By J. Ashton. University of Texas Southwestern Medical Center.

The most clin- From these nuclei buy januvia 100mg without prescription, there is a diffuse distribution ically significant aspects are: of connections to all parts of the cerebral cortex purchase januvia 100 mg amex. This whole system is concerned with con- • Cardiac and respiratory centers in the medulla sciousness and is known as the ascending retic- • Descending systems in the pons and medulla ular activating system (ARAS). These are not always tem © 2006 by Taylor & Francis Group, LLC Functional Systems 115 Ascending reticular activating system (ARAS) Locus ceruleus Lateral group Medial group Raphe nuclei Reticulo-spinal tracts FIGURE 42A: Reticular Formation 1 — Organization © 2006 by Taylor & Francis Group, LLC 116 Atlas of Functional Neutoanatomy FIGURE 42B located within the core region. These include the periaq- ueductal gray and the locus ceruleus. RETICULAR FORMATION 2 The periaqueductal gray of the midbrain (for its location see Figure 65 and Figure 65A) includes neurons that are found around the aqueduct of the midbrain (see RETICULAR FORMATION: NUCLEI also Figure 20B). This area also receives input (illustrated In this diagram, the reticular formation is being viewed but not labeled in this diagram) from the ascending sen- from the dorsal (posterior) perspective (see Figure 10 and sory systems conveying pain and temperature, the antero- Figure 40). Various nuclei of the reticular formation, RF, lateral pathway; the same occurs with the trigeminal sys- which have a significant (known) functional role, are tem. This area is part of a descending pathway to the spinal depicted, as well as the descending tracts emanating from cord, which is concerned with pain modulation (as shown some of these nuclei. Functionally, there are afferent and efferent nuclei in The locus ceruleus is a small nucleus in the upper the reticular formation and groups of neurons that are pontine region (see Figure 66 and Figure 66A). In some distinct because of the catecholamine neurotransmitter species (including humans), the neurons of this nucleus used, either serotonin or noradrenaline. The afferent and accumulate a pigment that can be seen when the brain is efferent nuclei of the RF include: sectioned (prior to histological processing, see photograph of the pons, Figure 66). Output from this small nucleus is • Neurons that receive the various inputs to the distributed widely throughout the brain to virtually every RF are found in the lateral group (as discussed part of the CNS, including all cortical areas, subcortical with the previous illustration).

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Aphasia is a association bundles within the hemispheres order januvia 100mg without a prescription. The superior general term for a disruption or disorder of language order januvia 100 mg with amex. In longitudinal fasciculus (fasciculus is another term for a conduction aphasia, the person has normal comprehension bundle of axons) interconnects the posterior parts of the (intact Wernicke’s area) and fluent speech (intact Broca’s hemisphere (e. The only language deficit seems to be an inability There are other association bundles present in the hemi- to repeat what has been heard. This is usually tested by spheres connecting the various portions of the cerebral asking the patient to repeat single words or phrases whose cortex. The various names of these association bundles meaning cannot be readily understood (e. There is some uncertainty whether tion to the CNS and only will be mentioned if need be. Sectioning through the brain in the midline (as in FIGURE 20A Figure 17) passes through the third ventricle. Note that VENTRICLES 1 the “hole” in the middle of the third ventricle represents the interthalamic adhesion, linking the two thalami across the midline (see Figure 6; discussed with Figure 11; see VENTRICLES: LATERAL VIEW also Figure 41B). The ventricles are cavities within the brain filled with CSF. The ventricular system then narrows considerably as The formation, circulation, and locations of the CSF will it goes through the midbrain and is now called the aque- be explained with Figure 21. In the hindbrain region, brain that remain from the original neural tube, the tube that was present during development. The cells of the the area consisting of pons, medulla, and cerebellum, the ventricle widens again to form the fourth ventricle (see nervous system, both neurons and glia, originated from a germinal matrix that was located adjacent to the lining of Figure 17, Figure 20B, and Figure 66). The channel con- tinues within the CNS and becomes the very narrow cen- this tube. The cells multiply and migrate away from the tral canal of the spinal cord (see Figure 17, Figure 20B, walls of the neural tube, forming the nuclei and cerebral cortex. As the nervous system develops, the mass of tissue Figure 21, and Figure 69).

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Mitochondrial defects are seen with anti-HIV agents that inhibit nucleoside or nucleotide reverse transcriptase and deplete mitochondrial DNA cheap januvia 100mg with visa. The resulting accumulation of abnormal mito- chondria results in formation of “ragged red fibers” januvia 100 mg free shipping. Zidovudine (AZT) is associated with mitochondrial changes, and sometimes with inflammation. Chronic alcohol use is also associated with similar changes. Another type of toxic myopathy, is the inflam- matory toxic myopathy – these have similar clinical features to dermatomyo- sitis. Typically D-penicillamine is associated with an inflammatory myopathy. A perivascular inflammation may be observed with phenytoin, procainamide, hydralazine, L-dopa, and streptokinase. Eosinophilic myositis and fasciitis asso- ciated with L-tryptophan is probably due to an allergic reaction. A range of mechanisms lead to necrosis in toxic myopathies including damage Pathogenesis to the muscle membrane, the presumed cause of myopathy observed with statin drugs. Other causes of muscle injury in necrotic myopathies include crush 422 injuries occurring in comatose or motionless patients, particularly taking drugs of addiction, and ischemia/impaired oxidative phosphorylation – as might be observed in cocaine-induced myopathy. Diagnosis Laboratory: CK levels are variable ranging from normal with steroid myopathies to very high where rhabdomyolysis is observed. Electrophysiology: There may be increased insertional activity in inflammatory and vacuolar myopathies. The motor units may range from small short-duration action potentials typical of myopathy, to polyphasic motor unit action potentials similar to those seen in dermatomyosi- tis. Muscle biopsy: Various changes may be observed including necrosis (Fig. Differential diagnosis –P M – DERM – IBM – Muscular dystrophies – Mt myopathies Therapy There is no specific treatment for the toxic myopathies. Early recognition of a potential toxin, and removal of the toxin is essential in limiting the muscle injury.