected to the triceps brachii, making it less likely to initiate an action potential. Without the antagonistic contraction, withdrawal from the hot stove is faster and keeps further tissue damage from occurring. Another example of a withdrawal reflex occurs when you step on a painful stimulus, like a tack or a sharp rock. The nociceptors that are activated by the painful stimulus activate the motor neurons responsible for contraction of the tibialis anterior muscle. An inhibitory interneuron, activated by a collateral branch of the nociceptor fiber, will inhibit the motor neurons of the gastrocnemius and soleus muscles to cancel plantar flexion. An important difference in this reflex is that plantar flexion is most likely in progress as the foot is pressing down onto the tack. Contraction of the tibialis anterior is not the most important aspect of the reflex, as continuation of plantar flexion will result in further damage from stepping onto the tack. A collateral of the muscle spindle fiber will also inhibit the motor neuron of the antagonist muscles. A common example of this reflex is the knee jerk that is elicited by a rubber hammer struck against the patellar ligament in a physical exam. A specialized reflex to protect the surface of the eye is the corneal reflex, or the eye blink reflex. When the cornea is stimulated by a tactile stimulus, or even by bright light in a related reflex, blinking is initiated. The sensory component travels through the trigeminal nerve, which carries somatosensory information from the face, or through the optic nerve, if the stimulus is bright light. The motor response travels through the facial nerve and innervates the orbicularis oculi on the same side. This reflex is commonly tested during a physical exam using an air puff or a gentle touch of a cotton-tipped applicator. Newborns have a set of reflexes that are expected to have been crucial to survival before the modern age. The video demonstrates a reflex called the Babinski reflex, in which the foot flexes dorsally and the toes splay out when the sole of the foot is lightly scratched. With the exception of somatosensation, this list represents the special senses, or those systems of the body that are associated with specific organs such as the tongue or eye. Somatosensation belongs to the general senses, which are those sensory structures that are distributed throughout the body and in the walls of various organs. The special senses are all primarily part of the somatic nervous system in that they are consciously perceived through cerebral processes, though some special senses contribute to autonomic function. The general senses can be divided into somatosensation, which is commonly considered touch, but includes tactile, pressure, vibration, temperature, and pain perception. The general senses also include the visceral senses, which are separate from the somatic nervous system function in that they do not normally rise to the level of conscious perception. The cells that transduce sensory stimuli into the electrochemical signals of the nervous system are classified on the basis of structural or functional aspects of the cells. The structural classifications are either based on the anatomy of the cell that is interacting with the stimulus (free nerve endings, encapsulated endings, or specialized receptor cell), or where the cell is located relative to the stimulus (interoceptor, exteroceptor, proprioceptor). Thirdly, the functional classification is based on how the cell transduces the stimulus into a neural signal. Related to chemoreceptors are osmoreceptors and nociceptors for fluid balance and pain reception, respectively. Mechanoreceptors respond to mechanical stimuli and are the basis for most aspects of somatosensation, as well as being the basis of audition and equilibrium in the inner ear. Thermoreceptors are sensitive to temperature changes, 650 Chapter 14 | The Somatic Nervous System and photoreceptors are sensitive to light energy. The sensory fibers connect to the spinal cord through the dorsal root, which is attached to the dorsal root ganglion. Sensory information from the body that is conveyed through spinal nerves will project to the opposite side of the brain to be processed by the cerebral cortex. The cranial nerves can be strictly sensory fibers, such as the olfactory, optic, and vestibulocochlear nerves, or mixed sensory and motor nerves, such as the trigeminal, facial, glossopharyngeal, and vagus nerves. The cranial nerves are connected to the same side of the brain from which the sensory information originates. This is necessary for all sensory systems to reach the cerebral cortex, except for the olfactory system that is directly connected to the frontal and temporal lobes. The two major tracts in the spinal cord, originating from sensory neurons in the dorsal root ganglia, are the dorsal column system and the spinothalamic tract. The major differences between the two are in the type of information that is relayed to the brain and where the tracts decussate. The dorsal column system primarily carries information about touch and proprioception and crosses the midline in the medulla. The spinothalamic tract is primarily responsible for pain and temperature sensation and crosses the midline in the spinal cord at the level at which it enters. The auditory pathway passes through multiple nuclei in the brain stem in which additional information is extracted from the basic frequency stimuli processed by the cochlea. The vestibular system enters the brain stem and influences activity in the cerebellum, spinal cord, and cerebral cortex. The visual pathway segregates information from the two eyes so that one half of the visual field projects to the other side of the brain. Within visual cortical areas, the perception of the stimuli and their location is passed along two streams, one ventral and one dorsal. The ventral visual stream connects to structures in the temporal lobe that are important for long-term memory formation. The dorsal visual stream interacts with the somatosensory cortex in the parietal lobe, and together they can influence the activity in the frontal lobe to generate movements of the body in relation to visual information. The integrative and associate functions of the prefrontal lobe feed into the secondary motor areas, which help plan movements. The premotor cortex and supplemental motor area then feed into the primary motor cortex that initiates movements.
Gas exchange occurs in the pulmonary capillaries (oxygen into the blood purchase alli 60 mg without prescription, carbon dioxide out) generic alli 60mg with visa, and blood high in oxygen and low in carbon dioxide is returned to the left atrium purchase alli 60 mg with amex. Following exchange in the systemic capillaries (oxygen and nutrients out of the capillaries and carbon dioxide and wastes in), blood returns to the right atrium and the cycle is repeated. Membranes, Surface Features, and Layers Our exploration of more in-depth heart structures begins by examining the membrane that surrounds the heart, the prominent surface features of the heart, and the layers that form the wall of the heart. Membranes The membrane that directly surrounds the heart and defines the pericardial cavity is called the pericardium or pericardial sac. The pericardium, which literally translates as “around the heart,” consists of two distinct sublayers: the sturdy outer fibrous pericardium and the inner serous pericardium. The fibrous pericardium is made of tough, dense connective tissue that protects the heart and maintains its position in the thorax. The more delicate serous pericardium consists of two layers: the parietal pericardium, which is fused to the fibrous pericardium, and an inner visceral pericardium, or epicardium, which is fused to the heart This OpenStax book is available for free at http://cnx. The pericardial cavity, filled with lubricating serous fluid, lies between the epicardium and the pericardium. However, in the case of the heart, it is not a microscopic layer but rather a macroscopic layer, consisting of a simple squamous epithelium called a mesothelium, reinforced with loose, irregular, or areolar connective tissue that attaches to the pericardium. This mesothelium secretes the lubricating serous fluid that fills the pericardial cavity and reduces friction as the heart contracts. Heart: Cardiac Tamponade If excess fluid builds within the pericardial space, it can lead to a condition called cardiac tamponade, or pericardial tamponade. With each contraction of the heart, more fluid—in most instances, blood—accumulates within the pericardial cavity. However, the excess fluid in the pericardial cavity puts pressure on the heart and prevents full relaxation, so the chambers within the heart contain slightly less blood as they begin each heart cycle. If the fluid builds up slowly, as in hypothyroidism, the pericardial cavity may be able to expand gradually to accommodate this extra volume. Premature removal of these drainage tubes, for example, following cardiac surgery, or clot formation within these tubes are causes of this condition. Surface Features of the Heart Inside the pericardium, the surface features of the heart are visible, including the four chambers. There is a superficial leaf- 830 Chapter 19 | The Cardiovascular System: The Heart like extension of the atria near the superior surface of the heart, one on each side, called an auricle—a name that means “ear like”—because its shape resembles the external ear of a human (Figure 19. Auricles are relatively thin-walled structures that can fill with blood and empty into the atria or upper chambers of the heart. Also prominent is a series of fat-filled grooves, each of which is known as a sulcus (plural = sulci), along the superior surfaces of the heart. Located between the left and right ventricles are two additional sulci that are not as deep as the coronary sulcus. The anterior interventricular sulcus is visible on the anterior surface of the heart, whereas the posterior interventricular sulcus is visible on the posterior surface of the heart. From superficial to deep, these are the epicardium, the myocardium, and the endocardium (see Figure 19. The outermost layer of the wall of the heart is also the innermost layer of the pericardium, the epicardium, or the visceral pericardium discussed earlier. It is built upon a framework of collagenous fibers, plus the blood vessels that supply the myocardium and the nerve fibers that help regulate the heart. It is the contraction of the myocardium that pumps blood through the heart and into the major arteries. The muscle pattern is elegant and complex, as the muscle cells swirl and spiral around the chambers of the heart. Deeper ventricular muscles also form a figure 8 around the two ventricles and proceed toward the apex. This complex swirling pattern allows the heart to pump blood more effectively than a simple linear pattern would. Although the ventricles on the right and left sides pump the same amount of blood per contraction, the muscle of the left ventricle is much thicker and better developed than that of the right ventricle. In order to overcome the high resistance required to pump blood into the long systemic circuit, the left ventricle must generate a great amount of pressure. The right ventricle does not need to generate as much pressure, since the pulmonary circuit is shorter and provides less resistance. Both ventricles pump the same amount of blood, but the left ventricle must generate a much greater pressure to overcome greater resistance in the systemic circuit. Note the differences in the relative size of the lumens, the region inside each ventricle where the blood is contained. The innermost layer of the heart wall, the endocardium, is joined to the myocardium with a thin layer of connective tissue. It is made of simple squamous epithelium called endothelium, which is continuous with the endothelial lining of the blood vessels (see Figure 19. Once regarded as a simple lining layer, recent evidence indicates that the endothelium of the endocardium and the coronary 832 Chapter 19 | The Cardiovascular System: The Heart capillaries may play active roles in regulating the contraction of the muscle within the myocardium. The endothelium may also regulate the growth patterns of the cardiac muscle cells throughout life, and the endothelins it secretes create an environment in the surrounding tissue fluids that regulates ionic concentrations and states of contractility. Endothelins are potent vasoconstrictors and, in a normal individual, establish a homeostatic balance with other vasoconstrictors and vasodilators. Internal Structure of the Heart Recall that the heart’s contraction cycle follows a dual pattern of circulation—the pulmonary and systemic circuits—because of the pairs of chambers that pump blood into the circulation. In order to develop a more precise understanding of cardiac function, it is first necessary to explore the internal anatomical structures in more detail. Septa of the Heart The word septum is derived from the Latin for “something that encloses;” in this case, a septum (plural = septa) refers to a wall or partition that divides the heart into chambers. Normally in an adult heart, the interatrial septum bears an oval-shaped depression known as the fossa ovalis, a remnant of an opening in the fetal heart known as the foramen ovale. The foramen ovale allowed blood in the fetal heart to pass directly from the right atrium to the left atrium, allowing some blood to bypass the pulmonary circuit. Within seconds after birth, a flap of tissue known as the septum primum that previously acted as a valve closes the foramen ovale and establishes the typical cardiac circulation pattern. Unlike the interatrial septum, the interventricular septum is normally intact after its formation during fetal development. It is substantially thicker than the interatrial septum, since the ventricles generate far greater pressure when they contract. It is marked by the presence of four openings that allow blood to move from the atria into the ventricles and from the ventricles into the pulmonary trunk and aorta. Located in each of these openings between the atria and ventricles is a valve, a specialized structure that ensures one-way flow of blood.
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