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The cusps close when the left ventricle begins to POSTERIOR POSTERIOR Chordae Left AV Cusps of Right AV tendineae valve open right AV valve closed valve Left AV valve closed Aortic Cusps of valve left AV Right AV closed valve valve open Coronary artery Cusps of aortic valve Coronary Cusps of Pulmonary Aortic valve Pulmonary artery pulmonary valve valve closed open valve open ANTERIOR ANTERIOR A Relaxation phase (diastole) B Contraction phase (systole) Figure 14-6 Valves of the heart (superior view from anterior order pilex 60caps with amex, atria removed) order pilex 60 caps overnight delivery. THE HEART AND HEART DISEASE ✦ 289 Table 14•4 Valves of the Heart VALVE LOCATION DESCRIPTION FUNCTION Right AV valve Between the right atrium Valve with three cusps; tricuspid valve Prevents blood from flowing back and right ventricle up into the right atrium when the right ventricle contracts (systole) Left AV valve Between the left atrium Valve with two cusps; bicuspid or mi- Prevents blood from flowing back and left ventricle tral valve up into the left atrium when the left ventricle contracts (systole) Pulmonary semi- At the entrance to the Valve with three half-moon shaped Prevents blood from flowing back lunar valve pulmonary artery cusps into the right ventricle when the right ventricle relaxes (diastole) At the entrance to the Valve with three half-moon shaped Prevents blood from flowing back Aortic semilunar aorta cusps into the left ventricle when the valve left ventricle relaxes (diastole) contract; this closure prevents blood from returning to the left atrium and ensures the forward flow of blood into the aorta. The higher pressure in the pulmonary artery, described as Right ventricle Left ventricle back pressure, closes the valve and prevents blood from returning to the Inferior vena cava ventricle. Blood from the systemic circuit pressure closes the aortic valve and enters the right atrium (1) through the superior and inferior venae cavae, flows through the right AV (tricuspid) valve (2), and enters the right ventricle (3). Blood returns from the lungs in the pulmonary veins, enters the left atrium (5), and Figure 14-7 traces a drop of blood flows through the left AV (mitral) valve (6) into the left ventricle (7). This active phase is called systole (SIS-to- Only the endocardium comes into contact with the blood le), and in each case, it is followed by a resting period that flows through the heart chambers. One complete sequence of myocardium must have its own blood vessels to provide heart contraction and relaxation is called the cardiac cycle oxygen and nourishment and to remove waste products. The main arteries that supply The contraction phase of the cardiac cycle begins with blood to the muscle of the heart are the right and left contraction of both atria, which forces blood through the coronary arteries (Fig. They receive blood when the heart relaxes be- Atrial contraction is completed at the time ventricular cause the aortic valve must be closed to expose the en- contraction begins. After passing through gins in the atria at the same time that a contraction (sys- capillaries in the myocardium, blood drains into a system tole) begins in the ventricles. Although both upper and lower chambers Superior Superior Aortic arch vena cava vena cava Left pulmonary Right artery pulmonary Left veins Left atrium pulmonary Right veins atrium Right Great Inferior atrium cardiac vena vein cava Right coronary Left Coronary artery coronary sinus artery Small cardiac Left vein Right ventricle ventricle Right ventricle A Anterior B Posterior Figure 14-8 Blood vessels that supply the myocardium. THE HEART AND HEART DISEASE ✦ 291 When the ventricle relaxes, backflow of Blood flow blood closes valve and causes filling of Right Left coronary arteries coronary coronary artery artery Pulmonary valve To heart muscle (myocardium) Right AV Aortic Left AV A Ventricular contraction B Ventricular relaxation valve valve valve (aortic valve open) (aortic valve closed) Figure 14-9 Opening of coronary arteries in the aortic valve (anterior view). It is the prod- uct of the stroke volume (SV)—the volume of blood A unique property of heart muscle is its ability to adjust the ejected from the ventricle with each beat—and the heart strength of contraction to the amount of blood received. Thus, as CO HR SV Diastole Atrial systole Ventricular systole Atria fill with blood, which begins to Contraction of atria pumps blood into Contraction of ventricles pumps flow into ventricles as soon as their the ventricles. They may be fine Based on a heart rate of 75 beats/minute and a stroke volume at rest but quickly become short of breath or fatigued when of 70 ml/beat, the average cardiac output for an adult at rest is exercising or even when carrying out the simple tasks of daily about 5 L/minute. Cardiac reserve can be measured using an exercise stress During mild exercise, this volume might double and even test that measures cardiac output while the patient walks on a double again during strenuous exercise. Ascending aorta Superior vena cava Sinoatrial node Left atrium Internodal pathways Left ventricle Right atrium Chordae tendineae Atrioventricular node Atrioventricular bundle (bundle Papillary of His) muscle Right and left bundle branches Right ventricle Purkinje fibers Figure 14-11 Conduction system of the heart. THE HEART AND HEART DISEASE ✦ 293 Checkpoint 14-6 The cardiac cycle consists of an alternating Checkpoint 14-8 The heartbeat is started by a small mass of tis- pattern of contraction and relaxation. This The autonomic nervous system (ANS) plays a major action potential is generated by specialized tissue within the role in modifying the heart rate according to need (Fig. During a fight-or-flight response, the sympa- sue masses called nodes, and the remainder consists of spe- thetic nerves can boost the cardiac output two to three cialized fibers that branch through the myocardium. The second node, located in the intera- pathetic nerve that supplies the heart is the vagus nerve trial septum at the bottom of the right atrium, is called (cranial nerve X). The atrioventricular bundle, also known as the bundle These ANS influences allow the heart to meet changing of His, is located at the top of the interventricular septum. Consequently, Smaller Purkinje (pur-KIN-je) fibers, also called conduction the circulatory needs of the body at rest can be met with a myofibers, then travel in a branching network throughout lower heart rate. Variations in Heart Rates The Conduction Pathway The order in which im- pulses travel through the heart is as follows: ◗ Bradycardia (brad-e-KAR-de-ah) is a relatively slow heart rate of less than 60 beats/ minute. A relatively ◗ Sinus arrhythmia (ah-RITH-me-ah) is a regular varia- slower rate of conduction through the AV node allows tion in heart rate caused by changes in the rate and time for the atria to contract and complete the filling depth of breathing. The excitation wave travels rapidly through the bundle of ◗ Premature beat, also called extrasystole, is a beat that His and then throughout the ventricular walls by means of comes before the expected normal beat. As a safety measure, a region of Heart Sounds the conduction system other than the sinoatrial node can generate a heartbeat if the sinoatrial node fails, but it does The normal heart sounds are usually described by the syl- so at a slower rate. Few the beginning of ventricular relaxation and is caused people escape having some damage to the heart and blood largely by sudden closure of the semilunar valves.

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In these experiments buy pilex 60 caps line, participants adapted a novel pattern of imposed forces buy pilex 60 caps with amex, which perturbed their reaching movements. For the data presented here, participants moved back and forth to a single target trial after trial. Three different, novel stimuli instructed rhesus monkeys to make three different movements of a joystick. The plot shows the average scores of four monkeys, each solving 40 sets of three arbitrary visuomotor mappings over the course of 50 trials. By one attribute, fast learning, a learning rate of less than 3 trials per problem conforms reasonably well with the notion that arbitrary sensorimotor mappings in monkeys, at least under certain circumstances, might be classed as explicit. For reasons described in a previous review,7 we plot only trials in which the stimulus on one trial has changed from that on the previous trial. Then, we examine only responses to the stimulus (of the three) that appeared on the first trial. For obvious reasons, the monkeys performed at chance levels on the first trial of a 50-trial block. Copyright © 2005 CRC Press LLC Fast Learning of Arbitrary Sensorimotor Mappings 100 80 chance 60 40 20 0 0 3 Trial FIGURE 10. The plot shows the average of four monkeys, each solving 40 sets of three arbitrary visuomotor mappings over the course of 50 trials. The plot shows only trials in which the stimulus changed from that on the previous trial. Therefore, no trial-two data are shown: the stimulus on trial two could not have both changed and been the same as that presented in trial one. Data reviewed in detail elsewhere7,8 show that ablations that include all of the hippocampus in both hemispheres abolish the fast learning illustrated in Figure 10. Because it is thought that the hippocampal system subserves the recording of new explicit knowledge in humans,73 these data also support the view that arbitrary sensorimotor mapping represents explicit knowledge and that remaining systems, possibly neocortical, remain intact to subserve the slower improvement. Taking all of these data into account, one can argue that arbitrary sensorimotor mappings of the type learned quickly by experienced animals differs, in kind, from that learned slowly, and that this difference may correspond to the distinction between explicit and implicit knowledge in humans. This understanding informs the results obtained by lesion-, neurophysiological-, and brain-imaging methods for studying arbitrary sensorimotor mapping. The next sections address the structures, in addition to the hippocampal system, that support this kind arbitrary mapping. For instance, Petrides74 demonstrated that monkeys with aspiration lesions that primarily removed dorsal PM were unable to emit the appropriate response (choosing Copyright © 2005 CRC Press LLC to open either a lit or an unlit box) when instructed to do so, and never reached criterion in this two-choice task, although they were given 1,020 trials. In contrast to this poor performance, control monkeys mastered the same task in approximately 300 trials. The lesioned monkeys were able to choose the responses normally, however, during sessions in which only one of the two responses was allowed, showing that the monkeys were able to detect the stimuli and were able to make the required movements. Halsband and Passingham75 produced a similarly profound deficit in monkeys that had undergone bilateral, combined removals of both the dorsal and ventral PM. Their lesioned monkeys could not relearn a preoperatively acquired arbitrary visuo- motor mapping task in which a colored visual cue instructed whether to pull or turn a handle. Unoperated animals relearned this task within 100 trials; lesioned monkeys failed to reach criterion after 1,000 trials. However, lesioned monkeys were able to learn arbitrary mappings between different visual stimuli. This pattern of results confirms that the critical mapping function mediated by PM is that between a cue and a motor response, rather than arbitrary mappings generally. Putting the results of Petrides and Passingham together, the critical region for arbitrary sensorimotor mapping appears to be dorsal PM. Subsequently, Kurata and Hoffman76 confirmed that injections of a GABAergic agonist, which transiently disrupts cortical informa- tion processing, impair the performance of arbitrary visuomotor performance for sites in the dorsal, but not the ventral, part of PM. These findings suggest that the deficits result from an inability to utilize visual information properly in the formation of arbitrary visuomotor mappings. The rationale for this approach was that both areas receive inputs from IT, which processes color and shape infor- mation.

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It first passes upwards and forwards to lie below the pubic symph- ysis and then in its flaccid state bends downwards and forwards order pilex 60 caps on line. Clinical features 1Where the urethra passes beneath the pubis is a common site for it to be ruptured by a fall astride a sharp object buy 60caps pilex amex, which crushes it against the edge of the symphysis. Immediately within the meatus, the urethra dilates into a terminal fossa whose roof bears a mucosal fold (the lacuna magna) which may catch the tip of a catheter. Instruments should always be introduced into the urethra beak downwards for this reason. The sphincter urethrae in the female is a tenuous structure and vesical control appears to depend mainly on the intrinsic sphincter of condensed circular muscle fibres of the bladder. The mucosa of the urinary tract The pelvis, ureter, bladder and urethra are lined by a transitional 116 The abdomen and pelvis epithelium as far as the entry of the ejaculatory ducts in the prostatic urethra. This is conveniently termed the uroepithelium since it has a uniform appear- ance and is subject to the same pathological processes — for example, the development of papillomata. The remainder of the urethra has a columnar lining except at its termination, where the epithelium becomes squamous. Radiology of the urinary tract The renal contours can often be identified on a soft tissue radiograph of the abdomen. Intravenous injection of iodine-containing compounds excreted by the kidney will produce an outline of the calyces and the ureter (intra- venous urogram). Further information can be obtained by passing a catheter up the ureter through a cystoscope and injecting radio-opaque fluid to fill the pelvis and calyx system (retrograde pyelogram). Similarly, injection of such fluid into the urethra or bladder may be used for the radiographic study of these viscera. Near the apex of the prostate, the puboprostatic ligament (a condensation of fibrous tissue) passes forward to the pubis. The ejaculatory ducts enter the upper posterior part of the gland to open into the urethra at the colliculus seminalis or verumontanum, one on either side of the prostatic utricle, dividing off a median prostatic lobe lying The male genital organs 117 between these three ducts. In benign prostatic hypertrophy, (but not in the normal prostate), a shallow posterior median groove (which can be felt on rectal examination) further divides the prostate into left and right lobes. Blood supply The arterial supply is derived from the inferior vesical artery (a branch of the internal iliac artery), a branch entering the prostate on each side at its lateral extremity. The veins form a prostatic plexus which receives the dorsal vein of the penis and drains into the internal iliac vein on each side. Some of the venous drainage passes to the plexus of veins lying in front of the vertebral bodies and within the neural canal. This communication may explain the readiness with which carcinoma of the prostate spreads to the pelvic bones and vertebrae. Clinical features 1Prostatectomy for benign prostatic hypertrophy involves removal of the hypertrophic mass of glandular tissue from the surrounding normal prostate, which is compressed as a thin rim around it—a false capsule (Fig. This is usually performed transurethrally by means of an operating cystoscope armed with a cutting diathermy loop. During this procedure, the verumontanum, (colliculus seminalis), is an important landmark. The surgeon keeps his resection above this structure in order not to damage the urethral sphincter. The gland is approached retropubically, the capsule incised transversely and the hypertophied mass of gland enucleated. Usually the lateral lobes are affected and such enlargement is readily detected on rectal examination. The median lobe may also be involved in this process or may be enlarged without the lateral lobes being affected. In such an instance, symp- toms of prostatic obstruction may occur (because of the valve-like effect of this hypertrophied lobe lying over the internal urethral orifice) without pro- static enlargement being detectable on rectal examination. Anterior to the urethra the prostate consists of a narrow fibromuscular isthmus containing little, if any, glandular tissue. Benign glandular hyper- trophy of the prostate, therefore, never affects this part of the organ. A carcinoma of the prostate only rarely penetrates this fascial barrier so that ulceration into the rectum is very unusual.

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