S. Baldar. Hampden-Sydney College.

Declining morbidity and mortality among patients with advanced human immunodeficiency virus infection buy discount levitra. Nosocomial transmission of multidrug- resistant Mycobacterium tuberculosis: a risk to patients and health care workers cheap levitra on line. A randomized trial of clarithromycin as prophylaxis against disseminated Mycobacterium avium complex infection in patients with advanced acquired immunodeficiency syndrome discount 10 mg levitra with amex. Effect of katG mutations on the virulence of Myco- bacterium tuberculosis and the implication for transmission in humans cheap levitra on line. Nosocomial spread of human immunodefi- ciency virus-related multidrug-resistant tuberculosis in Buenos Aires. High rate of tuberculosis reinfection during a nosocomial outbreak of multidrug-resistant tuberculosis caused by Mycobacterium bovis strain B. Molecular epidemiology of multidrug-resistant Mycobacterium bovis isolates with the same spoligotyping profile as isolates from ani- mals. Clinical characteristics and comparison with cryptococcal meningitis in patients with human immunodeficiency virus infection. Detection of rifampicin resistance in Mycobacterium tuberculosis isolates from diverse countries by a commer- cial line probe assay as an initial indicator of multidrug resistance. Public health impact of isoniazid-resistant Mycobacterium tuberculosis strains with a mutation at amino-acid position 315 of katG: a decade of experience in The Netherlands. Molecular epidemiology of tuberculosis in the Netherlands: a na- tionwide study from 1993 through 1997. A trial of three regimens to prevent tuberculo- sis in Ugandan adults infected with the human immunodeficiency virus. The study demonstrated that combined therapy was more effective and resulted in the first multidrug antituberculosis treatment that consisted of a long course of both drugs. Soon after the introduction of the first anti-mycobacterial drugs, drug resistant bacilli started to emerge, but the launch of both combination therapy and new and more effective drugs seemed to be enough to control the disease. Since 1970, no new drug has been discovered for antituberculosis treatment, which today seems insufficient to confront the disease. Fortunately, research efforts have been accomplished and today there is a wide range of new molecules with promis- ing antituberculosis activity. In the final part of this chapter we review the main new antimycobacterial drugs that are being devel- oped as candidates to be incorporated in the arsenal of anti-tuberculosis drugs. First, there is a need to rapidly kill those bacilli living extracellularly in lung cavities, which are metabolically active and are dividing continuously; this is required in order to attain the negativization of sputum and therefore to prevent further transmission of the disease. Overview of existing treatment schemes 595 be considered among the first-line drugs, and in the near future, it is quite likely that some fluoroquinolones could be incorporated into the standard anti- tuberculosis treatment, thus being considered as first-line drugs. The current short-course treatment for the complete elimination of active and dor- mant bacilli involves two phases: • initial phase: three or more drugs (usually isoniazid, rifampicin, pyrazina- mide and ethambutol or streptomycin) are used for two months, and allow a rapid killing of actively dividing bacteria, resulting in the negativization of sputum • continuation phase: fewer drugs (usually isoniazid and rifampicin) are used for 4 to 7 months, aimed at killing any remaining or dormant bacilli and preventing recurrence 18. For standard re- gimes, first-line drugs should be used at the doses summarized in Table 18-1 (data from Martindale 2004, and Centers for Disease Control and Prevention 2003a). The doses and periodicity of second-line drugs and other drugs are given in Table 18-2 (Centers for Disease Control and Preven- tion 2003a). Overview of existing treatment schemes 597 Table 18-2: Recommended doses for second-line anti-tuberculosis drugs Drug Adults or Dose (max. Treatment regimens There are many different anti-tuberculosis regimens described in the literature, mostly matching the premises, indications and doses indicated in the sections above (Centers for Disease Control and Prevention 2003a, World Health Organization 2003). In general, the duration of the continuation phase must be estimated once the first two months of treatment (initial phase) have been completed. If the patient had cavitations on initial chest radiography and cultures are still positive after two months of treatment, the continuation phase should be extended to 31 weeks (seven months). When drug resistance develops, patients should be treated with a new combination containing at least three drugs that they had never received before (or that do not show cross-resistance with those to which resistance is suspected). In these condi- tions, the treatment is longer, more toxic, more expensive and less effective than regimens containing first-line drugs, and should be directly observed. All antituberculosis drugs are compatible with breast feeding, although babies should be given chemoprophylaxis for at least three months after the mother is considered non-infectious. It is of prime importance to ensure the patient’s adherence to the antituberculosis treatment in order to achieve complete elimination of the bacilli (and hence avoid disease relapse), and also to prevent the emergence of drug resistance. Both the patient’s ad- herence and supervision are often difficult to manage when the antituberculosis treatment has to be administered on a daily basis. Alternative treatments based on an intermittent administration of drugs (three times, twice and even once per week) facilitate the patient’s adherence and the supervision of treatment. Intermittent treatment is possible because antituberculosis drugs have a marked post-antibiotic effect. After the tuberculous bacillus has been exposed to drugs, there is a lag pe- riod (up to several days) during which its growth is interrupted even after the drug concentration has fallen to sub-inhibitory levels. Thus, there is no need to maintain a continuous inhibitory drug concentration to kill the bacilli or prevent growth. Indeed, by reduc- ing the number of tablets to be taken, they facilitate the patient’s adherence to treatment and supervision of therapy. Most importantly, this form of preparation minimizes the possibility of monotherapy and therefore, reduces the risk of drug resistance development. Once activated, it inhibits the biosynthesis of mycolic acids, which are essential components of the mycobacterial cell wall. This drug is bactericidal against metabolically active bacilli and bacteriostatic against resting bacilli. Between 10 % and 20 % of patients may develop transient increases in liver enzymes at the beginning of treatment, and sometimes develop hepatic damage. It is bactericidal against dividing mycobac- teria and also has some activity against non-dividing bacilli. Adverse effects include diverse altera- tions in the gastrointestinal tract, skin, kidney and nervous system. Since it is metabolized in the liver, hepatic functions should be controlled before starting treatment and monitored regularly until the therapy ends. It is active against persisting and non-dividing bacilli, even against those residing intracellularly, being almost inactive at neutral pH. Serum concentrations reach a peak level of about 66 mg/L two hours after administration of a dose of 3 g. It is distributed in all body tissues and fluids, including the cere- brospinal fluid and breast milk. Therefore, it is contra-indicated in patients with liver damage, and it is advisable to test liver function before and regularly during treatment. After ab- sorption, it is distributed in most tissues and diffuses into the cerebrospinal fluid and breast milk; it also crosses the placenta. Following a dose of 25 mg/kg body weight a peak concentration of 5 mg/L in serum is reached after 4 hours. Usually, normal vision is recovered a few weeks after the end of the treatment, although in some cases, this recovery may not occur until some months after the completion of treatment. Other adverse effects include a reduction of urate excretion (hence producing gout), gastrointestinal disorders and hypersensitivity skin reactions. It is a white-whitish crystalline powder, highly hygroscopic and soluble in water that must be stored in airtight containers. It can also be used in the treatment of other bacterial infections such as those produced by Yersinia pestis, Francisella tularensis, and Brucella spp. It is less nephrotoxic than other aminoglycosides, although it may produce renal failure when administered with other nephrotoxic agents. Drugs: structure, pharmacokinetics and toxicity 609 Para-aminosalicylic acid This compound and its salts are active only against M. It is well absorbed in the gastrointestinal tract and distributes well throughout the body, although it is poorly distributed in the cerebrospinal fluid. Commonly, capreomycin affects the fre- quency of urination or the amount of urine, increases thirst and may produce loss of appetite, nausea and vomiting. Due to its toxic effects, it must not be given in com- bination with aminoglycosides such as kanamycin or streptomycin. Cycloserine This is a broad-spectrum antibiotic that inhibits many microorganisms such as Escherichia coli, Staphylococcus aureus, Nocardia spp. Due to its high toxicity, it is only used against bacilli resistant to the main antituberculosis drugs. It is fairly well absorbed in the gastrointestinal tract, being distributed to most tissues and fluids, including cerebrospinal fluid.

The acidophilic secretory material in the lumen of the gland is rich in fructose cheap levitra 20mg free shipping, thought to serve as an energy source for spermatozoa following ejaculation generic levitra 20mg otc. Also evident are the elongate tubules forming the parenchyma of the gland and the dense fibrous connective tissue capsule levitra 10 mg with amex. Compare its transitional epithelium with the epithelium lining the ducts and glands of the prostate buy levitra 10mg on-line, which can be cuboidal, columnar or pseudostratified. The tubulo-alveolar glands of the prostate are embedded in an abundant stroma of fibro-elastic connective tissue, which is interlaced with strands of smooth muscle. Fixation is much better in the H & E sections, and it should be studied for the structure of the lining epithelium of the glands. Examine the central penile urethra and the surrounding blood-filled vascular sinuses that comprise the erectile tissue of the corpus spongiosum. Note that the lining epithelium of the penile urethra has a stratified columnar or stratified cuboidal appearance. Study the erectile tissue surrounding the urethra and observe that the trabeculae between blood sinuses contain smooth muscle and connective tissue fibers. The connective tissue capsule surrounding the corpus spongiosum is not as thick as that surrounding the corpora cavernosa. At low power note the general division of the ovary into an outer cortex containing follicles in various stages of development and an inner medulla containing numerous blood vessels and dense fibrous connective tissue. Identify; Lining epithelium (classically called “germinal epithelium”) - a simple cuboidal covering the ovary, continuous with the mesothelium of the peritoneum. These are growing follicles Secondary (antral) follicles - 1 oocyte surrounded by granulosa cells among which fluid-filledo spaces are coalescing into a single space, or antrum. Outside the basal lamina of the granulosa layer, the theca has differentiated into a theca interna and a theca externa. Atresia is often first recognized in the granulosa cells as the nuclei become apoptotic and there is a loosening of the cells. Corpus luteum – Following ovulation follicular cells (both granulosa and luteal) fold into the empty follicle and undergo luteinization. Identify the two primary cellular components of the corpus luteum, the granulosa lutein and theca lutein cells. Notice the relationships of these two cell types to each other and to the vascularization of the developing corpus luteum. Granulosa lutein left, theca lutein right #64 Ovary, Corpus Luteum of Pregnancy Compare the development of this corpus luteum of pregnancy (probably from the first trimester) with that of the recently formed corpus luteum of slide #63. Note particularly the increase in thickness of the granulosa luteal layer as compared to the thin, peripheral zone of theca luteal cells. The extensive vacuolization of the granulosa luteal cells is due to the extraction of its abundant lipid droplets. This reflects the importance of the corpus luteum (particularly the granulosa lutein cells) as the primary ovarian source of the steroid hormone progesterone. Be certain that you understand the changes that occur within the follicle during follicular development. These folds decrease progressively from the ovarian (infundibular) end of the tube to the uterine (isthmus) portion. The uterine tubes are a common site of occlusion after pelvic inflammatory disease, resulting in sterility. It is important to understand the interrelationships among the pituitary, ovary, and uterus during different stages of the menstrual cycle. The proliferative stage follows menstruation and is characterized by the repair of the endometrium and the proliferation of relatively straight, tubular uterine glands. Note the rather dense, cellular appearance of the endometrial stroma (region between glands) at this stage. Left to right: spongy zone, stratum basale, myometrium What is the primary ovarian hormone stimulating the endometrium during this stage? There has been a considerable increase in glandular development, characterized by their convoluted and "saw- toothed" appearance in sections. The glands are Secretory endometrium 72 frequently distended by a lightly acidophilic secretion rich in glycogen and this serves as an important source of nutrients to the developing embryo prior to implantation. Note the coiled arterioles in the endometrium, and be certain that you understand the significance of the arterial supply to the endometrium. Locate at higher magnification some of the mucus-secreting epithelial cells, which line the cervical mucosa. Note also the abrupt transition between the simple columnar epithelium of the endocervix and the stratified squamous epithelium of the ectocervix. The bulk of the wall of the cervix is made up of bundles of smooth muscle interlaced with connective tissue. In what other regions of the body does one observe an abrupt junction between simple columnar and stratified epithelia? The period of placentation is initiated by the attachment of the blastocyst to the endometrium, and it is terminated by the delivery of the newborn infant at the time of parturition. The placenta is the first organ to be differentiated, and performs functions analogous to those of the lung (gas exchange), intestine (nutrient absorption), kidney (excretion and ion regulation), liver (synthesis of serum proteins, steroid metabolism), pituitary (synthesis of hormones including gonadotropic and prolactin-like hormones), and gonads (incomplete synthesis of progestins and estrogens). The fetal portion of the placenta consists of the chorionic plate, composed of an outer layer of trophoblast and an inner layer of vascularized extra- embryonic mesodermal connective tissue. The bulk of the placenta fetalis consists of outgrowths of villi from the surface of the chorionic plate. The villi are sectioned in many 73 different planes, and their attachment to the chorionic plate may not be evident. Attached to the inner (fetal) surface of the chorionic plate is the amnion, consisting of an inner squamous amniotic epithelium and an outer layer of avascular mesoderm. Study the chorionic villi in detail, and identify all of the layers that separate the maternal and fetal blood. Gases, nutrients, metabolites and other substances must pass through these layers to move from one circulation to the other. In life maternal blood fills the intervillous space, but it is generally washed out during tissue preparation. Note the loose appearance of the cells forming the cores of the villi, and compare this with the condition in the villi at 6 months gestational age. Occasional nucleated fetal red blood cells, characteristic of earlier stages, can still be observed in the fetal vessels of the villi. Note the abundance and location of the fetal capillaries, the sparsity of the cytotrophoblast, and the nature of the syncytiotrophoblast. Be certain that you know the layers that form the separation between fetal and maternal blood in the placenta. This network of ducts begins at the nipple with the excretory lactiferous duct, which branches as it extends into the collagen and adipose tissue of the breast until it eventually branches into terminal duct lobular units. The terminal duct lobular unit consists of interlobular stroma, interlobular duct, terminal duct and acini, and surrounding fat. With higher power, note that the ducts and acini are lined by simple cuboidal or columnar epithelium and surrounding myoepithelial cells. There is abundant connective tissue with embedded lactiferous ducts, ending in minimal lobule formation #69 Breast, Lactating, Osmium fixation Unsaturated lipid in the apical cytoplasm of the alveolar cells and in the milk in the lumina is stained black by reduced osmium tetroxide. Because osmium penetrates very poorly the tissue is well stained only at the periphery of the section. The connective tissue surrounding the alveolus is much more delicate (although compressed here) and is continuous with the papillary layer of the dermis. The digestive system consists of the oral cavity, the pharynx, the alimentary tract (canal), and the anal canal. There are both intrinsic and extrinsic glands, which may secrete digestive enzymes or mucus to facilitate the digestion and transport of ingested food. The extrinsic digestive glands are the major salivary glands including the parotid, sublingual and submandibular (submaxillary) glands; the pancreas; and the liver. Proceeding outward from the lumen these are: (1) the mucosa (mucous membrane), (2) the submucosa, (3) the muscularis (muscularis externa), and (4) the adventitia or serosa. The mucosa has three components: (a) the epithelium and its underlying basement membrane, (b) a thin underlying layer of loose, cellular connective tissue, the lamina propria, and (c) a relatively thin layer of smooth muscle called the muscularis mucosae. The submucosa is composed of a layer of dense, irregularly arranged connective tissue that contains nervous tissue (the submucosal plexus of Meissner) as well as blood vessels.

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Amongst the other causes of dementia are diseases of thyroid 10 mg levitra mastercard, parathyroid cheap levitra 20mg with visa, diabetes discount levitra 20 mg online, effect of toxic chemicals purchase levitra 20mg on line, and heavy metals etc. Symptoms of Alzheimer’s Dementia : In the initial stage of the disease the following symptoms are seen. Medically this disease can be divided into three stages and in the final stage the patient becomes completely dependent. It is a well known fact that many famous people like former American President Ronald Reagan, Rita Heyworth, Sugar Ray Robinson, E B White and others have suffered from this disease. However, extensive research is being carried out to design drugs to decrease the intensity of the symptoms. The patient and his relatives should have proper information and education regarding the disease in order to cope with day-to-day problems and difficulties. Diagnosis : l Along with the earlier mentioned symptoms, various cognitive tests for testing the patient’s memory, understanding, linguistic co-ordination can confirm the diagnosis of dementia. Mini mental status examination, word list memory test, work recall test and various neuropsychological measures are used to diagnose the disease and its intensity. For example if the patient has E-4 Apolipoprotein gene on the 19th chromosome, there are high chances of his offsprings suffering from Alzheimer’s disease. The formation of neurofibrillary tangles in the neurons of the brain and accumulation of plaques of a protein called Beta- amyloides outside the cells, causing damage and edema in the fragile brain cells, is the pathological hallmark of Alzheimer’s disease. Amongst newer medicines there are Rivastigmin (Exelon) and Galantamine (Reminyl) with even better results. In our country, cost is a problem and therefore Piracetam (Normabrain; Nootropil) or Ergot group of medicines are more popular to these costly newer drugs. Multi-infarct Dementia : When a decrease in the supply of blood to various small portions of the brain damages the ce;;s in those areas then Multi-infarct Dementia results. A rise in the blood pressure damages small capillaries and small clots are formed in these capillaries, which results in lowering of the blood supply in certain parts of the brain. The lipid profile, Doppler of the blood vessels of the neck, 2D Echo of the heart etc are the tests which are specially helpful in the detection of the disease. Along with the drugs for thinning of the blood, regulating blood pressure and diabetes strictly, maintaining discipline in eating habits and regular exercise are very essential to prevent this disease. It is a matter of debate whether healthy close relatives (daughter, son, sister, brother) of people suffering from Alzheimer’s dementia or others (which are hereditary) should get themselves examined as a precautionary measure. In some countries such facilities are available where genetic investigations can accurately predict the possibility of a person suffering from this disease in future. In many such cases, Alzheimer’s disease is wrongly diagnosed, for example, Hypothyroidism, vitamin deficiency, and many collagen diseases like S. Prevention of Dementia and Improving Brain Power : It is believed that as the age progresses the cells in the brain degenerate, gradually resulting in loss of memory as well as mind power. Recent research has shown that if the right kind of environment is provided there can be development of the new nerve fibres in the brain of older or aging people. This will result in more supply of blood and oxygen to the brain, which will keep the nervous system alert. After every one to one and half-hours of work, it is advisable to take a break for some minutes and move around for some time. Diverting the mind to a different subject after continuous working on a particular subject can make the brain more alert. After meals one feels drowsy because the blood supply to the brain decreases, so only limited food should be eaten in the afternoon. Try remembering telephone numbers or birthdays of friends and relatives or at least try to remember the birthdays of close relatives and family members. One should end the day with positive thoughts without any worries, which is not a very difficult task. Few tips for students to improve memory : l While you settle down to study, keep your textbooks, notebooks, pen etc. If you find the subject difficult, resort to deep-breathing for 2 minutes so as to increase your concentration. Note down the important points Discuss what you have read with your friends and then open the book and confirm what you have retained. Ribosomal Memory : As per the principles of Ribosomal memory following suggestions for retaining whatever is read are extremely useful. Similarly to read the next one and after reading for a while, to keep the book aside and try to remember everything. To write all important points, or discuss with the colleagues and then review if any points are left out. As mentioned early, there is no definite, effective or quick way to improve memory; however the method given above is time tested method to improve memory performance for students as well as other people. If there is an infection in the nose and the ears with pus discharge, throat infection, infectious boils on the face, pus in the other body parts like the chest or septicemia, then there is a possibility of infection in the brain. It is not possible to describe all these diseases here, but some important diseases will be discussed. Tuberculosis of the Brain : Usually, tuberculosis infection of the brain comes from other parts of the body like lungs or stomach. Headache, low-grade fever, vomiting, loss of appetite, excessive weakness or anxiety are the initial symptoms of this disease. Gradually, seizures, paralysis of one or more limbs can occur and in advanced stage, coma due to the edema of the brain and even death may occur. F are obstructed, the result is hydrocephalus, in which the cerebral ventricles dilate leading to unconsciousness or loss of eyesight. Diagnosis : In order to diagnose this disease, a detailed medical examination as well as blood tests are required. Lumbar Puncture is almost an essential test for the confirmatory diagnosis of the infectious diseases of the brain. This accuracy is necessary because once the diagnosis is confirmed the patient requires proper treatment for a minimum of one and a half years to two years. F reports may sometimes present a picture of a viral or pyogenic infection and if there is a laxity in the treatment of any of the three infections due to lack of proper diagnosis, it could lead to dangerous consequences. In resistant cases, sparfloxacin or ciprofloxacin, kanamycin injection, ethionamide or cycloserine can also be used as secondary medicines. All these drugs have some or the other side effects and therefore along with the symptoms of the patient, laboratory tests are regularly carried out. In this case, a small tube is introduced in to ventricles of the brain through the skull, and the extra fluid is drained out through a tunnel beneath the skin up to the stomach via the tube. Symptoms range from high fever, severe unbearable headache, vomiting, pain in the posterior part of the neck and photophobia to ultimately unconsciousness, seizures and eventually death in a short time, in the absence of proper treatment. The various types of Gram-positive and Gram- negative bacteria that can rapidly cause harm to the brain are, meningococcus, staphylococcus, pneumococcus, streptococcus, listeria, H. An early diagnosis and treatment can cure the patient without any long-term disability or side effects. This allows the doctor to decide whether the medicines, which are prescribed prior to the test, are accurate or need to be changed. Thus, it is confirmed that the patient is definitely suffering from pyogenic meningitis and appropriate drugs are given after identifying the disease causing organisms. Drugs : If necessary drugs like cephalosporin, penicillin, vancomycin, gentamycin, chloramphenicol, metronidazole etc. All these medicines are very effective and 80 to 95 % cases can be cured if these drugs are used in appropriate dose and combination at an early stage. Usually, these medicines are given for 10 to 14 days continuously and if required, changes can be made on the basis of the culture report. Even if a little infection remains in the brain, there is a possibility of a recurrence of the disease in a short time. Increase in the swelling of the brain (raised Intracranial tension), seizure, hydrocephalus, subdural effusion or subdural empyema (abscess between the membranes of the brain) or brain abscess, hearing loss, venous thrombosis, vasculitis etc. This disease starts with low grade fever, headache, weakness, anxiety and therefore, initially it is not diagnosed and the disease advances in the absence of proper treatment leading to unconsciousness and seizures etc. These medicines have severe side effects on the kidney, liver, ears etc and thus should be administered carefully. Viral Encephalitis : This is an extremely fast spreading disease in which the patient gets fever, headache, sudden behavioural changes, depression, photophobia. This disease quickly damages the cells of the brain and many times leaves residual damage in the body, like memory loss, seizures or behavioral changes. Sometimes, the virus affects only the membranes of the brain causing viral meningitis, which is not a very serious disease in comparison.

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The third ventricle is the space between the left and right sides of the diencephalon generic levitra 20mg line, which opens into the cerebral aqueduct that passes through the midbrain buy 20 mg levitra with mastercard. The aqueduct opens into the fourth ventricle purchase levitra 10 mg overnight delivery, which is the space between the cerebellum and the pons and upper medulla (Figure 13 buy levitra master card. As the telencephalon enlarges and grows into the cranial cavity, it is limited by the space within the skull. The telencephalon is the most anterior region of what was the neural tube, but cannot grow past the limit of the frontal bone of the skull. Because the cerebrum fits into this space, it takes on a C-shaped formation, through the frontal, parietal, occipital, and finally temporal regions. The two ventricles are in the left and right sides, and were at one time referred to as the first and second ventricles. The interventricular foramina connect the frontal region of the lateral ventricles with the third ventricle. The two thalami touch in the center in most brains as the massa intermedia, which is surrounded by the third ventricle. The tectum and tegmentum of the midbrain are the roof and floor of the cerebral aqueduct, respectively. The floor of the fourth ventricle is the dorsal surface of the pons and upper medulla (that gray matter making a continuation of the tegmentum of the midbrain). Cerebrospinal fluid is produced within the ventricles by a type of specialized membrane called a choroid plexus. Observed in dissection, they appear as soft, fuzzy structures that may This OpenStax book is available for free at http://cnx. By surrounding the entire system in the subarachnoid space, it provides a thin buffer around the organs within the strong, protective dura mater. From the dural sinuses, blood drains out of the head and neck through the jugular veins, along with the rest of the circulation for blood, to be reoxygenated by the lungs and wastes to be filtered out by the kidneys (Table 13. Without a steady supply of oxygen, and to a lesser extent glucose, the nervous tissue in the brain cannot keep up its extensive electrical activity. These nutrients get into the brain through the blood, and if blood flow is interrupted, neurological function is compromised. When the blood cannot travel through the artery, the surrounding tissue that is deprived starves and dies. Sometimes, seemingly unrelated functions will be lost because they are dependent on structures in the same region. Along with the swallowing in the previous example, a stroke in that region could affect sensory functions from the face or extremities because important white matter pathways also pass through the lateral medulla. Loss of blood flow to specific regions of the cortex can lead to the loss of specific higher functions, from the ability to recognize faces to the ability to move a particular region of the body. With physical, occupational, and speech therapy, victims of strokes can recover, or more accurately relearn, functions. Ganglia can be categorized, for the most part, as either sensory This OpenStax book is available for free at http://cnx. Under microscopic inspection, it can be seen to include the cell bodies of the neurons, as well as bundles of fibers that are the posterior nerve root (Figure 13. Also, the small round nuclei of satellite cells can be seen surrounding—as if they were orbiting—the neuron cell bodies. Also, the fibrous region is composed of the axons of these neurons that are passing through the ganglion to be part of the dorsal nerve root (tissue source: canine). If you zoom in on the dorsal root ganglion, you can see smaller satellite glial cells surrounding the large cell bodies of the sensory neurons. This is analogous to the dorsal root ganglion, except that it is associated with a cranial nerve instead of a spinal nerve. For example, the trigeminal ganglion is superficial to the temporal bone whereas its associated nerve is attached to the mid-pons region of the brain stem. The other major category of ganglia are those of the autonomic nervous system, which is divided into the sympathetic and parasympathetic nervous systems. The sympathetic chain ganglia constitute a row of ganglia along the vertebral column that receive central input from the lateral horn of the thoracic and upper lumbar spinal cord. Three other autonomic ganglia that are related to the sympathetic chain are the prevertebral ganglia, which are located outside of the chain but have similar functions. The neurons of these autonomic ganglia are multipolar in shape, with dendrites radiating out around the cell body where synapses from the spinal cord neurons are made. The neurons of the chain, paravertebral, and prevertebral ganglia then project to organs in the head and neck, thoracic, abdominal, and This OpenStax book is available for free at http://cnx. Another group of autonomic ganglia are the terminal ganglia that receive input from cranial nerves or sacral spinal nerves and are responsible for regulating the parasympathetic aspect of homeostatic mechanisms. These two sets of ganglia, sympathetic and parasympathetic, often project to the same organs—one input from the chain ganglia and one input from a terminal ganglion—to regulate the overall function of an organ. For example, the heart receives two inputs such as these; one increases heart rate, and the other decreases it. The terminal ganglia that receive input from cranial nerves are found in the head and neck, as well as the thoracic and upper abdominal cavities, whereas the terminal ganglia that receive sacral input are in the lower abdominal and pelvic cavities. Terminal ganglia below the head and neck are often incorporated into the wall of the target organ as a plexus. This can apply to nervous tissue (as in this instance) or structures containing blood vessels (such as a choroid plexus). For example, the enteric plexus is the extensive network of axons and neurons in the wall of the small and large intestines. The enteric plexus is actually part of the enteric nervous system, along with the gastric plexuses and the esophageal plexus. They have connective tissues invested in their structure, as well as blood vessels supplying the tissues with nourishment. The outer surface of a nerve is a surrounding layer of fibrous connective tissue called the epineurium. Within the nerve, axons are further bundled into fascicles, which are each surrounded by their own layer of fibrous connective tissue called perineurium. Finally, individual axons are surrounded by loose connective tissue called the endoneurium (Figure 13. With what structures in a skeletal muscle are the endoneurium, perineurium, and epineurium comparable? Cranial Nerves The nerves attached to the brain are the cranial nerves, which are primarily responsible for the sensory and motor functions of the head and neck (one of these nerves targets organs in the thoracic and abdominal cavities as part of the parasympathetic nervous system). They can be classified as sensory nerves, motor nerves, or a combination of both, meaning that the axons in these nerves originate out of sensory ganglia external to the cranium or motor nuclei within the brain stem. Three of the nerves are solely composed of sensory fibers; five are strictly motor; and the remaining four are mixed nerves. Learning the cranial nerves is a tradition in anatomy courses, and students have always used mnemonic devices to remember the nerve names. A traditional mnemonic is the rhyming couplet, “On Old Olympus’ Towering Tops/A Finn And German Viewed Some Hops,” in which the initial letter of each word corresponds to the initial letter in the name of each nerve. The names of the nerves have changed over the years to reflect current usage and more accurate naming. An exercise to help learn this sort of information is to generate a mnemonic using words that have personal significance. It is also responsible for lifting the upper eyelid when the eyes point up, and for pupillary constriction. The trochlear nerve and the abducens nerve are both responsible for eye movement, but do so by controlling different extraocular muscles. The trigeminal nerve is responsible for cutaneous sensations of the face and controlling the muscles of mastication. The facial nerve is responsible for the muscles involved in facial expressions, as well as part of the sense of taste and the production of saliva. The glossopharyngeal nerve is responsible for controlling muscles in the oral cavity and upper throat, as well as part of the sense of taste and the production of saliva. The vagus nerve is responsible for contributing to homeostatic control of the organs of the thoracic and upper abdominal cavities. The spinal accessory nerve is responsible for controlling the muscles of the neck, along with cervical spinal nerves.

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