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By B. Riordian. Florida Metropolitan University. 2019.

Fewer patients experience absorption of monoacylglycerols and fatty acids result- tachycardia buy sildenafil 75mg free shipping erectile dysfunction lexapro, but an increase of 4 order sildenafil 75 mg with amex doctor for erectile dysfunction in kolkata. Usual dosing is 120 mg three times the use of sibutramine is typically contraindicated for daily with meals and requires dietary counseling to patients taking serotonin-selective reuptake inhibitors encourage decreased consumption of high-fat foods. Over-the counter dosing is now available at 60 mg three In support of the notion that pharmacotherapy times daily and has been associated with a 50% greater should be combined with a treatment plan that includes weight loss after 4 months compared to placebo, for dietary, physical activity, and behavioral therapy, 5 Assessment and Treatment of Excess Weight 37 W adden et al. The other three treatment arms were criteria include an age range of 18–60 years, failure at sibutramine alone, lifestyle modifcation alone, and other more conservative treatment, and acceptable oper- sibutramine with brief primary care provider visits. Updated recommendations added by over the course of a year) experienced the second high- the American Society for Bariatric Surgery Consensus est weight loss among the four groups. Furthermore, for weight loss treatment beyond 3 months and both a multidisciplinary approach to the care of bariatric have been associated with modest results as well as patients is essential for long-term successful outcomes, weight regain when medications are discontinued [90]. W ith increased understanding of are particularly suited to these patients because of the the physiologic mechanisms that affect body weight negative interaction of obesity and the infammatory regulation, new targets for treating obesity have been physiological responses [94]. Additional benefts of the identifed and over 80 medications are currently in laparoscopic technique are decreased length of hospi- development [76]. Long-term weight control may in the talization and postoperative pain, fewer wound compli- future be managed by multiple medications with various cations, and more rapid normalization of bowel function mechanisms of action, but current pharmacotherapy is [95, 96], even though this technique also has an limited and must be combined with lifestyle modifca- increased intra-abdominal complication rate when tion that includes nutritional planning, increased physi- compared with the open technique [91]. Centers that reported over 100 cases tomical changes, surgery has the advantage of promot- annually had lower mortality rates, fewer complica- ing long-term weight loss. Guidelines for determining tions, shorter length of stay, and lower costs compared which patients are candidates for surgical intervention to facilities with fewer than 50 cases annually [97]. Turk weight; ideal weight is based on the 1983 M etropolitan Restrictive techniques are generally less diffcult to Life Insurance height and weight tables’ determination perform than malabsorptive techniques with fewer of the weight associated with the longest life expec- long-term complications but may result in less weight tancy [98]. Typically an open procedure, the vertical Three main categories of bariatric surgery exist – banded gastroplasty is performed by stapling off the malabsorptive, restrictive, and combined restrictive fundus parallel to the lesser curvature and applying a and malabsorptive procedures [99]. M alabsorptive sur- band to narrow the distal opening of this small com- geries cause a reduced absorption of calories and nutri- partment (~50 mL) into the body of the stomach. Resultant weight loss adjustable gastric banding procedure, the upper 5% of from malabsorptive techniques often comes with nutri- the stomach is partitioned off using an infatable, sili- tional defcits including protein, vitamin, and mineral cone band. A gastric pouch of approximately 20 mL is insuffciencies that must be medically managed long- created by infating the band using a subcutaneous term. This band can be adjusted by the physician at ity of the stomach to store food, thereby inducing offce visits to accommodate the needs of the patient, satiety earlier in the meal, which results in reduced and periodic adjustments may be necessary up to six energy intake. Four currently recommended sur- bariatric surgery worldwide [91] and has both restric- gical options – biliopancreatic diversion with/without tive and malabsorptive features. In the restrictive com- duodenal switch, vertical banded gastroplasty, laparo- ponent, a 15–25 mL gastric pouch is divided from the scopic adjustable gastric banding, and gastric bypass – distal stomach with four rows of staples or completely are used worldwide. Continuity of the pouch with the jejunum is the biliopancreatic diversion with/without duode- re-established using a Roux-Y limb, incorporating a nal switch is the least commonly performed bariatric malabsorptive element as the distal stomach, duode- procedure among the four [101] and is considered a num and part of the proximal jejunum are bypassed. Empirical evidence suggests that this sorption is controlled by the length of the common surgery results in decreased plasma levels of the hor- limb. W ith the duodenal switch, the pylorus is mone ghrelin [102, 103], mainly secreted in the fun- preserved using a vertical-sleeve gastrectomy, and a dus of the stomach and known to stimulate appetite duodeno-ileostomy is created. Surgical treatment of obesity results in substantial the vertical banded gastroplasty and laparoscopic weight loss that is largely maintained by patients and adjustable gastric banding are restrictive techniques leads to amelioration or even resolution of co-morbidities where a small upper gastric compartment is constructed [100] as well as decreased mortality [105]. Swedish Obesity Study is a large, prospective trial that 5 Assessment and Treatment of Excess Weight 39 compared bariatric surgery patients with matched, (67 lb) that has been maintained for 5. Although low in fat, regularly self-monitoring weight and food weight loss peaked at 1–2 years, long-term weight loss intake [112], limiting the variety of foods eaten [113], outcomes from bariatric surgeries at 15 years were eating breakfast [114], and restricting time spent 27 ± 12%, 18 ± 11%, and 13 ± 14%, for gastric bypass, watching television [115]. Factors associated with vertical banded gastroplasty, and gastric banding, weight regain in this group have included a greater ini- respectively; the mean 15-year weight change among tial weight loss, shorter period of time in weight main- the control group was ±2% [106]. Lifelong adjust- tenance and psychological factors like depressive ments in eating behaviors and medical supervision are symptoms, increases in disinhibition (vulnerability to essential following these surgical procedures, however, loss of control over eating), and decreases in eating and patients need to be counseled about the lifestyle restraint (conscious control of eating) [111, 115, 116]. Two elements of weight loss treatment have Long-term maintenance of lost weight has remained been noted as particularly beneficial for weight the Achilles heel of weight loss treatment as approxi- loss maintenance – pharmacotherapy and physical mately one third of weight lost among patients treated activity. Both sibutramine and orlistat, combined with with lifestyle modifcation is regained by the frst year dietary modifcation and caloric defcit, have been after treatment [107]. Average 4-year weight losses repeatedly shown to be effcacious in promoting long- approximate 1. The greatest challenge in obesity treatment for that received 15 mg of the drug continuously (−3. The intermittent sibutramine group received sustain the weight loss they have achieved. Turk Physical activity has been frequently highlighted as of encouragement for motivation and support [131]. A made by an individual who is known to the patient contributing factor to the need for physical activity has [133]. Additionally, a practitioner could suggest that a been labeled the energy gap [127]. Some experts believe that, Obesity and overweight are chronic conditions with in the current obesogenic environment promoting less- numerous adverse health effects that require direct, than-healthful foods in large portions, increasing ongoing attention by the health care provider. The goals energy expenditure through physical activity is an eas- of weight loss treatment are improved overall health and ier way to fll this energy gap [127]. Current frst-line treatment consists of physical activity for maintenance of weight loss of lifestyle modifcation that includes dietary, physical remains somewhat unclear however, because most evi- activity, and behavioral therapy, with pharmacotherapy dence does not come from randomized controlled and bariatric surgery as subsequent weight loss modali- trials [49]. The treatment of this chronic disor- among individuals who had lost at least 10% of their der requires a multidisciplinary approach including original weight and maintained that loss for 24 months, health professionals with expertise in nutrition, exercise, physical activity levels were 275 min per week; and possibly clinical psychology as members of the others have noted similar fndings with this level of comprehensive, weight management health care team activity at 2 years after a very-low-calorie diet [129]. Health care providers have a major part imately 60 min of daily, moderate-intensity physical in helping this ever-increasing subgroup of patients suc- activity, like brisk walking for 4 miles [49]. Although cessfully lose and maintain weight so that patients can these levels of physical activity may be challenging for continue to beneft from the physical and psychological many patients to maintain, they seem to be associated effects of a lower body weight. W ith weight loss typically peaking at 6 months after initiation of a behavioral lifestyle treatment plan [130], References a weight maintenance plan should be introduced at this time. National Institutes of Health (1998) Clinical guidelines on the identifcation, evaluation, and treatment of overweight sustained, frequent contact with the health care practi- and obesity in adults-the evidence report. Obes Res 6(suppl tioner who provides ongoing support, instruction, and 2):51S–209S health monitoring are recommended to promote long- 2. These visits might the obesity pandemic: W here have we been and where are we going? Obes Res 12(suppl 2):88S–101S be handled via an offce nurse, allowing patients to 3. Retrieved from http:// W -C (2004) Body mass index and obesity-related metabolic www. Kushner’s personality Eriksen M P (2009) Are Asians at greater mortality risks for type diet. Public Health Nutr 12(4):497–506 questionnaire and a food diary in a short-term recall situa- 11.

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Once the tension in the muscle is greater than the opposing load order 25mg sildenafil erectile dysfunction natural treatment reviews, shortening contraction of the muscle Isotonic Contraction lifts the object and brings it to the new position; here the fibers undergo isotonic contraction discount 50 mg sildenafil with amex erectile dysfunction drugs research. When muscle contraction is associated with no apparent change in muscle tone, the phenomenon is called isotonic 2. The shortening of the muscle fiber occurs due to tension generated being just equal and opposite to the sliding of thin over thick filaments. Sliding filament theory of muscle contraction is based on cross-bridge formation, in which myosin head pulls the thin filament on thick filament. During each cross bridge cycle, cross bridge (myosin head) attaches to thin filament causing displacement of thick filament over thin filament followed by detachment of myosin head in a repetitive fashion. In skeletal muscle, the contractile response (that lasts for about 15 ms) begins almost toward the end of electrical response (that lasts for about 4 ms). In examinations, “Describe the molecular basis of muscle contraction” is a very common Long Question. Excitation-contraction coupling, Molecular basis of muscle contraction, Cross bridge cycle, Relationship between electrical and mechanical response in skeletal muscle, Types of muscle contraction, are usual Short Questions in exams. In Viva, examiners usually ask… What is the meaning of Excitation-contraction coupling, Who described Sliding-Filament Theory, What is the meaning of Sliding-Filament Theory, Steps in molecular basis of muscle contraction, Mechanism of calcium release from cisterns, Mechanism of cross-bridge cycle, Role of troponins and tropomyosin, Steps of muscle relaxation, Relationship between electrical and mechanical response in skeletal muscle and its importance, and Types of muscle contraction. Mechanism of skeletal muscle contraction is invariably asked in both theory and oral exams. Important properties of skeletal muscles (in addition to the If a second twitch is produced when the contraction properties, like contractility, excitability, fatigability, etc. Summation of contraction contraction of the second twitch is added to the phase of 2. Length-tension relationship is added to the Ca released due to the first action ++ 6. Load-velocity relationship potential, producing a higher sarcoplasmic Ca con- centration that results in a bigger contractile response. Summation of Contraction Therefore, the tension generated during summated response is greater than that of a single twitch. The It states that isometric tension developed in a single fiber tension increases further as the stimulus interval or a muscle depends on the frequency of the stimulus shortens (Fig. The action potential of the skeletal muscle is brief ation has occurred produces a phenomenon known as (1–4 ms) compared to its contraction time. Thus, during the contraction period, if the motor neu- If a skeletal muscle is stimulated rapidly (but below the ron is stimulated repeatedly, it will generate several tetanizing frequency) with a maximal stimulus, there is action potentials in the muscle fiber. The contractile a progressive increase in the force of contraction for the Chapter 28: Skeletal Muscle: Properties, Fiber Types and Applied Aspects 267 A B Figs. Note that the second stimulus applied before relaxation period of first response leads to summation of con- C traction and increases in magnitude of contraction. This is the staircase phenom- If the muscle is stimulated repeatedly at a very high enon or treppe (in German). Treppe is also seen in cardiac frequency, continuous activation of the contractile mech- muscle. In 1871, Bowditch first described Treppe in the anism occurs without any relaxation, resulting in a sus- frog’s heart. In complete/fused tetanus, there is no relaxation contraction occurs during the relaxation phase of the between the contraction phases. In clonus or incomplete or unfused tetanus, there are to be higher than the first one (Figs. While the frequency of the action potentials progres- elevated as all the calcium released due to the first sively increases to tetanizing frequency, the tension stimulus has not been pumped back into the sarco- generated in the muscle gradually rises and summated plasmic reticulum. This leftover calcium is added to the calcium released this, tension does not increase further with increase in during the second contraction and results in greater frequency of the action potentials. This is known as staircase phenomenon as the graph is When a muscle is stimulated with a frequency more in an ascending order, like a staircase. The tension generated during a complete tet- There is an autoregulation method by which anus is usually about four times that of a single twitch. Following a single action potential, enough Ca is relea- phenomenon, Treppe effect or staircase effect. But, the attachment of activated myosin heads to Henry Pickering Bowditch in 1871, in cardiac ++ these sites takes time. Therefore, all the cross-bridges are not engaged and the tension‑generating mechanism is not saturated. In a tetanic contraction, more and more Ca is released with each successive action potential, exhausting the pumping-back mechanism. Thus, the cytosolic calcium remains at a constantly high level so that all the myosin-binding sites on the thin filaments are available. Such contraction occurs in a dis- ease called tetanus caused by the clostridium tetani. Post-Tetanic Potentiation When a single stimulus is applied to a muscle immediately after the tetanic contraction is over, the amplitude of con- traction is higher than that of a single twitch. Following tetanic contraction, the released Ca takes some time to be pumped back into the sarcoplasmic reticulum. This left-over Ca is added to the Ca released by the ++ next stimulus resulting in a higher cytosolic Ca level and, therefore, a bigger contraction. Length-Tension Relationship Isometric tension developed in a muscle depends on the 2. At any length, the amount of tension actually gener- cle are attached to two fixing points so that changing the ated by the cross-bridge movements is known as the distance between the fixing points can alter the length of active tension, which is the difference between the the muscle. With extreme reduction in length, the thin filaments at the peak of active tension, which corresponds to the resting overlap each other in the center of the sarcomere so muscle length. The length of the muscle prior to contraction is called optimal sarcomeric length in frog muscle is 2. The length of the muscle at which it develops maxi- Load-Velocity Relationship mal isometric active tension is known as the optimal When a muscle contracts against a load (isotonic contrac- length or resting length, beyond which the tension tion), the velocity of fiber-shortening is inversely propor- generated on stimulation decreases until the muscle tional to the degree of load. It has been found that when the skeletal muscles in decreases with increasing load on the muscle (Fig. When the load becomes equal to the maximal isomet- attachment, the muscle shortens about 20%. This indi- ric tension the muscle can develop, the shortening cates that the skeletal muscles are under a certain velocity is zero. This load-velocity relationship is a common experience of resting muscles generates maximum tension on in our day-to-day life. The rate of cross-bridge cycling in a muscle, which response is produced when it is stimulated. In general, a light load length-tension relationship in skeletal muscle has been offers less resistance to the sliding of the filaments so explained by the sliding filament mechanism of muscle that thin filaments move quickly over thick filaments contraction described earlier. According to this mecha- allowing few cross-bridges to form at a time, produc- nism, during contraction, the amount of tension generated ing less tension and faster contraction. On the contrary, increasing the load on a cross-bridge to interaction between actin and myosin molecules.

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The cell bodies are found in the brainstem cranial nerve charge rate in one division is increased buy sildenafil 100 mg cheap drugs for erectile dysfunction ppt, the rate in the nuclei (cranial component) discount 50mg sildenafil otc erectile dysfunction pills canada, and in the most caudal part other division is decreased. It is concerned with the regulation simultaneous sympathetic activation contributes to of gastrointestinal function. Somatic vs Autonomic Nervous System Receptors the nervous system contacts all organs and tissues of the Receptors are located in the body surface or in the muscu­ body via the sensory system (afferent innervation), motor loskeletal system in somatic system. Central Connections Afferent Pathway For efferent innervation of somatic system (i. The cell bodies of autonomic motor neurons are Central component in somatic system consists of the cell located in the intermediolateral horn of spinal cord or body of a motor neuron in the ventral horn of the spinal in the specific brainstem cranial nerve nuclei. The afferent neuron may also contact glionic axon and then synapses with the cell bod­ motor neuron through interneurons via disynaptic or poly­ ies of neurons located in a peripheral ganglion. The first efferent neuron is the preganglionic neuron onic neuron, the axons of which terminate on effector that has cell body in the intermediolateral horn of spi­ organ. The postganglionic sympathetic neurons to head nal cord or in the cranial nerve nuclei in brainstem. These ganglia are in fact extension of ron that has cell body in the ganglia outside the spinal sympathetic ganglion chain into the neck. Axons of preganglionic neurons give collaterals to ter­ minate on another set of cell bodies in the paraver­ Effector Organs tebral ganglion chain. Some of the preganglionic neurons do not relay in paravertebral ganglion chain, rather they come out directly of the ganglion chain to terminate on the cell bodies of postganglionic neurons located in collateral ganglion that are present close to the effector organ. In this efferent pathway of sympathetic system, the preganglionic fibers are longer than the postganglionic fibers. Parasympathetic System In parasympathetic system, the preganglionic neurons of Fig. The electrical activity for discharge of autonomic fibers the postganglionic neuron located very close to or in the originates in some of the effector cells and then propa­ visceral organ. The preganglionic neurons of sacral part gates to cells of rest of the tissue via gap junctions. In general, in sympathetic system, the preganglionic Acetylcholine fibers are smaller than the postganglionic fibers (Appli­ Acetylcholine is the neurotransmitter at the following cation Box 30. Postganglionic sympathetic neurons to sweat glands Intrinsic cardiac adrenergic cells: Evidences of recent research studies and blood vessels in skeletal muscle. The synapse between the postganglionic neuron accounts for about 15% of adrenaline and noradrenaline content of the and the target tissues utilizes muscarinic receptors. The nicotinic receptor is blocked by hexamethonium in In the somatic nervous system, the efferent fibers terminate autonomic ganglion, in contrast to blockade by curare on motor end plate usually with one axon terminal to one at neuromuscular junction. The the transmitter into the extracellular space surround­ muscarinic receptor is of indirect ligand-gated type ing the effector cells. The action of acetylcholine is terminated by acetyl- neurotransmitter produced by autonomic fibers. The cholinesterase, the enzyme present at the cholinergic terms nonadrenergic noncholinergic fibers apply to such synapses. Adrenergic receptors are broadly classified into two bic areas and prefrontal cortex. The sympathetic responses to emotion originate in the and less to epinephrine, and least to isoproterenol, the limbic and prefrontal cortical areas. Each class of receptors is further classified as α1 or α2, and β , β1 2 or β3 (for details, refer Hypothalamic Organization ‘Adrenal Medulla’ in ‘Endocrine Physiology’). The adrenergic receptors are of the indirect ligand- Hypothalamus considerably influences autonomic func­ gated type as they utilize G protein for their effects. Hypothalamus via hypothalamo­pituitary axis con­ trols secretions of major endocrine glands. Hypothalamus receives collaterals from ascending receptors inhibit adenylyl cyclase, whereas β recep- pathways, especially from spinothalamic tracts that tors stimulate it. Location Sympathetic Parasympathetic Neck Superior, middle and In the wall of the cervical inferior cervical viscera Thorax Paravertebral Cardiac and pulmonary plexus Abdomen Paravertebral and plexus In the wall of the viscera along the abdominal aorta (myenteric and submu- (e. These are broadly classified into two categories: parasympathetic nuclei and sympathetic nuclei. The cranial outflow of parasympathetic system originates from cranial nerve nuclei that are located in the brain­ stem. Sympathetic fibers originate from thoracic and lumbar It is also closely connected with reticular formation segments (T to L ) of spinal cord. Edinger-Westphal nucleus in the midbrain is the from sacral segments (S2 to S4) of spinal cord. Nucleus gigantocellularis and parvocellularis in the target organs via various ganglions (Table 30. The gan­ reticular formation on stimulation depress activity of glia of sympathetic system are close to spinal cord and the vasomotor center. In parasympathetic system, preganglionic neurons are much longer than postganglionic neurons, as the gan- Preganglionic neurons of sympathetic system originate glion is located either near the viscera or in the viscera. They terminate in sympathetic chain of Postganglionic Neurons ganglion from where postganglionic fibers originate and innervate the viscera. In sympathetic system, preganglionic neurons are from sympathetic chain of ganglia and terminate in shorter than postganglionic neurons. In parasympathetic system, postganglionic fibers are cranial nerve nuclei in brainstem and intermediolat­ located close to or in the effector organs. In sympathetic system, postganglionic fibers originate from sympathetic chain of ganglia close to spinal cord. Therefore, preganglionic fibers are small, whereas postganglionic fibers are long. Therefore, preganglionic fibers are long, whereas postganglionic fibers are very small. Postganglionic parasympathetic is cholinergic, and postganglionic sympathetic is adrenergic. Name the sympathetic ganglia and give the segmental distribution of sympathetic fibers to various visceral organs. Give the effects of sympathetic stimulation to various organs and name the receptors that mediate these effects. Scientists contributed At the time of activity, urgency, anxiety, emotion, excite- ment and combating stressful situations, sympathetic sys- tem is activated to provide energy to the body. Excessive and chronic stimulation of this system leads to leanness, degeneration ad decay, and underutilization of it leads to lethargy and adiposity. Ernst Heinrich first made a comparative study of division are located in the intermediolateral horn of the sympathetic nerves. With his younger brother, Eduard Friedrich thoracic (T1 to T12) and upper lumbar (L1 to L3) segments measured the speed of pulse wave and correctly explained the nature of of spinal cord. The preganglionic neu- and Eduard completed the full study of locomotion and demonstrated rons come out of the spinal cord via ventral roots. The preganglionic axons may pass through the para- vertebral ganglia en route without synapsing there to terminate in a prevertebral ganglion (collateral gan- glion), which is located close to the organ. Postganglionic Neurons Postganglionic neurons for somatic structures such as sweat glands, piloerector muscles, cutaneous blood ves- sels and blood vessels of skeletal muscles leave the para- vertebral ganglion in the gray rami communicantes and reenter the spinal nerve to supply the target tissues.

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