By H. Lukar. University of Illinois at Springfield.
The kidney may be divided into 2 layers: an outer layer called the cortex and an inner layer called the medulla 100mg norpace overnight delivery. These layers are like the rings of a tree since one layer wraps around the other layer discount 100 mg norpace overnight delivery. One can consider the kidney as a pie buy discount norpace 100 mg online, which is divided into slices, which are called lobes. There are 10 to 18 lobes and each lobe contains a medullary pyramid, which serves as the drainage for the kidneys, to the ureters. In the medulla, the lobes are easily separated but in the cortex distinct lobes are difficulty to see. The circulation of the kidney is critical to its role as a fundamental excretory organ. The kidney is heavily perfused, receiving approximately 20-25% of the cardiac output. This extensive blood flow is critical to the task of clearing toxins and regulating salt and water from the blood. In addition, there are arcuate arteries in the zone between the cortex and medulla. There are afferent arterioles which carry the blood to each glomerulus by forming capillary loops, which rejoin to form efferent arterioles. The critical work of the kidneys occurs in the glomerulus and the most critical elements of the renal circulation are the glomerular capillaries. Because of the remarkable permeability of the glomerular capillaries, salt and water exchange is possible just as the pulmonary capillary permeability permits oxygen and carbon dioxide exchange. There is a step-wise sequence of elements of the renal arterial circulation that brings blood to the glomerular capillaries and the elements of the renal venous circulation that bring blood away from the glomerular circulation. The elements of the renal arterial system follow the following sequence: Renal Artery Segmental Arteries Interlobular Arteries Arcuate Arteries Afferent Arterioles Glomerular Capillaries. The elements of the renal venous system follow the following sequence: Glomerular Capillaries Efferent Arterioles Peritubular Capillaries (A subset of which is called the Vasa Recta) Venules Arcuate Veins Interlobular Veins Segmental Veins Renal Vein. The kidney plays a critical role in physiological homeostasis by regulating blood pressure and by regulating salt and water excretion and retention. The kidney must maintain blood pressure to create relatively constant perfusion of critical bodily organs such as the heart and brain despite physiological changes in the body. The elements of the renal arterial system follow the following sequence: Renal Artery Segmental Arteries Interlobular Arteries Arcuate Arteries Afferent Arterioles Glomerular Capillaries. The elements of the renal venous system follow the following sequence: Glomerular Capillaries Efferent Arterioles Peritubular Capillaries (A subset of which is called the Vasa Recta) Venules Arcuate Veins Interlobular Veins Segmental Veins Renal Vein. The kidney must balance its role in regulating blood pressure and regulating salt and water retention. Under marked physiological changes, particularly changes in arterial blood pressure, the kidney must continue to regulate salt and water. In order to achieve a constant glomerular filtration rate, the kidney maintains a relatively constant renal blood flow. Regulation of the afferent arteriole plays a particularly important role in autoregulation of both renal artery blood flow and glomerular filtration rate. The basic mechanisms of autoregulation are twofold: 1) pressure sensor or myogenic mechanism; 2) tubuloglomerular feedback. The pressure sensor or myogenic mechanism is quite simple: when the arterial blood pressure rises the renal afferent arteriole is stretched. The increased resistance largely offsets the increase in arterial pressure, causing the renal blood flow and therefore glomerular filtration rate to be constant. In the tubuloglomerular feedback mechanism, the macula densa of the juxtaglomerular apparatus (the juxtaglomerular apparatus consists of macula densa cells in the initial portion of the distal tubule and juxtaglomerular cells in the walls of the afferent and efferent arterioles) senses a change in the flow of tubular fluid, such as sodium chloride resorption. This stimulus results in a signal that modulates the renal afferent arteriolar resistance. These mechanisms permit the autoregulation of renal blood flow and glomerular filtration rate to be constant despite changes in arterial blood pressure. There are several basic principles of autoregulation [one should know how vasoconstriction and vasodilatation affect renal blood flow and glomerular filtration rate]: 1. Vasoconstriction of afferent arterioles means less flow gets to glomerulus and also less pressure; 3. Vasoconstriction of efferent arterioles means there is increased pressure within the glomerulus (“back-up” effect); since overall resistance to flow is increased, the overall renal blood flow rate is decreased. When there is vasoconstriction of either the afferent or efferent arterioles, the renal blood flow declines. However, the effect of vasoconstriction on glomerular filtration rate will differ depending on whether the site of vasoconstriction is in the afferent or efferent arterioles. We can consider the afferent arterioles as the input and the efferent arterioles as the output. The perfusion pressure in the glomerulus determines the glomerular filtration rate (see Figure). If there is vasodilatation, which we can consider as less vasoconstriction, in the afferent arterioles, we see that the renal blood flow increases. It may be helpful to think of blood backing up from the efferent arterioles since the flow has increased. If there is increased vasoconstriction of the afferent arterioles, there is decreased renal blood flow and the corresponding glomerular filtration decreases. The renal blood flow and the glomerular filtration rate either increase or decrease together.
The former may just involve involuntary contractions of a group of muscles or a single limb (Jacksonian motor epilepsy) or abnormal but localised sensory disturbances (Jacksonian sensory epilepsy) discount norpace 100mg free shipping. Complex partial seizures manifest themselves as bizarre behaviours which are also known as psychomotor or temporal lobe epilepsy purchase 100mg norpace fast delivery, since a lesion (focus) is often found in that brain area order 100mg norpace mastercard. Repetitive and apparently purposeful movements vary from simple hand clenching or rubbing to more bizarre hand movements and walking. These can last a few minutes, often disrupt other ongoing activity or speech and the patient has no subsequent memory of them. These involve more, or even the whole, of the brain including the reticular system so that consciousness is lost, although in some instances (absence seizures) this is more a loss of awareness rather than any collapse. It starts with a tonic spasm of all musculature and rigid extension of the body, a temporary cessation of respiration, generally salivation and often defecation and micturition. After about one minute this gives way to violent synchronous clonic jerking movements (convulsions) which may continue for a few minutes. They entail a brief and abrupt loss of awareness (consciousness) in which the patient suddenly ceases ongoing activity or speech and stares vacantly for a few seconds before recovering equally quickly. Motor disturbances are rare apart from blinking of the eyes and the patient has no recollection of the event. In addition to the above main categories seizures can be just myoclonic, isolated clonic jerks, or atonic, loss of postural control with just head drooping or the patient actually falling. Convulsions associated with metabolic disturbances are not considered to be epileptic. Perhaps the most striking is the 3 per second spike wave activity seen in most leads (cortical areas) in absence seizures, which can be invoked by hyperventilation. If they are applied locally to specific brain areas, the same approaches induce activity indicative of partial seizures. Also some animals can be bred in which seizures either occur spontaneously or can be induced easily by appropriate sensory stimulation. Electroencephalograms are shown for, a normal subject (a), those suffering from general tonic±clonic seizures (grand mal, (b)), generalised absence seizures (petit mal, (c)), and partial seizures (d). Spikes are seen in both right- and left- sided leads from all three cortical areas, frontal (F), temporal (T) and occipital (C) in the generalised seizures (b, c) but only in the occipital leads in the example of partial seizures (d). The typical 3 s71 spike and wave discharge of petit mal (c) may be seen during routine recording or induced by procedures such as hyperventilation but the spiking of grand mal and partial epilepsy is only seen during seizures. Strychnine convulsions have no predictive value since they arise through antagonism of spinal (glycine-mediated) rather than cortical inhibition. The anticonvulsant activity of a drug may also be evaluated by measuring its ability to raise the convulsive threshold, i. Comparison of the efficacy of drugs in the threshold and maximal seizure tests may distinguish between their abilities to raise seizure threshold or reduce seizure spread and development. A similar effect can be obtained by the repeated localised injection of subconvulsive doses of some convulsants. The ability of a drug to reduce the kindled seizure itself may be indicative of value in partial seizure but if it slows the actual development of kindling that may indicate some ability to retard epileptogenesis. Some drugs are effective in only one test and clinical condition whilst a few are active in both (Table 16. It could be argued that an antiepileptic drug should really stop the development of epilepsy, i. Clinical comparisons are not related to recommended doses but simply indicate whether a drug is effective () or not (7). Generally, drugs that are to be used clinically to control tonic± clonic seizures control electroshock but not pentylenetetrazol-induced convulsions in rats and mice, whilst the converse applies to drugs effective in absence seizures. Na valproate is effective in both experimental models and is used in both clinical conditions, although in all cases higher doses have to be used than for any other drug. Phenytoin and carbamazepine do not stop the development of kindling, although acutely they reduce the fully kindled seizure, and in studies of post- traumatic epilepsy following brain damage in humans (car accidents) these drugs stop the appearance of seizures in the first week or so but do not control epileptogenesis, since seizures can develop subsequently in those patients after therapy has stopped. The actual symptoms would then be determined simply by the location of the focus and their extent, partial or general, by how easily or widely the influence of the focal neurons spread. The fact that different drugs with different mechanisms of action are effective in different epilepsies may support that view. Epilepsy may be secondary to focal lesions such as congenital malformations, infarcts, tumours, cysts or inflections but fortunately many patients with these problems do not develop epilepsy. Brain damage such as neuronal loss and glial proliferation may in fact be seen in epileptics but these changes may be secondary to, rather than the cause of, epilepsy. They probably reflect the consequences of intense neuronal activation since in patients dying in status epilepticus they appear to be of recent origin and can be induced in animals by systemic or locally administered convulsant (see Meldrum and Corsellis 1984). Everyone is capable of having a convulsion, indeed their induction has been a common treatment for depression. The convulsive threshold of an epileptic, or more precisely that of some of their neurons, is just lower than normal. There is no known genetic basis for most of the common epilepsies apart from juvenile myoclonic epilepsy and childhood absence epilepsy which are dependent on inheritance of two or more susceptible genes, although genetic factors might more generally determine predisposition. Single distinct mutant genes have been established, however, in three rare forms of epilepsy (less than 1% of total), namely generalised epilepsy with febrile seizures, benign familial neonatal convulsions and autosomal dominant epilepsy (see McNamara 1999). All could lead to increased neuronal excitability and in fact co-expression in oocytes of the Na channel a subunit with the b subunit found in febrile convulsions produces a channel that inactivates more slowly than when it is expressed with normal b subunits. Each of them represents the field potential associated with a burst of action potentials in a group of neurons within the epileptic focus (Fig. Neurons showing this burst firing are also called Group I, pacemaker or epileptic neurons and their activation always results in a burst discharge and not a single impulse. Thus they could have a persisting abnormality in membrane or ion channel excitability. What we need to know is not only how such neurons arise but how their influence can spread to affect neighbouring neurons to produce the interictal spike and, more importantly, how this can sometimes, and at immensely variable intervals, develop into a full ictal discharge and seizure (Fig.
You can imagine how the stronger muscles on one side of your body—with little counterbalancing resistance from the weaker ones on the other side—can pull your spine buy discount norpace 100 mg, hips generic norpace 100 mg mastercard, and other joints slightly out of alignment generic norpace 100 mg. Many people tend to lean forward more than backward for activities such as driving, reading, mowing the lawn, woodwork, crafts, playing games, and, of 27 The 7-Day Back Pain Cure The Body: The Physical Causes of Pain 28 Muscle Imbalances: course, working at the computer. You lift heavy items by The Tug of War Inside Your Body leaning forward, not backward. For sports such as skiing, running, cycling, soccer, and baseball, you’re almost always Human beings are born with well-balanced bodies, but leaning forward. Throughout our lives we learn to If you’re not performing backward-type stretches and use our muscles to master various activities, but because we exercises to counteract these “bending forward” habits, the tend to favor one side, or do some activities over and over muscles in the front of your body will become stronger and again, we work some muscles too much and others too little. Again, when the front of your body is much stronger Most of us sit far more than we stand or engage in activity. If we There are many more examples of how we use our muscles were to log the hours we spend sitting, as opposed to other unevenly. You may prop a telephone on one ear while doing activities, we’d probably find that sitting takes up the majority other tasks, using just one side of your neck. We’re a society of “too much” sitting—especially purse, laptop bag, or backpack on one shoulder may cause compared to 50 or 100 years ago. Consider the course of your own typical A similar thing happens if you have young children or day. Most likely you use one hand more than the other to grandchildren and carry them on one hip. That hand hip to support the extra weight—without copying the action and arm also are probably more prominent in activities such on the opposite side. When you drive, Another example: If you have a wallet or cell phone in you use the right leg for both pedals, while your left does your back pocket all the time, it tends to tilt your hip and the nothing, unless you’re operating a manual transmission. Since you do these activities most every day, these muscles The result of all this uneven body use is that certain parts are used over and over again, while others—like your left leg of the body grow strong while other parts weaken, creating a when driving—are hardly ever worked. Many people tend to lean forward more than backward for activities such as driving, reading, mowing the lawn, woodwork, crafts, playing games, and, of 29 The 7-Day Back Pain Cure Common Muscle Imbalance Examples One of the most common examples of a muscle imbalance that causes back pain occurs in many people today who work in sedentary positions. Meanwhile, the stomach (abdominal), hamstring, and buttock muscles become weak from being underused. Forward-Tipped Pelvis Figure 1: Forward-tipped pelvis versus neutral pelvis 29 The 7-Day Back Pain Cure The Body: The Physical Causes of Pain 30 Common Muscle Imbalance Examples The tight muscles pull the pelvis down and forward, creating an excessive curve in the lower torso and causing the One of the most common examples of a muscle imbalance abdomen to protrude forward. The resulting pressure on the that causes back pain occurs in many people today who work lower spine can eventually cause dysfunction and injury, such in sedentary positions. Another widespread muscle imbalance is one we like to call Meanwhile, the stomach (abdominal), hamstring, and “forward head and shoulders. Forward Head & Neck Forward-Tipped Pelvis Figure 2: Forward head and neck versus neutral spine Figure 1: Forward-tipped pelvis versus neutral pelvis 31 The 7-Day Back Pain Cure This occurs frequently because people spend so much time hunched over computers, steering wheels, office desks, stoves—almost every activity we do requires us to lean forward. This causes the muscles in the chest and at the base of the neck to tighten up, while the muscles in the upper back and shoulders weaken and stretch out, putting pressure on the upper spine and causing upper back and neck pain. There are other common muscle imbalances, but perhaps you can begin to see how our everyday routines work our muscles unevenly, create bad posture, and eventually lead to pain. In contrast, if you drive your car for thousands of miles, it’s not going to drive any faster or get better gas mileage. If you play your upright piano for years, it’s never going to grow into a grand piano. The human body, on the other hand, responds to work by becoming stronger and more efficient—especially in the muscles. As you go about your daily routine, using one hand, arm, or leg more than the other, that part of the body becomes stronger. Imagine if you lifted weights with only your left arm for several months and did very little with your right arm. When you exercise or use a muscle, the fibers are stimulated, stressed, or slightly “damaged. During rest, the body repairs the muscle, building it back up to withstand similar work in the future. The fascinating thing is that the body goes the extra mile in reconstruction, building the muscle up 31 The 7-Day Back Pain Cure The Body: The Physical Causes of Pain 32 This occurs frequently because people spend so much time stronger than it was before, so you can handle the same hunched over computers, steering wheels, office desks, activity with greater ease. If neck to tighten up, while the muscles in the upper back and you’ve ever had an operation on one leg or arm and had to shoulders weaken and stretch out, putting pressure on the build the muscles back up again, you know this fact well! Or, if you’ve ever been confined to bed for a week or two There are other common muscle imbalances, but perhaps due to a medical condition, you’ll remember how wobbly you you can begin to see how our everyday routines work our felt when you tried to get up again. This is because your muscles unevenly, create bad posture, and eventually lead to muscles had already started to weaken from inactivity. Your Muscle Strength: Use It or Lose It Striving for Balance The body is truly an amazing machine. In contrast, if you drive your car When we think of balance, we often imagine two things for thousands of miles, it’s not going to drive any faster or get working in opposition to one another. If you play your upright piano for years, children on a teeter-totter, for instance, or the two ropes that it’s never going to grow into a grand piano. Muscles work much the same on the other hand, responds to work by becoming stronger way—in twos. In order for you to be able to move forward and more efficient—especially in the muscles.