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Excessive accumulation of CO2 damages or ciliated mucous membrane that lines the entire respiratory kills body cells discount 100mg amantadine with amex. The efficiency of the respiratory system depends on the qual- tract cheap amantadine 100mg on line, except the pharynx and alveoli 100mg amantadine amex. Cilia are tiny, hair-like ity and quantity of air inhaled, the patency of air passageways, projections that sweep mucus toward the pharynx to be ex- the ability of the lungs to expand and contract, and the ability pectorated or swallowed. The mucous membrane secretes of O and CO to cross the alveolar–capillary membrane. In mucus, which forms a protective blanket and traps foreign 2 2 addition to the respiratory system, the circulatory, nervous, and particles, such as bacteria and dust. Additional characteristics of the respiratory system and the the nasal mucosa. When the nasal passages are blocked, the process of respiration are described in the following sections. Respiration Pharynx, Larynx, and Trachea Respiration is the process of gas exchange by which O2 is ob- tained and CO2 is eliminated. This gas exchange occurs be- Air passes from the nasal cavities to the pharynx (throat). The pharynx con- specifically, the four parts of respiration are: tains the palatine tonsils, which are large masses of lymphatic • Ventilation—the movement of air between the atmos- tissue. It contains the and body cells vocal cords and forms the upper end of the trachea. It closes 694 CHAPTER 46 PHYSIOLOGY OF THE RESPIRATORY SYSTEM 695 on swallowing to prevent aspiration of food and fluids into rubber band) to expel air. It is a cartilaginous tube lined with cili- In addition to exchanging O2 and CO2, the lungs synthesize, ated epithelium and mucous-secreting cells. Cilia and mucus store, release, remove, metabolize, or inactivate a variety of help to protect and defend the lungs. These substances, which may be locally released or carried in blood or tissue fluids, partici- pate in both physiologic and pathologic processes. Specific sub- Lungs stances that may be released from the lungs include biogenic amines (eg, catecholamines, histamine, serotonin), arachi- The lungs begin where the trachea divides into the right and donic acid metabolites (eg, prostaglandins, leukotrienes), left mainstem bronchi and contain the remaining respiratory angiotensin-converting enzyme, and heparin. They are divided into five lobes, each with a sec- important in regulating smooth muscle tone (ie, constriction ondary bronchus. The lobes are further subdivided into bron- or dilation) in the airways and blood vessels. Heparin helps to dissolve blood clots, especially in the a venule, and a lymphatic vessel. The lungs also through a pulmonary artery and exits through a pulmonary process peptides, lipids, hormones, and drugs and inactivate vein. Lymphatic structures surround the lobule and aid in the removal of plasma proteins and other particles from interstitial bradykinin. The mainstem bronchi branch into smaller bronchi, then Lung Circulation into bronchioles. Bronchioles are approximately the size of a pencil lead and do not contain cartilage or mucus-secreting The pulmonary circulatory system transports O and CO. The walls of the bronchioles contain smooth mus- After oxygen enters the bloodstream across the alveolar– cle, which is controlled by the autonomic nervous system. Car- stimulation of sympathetic nerves causes relaxation or bon dioxide combines with hemoglobin in the cells for return dilation. The epithelial lining of the bronchioles becomes thinner with The lungs receive the total cardiac output of blood and progressive branchings until only one cell layer is apparent. The are supplied with blood from two sources, the pulmonary bronchioles give rise to the alveoli, which are grape-like clus- and bronchial circulations. The pulmonary circulation pro- ters of air sacs surrounded by capillaries. Type I oxygenated blood to the lungs and the pulmonary veins cells are flat, thin epithelial cells that fuse with capillaries to return oxygenated blood to the heart. The bronchial arter- form the alveolar–capillary membrane across which gas ex- ies arise from the thoracic aorta and supply the air passages change occurs. The bronchial circulation also ported to body cells; CO2 enters the alveoli to be exhaled warms and humidifies incoming air and can form new ves- from the lungs.

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Within each vol- the cord and provide a clinical benefit (see ume or module buy amantadine 100mg online, a discrete set of synergistic Chapters 6 and 9) effective 100 mg amantadine. This sensory information limb muscle contractions was elicited that di- also activates and reorganizes spared cortical rected the limb toward an equilibrium point discount amantadine 100 mg mastercard. Functional neuroimaging stud- the leg in four positions within its usual work- ies reveal the details of the networks involved. By superimposing the to our knowledge of neuroplasticity after brain vectors of the force fields that were elicited and spinal cord lesions, are provided in Chap- across all the spinal modules, the investigators ter 3. Functional neuroimaging studies also re- calculated that the set of modules, which they veal the physiologic anatomy of the sensori- call primitives, stored the movements that motor network. This intrinsic spinal organization, ment representations in the primary sensori- which is likely to be present in man, permits motor cortex in remarkable detail. The primitives specific activities such as preparation for a presumably act together under the control of movement, internal generation of the move- supraspinal commands to create a rich reper- ment, and visualizing or imagining an action. When M1 or Association cortex and regions that represent other regional motoneurons fire in a direc- cognitive functions become more active as the 38 Neuroscientific Foundations for Rehabilitation task grows in complexity. Of great interest for after a cerebral, spinal, or peripheral nerve rehabilitation, PET, fMRI, TMS, and other injury. For example, a high level of synaptic activity in primary and secondary sen- Regional cerebral blood flow (rCBF) studies of sorimotor cortices accompanies the early stages normal subjects by PET reveal cortical areas of learning a motor skill. Activity increases in the con- used to monitor this gain in cerebral activity tralateral M1 and the premotor, SMA, ventral and its relationship to the success of the reha- premotor, and parietal cortical areas that are bilitation strategy. The toe activated the dorsal putamen ments by trial and error, revealed that the and the fingers localized more ventral and me- right-handed task activated the left dorsolateral dial. When a subject decides which fingers to prefrontal cortex (DLPFC) that includes BA 9 move or learns a finger tapping sequence, the and 46 and the right anterior cingulate cortex caudate and putamen become active rostral (BA 24 and 32). Passive movements of the hand and foot then, subjects must monitor their movements also activate sensorimotor cortices (see Chap- and maintain successful responses in their ter 3), which is useful for studying plasticity- working memories. Once subjects perform a related motor recovery over time when sub- skilled task automatically, they may be able to jects start with paralysis of a limb. When the sub- In a PET experiment that helps define the jects were asked to pay attention to their over- distributed motor system, subjects were stud- learned movements, the anterior cerebral re- ied under four conditions. The bilateral directions, (3) when the correct movement was cerebellar nuclei and the vermis and caudate specified by one of the four tones they heard, were also activated significantly during new and (4) when the correct movement was the learning and novel problem-solving, compared opposite of what had been specified by the to the other conditions. The SMA had critical tissue for learning is activated by the greater metabolic activity in the first two con- training strategy. These tasks required internal genera- prelearned finger movements is associated tion of a movement, whereas the second two with activation of the same primary sensori- were directed by external cues. Activity within motor and SMA cortices as learning a novel, the left superior parietal cortex increased in all difficult task. The eration and testing of hypotheses about motor bilateral premotor cortices, which are synapti- and cognitive processes and, as discussed in cally linked to the parietal region, were acti- Chapter 3, about adaptive functional changes vated in all conditions as well. In the random Plasticity in Sensorimotor and Cognitive Networks 39 condition, several frontal areas and the cingu- gration of visual and somatosensory informa- late sulcus were activated, pointing to the con- tion with motor activity in the leg region for tribution of these areas for self-initiated acts. In some studies, the anterior cingulate and pre- frontal cortices are active, perhaps especially in Control of Muscle Strength relation to the rhythmic movement and atten- Another experiment points to the contribution tion needed for treadmill locomotion. When of parallel, cortical networks in a distributed normal subjects imagine doing locomotive leg motor system. Muscle strength increased by movements while supine, functional imaging having individuals practice at imagining they reveals significant increases in activation in the were contracting a particular muscle. This ists will be able to apply PET, fMRI, and other neural, as opposed to muscular, origin for functional imaging techniques to detect and strengthening also seems to occur during phys- promote the reorganization of cortical net- ical exercise before any muscle hypertrophy is works for walking. Mental exercise that improves muscle strength is associated with an increase in elec- troencephalographic-derived cortical poten- STUDIES OF tials. These areas permanently fixed in the way they subserve increase the coordination and strength of out- sensing and movement. It appears, (see Experimental Case Studies 1–3 and 1–4) from limited studies, that BA 4 makes callosal and in humans (see Chapter 3), the topo- connections, but not in the hand and foot areas. This mutability is a ubiquitous property of adult cor- LOCOMOTOR NETWORKS tical output and receptive fields. Positron emission tomography,45 SPECT,215 Table 1–3 summarizes the sequence of im- and near-infrared spectroscopy46 can be car- portant steps that lead to a memory trace for ried out in association with walking on a tread- a skill. Supine rest was compared to 30 minutes clinicians insight into the training and other of treadmill walking after injection with a flu- input conditions that optimize remodeling orodeoxyglucose tracer and placing the subject and, in turn, improve motor control and back into the scanner. Cerebral activity for glu- higher cognitive activities during rehabilita- cose increased bilaterally in the cerebellar ver- tion.

This al- dysrhythmias 100 mg amantadine, angina pectoris cheap amantadine 100mg without a prescription, hypertension effective 100 mg amantadine, hyperthyroidism, lows shunting of blood to the heart and brain, with in- and cerebrovascular disease because stimulation of the sym- creased perfusion pressure in the coronary and cerebral CHAPTER 18 ADRENERGIC DRUGS 273 circulations. They must be used correctly to avoid potentially eficial effect in cardiac arrest and cardiopulmonary serious hazards. When given by injection, it acts rapidly but has a short stimulation of conducting tissues in the heart. When given intravenously, epinephrine acts bradycardia may occur when blood pressure is raised. Relaxation of GI smooth muscle a positive inotropic and positive chronotropic effect on the myo- 6. Relaxation or dilation of bronchial smooth muscle cardium, hyperglycemia, bronchodilation, and vasoconstric- 7. Increased glucose, lactate, and fatty acids in the blood tion of arterioles in the skin, mucosa, and most viscera. For due to metabolic effects acute asthma attacks, subcutaneous (SC) administration usu- 8. Inhibition of insulin secretion ally produces bronchodilation within 5 to 10 minutes; maximal 9. Miscellaneous effects, including increased total leuko- effects may occur within 20 minutes. Most epinephrine is cyte count, increased rate of blood coagulation, and de- rapidly metabolized in the liver to inactive metabolites, which creased intraocular pressure in wide-angle glaucoma. The remaining epinephrine is de- When given locally, the main effect is vasoconstriction. However, at high stimulating alpha and beta receptors and causing release of doses, alpha-adrenergic effects (eg, vasoconstriction) pre- norepinephrine. The effects and clinical indications for epineph- than those of epinephrine. Ephedrine produces more CNS rine, the prototype of adrenergic drugs, are the same as for stimulation than other adrenergic drugs. In addition, epinephrine is the adren- treatment of bronchial asthma to prevent bronchospasm, but ergic drug of choice for relieving the acute bronchospasm and it is less effective than epinephrine for acute bronchospasm laryngeal edema of anaphylactic shock, the most serious al- and respiratory distress. Epinephrine is used in cardiac arrest for its Ephedrine can be given orally or parenterally. It given orally, therapeutic effects occur within 1 hour and last also is added to local anesthetics for vasoconstrictive effects, 3 to 5 hours. When given SC, it acts in approximately 20 min- which prolong the action of the local anesthetic drug, prevent utes and effects last approximately 60 minutes; with intramus- systemic absorption, and minimize bleeding. Ephedrine is excreted un- children; syncope has occurred with use in asthmatic chil- changed in the urine. The tablets contain disease or are elderly should not use these products on a reg- 12. These preparations have a short duration of action, phylline, a xanthine bronchodilator. Prolonged use may cause adverse effects and result in the development of clude shock associated with spinal or epidural anesthesia, tolerance to the therapeutic effects of the drug. Stokes-Adams syndrome (sudden attacks of unconsciousness Epinephrine is not given orally because enzymes in the GI caused by heart block), allergic disorders, nasal congestion, tract and liver destroy it. Numerous epinephrine solutions Pseudoephedrine (Sudafed) is a related drug with similar are available for various uses and routes of administration actions. Pseudoephedrine is given orally and is available OTC alone and as an ingredient in several multi-ingredient sinus, allergy, and cold remedies. Its elimination may be slowed by alkaline urine, which promotes drug reabsorption in the Epinephrine Concentrations TABLE 18–2 renal tubules. Its main ac- 1% (1:100) tions are to stimulate the heart, dilate blood vessels in skele- Inhalation 0. However, absorption is unreliable local anesthetics) with sublingual and oral preparations, so their use is not 274 SECTION 3 DRUGS AFFECTING THE AUTONOMIC NERVOUS SYSTEM recommended. It is metabolized more slowly than epineph- bronchospasm and laryngeal edema) and profound hypo- rine by the enzyme catechol-O-methyltransferase (COMT). If the client is known to have asthma, assess the which may account for its slightly longer duration of action frequency of attacks, the specific signs and symptoms ex- than epinephrine. Isoproterenol may be used as a cardiac perienced, the precipitating factors, the actions taken to stimulant in heart block and cardiogenic shock and as a obtain relief, and the use of bronchodilators or other med- bronchodilator in respiratory conditions characterized by bron- ications on a long-term basis. However, beta2-selective agonists (eg, albuterol, respiratory distress is clearly evidenced by loud, rapid, others) are preferred for bronchodilating effects because gasping, wheezing respirations.

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