By J. Leon. Springfield College.

We used the UEA to vi- Imaging 2-D Neural Activity Patterns 57 -300 0 100 200 300 400 700 Figure 3 order propecia 1 mg amex. The numbers above each column indicate the time of the frame when time zero was selected to maximize the activity in the 100- cheap propecia 1 mg otc, 200-, and 300-ms frames. The speed and width of the bar used in this experiment, 8 degrees/s and 2 degrees, respectively, and the 4-degree spatial window sampled by the UEA (figure 3. To allow the visual system to re- cover from each sweeping bar, we initiated a new sweeping bar every 4 s. In this figure, each frame shows the summated firing at all 98 electrode sites for a 100-ms period. Above each column is the time, in milliseconds, of the frame where time zero was selected to maximize the activity in the 100-, 200-, and 300-ms frames. The bar to the left of each movie shows the orientation of the moving bar, and the arrow indicates its direction of motion through the visual field. Close inspection of the movies reveals the following patterns: For the 0-degree orientation (top movie), there is a wave of activity that appears at the left for the 100-ms frame and pro- gresses to the right. In the 90-degree orientation (second movie from the top), there is a subtler wave of activity that starts at the bottom of the frames and moves up- ward. In the 180-degree orientation (third movie from the top), there is a wave of activity that enters from the right and moves to the left. Koulakov orientation (bottom movie), there is a wave of activity that enters from the top and progresses downward. This wave of activity, like that for the 90-degree orientation, is subtler. Each of these frames was made using the spatiotemporal activity pattern for only a single passage of the bar. That is, the firing rate at each electrode was normalized to the max- imum firing rate over the 4-s period of the passage of the bar. Thus the maps indicate that the multiunits recorded on each electrode generally modulate their firing activity as the bar sweeps through the receptive fields of the recorded units, regardless of the orientation of the bar and the principal angle orientations of the units. Discussion The goals of this chapter are twofold: to demonstrate the use of microelectrode arrays to achieve high-resolution, spatiotemporal imaging of the activity patterns of neural ensembles in the sensory cortex, and to use an electrode array to record the activity patterns that are produced by single presentations of simple, moving visual stimuli. We are using these maps and activity patterns to model how patterned visual stimuli could be encoded by the firing properties of cortical neurons (Normann et al. The Functional Architecture of the Cat Visual Cortex Before one can model encoding strategies that could be used by the vertebrate visual system to represent spatiotemporal patterns of retinal illumination, one needs to characterize the receptive field properties of the units upon which the models are built. The three organizational maps described in this chapter provide such a func- tional characterization. Because the 98 parallel measurements from which the maps have been made were performed simultaneously, any distortions in the maps that are due to eye drift or uncertainties in electrode position are significantly reduced. Furthermore, because the maps were made directly from multi- and single-unit activity, they did not require the inferences of causality that are necessary with some optical techniques. However, one significant limitation of this multielectrode technique is the spatial sampling imposed by the 400-mm spacing of the electrodes in the UEA. This is con- trasted with the optical visualization techniques that provide a virtually continuous image of the cortex, with spatial optical sampling on the order of 10 mm (Shtoyer- man et al. The recently introduced method of electrophysiological imaging (Diogo et al. The low-pass filtering associated with the interpolation of a single condi- Imaging 2-D Neural Activity Patterns 59 tion map is justifiable only in the context of the low spatial frequency periodicity of the columnar organization of the cortex. As was shown in the early work of Hubel and Wiesel (1962), single-electrode tracks of the orientation sensitivity of complex cells in monkey area 17 show an or- derly progression of preferred orientation with distance across the cortex. Cells sepa- rated by approximately 20 mm will have their orientation sensitivity changed by 5 to 10 degrees. Thus, a trajectory approximately 1 mm long will encounter a set of units that encompasses a full 360 degrees of orientation sensitivity. When this architecture has been studied with optical visualization (Blasdel, 1992; Arieli et al. Based upon the Nyquist sampling theorem, the min- imum spacing required to sample this spatial information is half of this spatial period, or 0. Clearly, more closely spaced electrodes would provide an even better sam- pling of these architectures, and work is underway in our laboratory to develop electrode arrays with closer spacing. Multiunit Activity Patterns Produced by Moving Bars The second goal of this chapter is to demonstrate the neural activity pattern pro- duced by simple visual stimuli. While optical techniques with extrinsic dye-enhanced signal-to-noise ratios can begin to reveal single-trial-evoked activity patterns, the recording of single- and multiunit activity with an electrode array directly enables the visualization of such single-trial-evoked activity. This capability is particularly important in light of the variability that has been described in cortical responses (Abeles, 1991; Rieke et al. We stress that these data were obtained from single passes of the bar and that the 98 single-unit responses have not been temporally averaged over multiple passes of the bar to enhance the signal-to- noise ratio of the measurement.

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The lungs are encased in a membrane called the pleura quality propecia 5 mg, Capillaries in the lungs are lined by a single layer of ep- which is composed of two layers generic propecia 1mg on line. Once thought to be a pas- adheres to the surface of the lung, is called the visceral sive conduit for blood, it is now known that the endothelium pleura. The outer layer, which lines the thoracic cavity, is performs several important functions. The potential space between the rier that prevents leakage of water and other substances into layers is called the pleural cavity. Second, it participates in the transport of respi- allows the layers to glide over each other and minimizes ratory gases, water, and solutes. The lungs expand and relax in response to changes in pres- Nitric oxide also regulates smooth muscle tone in the sure relationships (intrapulmonic and intrapleural pressures). Elastic tissue in the bronchioles and alveoli allows the lungs When pulmonary endothelium is injured (eg, by endotoxins to stretch or expand to accommodate incoming air. This abil- or drugs such as bleomycin, an anticancer drug), these func- ity is called compliance. The respiratory center is stimulated orders may be caused by agents that reach the system through primarily by increased CO2 in the fluids of the center. A lesser tract secretions, asthma, and other chronic obstructive pul- stimulus to the respiratory center is decreased oxygen in monary diseases). The cough reflex is especially important edema, acute respiratory distress syndrome) is associated because it helps protect the lungs from foreign particles, air with the release of histamine and other biologically active pollutants, bacteria, and other potentially harmful substances. These mediators often A cough occurs when nerve endings in the respiratory tract cause inflammation and constriction of the airways. Once injured, cellular functions are impaired (eg, decreased mu- Musculoskeletal System cociliary clearance). Common signs and symptoms of respira- tory disorders include cough, increased secretions, mucosal The musculoskeletal system participates in chest expansion congestion, and bronchospasm. Normally, the diaphragm and external inter- treatment may lead to cell necrosis or respiratory failure. The abdominal and internal intercostal muscles are the muscles of expiration. DRUG THERAPY In general, drug therapy is more effective in relieving respira- SUMMARY tory symptoms than in curing the underlying disorders that cause the symptoms. Major drug groups used to treat respi- Overall, normal respiration requires: ratory symptoms are bronchodilating and anti-inflammatory 1. Ventilation, in turn, requires decongestants, antitussives, and cold remedies (see Chap. Adequate diffusion of O2 and CO2 through the alveolar– capillary membrane. Where does the exchange of oxygen and carbon dioxide and pressure differences between gases on each side of occur? What are common signs and symptoms of respiratory dis- orders for which drug therapy is often used? Approximately 500 mL of air is inspired and expired with a normal breath (tidal volume); deep breaths or sighs occur 6 to 10 times SELECTED REFERENCES per hour to ventilate more alveoli. Pathophysiology: Concepts of altered health tives, and opioid analgesics, slow respiration. Discuss reasons for using inhaled drugs when istics of asthma and other bronchoconstrictive possible. Discuss the uses and effects of bronchodilat- term control of asthma symptoms. Teach clients self-care and long-term control inhaled beta2-adrenergic agonists in terms of measures. Discuss the uses of anti-inflammatory drugs, including corticosteroids, leukotriene modi- fiers, and mast cell stabilizers. Critical Thinking Scenario Gwen, a 12-year-old middle schooler, was recently diagnosed with asthma. She uses two inhalers four times a day, in addition to using a rescue inhaler during periods of dyspnea. Occupational asthma (ie, asthma resulting from repeated and prolonged The drugs described in this chapter are used to treat respira- exposure to industrial inhalants) is also a major health prob- tory disorders characterized by bronchoconstriction, inflam- lem. Persons with occupational asthma often have symptoms mation, mucosal edema, and excessive mucus production while in the work environment, with improvement on days (asthma, bronchitis, and emphysema). Symptoms sometime persist after because of its widespread prevalence, especially in urban termination of exposure. Compared with whites, African Americans and especially common in children and older adults. Children Hispanics have a higher prevalence and African Americans who are exposed to allergens and airway irritants such as to- have a higher death rate from asthma.

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Other formulations contain various substances that the bloodstream buy propecia 5mg amex, breaks in sterile technique can lead to serious are not sterile purchase 5mg propecia overnight delivery, pure enough, or soluble enough to be in- systemic infections (septicemia) and death. In recent years, there have been • When two or more medications are to be given one after the numerous reports of medication errors resulting from IV other, flush the IV tubing and catheter (with the infusing IV fluid administration of drug preparations intended for oral use!! After irriga- should have a blunt tip that will not connect to or penetrate tion, heparin then needs to be reinstilled. Most drugs given by IV push (direct diluted prior to IV administration and powdered medications injection) can be given over 2–5 minutes and most drugs diluted must be reconstituted appropriately (eg, the correct amount in 50–100 mL of IV fluid can be infused in 30–60 minutes. In addition, be sure potassium or magnesium), be sure the medications are compati- any reconstituted drug is completely dissolved to avoid par- ble with the other substances. Consult compatibility charts (usu- ticles that may be injected into the systemic circulation and ally available on nursing units) or pharmacists when indicated. A filtered aspira- • IV flow rates are usually calculated in mL/hour and drops per tion needle should be used when withdrawing medication minute. Required information includes the amount of solution or from a vial or ampule, to remove any particles in the solu- medication to be infused, the time or duration of the infusion, and tion. The filter needle should then be discarded, to prevent the drop factor of the IV administration set to be used. The drop filtered particles from being injected when the medication is factor of macrodrip sets may be 10, 15, or 20 drops per milliliter, added to the IV fluid. The drop factor of all microdrip sets is • Check the expiration date on all IV medications. Following is a sample calculation: have a limited period of stability after they are reconstituted Order: Cefazolin 1 g IV q8h or diluted for IV administration. Most are compatible with 5% dextrose in water or Solution: Divide 100 by 60 to determine mL/min (1. CHAPTER 3 ADMINISTERING MEDICATIONS 39 In many settings, needleless systems are being used. These Nursing Notes: Apply Your Knowledge involve a plastic tip on the syringe that can be used to enter vials and injection sites on IV tubing. Needleless systems were developed Your client has a nasogastric feeding tube in place. You will be ad- ministering morning medications, including 4 tablets, 1 capsule, because of the risk of injury and spread of blood-borne and 10 cc of an elixir. Describe how you will safely administer pathogens, such as the viruses that cause acquired immuno- medications through a feeding tube to this client. When vials or ampules contain a powder able with or without an attached needle. Syringes are calibrated form of the drug, a sterile solution of water or 0. However, the chloride must be added and the drug dissolved before with- calibrations vary according to the size and type of syringe. Use a filter needle to withdraw the medication from Insulin and tuberculin syringes are used for specific an ampule or vial because broken glass or rubber fragments purposes. Insulin syringes are calibrated to measure up to may need to be removed from the drug solution. Safe practice requires that only insulin filter needle with a regular needle before injecting the client. Tuberculin syringes have a capacity of able in prefilled syringes with attached needles. They should be used for small doses of any drug are inserted into specially designed holders and used like because measurements are more accurate than with larger other needle/syringe units. Equipment for Injections Sites for Injections Sterile needles and syringes are used to measure and adminis- ter parenteral medications; they may be packaged together Common sites for subcutaneous injections are the upper arms, or separately. Needles are available in various gauges and abdomen, back, and thighs (Fig. The term gauge refers to lumen size, with larger num- injections are the deltoid, dorsogluteal, ventrogluteal, and bers indicating smaller lumen sizes. These sites must be selected by first needle is smaller than an 18-gauge needle. Common sites for gauge and length depends on the route of administration, the intravenous injections are the veins on the back of the hands viscosity (thickness) of the solution to be given, and the size of and on the forearms (Fig. Usually, a 25-gauge, 5⁄ -inch needle is used for SC jugular veins) are also used, mainly in critically ill clients. Other needle sizes are available for special uses, the skin (intradermal), arteries (intra-arterial), joints (intra- such as insulin or intradermal injections. Nurses may used, avoid recapping them and dispose of them in appropriate administer drugs intradermally or intra-arterially (if an estab- containers. Such containers are designed to prevent accidental lished arterial line is present); physicians administer intra- needle-stick injuries to health care and housekeeping personnel.

Ethosuximide may be used with other disorders cheap propecia 1 mg amex, alone or with other AEDs purchase propecia 1 mg line. Clonazepam has a long Gabapentin (Neurontin) is used with other AEDs for half-life and may require weeks of continued administration treatment of partial seizures. As with other benzo- doses, circulates largely in a free state because of minimal diazepines, clonazepam produces physical dependence and binding to plasma proteins, is not appreciably metabolized, withdrawal symptoms. The elim- life, withdrawal symptoms may appear several days after ad- ination half-life is 5 to 7 hours with normal renal function and ministration is stopped. Abrupt withdrawal may precipitate up to 50 hours with impaired renal function, depending on cre- seizure activity or status epilepticus. Diazepam and lorazepam are used to terminate acute con- Adverse effects include dizziness, drowsiness, fatigue, vulsive seizures, especially the life-threatening seizures of sta- loss of muscle coordination, tremor, nausea, vomiting, ab- tus epilepticus. Diazepam has a short duration of action and normal vision, gingivitis, and pruritus. In status epilepticus, it is subside spontaneously or with dosage reduction. Gabapentin followed with a long-acting anticonvulsant, such as phenytoin. Lorazepam has become the drug of choice for status epilepticus Because the drug is eliminated only by the kidneys, dosage because its effects last longer than those of diazepam. CHAPTER 11 ANTISEIZURE DRUGS 189 Lamotrigine (Lamictal) is used with other AEDs for treat- Oxcarbazepine (Trileptal) is a newer drug that is struc- ment of partial seizures. It is thought to reduce the release of turally related to carbamazepine. It is approved for both glutamate, an excitatory neurotransmitter, in the brain. It is monotherapy and adjunctive (with other AEDs) therapy in well absorbed after oral administration, with peak plasma lev- adults with partial seizures and for adjunctive therapy only in els reached in 1. For patients receiving carbamazepine or oxcar- bound to plasma proteins. It is metabolized in the liver to an bazepine, either drug may be substituted for the other with- inactive metabolite and eliminated mainly in the urine. However, the equivalent dose of oxcarbazepine ataxia, blurred or double vision, nausea and vomiting, and is 50% higher than the carbamazepine dosage. Because a serious skin rash may occur, especially the recommended equivalent oxcarbazepine dosage is 20% in children, lamotrigine should not be given to children higher than the carbamazepine dosage. Most effects are attrib- to occur with concomitant valproic acid therapy, high lamo- uted to an active metabolite produced during first-pass trigine starting dose, and rapid titration rate. It may resolve if metabolism in the liver; the metabolite is 40% protein lamotrigine is discontinued, but it progresses in some clients bound. The elimination half-life is 2 hours for oxcarbazepine to a more severe form, such as Stevens-Johnson syndrome. Dosage must Phenytoin, carbamazepine, and phenobarbital induce drug- be reduced in patients with severe renal impairment (ie, crea- metabolizing enzymes in the liver and accelerate lamotrig- tinine clearance < 30 mL/min). If lamotrigine is combined with other AEDs plus valproic or with other AEDs. They included cardiac dysrhythmias, acid, dosage must be substantially reduced. To discontinue, drowsiness, dizziness, hypotension, nausea, vomiting, skin dosage should be tapered over at least 2 weeks. Because of the risk of hyponatremia, Levetiracetam (Keppra) is a newer drug approved for oxcarbazepine should be used with caution in clients taking treatment of partial seizures, in combination with other other drugs that decrease serum sodium levels, and serum AEDs. It is chemically unrelated to other AEDs and its sodium levels should be monitored periodically during main- mechanism of action is unknown. Some studies indicate that skin reactions ronal firing but does not affect normal neuronal excitability occur less often with oxcarbazepine than with carbamazepine. Several drug–drug interactions may occur with oxcar- Levetiracetam is well and rapidly absorbed with oral ad- bazepine. The drug inhibits cytochrome P450 2C19 enzymes ministration; peak plasma levels occur in about one hour. This rapid attainment of thera- induce cytochrome P450 enzymes, including phenytoin, peutic effects is especially useful for patients with frequent may reduce plasma levels of the active metabolite by about or severe seizures. Dosage must be reduced with impaired renal oxcarbazepine or its metabolite. The drug is not metabolized by the liver and does Phenobarbital is a long-acting barbiturate that is used not affect the hepatic metabolism of other drugs. It was well tolerated in declined with the advent of other AEDs that cause less seda- clinical trials and the incidence of adverse events was similar tion and cognitive impairment. Common adverse effects include drowsi- verse effects associated with barbiturates may occur, but drug ness, dizziness, and fatigue; others include decreases in red dependence and barbiturate intoxication are unlikely with and white blood cell counts, double vision, amnesia, anxiety, usual antiepileptic doses.

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