By C. Tyler. University of Colorado, Colorado Springs. 2018.
There are many fallacious or over-interpreted reports in the litera- Some tendon organs can respond to tendon vibra- turebasedontheassumptionthattransversetendon tion in relaxed muscles and many do so during vol- vibration in intact human subjects can be a selec- untary contractions discount 100 ml mentat ds syrup amex. Indeed buy 100 ml mentat ds syrup, all three tendon organs tive stimulus for primary spindle endings discount mentat ds syrup 100 ml with mastercard, driving in the study of Burke et al best mentat ds syrup 100 ml. That all did so may be the result of a sam- intact subject, vibration is commonly not selective pling bias of microneurography towards stretch- for muscle spindle receptors and, in intact human responsive receptors (see p. Further studies subjects, it may not excite only the primary spindle isolating Ib afferents during a voluntary contrac- ending. Nevertheless, response of the primary ending switches off during the data in Figs. Responses during voluntary Cutaneous mechanoreceptors movements will not be accurately predictable, par- Most cutaneous mechanoreceptors respond to ticularlyifthevibratorisnotservo-controlledsothat vibration (e. Ribot-Ciscar, Vedel & Roll, 1989), and there is a constant force of application to the mov- it is probable that Ruffini endings in joints do so as ing tendon (Cordo et al. Motor tasks and physiological Contracting muscles implications In contractingmuscles,fusimotordrivecanenhance the spindle response to vibration (Burke et al. First, the application of the vibra- Remote contractions may be of limited functional tor to the tendon is not exactly the same as in the significance, but the mechanisms responsible for relaxed state, secondly, the spread of the vibration the widespread reflex enhancement accompanying wave to the muscle belly is altered when the mus- such contractions have long been a matter of dis- cle contracts and the tendon stiffens, and thirdly, the pute, and the manoeuvre is important in the clin- contraction may not be associated with a sufficient ical examination. It was previously thought that per- increase in drive to offset these effects. Indeed, if formance of the Jendrassik manoeuvre potentiated thecontractionisareflexcontractiontothevibration tendonjerksinuninvolvednon-contractingmuscles (tonic vibration reflex, TVR), unloading is the rule, in duetowidespreadactivationofdynamic motoneu- human subjects (Burke et al. Similarly, the reflex potentiation accompany- (Clark, Matthews & Muir, 1981). These problems are ing other alerting stimuli, such as a warning cue, has even greater if overt movement occurs at the joint, been attributed to the same mechanism. However, because movement can displace the vibrator and attractive as it may be, this hypothesis is seriously because the responses of different endings are not flawed for a number of reasons. For (i) It is based on the belief that the H reflex is not example, the response of primary endings is maxi- potentiated to the same extent by the reinforcement malduringthestretchingphaseofpassiveoscillating manoeuvre. The effects of alternating passive movements on the spindle response to vibration. The response increases more gradually through subharmonics during the stretching phase to 1:2. With shortening, the response gradually decreases again through subharmonics. If a mechanism was responsible Increased spindle discharge for the reflex reinforcement, one would expect the during contraction effects on spindle activity to be large, not small, not restricted to a few afferents, and one would expect Evidence for activation of γ motoneurones all studies to have no difficulty demonstrating this When movement is prevented so that contractions same finding. Panel (b ) plots the size sure block experiments suggest that this increase in of the muscle afferent volley from soleus against the spindle discharge is mediated, at least in part, by the intensity of tendon percussion. The round symbols activation of motoneurones (Burke, Hagbarth & represent data when the subject was at rest and the Skuse,1979). Theunloadingreflexprovidesevidence triangles when the subject performed the Jendrassik that muscle afferent feedback (presumably mainly manoeuvre. There is no difference in the relation- of spindle origin) contributes to the maintenance ships. However, the manoeuvres were effective re- of motor firing during a tonic isometric contrac- inforcing manoeuvres because a tendon jerk tion. When a muscle is pulling against a fixed resis- occurred (filled symbols) with weaker percussion tancethatsuddenlygivesway,asilentperiodappears and a lesser afferent volley. Panel (c ) plots, for the in the EMG of the contracting muscle at a latency same data, the size of the reflex response against the appropriate for the withdrawal of Ia afferent support intensity of the afferent volley. Jendrassikmanoeuvre(triangles),thereflexresponse Thus, overall the fusimotor-driven inflow from pri- was obtained at lower threshold than at rest (circles) maryandsecondaryendingsduringavoluntarycon- and was larger for any given size of afferent volley. Decreased presynaptic inhibition of Ia terminals has been suggested (Zehr & Stein, 1999), but, if any- Spindle acceleration after the onset of EMG thing,presynapticinhibitionofIaterminalstosoleus motoneurones is slightly increased at the onset of With brisk phasic contractions, the increase in spin- abrisk ECR contraction (Meunier & Morin, 1989; dle discharge follows the appearance of EMG in the Chapter8,p. Teethclenchinghasbeenreported contracting muscle by up to 50 ms (Vallbo, 1971), to enhance the H reflexes of both soleus and tibialis evidence that is inconsistent with the follow-up anterior (as might be expected for a reinforcement length servo hypothesis (Merton, 1951, 1953; see manoeuvre) but also to decrease peroneal-induced Matthews, 1972).
Muscle spasms and tetany generic mentat ds syrup 100 ml free shipping, which cannot ciency is metabolic alkalosis buy 100 ml mentat ds syrup with visa, a relative defi- be distinguished from the tetany pro- 2 buy mentat ds syrup 100 ml with mastercard. Excessive ingestion of bicarbonate ciency of acid order 100 ml mentat ds syrup with visa, and a relative excess duced by hypocalcemia or base of base. Retention of carbon dioxide (acid) as a compensatory attempt to restore acid–base balance 5. Fluid loss and decreased plasma volume Hyperchloremic Metabolic Acidosis 1. Increased rate and depth of respiration chloride or ammonium chloride is metabolic acidosis, a relative excess of acid, and a relative deficiency of base. Stored in the liver, spleen, kidneys, A component of vitamin B12, Approximately 1 mg in the Animal foods, including liver, and pancreas which is required for normal form of vitamin B12 muscle meats, and shell- 2. Deficiency of vitamin B12 produces for maturation of red blood cereals contain no cobalt as pernicious anemia. In animals, excess cobalt produces polycythemia, bone mar- row hyperplasia, and increased blood volume. A component of many en- Not established; estimated at Many foods, including liver, neys, bone, and muscle zymes approximately 2 mg shellfish, nuts, cereals, 2. Essential for correct func- poultry, dried fruits and menstrual flow tioning of the central ner- 3. Deficiency occurs with lack of food in- vous, cardiovascular, and take, malabsorption syndromes, and skeletal systems prolonged administration of copper- 3. Important in formation of free IV hyperalimentation solutions red blood cells, apparently 4. Signs and symptoms of deficiency by regulating storage include decreased serum levels of and release of iron for copper and ceruloplasmin (a plasma hemoglobin protein that transports copper); decreased iron absorption; anemia from impaired erythropoiesis; leukopenia. Copper excess (hypercupremia) may occur in women who take oral contraceptives or who are pregnant and in clients with infections or liver disease. A component of tooth Adults (AIs): males 19–>70 y, Beef, canned salmon, eggs. Often enamel 4 mg; females 19–>70 y, Very little in milk, cereal added to community supplies of 2. Strengthens bones, proba- 3 mg; pregnancy and lacta- grains, fruits, and vegeta- drinking water. Accumulates in the body until ap- tention in bones Infants (AIs): 0–6 mo, 0. Fluoride deficiency is indicated by ages 50–60 years may de- Other children (AIs): 1–3 y, are grown. Iodine deficiency causes thyroid Essential component of thyroid Adults (RDAs): males and fe- Seafood is the best source. In gland enlargement and may cause hormones males, 19–51+, 150 mcg; vegetables, iodine content hypothyroidism pregnancy, 175 mcg; lacta- varies with the amount of 2. Iodine excess (iodism) produces tion, 200 mcg iodine in soil where grown. Iodism is unlikely Other Children: 1–10 y, 10 mg; present in animal feed. Essential component of he- Adults (RDAs): males 19–51+, Liver and other organ meats, globin in red blood cells; approxi- moglobin, myoglobin, and 10 mg; females 19–50, 15 lean meat, shellfish, dried mately 25% is stored in the liver, several enzymes mg; 51+, 10 mg; pregnancy, beans and vegetables, egg bone marrow, and spleen as ferritin 2. Hemoglobin is required for 30 mg; lactation, 15 mg yolks, dried fruits, mo- and hemosiderin; the remaining transport and use of oxygen Infants: 0–6 mo, 6 mg; 6–12 lasses, whole grain and en- small amount is in myoglobin and by body cells; myoglobin mo, 10 mg riched breads. Milk and milk enzymes or bound to transferrin in aids oxygen transport and Other Children: 1–10 y, 10 products contain essentially plasma. Absorption from foods is approxi- zymes are important for females 11–18 y, 15 mg mately 10%. Factors that increase absorption: (1) Presence of dietary ascorbic acid (2) Acidity of gastric fluids in- creases solubility of dietary iron. If this reaction does not occur, iron combines with these sub- stances and produces non- absorbable compounds. Factors that decrease absorption: (1) Lack of hydrochloric acid in the stomach or adminis- tration of antacids, which produces an alkaline environment (2) Combination of iron with phosphates, oxalates, or phytates in the intestine.
For example discount mentat ds syrup 100 ml overnight delivery, neurons in the Primary somatosensory cortex has a key role superior parietal lobe of monkeys distinguish in both the storage and retrieval of represen- between the presentation of a right or left arm 100 ml mentat ds syrup visa, tations of sensory information buy mentat ds syrup 100 ml amex. Each area of S1 that processes special- stroke often involve this region discount mentat ds syrup 100 ml with amex. Plasticity in Sensorimotor and Cognitive Networks 21 Neurons in BA 7 have large visual receptive tions. A lesion here im- guidance of movements, especially actions re- pairs following meaningless actions on com- trieved from memory. As dis- parasensory region participates in the visu- cussed previously, neurons in BA 7 become ospatial analysis of gestures. Approaches to re- preferentially activated for preshaping a hand habilitation may differ, depending on the to match the shape of the object before the mechanism of the apraxia (see Chapter 9). Neurons in the posterior parietal cortex and Estimates of the contribution of M1 in man to intraparietal sulcus become active when a per- the corticospinal tract that enters each son prepares to move a hand. Localizing the medullary pyramid range from 40% to 60% of distributed network for motor intention leads the 1 million fibers within the white matter further away from primary and secondary sen- tract. In this case, the posterior cospinal tract arises from the primary and non- temporal cortex is also activated during the ex- primary motor cortices and approximately 30% traction of contextual and intentional sensory arises from the primary somatosensory cortices cues for a goal-driven behavior. From 70% to 90% of pyramidal with an apraxia from a left parietal lesion may fibers decussate into the lateral corticospinal not be able to mimic the use of objects because tract in the cord and 10% to 30% remain un- of a disturbance in the ability to evoke actions crossed and form the ventral corticospinal from stored motor representations or because tract. The drawing reconstructs the corticospinal pathways derived from antegrade labeling of primary sensori- motor cortex in the macaque and other nonhuman primates. The top figure shows the mostly decussated inputs to the dorsal horn (right) after injection of WGA-horseradish peroxidase into the cortical lamina of BA 3b, 1, and 2 on the left. Note that some fibers cross dorsal to the central canal of the spinal cord to return to the side of origin and a modest num- ber of fibers descend uncrossed in the ipsilateral lateral corticospinal tract. The bottom figure shows the crossed and un- crossed projections revealed after injection of BA 4 on the left with WGA-horseradish peroxidase. Although most de- scending fibers (right) have decussated, a moderate number recross under the central canal and two separate tracts in the lateral and ventral funiculi contain undecussated fibers. These ipsilateral inputs may be important for bilateral proximal movements and bimanual movements. The uncrossed and recrossed fibers are a resource of spared pathways for motor gains after a unilateral cerebral injury. Source: adapted from Ralston and Ralston, 198554 and Tuszynski, M (in press). In addition, some sensory and mo- crossed and recrossing axons may contribute to tor fibers of the pyramidal projections into the some recovery of function after a unilateral cere- spinal cord recross within the cord. The asymmetry in the cor- tion is uncertain, perhaps related to the coordi- ticospinal tracts, in which the ventral and lateral Plasticity in Sensorimotor and Cognitive Networks 23 tracts are larger in about 75% of spinal cords on heterogeneous, supporting direct as well as in- the right side,105 may offer another source of direct excitatory and inhibitory responses in spared fibers after a cerebral injury to enable spinal neurons. UNCROSSED AND The dorsal and ventral horn targets of the RECROSSING AXONS descending corticospinal fibers have perhaps been underappreciated (Fig. Each has a rather and recross through the isthmus above the cen- distinctive distribution of excitatory axon tral canal back to the side of cerebral origin branches. It also includes a small undecus- in the spinal intermediate zone (Rexed lami- sated projection to laminae V/VI. Some M1 ax- nae V–VII), where they end on intrinsic in- ons from the lateral funiculus also cross the terneurons and propriospinal neurons. Pro- isthmus under the central canal to medial and priospinal neurons, in turn, have broad ventral regions of the ventral horn on the side segmental and rostrocaudal connections, fur- of their cortical origins. They cingulate axons terminate in the neck of the are said to minimally, if at all, reach the lum- dorsal horn (laminae IV and V), but not in the bar cord. Several spinal cord regeneration stud- pure sensory input regions of the substantia ies described in Chapter 2 suggest, however, gelatinosa (laminae I and II). A modest num- that the ventromedial uncrossed tract is robust ber of fibers from areas 3a, 3b, 1, 2, and 5 and enough to play a role in the recovery of lower insular cortex do terminate in laminae I and II, extremity function. Some of the ventral fu- but most end in the intermediate zone, medi- niculus pyramidal fibers also cross the anterior ally in the neck of dorsal laminae III–VI. The commissure below the isthmus to connect to descending inputs from M1 and SMA appear motoneurons of the opposite ventral horn. Thus, the a developmental, activity-dependent pruning descending motor inputs have powerful depo- of descending axons.
With antacids containing magnesium buy mentat ds syrup 100 ml overnight delivery, observe for diarrhea Diarrhea may be prevented by combining these antacids with other and hypermagnesemia order 100 ml mentat ds syrup with amex. With antacids containing aluminum or calcium purchase 100 ml mentat ds syrup with amex, observe for Constipation may be prevented by combining these antacids with constipation generic 100 ml mentat ds syrup with amex. A high-fiber diet, adequate fluid intake (2000–3000 mL daily), and exercise also help prevent constipation. The drug is not absorbed systemically and constipation is the most commonly reported adverse effect. With misoprostol, observe for diarrhea, abdominal pain, Diarrhea commonly occurs and may be severe enough to indicate nausea, and vomiting, headache, uterine cramping, vaginal dosage reduction or stopping the drug. This is a harmless discoloration of feces; it does not indicate GI bleeding. Observe for drug interactions Most significant drug interactions alter the effect of the other drug rather than that of the antiulcer or anti–gastroesophageal reflux disease (GERD) drug. Drugs that alter effects of proton pump inhibitors: (1) Clarithromycin increases effects of omeprazole. May increase blood levels (2) Sucralfate decreases effects of lansoprazole. Decreases absorption of lansoprazole, which should be given about 30 min before sucralfate if both are used. Drugs that decrease effects of H2 antagonists: (1) Antacids Antacids decrease absorption of cimetidine and probably ranitidine. Drugs that alter effects of antacids: (1) Anticholinergic drugs (eg, atropine) increase effects May increase effects by delaying gastric emptying and by decreas- ing acid secretion themselves (2) Cholinergic drugs (eg, dexpanthenol [Ilopan]) decrease May decrease effects by increasing GI motility and rate of gastric effects emptying d. Drugs that decrease effects of sucralfate: (1) Antacids Antacids should not be given within 30 min before or after admin- istration of sucralfate. Nursing Notes: Apply Your Knowledge How Can You Avoid This Medication Error? Fallot should not be given this drug with water be- cause she has difficulty swallowing and is at risk for aspiration. This is not the case with lansoprazole, because most likely reason for this is the concurrent use of cimetidine the protective granules within the capsule can be preserved if given because both cimetidine and carbamazepine are metabolized by with acidic foods such as applesauce or yogurt. When a dispute regarding medications probably want to draw a blood level to confirm this is the cause arises, it is wise to consult a drug resource or a pharmacist. Ellen needs to be cautioned to check with her health care provider before using over-the counter medications because drug interactions can occur. The provider may switch Ellen to a proton pump inhibitor or a different histamine-2 recep- tor antagonist, such as famotidine (Pepcid) or ranitidine (Zantac) because these drugs are not metabolized through the P450 sys- tem and will not interact with her antiseizure medication. How do the various drug groups heal ulcers or prevent disease management, 7th ed. Compare H2RAs and PPIs in indications for use and for acid peptic disorders. Philadelphia: with peptic ulcer disease, how would you explain that Lippincott Williams & Wilkins. Compare and contrast peptic ulcer disease and GERD in terms of risk factors, drug therapy, and client teaching needs. Discuss bulk-forming laxatives as the most cording to effects on the gastrointestinal tract. Discuss possible reasons for and hazards of use from those of chronic use. Discuss rational choices of laxatives for se- lected client populations or purposes. Critical Thinking Scenario Elmer Wong, a 67-year-old teacher, fractured his hip when he fell on a patch of ice. He is scheduled for hip surgery to repair the fracture; this will be followed by a period of rehabilitation as he regains his mobility. Reflect on: Factors that increase his risk for constipation during the postoperative period. Expectation for postoperative bowel elimination, considering his history. Nonpharmacologic interventions that can promote normal bowel function during the postoperative period.