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By X. Hamil. Texas Lutheran University.
In children with GH deficiency discount 200 mg viagra extra dosage mastercard, the con- Despite the availability of recombinant GH cheap 130mg viagra extra dosage otc, the diagno- centration of IGFs and IGFBP3 are low. GH is combinant GH will increase IGF-I, IGF-II, and IGFBP3 in the released in periodic bursts, the greatest of which occur in blood, which will result in increased long bone growth. Between pulses of secretion, the The epiphyseal growth plate in the bone becomes less re- blood concentration of GH is nearly undetectable by most sponsive to GH and IGF-I several years after puberty, and techniques. For these reasons, a random measure of GH in long bone growth stops in adulthood (see Chapter 36). GH is also thought to function as one of the counter- Gonadotropins Regulate Reproduction regulatory hormones that limit the actions of insulin on The testes and ovaries have two essential functions in hu- muscle, adipose tissue, and the liver. The first is to produce sperm cells and hibits glucose use by muscle and adipose tissue and in- ova (egg cells), respectively. These effects are array of steroid and peptide hormones, which influence vir- opposite those of insulin. Also, GH makes muscle and fat tually every aspect of the reproductive process. Thus, GH nor- nadotropic hormones FSH and LH regulate both of these mally has a tonic inhibitory effect on the actions of insulin, functions. The production and secretion of the go- much like the glucocorticoid hormones (see Chapter 34). The regulation of human repro- large amounts of GH for an extended time. They may de- duction by this hypothalamic-pituitary-gonad axis is dis- velop insulin resistance and an elevated insulin level in the blood. They may also have hyperglycemia caused by the underutilization and overproduction of glucose. These dis- turbances are much like those in individuals with non-in- TABLE 32. For this reason, this metabolic response to excess GH is called its diabeto- Growth-promoting Stimulates IGF-I gene expression by target genic action. For example, intravenous injection of GH on cell division, resulting in growth in a person who is GH-deficient produces hypoglycemia. Lipolytic Stimulates mobilization of triglycerides from fat deposits The hypoglycemia is caused by the ability of GH to stimu- Diabetogenic Inhibits glucose use by muscle and adipose late the uptake and use of glucose by muscle and adipose tissue and increases glucose production by tissue and to inhibit glucose production by the liver. After the liver about 1 hour, the blood glucose level returns to normal. If Inhibits the action of insulin on glucose this person is given a second injection of GH, hypo- and lipid metabolism by muscle and glycemia does not occur because the person has become in- adipose tissue sensitive or refractory to the insulin-like action of GH and Insulin-like Transitory stimulatory effect on uptake remains so for some hours. Normal individuals do not re- and use of glucose by muscle and adipose spond to the insulin-like action of GH, presumably because tissue in GH-deficient individuals they are always refractory from being exposed to their own Transitory inhibitory effect on glucose production by liver of GH-deficient endogenous GH. Here, we describe the chem- Prolactin Regulates the Synthesis of Milk istry and formation of the gonadotropins. Lactation is the final phase of the process of human re- Like TSH, human FSH and LH are composed of two production. During pregnancy, alveolar cells of the structurally different glycoprotein subunits, called and mammary glands develop the capacity to synthesize milk , which are held together by noncovalent bonds. The in response to stimulation by a variety of steroid and pep- subunit of human FSH consists of a peptide chain of 111 tide hormones. Milk synthesis by these cells begins amino acid residues, to which two chains of carbohydrate shortly after childbirth. The subunit of human LH is a peptide of these cells must be stimulated periodically by prolactin 121 amino acid residues. It is also glycosylated with two (PRL), and this is thought to be the main physiological carbohydrate chains. What role, if any, FSH and LH give these hormones a molecular size of PRL has in the human male is unclear. They must be mones on the male reproductive tract, but whether this is combined with each other in a 1:1 ratio in order to have an important physiological function of PRL is not estab- activity. There are separate genes for the Human PRL has considerable structural similarity to human and subunits in the gonadotroph; hence, the peptide GH and to a PRL-like hormone produced by the human chains of these subunits are translated from separate placenta called placental lactogen (hPL). Glycosylation of these chains begins as these hormones are structurally related because their genes they are synthesized and before they are released from the evolved from a common ancestral gene during the course of ribosome. Because of its structural similarity to final three-dimensional structure, the combination of an human PRL, human GH has substantial PRL-like or lacto- subunit and a subunit, and the completion of glycosyla- genic activity.
Both H1 antagonists and agonists of H3-autoreceptors depress release of histamine and reduce arousal (see text for details) GABAergic neurons in the ventrolateral preoptic area (VLPO) order viagra extra dosage 150 mg. Since the VLPO is more active in SWS sleep generic viagra extra dosage 150 mg on line, this phase of the sleep cycle could depend in part on GABAergic inhibition of histamine-releasing neurons that project to the cortex (Fig. There also seems to be some feedback control of histamine release because H3-receptor agonists, that activate the autoreceptors on histamine-releasing neurons and reduce release of this transmitter, augment SWS while H3-receptor antagonists have the opposite effect. Finally, other effects of histamine that could contribute to increased arousal are increasing the activity of excitatory cholinergic neurons in the basal forebrain and inhibition of neurons in the hypothalamic preoptic area which promote sleep. A much higher profile has recently been claimed for histamine in the control of circadian rhythm (see Jacobs, Yamatodani and Timmerman 2000). When injected intracerebroventricularly in rats it appears to alter locomotor and drinking rhythms in a somewhat complex manner depending on when it is given in the light±dark cycle, being most active when the animals are in constant darkness. Some of the effects can also be mimicked by increasing the amount of endogenous histamine released with the H3 autoreceptor antagonist thioperamine. Certainly histamine has both excitatory (H1) and inhibitory (H2) effects on SCN neuron firing and autoradiography has revealed the presence there of H1 receptors. Since glutamate and 5-HT have been shown to increase histamine release in the SCN and GABA to inhibit it, the above authors consider histamine to be the final mediator of their effects. Whether this is so remains to be seen for, despite the sedative effects of some H1 antagonists, rhythm changes have not been reported with their long-term clinical use. NORADRENALINE Although some studies show that noradrenaline inhibits neuronal firing it is generally considered to increase behavioural activity and arousal. This impression is borne out to the extent that CNS stimulants, like amphetamine, increase release of noradrenaline and produce behavioural and EEG arousal, while reserpine, which reduces noradrena- line storage and hence release, causes psychomotor retardation. It is also supported by SLEEP AND WAKING 489 evidence that the firing rate of neurons projecting from the locus coeruleus is greater during waking (1±2 Hz) than during SWS (0. Furthermore, stimulation of the locus coeruleus in cats causes EEG desynchronisation and increases arousal, while a neurotoxic lesion of these neurons leads to EEG synchrony, increases SWS and reduces REM sleep. Because a reduction in the activity of noradrenergic neurons precedes the onset of sleep, this change in activity is thought to have a permissive role in sleep induction. How all these actions of noradrenaline are manifest is not clear and, unfortunately, most experiments in this area have been carried out on anaesthetised animals which, arguably, are not ideal for investigating mechanisms underlying arousal! One of the few investigations to have been carried out in unanaesthetised rats has shown that infusions of noradrenaline into the nucleus basalis of the medial septum increases waking (and the g-wave activity of the waking phase), but reduces the g-waves of SWS. These changes, which are thought to be mediated by activation of b-adrenoceptors, suggest that noradrenaline increases cholinergic influences on arousal, in the nucleus basalis, at least (Cape and Jones 1998). However, a fairly common side-effect of b-adrenoceptor antagonists, used clinically to relieve hypertension, is sleep disturbance which is expressed as nightmares, insomnia and increased waking. Clearly, these drugs must have additional actions either in other brain centres, or non-selective effects on other (possibly 5-HT1A) receptors that have quite different effects on arousal. It has even been suggested that b-blockers disrupt sleep patterns by inhibiting melatonin synthesis and release, but this is controversial. In contrast, a2-adrenoceptor agonists are well-known for their sedative effects. Since their activation of presynaptic a2-autoreceptors will reduce noradrenergic transmission, by depressing the firing of neurons in the locus coeruleus and release of noradrenaline from their terminals, this action is entirely consistent with the proposal that increased noradrenergic transmission increases arousal. Although this presynaptic action of a2-agonists would explain their sedative effects it must be borne in mind that many a2-adrenoceptors in the brain are in fact postsynaptic. Their role (if any) in sedation is unclear but it must be inferred that, if they make any contribution to sedation, then either a specific brain region or a specific a2-adrenoceptor subtype is involved. Another possible confounding factor is that many a2-adrenoceptor ligands have an imidazoline structure (see Chapter 8) and the recently discovered imidazoline receptors are also thought to influence the sleep cycle and arousal. Even less is known about the role of a1-adrenoceptors on arousal partly because most drugs acting at these receptors do not readily cross the blood±brain barrier. The role of noradrenergic neurons from the locus coeruleus on behaviour during the waking phase is rather controversial.
A fracture lows the developmental pattern of the shoulder and upper ex- of the olecranon of the ulna often damages the ulnar nerve cheap viagra extra dosage 150 mg overnight delivery, re- tremity: the appearance of the limb bud is followed by the sulting in paralysis of the flexor muscles of the hand and the ad- formation of the mesenchymal primordium of bone and muscle in ductor muscles of the thumb discount viagra extra dosage 120mg without prescription. Development of the lower extremity, frequently fractured (Colles’ fracture) by falling on an out- however,lags behind that of the upper extremity by 3 or 4 days. In this fracture, the hand is displaced backward The likelihood of congenital deformities of the hips and and upward. The few congenital malformations that during the backhand stroke in tennis, may cause lateral epi- occur generally have a genetic basis. Wearing In congenital dislocation of the hip, the acetabulum fails an elbow brace or a compression band may help reduce the to develop adequately,and the head of the femur slides out of the pain, but only if the cause is eliminated will the area be al- acetabulum onto the gluteal surface of the ilium. Athletes frequently jam a finger when a ball forcefully Polydactyly and syndactyly occur in the feet as well as in the strikes a distal phalanx as the fingers are extended, causing a hands. Erb, German neurologist, 1840–1921, tain whether abnormal positioning or restricted movement in and Guillaume G. Duchenne, French neurologist, 1806–75 utero causes talipes, but both genetic and environmental factors Colles’ fracture: from Abraham Colles, Irish surgeon, 1773–1843 are involved in most cases. Surface and Regional © The McGraw−Hill Anatomy, Sixth Edition Anatomy Companies, 2001 Chapter 10 Surface and Regional Anatomy 339 Trauma to the Hip and Lower Extremity not show up on radiographs. Frequently, the only way to heal stress fractures is to abstain from exercise. As with the shoulder and upper extremity, a variety of traumatic Sprains are common in the joints of the lower extremity. These range from injury to the bones and surrounding muscles, Sprains are usually accompanied by synovitis, an inflammation of tendons, vessels, and nerves to damage of the joints in the form the joint capsule. Dislocation of the hip is a common and severe result of an automobile accident when a seat belt is not worn. When the hip Diseases of the Hip and Lower Extremity is in the flexed position, as in sitting in a seat, a sudden force ap- As in the shoulder and upper extremity, infections in the hip and plied at the distal end of the femur will drive the head of the lower extremity–such as bursitis and tendinitis–can be localized femur out of the acetabular socket, fracturing the posterior ac- in any part of the hip or lower extremity. In this kind of injury, there is usually damage to the of arthritis may affect joints in these regions. A variety of skin diseases afflict the foot, including ath- Trauma to the nerve roots that form the sciatic nerve may lete’s foot, plantar warts, and dyshidrosis. Most of the diseases of also occur from a herniated disc or pressure from the uterus dur- the feet can be prevented, or if they do occur, they can be ing pregnancy. Sciatic nerve dam- Because arterial occlusive disease is common in elderly peo- age is usually very painful and is expressed throughout the poste- ple, palpation of the posterior tibial artery is clinically important rior length of the lower extremity. This can be accomplished by gently Fractures are common in any location of the hip and lower palpating between the medial malleolus and the tendo calcaneus. Athletes (such as skiers) and elderly people seem to Many neuromuscular diseases have a direct effect on the be most vulnerable. Osteoporosis markedly weakens the bones of functional capabilities of the lower extremities. Muscular dystro- the hip and thigh regions, making them vulnerable to fracture. A phy and poliomyelitis are both serious immobilizing diseases be- common fracture site, especially in elderly women, is across the cause of muscle paralysis. A fracture of this kind may be complicated by vas- cular and nerve interruption. A potentially more serious knee trauma, however, is a clipping injury, caused by a blow to the lat- Clinical Case Study Answer eral side. In this type of injury, there is generally damage to the cruciate ligament and menisci. Serious complications arise if the The patient experienced a tension pneumothorax because a fractured rib opened an abnormal channel between the pleural cavity and the common fibular (peroneal) nerve, traversing the popliteal fossa, outside air. Damage to this nerve results in paralysis of the ankle pressure sucked air into the pleural cavity, but no air escaped with expi- and foot extensors (footdrop) and inversion of the foot. In only a short time, her left hemithorax became distended and Stress fractures of the long bones of the lower extremity compressed the mediastinal contents into the right thorax, resulting in a are common to athletes. This condition is fatal unless air is removed from anterior muscles of the leg and their periosteal attachments, are the affected pleural cavity. The internal jugular vein is medically re- often accompanied by tibial stress fractures.
The present atlas is no exception purchase viagra extra dosage 130 mg line, and as a re- of clinical deﬁcits are inseparable components of the learn- sult best 150mg viagra extra dosage, several factors have guided its further development. An effort has been made to provide a for- These include an appreciation of what enhances learning in mat that is dynamic and ﬂexible—one that makes the learn- the laboratory and classroom, the inherent value of corre- ing experience an interesting and rewarding exercise. The goal is to make considering that approximately 50% of what goes wrong in- it obvious to the user that structure and function in the CNS side the skull, producing neurological deﬁcits, is vascular- are integrated elements and not separate entities. To emphasize the value of this information, the dis- Most neuroanatomic atlases approach the study of the tribution pattern of blood vessels is correlated with external CNS from fundamentally similar viewpoints. These atlases spinal cord and brain anatomy (Chapter 2) and with inter- present brain anatomy followed by illustrations of stained nal structures such as tracts and nuclei (Chapter 5), re- sections, in one or more planes. Although variations on this viewed in each pathway drawing (Chapter 7), and shown in theme exist, the basic approach is similar. This approach atlases do not make a concerted effort to correlate vascular has several advantages: 1) the vascular pattern is immediately patterns with external or internal brain structures. Also, related to the structures just learned, 2) vascular patterns most atlases include little or no information on neurotrans- are shown in the sections of the atlas in which they belong, mitters and do not integrate clinical examples and informa- 3) the reader cannot proceed from one part of the atlas to tion with the study of functional systems. Following a brief period The ability to diagnose a neurologically compromised pa- devoted to the study of CNS morphology, a signiﬁcant por- tient is speciﬁcally related to a thorough understanding of tion of many courses is spent learning functional systems. This pathway structure, function, blood supply, and the rela- learning experience may take place in the laboratory because tionships of this pathway to adjacent structures. To this end it is here that the student deals with images of representative Chapter 7 provides a series of semidiagrammatic illustrations levels of the entire neuraxis. Each ﬁgure shows 1) been made to provide the student with a comprehensive and in- the trajectory of ﬁbers that comprise the entire pathway; 2) tegrated guide—one that correlates, 1) external brain anatomy the laterality of ﬁbers comprising the pathway, this being an with MRI and blood supply; 2) meninges and ventricles with extremely important concept in diagnosis; 3) the positions examples of meningeal, ventricular, and brain hemorrhage; and somatotopy of ﬁbers comprising each pathway at repre- 3) internal brain anatomy with MRI, blood supply, the orga- sentative levels; 4) a review of the blood supply to the en- nization of tracts and nuclei and selected clinical examples; 4) tire pathway; 5) important neurotransmitters associated summaries of clinically relevant pathways with neurotrans- with ﬁbers of the pathway; and 6) examples of deﬁcits seen mitters, numerous clinical correlations, and the essential con- following lesions of the pathway at various levels through- cept of laterality; and 5) includes a large variety of images such out the neuraxis. This chapter is designed to be used by itself as angiogram, computed tomography (CT), magnetic reso- or integrated with other sections of the atlas; it is designed to nance imaging (MRI), magnetic resonance angiography provide the reader with the structural and clinical essentials (MRA), and magnetic resonance venography (MRV). Introduction and Reader’s Guide 3 The advent and common use of imaging methods (MRI, The Brain and Related Structures in CT MRA, and MRV) mandates that such images become an inte- STRUCTURE/FLUID/SPACE GREY SCALE gral part of the educational process when teaching and/or Bone, acute blood Very white learning clinically applicable neuroscience. To this end, this Enhanced tumor Very white book contains about 175 MRI and CT images and 12 MRA and Subacute blood Light grey MRV. All of these images are directly correlated with external Muscle Light grey brain anatomy such as gyri and sulci, internal structures in- Grey matter Light grey cluding pathways and nuclei, cranial nerves and adjacent struc- White matter Medium grey tures, or they demonstrate examples of hemorrhages related Cerebrospinal ﬂuid Medium grey to black to the meninges and ventricles or the parenchyma of the brain. Air, Fat Very black Imaging the Brain (CT and MRI): Imaging the brain in vivo is now commonplace for the patient with neurological The advantages of CT are 1) it is rapidly done, which is deﬁcits that may indicate a compromise of the central nervous especially important in trauma; 2) it clearly shows acute and system. Even most rural hospitals have, or have easy access to, subacute hemorrhages into the meningeal spaces and brain; CT or MRI. With these facts in mind, it is appropriate to make 3) it shows bone (and skull fractures) to advantage; and 4) a few general comments on these imaging techniques and what it is less expensive than MRI. For details of the meth- 1) it does not clearly show acute or subacute infarcts or is- ods and techniques of CT and MRI consult sources such as chemia, or brain edema; 2) it does not clearly differentiate Grossman (1996), Lee et al. Magnetic Resonance Imaging (MRI): The tissues Tissue density is measured by the effects of x-rays on atoms of the body contain proportionately large amounts of pro- within the tissue as these x-rays pass through the tissue. Protons have a positive nucleus, a shell of Atoms of higher number have a greater ability to attenuate negative electrons, and a north and south pole; they func- (stop) x-rays while those with lower numbers are less able to tion like tiny spinning bar magnets. The various attenuation intensities are are arranged randomly in relation to each other due to the computerized into numbers (Hounsﬁeld units or CT num- constantly changing magnetic ﬁeld produced by the elec- bers). MRI uses this characteristic of protons to generate air is given a value of 1,000 and is black. When the fre- arachnoid hemorrhage illustrates the various shades seen in a quency of the RP matches the frequency of the spinning pro- CT (Fig. In general, the following table summarizes the ton, the proton will absorb energy from the radio wave (res- white to black intensities seen for selected tissues in CT. First, the magnetic effects of some protons are cancelled out and second, the magnetic effects and energy levels in others are increased. When the RP is turned off, the relaxed protons release energy (an “echo”) that is received by a coil and computed into an im- age of that part of the body.
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