W. Trano. American Global University.

Sensorium Those parts of the brain involved in the reception and interpretation of sensory stimuli are referred to collectively as the sensorium purchase 100mg gyne-lotrimin with visa. From the primary cortical areas of the somatosensory generic 100 mg gyne-lotrimin overnight delivery, visual cheap gyne-lotrimin 100mg on line, auditory discount gyne-lotrimin 100 mg free shipping, and gustatory senses to the association areas that process information in these modalities, the cerebral cortex is the seat of conscious sensory perception. In contrast, sensory information can also be processed by deeper brain regions, which we may vaguely describe as subconscious—for instance, we are not constantly aware of the proprioceptive information that the cerebellum uses to maintain balance. Several of the subtests can reveal activity associated with these sensory modalities, such as being able to hear a question or see a picture. The first is praxis, a practical exercise in which the patient performs a task completely on the basis of verbal description without any demonstration from the examiner. For example, the patient can be told to take their left hand and place it palm down on their left thigh, then flip it over so the palm is facing up, and then repeat this four times. The examiner describes the activity without any movements on their part to suggest how the movements are to be performed. The patient needs to understand the instructions, transform them into movements, and use sensory feedback, both visual and proprioceptive, to perform the movements correctly. The patient keeps their eyes closed and is given a common object, such as a coin, that they have to identify. The patient should be able to indicate the particular type of coin, such as a dime versus a penny, or a nickel versus a quarter, on the basis of the sensory cues involved. For example, the size, thickness, or weight of the coin may be an indication, or to differentiate the pairs of coins suggested here, the smooth or corrugated edge of the coin will correspond to the particular denomination. The second task, graphesthesia, is to recognize numbers or letters written on the palm of the hand with a dull pointer, such as a pen cap. Praxis and gnosis are related to the conscious perception and cortical processing of sensory information. Being able to transform verbal commands into a sequence of motor responses, or to manipulate and recognize a common object and associate it with a name for that object. The relationship between the words that describe actions, or the nouns that represent objects, and the cerebral location of these concepts is suggested to be localized to particular cortical areas. Certain aphasias can be characterized by a deficit of verbs or nouns, known as V impairment or N impairment, or may be classified as V–N dissociation. To describe what is happening in a photograph as part of the expressive language subtest, a patient will use active- or image-based language. The lack of one or the other of these components of language can relate to the ability to use verbs or nouns. Damage to the region at which the frontal and temporal lobes meet, including the region known as the insula, is associated with V impairment; damage to the middle and inferior temporal lobe is associated with N impairment. Judgment and Abstract Reasoning Planning and producing responses requires an ability to make sense of the world around us. Making judgments and reasoning in the abstract are necessary to produce movements as part of larger responses. Will hitting the snooze button multiple times lead to feeling more rested or result in a panic as you run late? In the mental status exam, the subtest that assesses judgment and reasoning is directed at three aspects of frontal lobe function. First, the examiner asks questions about problem solving, such as “If you see a house on fire, what would you do? The prefrontal cortex is composed of the regions of the frontal lobe that are not directly related to specific motor functions. Anterior to that are the premotor cortex, Broca’s area, and the frontal eye fields, which are all related to planning certain types of movements. Anterior to what could be described as motor association areas are the regions of the prefrontal cortex. The antecedents to planning certain movements are judging whether those movements should be made, as in the example of deciding whether to hit the snooze button. The neurological exam does not necessarily assess personality, but it can be within the realm of neurology or psychiatry. A clinical situation that suggests this link between the prefrontal cortex and personality comes from the story of Phineas Gage, the railroad worker from the mid-1800s who had a metal spike impale his prefrontal cortex. Later anecdotal evidence from his life suggests that he was able to support himself, although he had to relocate and take on a different career as a stagecoach driver. The disorders associated with this procedure included some aspects of what are now referred to as personality disorders, but also included mood disorders and psychoses. Depictions of lobotomies in popular media suggest a link between cutting the white matter of the prefrontal cortex and changes in a patient’s mood and personality, though this correlation is not well understood. As an extreme measure to deal with a debilitating condition, the corpus callosum may be sectioned to overcome intractable epilepsy. When the connections between the two cerebral hemispheres are cut, interesting effects can be observed. If a person with an intact corpus callosum is asked to put their hands in their pockets and describe what is there on the basis of what their hands feel, they might say that they have keys in their right pocket and loose change in the left. They may even be able to count the coins in their pocket and say if they can afford to buy a candy bar from the vending machine. If a person with a sectioned corpus callosum is given the same instructions, they will do something quite peculiar. They will not even move their left hand, much less report that there is loose change in the left pocket. The reason for this is that the language functions of the cerebral cortex are localized to the left hemisphere in 95 percent of the population. Additionally, the left hemisphere is connected to the right side of the body through the corticospinal tract and the ascending tracts of the spinal cord. Motor commands from the precentral gyrus control the opposite side of the body, whereas sensory information processed by the postcentral gyrus is received from the opposite side of the body. For a verbal command to initiate movement of the right arm and hand, the left side of the brain needs to be connected by the corpus callosum. Language is processed in the left side of the brain and directly influences the left brain and right arm motor functions, but is sent to influence the right brain and left arm motor functions through the corpus callosum. Likewise, the left-handed sensory perception of what is in the left pocket travels across the corpus callosum from the right brain, so no verbal report on those contents would be possible if the hand happened to be in the pocket. Unlike normal people, this patient can perform two independent tasks at the same time because the lines of communication between the right and left sides of his brain have been removed. Whereas a person with an intact corpus callosum cannot overcome the dominance of one hemisphere over the other, this patient can. If the left cerebral hemisphere is dominant in the majority of people, why would right-handedness be most common? The Mental Status Exam The cerebrum, particularly the cerebral cortex, is the location of important cognitive functions that are the focus of the mental status exam. The regionalization of the cortex, initially described on the basis of anatomical evidence of cytoarchitecture, reveals the distribution of functionally distinct areas. Cortical regions can be described as primary sensory or motor areas, association areas, or multimodal integration areas. The functions attributed to these regions include attention, memory, language, speech, sensation, judgment, and abstract reasoning. The mental status exam addresses these cognitive abilities through a series of subtests designed to elicit particular behaviors ascribed to these functions. Losses of language and speech functions, known as aphasias, are associated with damage to the important integration areas in the left hemisphere known as Broca’s or Wernicke’s areas, as well as the connections in the white matter between them. The subtests related to these functions depend on multimodal integration, as well as language-dependent processing. The prefrontal cortex contains structures important for planning, judgment, reasoning, and working memory. The famous case of Phineas Gage suggests a role for this cortex in personality, as does the outdated practice of prefrontal lobectomy. But knowing the names of the nerves in order often leaves much to be desired in understanding what the nerves do. The nerves can be categorized by functions, and subtests of the cranial nerve exam can clarify these functional groupings. Three of the nerves are strictly responsible for special senses whereas four others contain fibers for special and general senses. Four nerves connect to muscles of the face, oral cavity, and pharynx, controlling facial expressions, mastication, swallowing, and speech.

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In people who have cystic fibrosis order gyne-lotrimin 100 mg without a prescription, chloride levels in sweat are two to five times those of normal levels purchase gyne-lotrimin 100 mg mastercard, and analysis of sweat is often used in the diagnosis of the disease purchase 100mg gyne-lotrimin. Carbon dioxide is converted into bicarbonate in the cytoplasm of red blood cells through the action of an enzyme called carbonic anhydrase cheap gyne-lotrimin 100mg otc. Calcium About two pounds of calcium in your body are bound up in bone, which provides hardness to the bone and serves as a mineral reserve for calcium and its salts for the rest of the tissues. A little more than one-half of blood calcium is bound to proteins, leaving the rest in its ionized form. In addition, calcium helps to stabilize cell membranes and is essential for the release of neurotransmitters from neurons and of hormones from endocrine glands. A deficiency of vitamin D leads to a decrease in absorbed calcium and, eventually, a depletion of calcium stores from the skeletal system, potentially leading to rickets in children and osteomalacia in adults, contributing to osteoporosis. Hypocalcemia, or abnormally low calcium blood levels, is seen in hypoparathyroidism, which may follow the removal of the thyroid gland, because the four nodules of the parathyroid gland are embedded in it. Hypophosphatemia, or abnormally low phosphate blood levels, occurs with heavy use of antacids, during alcohol withdrawal, and during malnourishment. In the face of phosphate depletion, the kidneys usually conserve phosphate, but during starvation, this conservation is impaired greatly. Hyperphosphatemia, or abnormally increased levels of phosphates in the blood, occurs if there is decreased renal function or in cases of acute lymphocytic leukemia. Regulation of Sodium and Potassium Sodium is reabsorbed from the renal filtrate, and potassium is excreted into the filtrate in the renal collecting tubule. Aldosterone Recall that aldosterone increases the excretion of potassium and the reabsorption of sodium in the distal tubule. Aldosterone is released if blood levels of potassium increase, if blood levels of sodium severely decrease, or if blood pressure decreases. Its net effect is to conserve and increase water levels in the plasma by reducing the excretion of sodium, and thus water, from the kidneys. This action increases the glomerular filtration rate, resulting in more material filtered out of the glomerular capillaries and into Bowman’s capsule. In the distal convoluted tubules and collecting ducts of the kidneys, aldosterone stimulates the synthesis and activation of the sodium-potassium pump (Figure 26. Aldosterone’s effect on potassium is the reverse of that of sodium; under its influence, excess potassium is pumped into the renal filtrate for excretion from the body. The hormone activates osteoclasts to break down bone matrix and release inorganic calcium-phosphate salts. The hormone increases the activity of osteoblasts, which remove calcium from the blood and incorporate calcium into the bony matrix. A variety of buffering systems permits blood and other bodily fluids to maintain a narrow pH range, even in the face of perturbations. A buffer is a chemical system that prevents a radical change in fluid pH by dampening the change in hydrogen ion concentrations in the case of excess acid or base. Most commonly, the substance that absorbs the ions is either a weak acid, which takes up hydroxyl ions, or a weak base, which takes up hydrogen ions. Buffer Systems in the Body The buffer systems in the human body are extremely efficient, and different systems work at different rates. The renal system can also adjust blood pH through the excretion of + hydrogen ions (H ) and the conservation of bicarbonate, but this process takes hours to days to have an effect. The buffer systems functioning in blood plasma include plasma proteins, phosphate, and bicarbonate and carbonic acid buffers. The kidneys help control acid-base balance by excreting hydrogen ions and generating bicarbonate that helps maintain blood plasma pH within a normal range. Proteins are made up of amino acids, which contain positively charged amino groups and negatively charged carboxyl groups. The charged regions of these molecules can bind hydrogen and hydroxyl ions, and thus function as buffers. Buffering by proteins accounts for two-thirds of the buffering power of the blood and most of the buffering within cells. Hemoglobin as a Buffer Hemoglobin is the principal protein inside of red blood cells and accounts for one-third of the mass of the cell. Bicarbonate ions and carbonic acid are present in the blood in a 20:1 ratio if the blood pH is within the normal range. With 20 times more bicarbonate than carbonic acid, this capture system is most efficient at buffering changes that would make the blood more acidic. This is useful because most of the body’s metabolic wastes, such as lactic acid and ketones, are acids. In red blood cells,2 carbonic anhydrase forces the dissociation of the acid, rendering the blood less acidic. The level of bicarbonate in the blood is controlled through the renal system, where2 bicarbonate ions in the renal filtrate are conserved and passed back into the blood. Respiratory Regulation of Acid-Base Balance The respiratory system contributes to the balance of acids and bases in the body by regulating the blood levels of carbonic acid (Figure 26. Reduced breathing (hypoventilation) due to drugs such as morphine, barbiturates, or ethanol (or even just holding one’s breath) can also result in hypercapnia. A decrease of blood bicarbonate can result2 from the inhibition of carbonic anhydrase by certain diuretics or from excessive bicarbonate loss due to diarrhea. Blood bicarbonate levels are also typically lower in people who have Addison’s disease (chronic adrenal insufficiency), in which aldosterone levels are reduced, and in people who have renal damage, such as chronic nephritis. Finally, low bicarbonate blood levels can result from elevated levels of ketones (common in unmanaged diabetes mellitus), which bind bicarbonate in the filtrate and prevent its conservation. The hydrogen ion is secreted into the filtrate, where it can become part of new water molecules and be reabsorbed as such, or removed in the urine. It is also possible that salts in the filtrate, such as sulfates, phosphates, or ammonia, will capture hydrogen ions. In such cases,2 bicarbonate ions are not conserved from the filtrate to the blood, which will also contribute to a pH imbalance and acidosis. If more potassium is present than normal, potassium, rather than the hydrogen ions, will be exchanged, and increased potassium enters the filtrate. If there is less potassium, more hydrogen ions enter the filtrate to be exchanged with sodium and more bicarbonate is conserved. If chloride is lost, the body uses bicarbonate This OpenStax book is available for free at http://cnx. Acid-Base Balance: Ketoacidosis Diabetic acidosis, or ketoacidosis, occurs most frequently in people with poorly controlled diabetes mellitus. When certain tissues in the body cannot get adequate amounts of glucose, they depend on the breakdown of fatty acids for energy. When acetyl groups break off the fatty acid chains, the acetyl groups then non-enzymatically combine to form ketone bodies, acetoacetic acid, beta-hydroxybutyric acid, and acetone, all of which increase the acidity of the blood. Ketoacidosis can be severe and, if not detected and treated properly, can lead to diabetic coma, which can be fatal. Treatment for diabetic coma is ingestion or injection of sugar; its prevention is the proper daily administration of insulin. Among people with type 2 diabetes, those of Hispanic and African-American descent are more likely to go into ketoacidosis than those of other ethnic backgrounds, although the reason for this is unknown. Acidosis has several symptoms, including headache and confusion, and the individual can become lethargic and easily fatigued (Figure 26. Some symptoms of alkalosis include cognitive impairment (which can progress to unconsciousness), tingling or numbness in the extremities, muscle twitching and spasm, and nausea and vomiting. Metabolic Acidosis: Primary Bicarbonate Deficiency Metabolic acidosis occurs when the blood is too acidic (pH below 7. The most common cause of metabolic acidosis is the presence of organic acids or excessive ketones in the blood. The first three of the eight causes of metabolic acidosis listed are medical (or unusual physiological) conditions. Metabolic acidosis can also arise from diabetic ketoacidosis, wherein an excess of ketones is present in the blood.

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Use this slide to review the histology of smooth and skeletal muscle gyne-lotrimin 100mg lowest price, comparing them with the adjacent connective tissue of both the lamina propria and the submucosa cheap gyne-lotrimin 100mg overnight delivery. Compare the muscle of the muscularis externa of the esophagus with that of the previous esophageal slides purchase 100mg gyne-lotrimin mastercard. Note both the diffuse infiltration of lymphocytes and the scattered lymph nodules within the lamina propria of the stomach order 100mg gyne-lotrimin overnight delivery. A more detailed study of the various cell types of the gastric epithelium is considered on the next slide. The distensible stomach is involved in both the mechanical and chemical breakdown of food, and also serves as a temporary reservoir. The gastric mucosa contains gastric pits (foveolae), which are surface invaginations that also serve as the ducts of the underlying intrinsic gastric glands. Three basic cell types contribute to the secretion of gastric juice, and each has a characteristic appearance under the light and electron microscope. Mucus-secreting cells: These cells form the surface epithelium and extend inward to line the gastric pits. Nuclei are basal, and the supranuclear cytoplasm containing mucinogen granules appears clear or vacuolated with H & E stain. Mucous neck cells occur in the junctional region of the gastric pits and glands, and it is in this region that cell proliferation for the renewal of the epithelium occurs. Parietal cells: These pyramidal or spherical cells appear wedged in between other cells of the gastric glands. They are characterized by their finely granular acidophilic cytoplasm due to an abundance of mitochondria, and by their central, spherical nucleus. Chief (zymogen) cells: These cells are involved in the secretion of enzymes, particularly the proteolytic enzyme pepsinogen (pepsin in the active state). As is characteristic of cells involved in protein synthesis and secretion, these cells contain basophilic cytoplasm, particularly at their base due to the extensive development of rough endoplasmic reticulum. Locate the following elements of the mucosa: the luminal surface mucous secreting cells, the gastric pits and the cells lining them. Note the loose connective tissue surrounding the gastric pits, the muscularis mucosae, which forms a boundary between the mucosa and submucosa, and the blood vessels in the submucosa. Examine the muscularis externa and notice that the smooth muscle is oriented in several different planes. Look for differences in the epithelial surface and note the thickening of the muscularis externa of the stomach as it becomes the pyloric sphincter. Although the gastric mucosa is characterized by surface pits and the intestinal mucosa is characterized by finger-like villi, this distinction is not always readily apparent on sections. One of the best ways to distinguish between the two organs is to examine the surface Small intestine on right, stomach on left 80 epithelium that lines the pits or villi. In the intestinal villi however, most of the cells are absorptive cells, and interspersed between these are the characteristic mucous-secreting goblet cells. In addition, a brush border can sometimes be seen on the free surface of the absorptive cells in well-preserved intestinal villi. The duodenum is also characterized by the presence of mucous-secreting duodenal glands (of Brunner) in its submucosa. These are characterized by the accumulation of large acidophilic granules in their apical cytoplasm, and by their strongly basophilic basal cytoplasm. Note also the staining in the loose connective tissue of the lamina propria and the intense staining of goblet cells in the epithelium. There are also mast cells, which are smaller than macrophages and filled with intensely stained granules. This is a good slide in which to review the structure of arteries, veins, and the peripheral autonomic plexus. There is an abrupt transition between the rectal simple columnar epithelium and the stratified epithelium of the anal canal. The anal epithelium may appear stratified cuboidal at the junction with the rectum, but it assumes a typical stratified squamous appearance more distally. The inner circular layer of the muscularis externa is thickened considerably to form the internal anal sphincter. Abnormal dilation and varicosity of these vessels causes an inward bulging of the mucous membrane and a partial occlusion of the anal canal, resulting in internal hemorrhoids. These glands are classified according to: (1) the organization of the cells in the secretory portion of the gland e. The parotid, submandibular, and sublingual glands are all compound (branched), tubulo-alveolar (acinar) glands with a merocrine (exocytotic) type of secretion. The secretory product is either serous (a protein product secreted in vesicles) or mucous (a large sulfated glycoprotein). The cytoplasm of mucous cells appears unstained due to the loss of the mucus product during tissue preparation. There are myoepithelial cells between the basal lamina and the basal plasma membrane of the secretory cells. A fibrous connective tissue capsule surrounds the gland and sends septa inward that subdivide the gland into lobules. Scan the slide on low power and observe that within each lobule there are several prominent ducts with a more distinct lumen, which stand out sharply from the surrounding acini because of their acidophilia. Larger interlobular or excretory ducts are embedded in the extensive interlobular connective tissue, and their epithelium may be either simple columnar, pseudostratified, or stratified. The secretory acinus is connected to the intralobular duct by a thin intercalated duct, which is difficult to see in this slide. These intercalated ducts consist of a cuboidal epithelium, and their diameter is less than that of either the acinus or the intralobular duct. The mixed secretory units consist of a mucous acinus capped by a crescent-shaped aggregation of serous cells called a serous demilune. Blood enters the liver via the hepatic artery and portal vein, which send branches to the hepatic lobules. Within the lobules, blood travels between the plates of hepatic cells in sinusoids toward a central vein. The axis of the classic or anatomical lobule is the central vein, which is the beginning of the hepatic vein. In this case, each lobule consists of plates of hepatic parenchymal cells that radiate out from the central vein. Separating the radial plates of the cells are the hepatic sinusoids, which are lined by endothelial cells. The other cell type found in the perisinusoidal space is the hepatic stellate cell (Ito cell), which is the primary storage site for hepatic vitamin A. The sinusoids receive blood from branches of the hepatic portal vein and, to a lesser extent, from branches of the hepatic artery (located in the portal canal) at the outer margins of the lobule. The central vein connects at right angles with a sublobular vein which courses along the base of a lobule. Bile, produced by the hepatic cells, is collected first in small bile canaliculi and then in small hepatic ductules. Its three components, known collectively as the hepatic triad, are branches of 1) the hepatic artery, 2) the portal vein, and 3) the bile duct. Hepatic triad 84 In addition to recognizing the landmarks of the classic lobule, be aware of the boundaries of the portal lobule and liver acinus. Organization of the Liver classic lobule acinus portal lobule #45 Liver, (H&E) Identify the vessels and structures discussed above. Notice that a thin space is present between the endothelial cells lining the sinusoids and the parenchymal cells. This is the space of Disse, and it is in continuity with the lumen of the sinusoids via small spaces between the endothelial cells that form the wall of the sinusoids. In addition, the bile canaliculi are revealed as delicate tubules that course between the apposed surfaces of the parenchymal cells. The muscularis externa contains elastic and collagen fibers among the bands of irregularly arranged smooth muscle. These are Islet of Langerhans surrounded by serous glands 85 delivered through a duct system that is similar to that in the salivary glands: intercalated duct to intralobular duct to interlobular duct. The pale-staining nuclei of the centro-acinar cells appear in the center of an acinus (hence their name). For a more detailed description of the endocrine portion of the pancreas see the endocrine glands lab on page 61. Islets of Langerhans are clearly visible, however the classes of hormone producing cells are not distinguishable.

If high levels of the drug need to be maintained order 100mg gyne-lotrimin mastercard, the drops must be applied frequently discount 100 mg gyne-lotrimin overnight delivery. Predispose to infection by reducing local immunity Contra indication of steroids 1 buy cheap gyne-lotrimin 100mg online. Equipment and supplies - Snellen’s E- chart -Reading chart - Occluder - Pinhole - Torch -2 generic 100mg gyne-lotrimin. How to apply eye medication - explain to the patient what is to be done - read the instruction on the eye drop/ointment carefully and sit the patient with the head tilted back. Making and Applying an Eye Pad - Cut the cotton and gauze rolls - Place layers of gauze on the working bench or table - Place a thick cotton layer on top of the gauze - Further place another layer of gauze on top of the cotton - This makes a three layered patch: gauze-cotton wool-gauze - Cut the patch in to smaller patches and trim it with scissor to make it oval. Making and Applying a Protective shield - Trace the edge of a drinking cup or gally pot on card board or x-ray film - Cut a circle of thin card from the card board or used x- ray film from the traced and make a cut to the center of the circle or tip of the fold using one of the radius. We hope that you will find this to be a pleasurable and challenging introduction to diseases of the nervous system. During this phase of your medical school experience, you are expected to become familiar with the vocabulary, basic pathologic concepts and morphologic aspects of neurologic diseases. Traditionally, diseases of the nervous system have been classified or divided etiologically into vascular, metabolic, neoplastic, infectious, degenerative, demyelinative, traumatic and developmental categories. Diseases of the neuromuscular system have been segregated somewhat, but can be divided similarly. This approach is still considered to be the most effective and understandable way to present this myriad of afflictions, but it often seems disjointed to the novice. So, be patient and we believe that things will fall into place by the end of the course. We shall try to emphasize common entities in the lectures, the small groups and images reviews, but prototypes of rare diseases also will be presented to provide you with an overview and perspective. The main purpose of the formal lectures is the presentation of conceptual, nosological, or pathogenetic aspects of neuropathology. In the small groups, we will reinforce material from lectures largely through review of images. Additionally, we will illustrate the application of basic neuropathologic principles to problem solving and analysis in the clinical setting. We will enlist your help in generating differential diagnoses to give you a feel for how we approach neurological diseases. We have included a lecture on Neuroimaging since this area is currently expanding tremendously and a basic appreciation of techniques and the value, and limitations, of those techniques will assist you in many areas of your clinical training. We have intentionally listed somewhat extensive chapters, too much to be used in a short course. This will lead you to the site that contains images for all pathology courses (topic bar will say ‘General Pathology’). A large number of additional websites are available that may enhance your learning, if you wish to investigate them. If you want to review some normal neurohistology, there is an interesting “virtual slide box of histology” at www. Finally, constructive criticism and comments are welcome and should be referred to the course director. Phone and office numbers are given for the preceptors and we encourage you to make use of this resource outside of our formal teaching plan. Introduction to Cellular Neuropathology/Cerebral Edema Cerebrovascular Diseases R eview Weds. Dementia and Degenerative Diseases & M etabolic D iseasesR eview Case 2: Dementia Fri. You will discover that these alterations are common to a variety of neuropathological disorders. Acute ischemic or hypoxic damage produces a shrinkage of the cell body and a hypereosinophilia. The neuron may be involved directly or indirectly, through retrograde (via efferents) or anterograde (via afferents) transneuronal or transynaptic degeneration. Chromatolysis may be followed by regrowth of the axon from the point of damage, a phenomenon more often seen in the peripheral than in the central nervous system. In neuronal storage diseases, excessive amounts of lipids, carbohydrates, glycosaminoglycans, or glycoproteins accumulate within neurons, enlarging and distorting the normal geometry of the cell body and proximal processes. These are usually seen in the context of inherited disorders of lipid or glycosaminoglycan catabolism (eg. Some reflect the focal storage of metabolites, some the presence of viral proteins or nucleoproteins, and some the abnormal accumulation of structural proteins (eg. Lipofuscin is an insoluble mix of proteins, lipids, and minerals that accumulates in neurons and astrocytes during the normal aging process. Neuronophagia is the phagocytosis of degenerating neurons, usually by macrophages. This is commonly seen after hypoxic or ischemic insults or during viral infections. Dying back degeneration, a degeneration of the most distal axon, followed by the progressive loss of more and more proximal regions, is often seen in toxic peripheral neuropathies. Demyelination refers to the primary loss of myelin with relative preservation of the axon (eg. Spheroids contain mixtures of lysosomes, mitochondria, neurofilaments, and other cytoplasmic constituents. Slowing or cessation of axoplasmic transport at sites of damage presumably account for spheroids. This is seen in many types of mental retardation, including congenital hypothyroidism (cretinism). Atrophy is a reduction in the volume and surface area of dendritic branches, commonly seen in neurodegenerative diseases. Neuritic plaques are collections of degenerating axons and dendrites, mixed with microglia and astrocytes and associated with the extracellular deposition of amyloid (beta-amyloid, see lecture on Neurodegenerative diseases). Status spongiosis refers to a spongy state of the neuropil, the formation of fine to medium sized vacuoles representing swollen neuronal and astrocytic processes. This change is typical of transmissible spongiform encephalopathies, such as Creutzfeldt- Jacob disease. They contact blood vessels, pial surfaces, and enfold synapses in their functions to maintain the concentration of ions, neurotransmitters, and other metabolites within normal levels in the extracellular space. Astrocytes undergo hypertrophy (enlargement) and hyperplasia (proliferation) in response to a great many pathological processes, including hypoxic-ischemic damage and trauma. Astrocytes develop abundant pink cytoplasm, either due to imbibing plasma proteins and fluid in the short-term (when the blood-brain-barrier is broken) or filling up with intermediate filaments (in long-term scarring). The descriptive term of reactive, hypertrophic or gemistocytic is often used to describe this change. They are thought to be related to the hyperammonemia of hepatic failure (see notes on Metabolic diseases). Corpora amylacea are spherical accumulations of polyglucosan (branched-chain glucose polymers), which increase in numbers with age, particularly in a subventricular and subpial locations, and in glial scars. Neoplasia: Astrocytomas represent a common form of brain tumor (see notes on neoplasia) 5. Note that oligodendrocytes or progenitors of oligodendrocytes are able to remyelinate demyelinated axons, and thus help to repair demyelinated lesions. Myelin edema: In certain toxic and metabolic settings, fluid accumulates within myelin sheaths, leading to intramyelinic edema. Cell loss of oligodendrocytes occurs in a variety of disorders, including immune mediated (multiple sclerosis), viral (papova virus of progressive multifocal leukoencephalopathy), and toxic (e. Viral inclusions form in oligodendrocytes in progressive multifocal leukoencephalopathy. Hypertrophy and hyperplasia of endothelial cells is commonly seen in ischemia and in the vicinity of primary and metastatic neoplasms. Schwannomas are common, usually benign, neoplasms of peripheral nerves (see notes on neoplasia). It is important to review gross neuroanatomy and appreciate the anatomic relationships among the medial temporal lobe, tentorium cerebelli, the brain stem and upper cranial nerves, and the vertebro-basilar artery system (posterior circulation). The falx cerebri acts as an incomplete partition separating the hemispheres in the sagittal plane, stopping just above the corpus callosum. The tentorium cerebelli, a horizontal reflection, which lies on the superior surface of the cerebellum, separates supra- from infra-tentorial spaces.

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