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By K. Folleck. Tennessee State University.

Neurochirurgie 1964;10: no cases reported in the more recent larger series with sufciently 507–522 order cialis soft without a prescription erectile dysfunction acupuncture. Persistent intracranial bleeding as a complication ment to a meticulous haemostasis [19 buy discount cialis soft 20mg on line erectile dysfunction juice recipe,60] generic 20 mg cialis soft with visa erectile dysfunction green tea. Can J Neurol Sci 1983; 10: documented cheap cialis soft online mastercard erectile dysfunction reviews, including a meticulous analysis of the integrity of the 71–78. Language recovery afer lef hemispherec- Lippincott Williams & Wilkins, 2000: 741–746. Exceptional verbal intelligence surgical procedures and clinical long-term outcomes in a population of 83 chil- afer hemispherotomy in a child with Rasmussen encephalitis. Complications related to delayed hemorrhage afer hem- Tuxhorn I, Holthausen H, Boenig H (eds). Epilepsy surgery for hemispheric syndromes in come with respect to epileptic seizures. Surgical Treatment of infants: hemimegalencephaly and hemispheric cortical dysplasia. Modifcation of peri-insular hemispherotomy and surgical initial description: Promising prospects and a dilemma. The nonmalformed hemisphere is secondari- The reorganization of sensorimotor function in children afer hemispherectomy. Brain 2006; 129: 1822– outcome of 58 children afer hemispherectomy: the Johns Hopkins experience: 1832. Late plasticity for language in a ale, indications, results, and comparison with callosotomy. Distinct right frontal lobe activation in intractable seizures: excellent seizure control, low morbidity and no superfcial language processing following lef hemisphere injury. Tere was laboratory evidence sup- forme fruste infantile hemiplegia, Rasmussen syndrome, Lennox– porting the rationale for this procedure, notably that of Erickson Gastaut syndrome, frontal lobe epilepsy and other secondarily gen- [2], who in non-human primates demonstrated prevention of the eralized epileptics. Slightly better outcomes were found in the frst spread of the epileptic discharge to the opposite hemisphere when two groups but there was sufcient improvement in all categories to the corpus callosum had been divided. Today, most epilepsy centres perform commis- by a number of investigators [13,14,19,21,25,29,33,38,39,44,45,50, surotomy, and it retains an important role in the armamentarium of 57,58,67,69,72,74,77,79,81,85,86,89,92,95,96,97,98,99,100,101,102, interventions for intractable epilepsy. The majority of patients have evi- Although resection of an epileptogenic region with the goal of sur- dence of bilaterally synchronous epileptiform activity and this does gical cure has always been the surgical procedure of choice, in those not necessarily represent a bad prognostic sign. The signifcance of patients with generalized seizures in whom a discrete epileptogenic bilateral, independent foci remains undetermined. Other palliative pro- has been believed to be associated with a better surgical outcome cedures, including multiple subpial transection, vagal nerve stim- [12,115], but in the selection process their presence or absence has ulation and deep brain stimulation, have also been developed, and always been secondary to clinical and electrophysiological informa- the strategy for optimal utilization or prioritization of these various tion. The impact of neuroimaging on the callosotomy experience non-ablative strategies remains to be determined [23,24,25]. As imaging technologies continue to evolve with From the earliest days of callosotomy it has been appreciated that increasing sensitivity and specifcity, they are directing such aspects drop attacks (variously classifed as atonic and akinetic seizures) of the seizure evaluation as intracranial recording electrode place- are among the most likely of seizure types to beneft from discon- ment, and this will obviously afect patient selection and perhaps nection; tonic and tonic–clonic generalized seizures similarly have the surgery itself. Patients in whom Given the difcult evaluation in this patient population, it is both seizure semiology, electrophysiological studies, neuroimaging and The Treatment of Epilepsy. The remaining candidate pool will be section [16], and difuse disease may render any partial section heterogeneous, including patients with infantile hemiplegia, forme futile. The correlation between extent of disease and successful fruste infantile hemiplegia, Rasmussen syndrome, Lennox–Gastaut section, however, is insufcient to place great reliance on these syndrome, frontal lobe epilepsy and other secondarily generalized factors. Although the outcome of a seizure-free patient most have not adopted this practice. The patient is placed in a su- is always hoped for, this is achieved in only 5–10% of cases [118]. For the anterior division, the of other epilepsy surgeries as it is usually palliative rather than neck is kept in neutral position; for the posterior division, fexion of curative. Alternatively, one may po- sition the head parallel to the foor such that the hemisphere to be retracted is dependent, thereby allowing gravity to help provide the Surgical technique exposure [65,124]. This has the appeal of minimizing any retracting Early clinical series ofen included division of the corpus callosum, force placed interhemispherically, although whether this retraction the underlying hippocampal commissure and additional structures, is signifcant enough to warrant the perhaps less comfortable and including the anterior commissure and, in some instances, one for- diferently oriented horizontal positioning is open to discussion. Nearly all series today restrict division to the The incision and type of craniotomy used is a matter of the sur- corpus callosum and, in posterior or complete callosal section, to geon’s personal preference. We have used linear incisions and 5-cm the hippocampal commissure that is immediately apposed to the trephinations [10,125], but the actual type and extent of craniotomy ventral aspect of the posterior portion of the callosum. A 9-cm transverse incision with one-third mains variation, however, with regard to which part or how much of its length across the midline and placed 2 cm in front of the coro- of the structure is divided. Seizure outcome appears to have some nal suture is used for the anterior procedure. As neuropsycho- trephination at the level of the parietal eminence is employed for logical consequences of callosal section are encountered primarily the posterior procedure. The placement of the craniotomy across with complete section [120,121], most centres today usually divide the sagittal sinus requires caution but facilitates exposure down the the anterior two-thirds to three-quarters and spare the splenium at interhemispheric fssure with minimal retraction, and this is im- initial surgery. Exceptions to this approach are division of a smaller, select or to transcallosal procedures has been advocated, but this has not portion of the callosum, division of the posterior half as an initial been a routine step for most centres, including ours. The been possible to work on either or both sides of such a vein without presurgical evaluation and preoperative substrate may infuence the requiring its sacrifce using a microsurgical technique. Such angiographic information may be available in the consideration of the risk–beneft ratio for partial or complete in those patients who have previously undergone amytal testing section. This down the interhemispheric fssure under loupe magnifcation, and is especially true if drop attacks, which usually respond to anteri- retraction is aided by the earlier administration of mannitol (1 g/ or section, are not the predominant seizure pattern. The both anterior cerebral arteries, the white corpus callosum, and the slightly exposure is that of the residual cavum septum pellucidum, and dissection darker cingulate gyri. Adhesions between the hemispheres may make initial expo- The actual direction of subsequent section is not particular- sure difcult, especially when there is a history of previous in- ly important. With patient microsurgical technique, one performed extraventricularly as far as possible. The rostrum at this can generally obtain good exposure; approaching the callosum point is nearly paper thin, and any remaining fbres are insignif- more posteriorly and utilizing the deeper extension of the falx cant. The corpus callosum is dis- Division posteriorly is readily performed following the midline tinguished from the more superfcial cingulate gyrus by its glis- clef. If an attempt is being made to achieve success with a partial tening white appearance (Figure 70. The pericallosal arteries are identifed overlying the callosum and care is taken to avoid their injury. Actual sectioning of callosal fbres is usually carried out between these arteries, although division lateral to these vessels can be performed if more convenient. It is standard practice today to use the operating microscope, whose superior magnifcation and illumination have proven inval- uable during the exposure and actual sectioning. Bipolar cautery is used for coagulation of small vessels supplying only the callosum itself. The actual division of callosal fbres is carried out with a mi- croseptal or microsuction tip. The ultrasonic aspirator may prove to be of greater utility in this step as it becomes more refned and thinner. The slightly darker, bluish appearance of the underlying ventricu- lar ependymal surface, described in early reports of callosal section recommending its use as the limit of division [10], will indicate the approach to the ventral aspect of the callosum. The alternative of identifying the midline, however, ofers numerous advantages in- creasingly evident over the course of our series. Tese include un- equivocal assurance of completeness of fbre division, elimination of possible lateral deviation (especially in the frontal region), de- Figure 70. If image-guidance and a preoperatively determined length of section are not being used, the surgeon can use intraoperative time. A blunt microinstrument is gently swept from side to side as measurement to assure desired length of section. The thinning of the the callosum is nearly traversed, and this will usually expose the posterior body of the callosum can be appreciated intraoperatively. This is usually relationship of the fornices to the ventral aspect of the callosum, which can easiest at the most posterior portion of the genu or the anterior por- also be of assistance, is highly variable and useful with reference to only the tion of the body. Once this clef has been identifed, the remainder individual case; in this instance, their more ventral location would render of the section is easily accomplished. Coronal images can be helpful in demonstrating completeness of section when the section is not entirely in the same plane The fbres of the splenium are divided with similar instrumenta- of a sagittal image. The underlying arachnoid, beneath which lie of methods have been employed to assure accomplishment of the the pineal and quadrigeminal cistern, is preserved. Tese include physical measurement of hippocampal commissure may be difcult to distinguish from the the exposed callosum to be sectioned, identifcation of structural overlying callosal fbres, but this is of no practical signifcance as it features (such as the thinning of commissure generally seen in the is divided as well. If an anterior section has already been performed, posterior body or the appearance of the fornices), intraoperative the previously placed clip is retrieved. If the posterior section is the radiographs [127] and, more recently, the image-guidance of frame- initial commissurotomy procedure, a clip is lef as a marker at the less stereotactic navigational systems. Exposure down the interhemispheric fssure is in tient is observed in the neurosurgical observation unit overnight this instance facilitated by the deeper falx cerebri (Figure 70. Mobilization begins immediately, and the patient is typically dis- charged 3 or 4 days afer surgery; in anterior section alone, or in children, hospitalization may be shorter. Anticonvulsant medica- tion is generally lef unaltered until at least subsequent follow-up. A decision regarding completion of the callosotomy is usually de- ferred 6 months or more afer the initial procedure. Endoscopy [128,129,130], stereotactic lesioning [131,132] and radiosurgery [41,43,46,73,75,76,78,133,134,135,136] have been described, but experience with these techniques for this specif- ic purpose is limited. Any such technique must be assured of not inadvertently sparing commissural fbres, as suboptimal seizure outcomes have been attributed to such sparing during open pro- cedures. Such techniques must also match the low morbidity and mortality of today’s microsurgical procedure. The utilization of image-guidance (neuronavigation) for this sur- gery has paralleled its increasing incorporation into the majority Figure 70.

Exposure of this binding site allows myosin heads to interact with actin and engage in cross-bridge cycling 20 mg cialis soft amex erectile dysfunction at the age of 17. Whereas generic cialis soft 20mg line impotence thesaurus, in cardiac and smooth muscle purchase cheapest cialis soft and cialis soft erectile dysfunction daily pill, the amount angle of about 45 degrees pulling the actin filament of calcium regulates the degree of actin-myosin inter- about 11 nm toward the center of the sarcomere action as the contractile system is only partially satu- (Fig buy cialis soft 20mg line erectile dysfunction treatment manila. That means the myosin head stay attached to the actin molecule in the the sequence of events that occur during the interaction same position and at a 45° angle with respect to between the myosin cross-bridges and the actin molecules the thick and thin filaments. During each cycle, cross bridge (myosin head) attaches bind to the myosin head and initiate next cycle. This decreases the affinity of myosin for actin result- same phase at any instant during a cycle. This helps in ing in detachment of cross-bridges from the thin fila- a smooth and sustained contraction. This results in rotation of the myosin head around the hinge in such a way that the globular head is posi- Effects of Cross-Bridge Formation tioned at 90° angle in relation to the thick filament, During contraction, being attached to an actin molecule, pointing toward, but not attached to the thin filament. This rotation moves the myosin head about 10 nm thick filament has 500–600 myosin heads, and each one along the thin filament, so that, the head is positioned can pivot about five times per second during a rapid con- against a new actin molecule. One stroke of a cross-bridge produces 11 nm displace- position of the myosin head’ in which, energy is stored ment of the thin filament over the thick filament. When most of the cross-bridges in a muscle are in this repeating its cycle many times, drag the thin filaments energized state, it keeps the muscle in a relaxed state. This leads to decrease in the sarcomeric length and Events in the Stimulated Muscle ultimately muscle shortening. If most of the cross-bridges in a muscle remain in the death, the cross-bridges cannot detach and it is called detached state, it would produce relaxation in the a rigor cross bridge, the cycle stops there and the muscle. Not all the cross bridges remain in the detached state stiffening in the muscle, known as rigor mortis (Clinical even in a completely relaxed muscle; some of them Box 27. Note, during muscle contraction, Z lines move toward B M line that decreases sarcomeric length (muscle shorten- Figs. In this process of contraction and state, I and H bands almost obliterate, whereas A band remains same in both contracted and relaxed states. Therefore, muscle remains in a state of quickly revise, understand and memorize quickly, it is sum- contraction or rigidity. Due to rigor mortis, body remains Mechanism of Muscle Relaxation in same position for a longer time. Thus, rigor mortis not only speaks Like muscle contraction, relaxation is also an active process. Cross-bridge formation in the presence of increased concentration in the vicinity of the myofilaments to a calcium. When the action potential and the twitch contrac- the resting membrane potential of skeletal muscle is tion are plotted on the same time scale, the contrac- –90 mV. The action potential is generated at the end plate tile response begins about 2 ms after the onset of the action potential. This delay is known as the latent region and spreads at a speed of 5 m/sec along the sarco- period, during which the excitation-contraction cou- lemma and down the T tubules activating the myofilaments. The duration of the action potential is 2–4 ms and In nerve-muscle preparation, where a motor nerve absolute refractory period is 1–3 ms. The depolarization phase of the action potential is occurs due to the time taken for: due to sodium influx and repolarization is a manifes- 1. Secretion of Ach, its diffusion through the synaptic contractile proteins but instead produces a state of cleft and generation of end plate potential. Origin and spread of action potential along the sarco- vates the contractile apparatus long after the electrical lemma and T tubules activity in the membrane has ceased (Fig. Overcoming the inertia of the writing lever (if the In response to the motor nerve discharge, the thick and twitch is being recorded). This contractile response (twitch con- contractile machinery, but the relaxation process starts traction) can be recorded in a graphical form (Fig. The duration from the start of the con- gle muscle fiber to an action potential consisting of a tractile response to the attainment of peak tension is the phase of contraction followed by a relaxation phase. Length of muscle Remains same Shortening occurs the clinics, twitches are usually elicited while testing the tendon jerks (myotatic reflexes). Tension Tension increases No change diseases, presence of twitches that occur spontaneously 3. The major difference from isometric contraction is Types of Contraction that in isotonic contraction, the external work is done (Table 27. Load is the force exerted on the muscle by an Positive and Negative Works object, i. Thus, muscle tension and load act against each the muscle does positive work when an object is lifted other. Isotonic contraction exerted on the muscle is greater than the tension gen- erated due to actomyosin interaction, the load pulls Isometric Contraction the muscle to a longer length. Such lengthening of the When muscle contraction is associated with no apparent muscle is called lengthening contraction or eccentric change in muscle length, the phenomenon is called iso- contraction, for example, the extensors of the knee metric contraction. This is not an active process produced by cross bridge trying to lift a heavy object. During this type of contraction, the cross bridges bind nal load stretches the muscle. While recording for isotonic contraction, one end of the This exerts a force on the thin filament, the isometric muscle is fixed and the other kept free, so that on stimula- tension. According to the law of physics, if displacement is zero Processes in Isometric and Isotonic Contractions (position of the object does not change), the work When an object is to be lifted, initially tension increases done (force × displacement) is also nil, though force is in the muscle till it becomes equal to the downward pull- generated and energy is spent. Thus, in isometric con- ing force (due to the weight of the object) without any traction no external work is done. Once the tension in the muscle is greater than the opposing load, shortening contraction of the muscle Isotonic Contraction lifts the object and brings it to the new position; here the fibers undergo isotonic contraction. 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.

The force of contraction depends on the degree purchase line cialis soft erectile dysfunction 19 year old male, fre- Receptive Relaxation quency and duration of depolarization purchase cialis soft 20 mg online erectile dysfunction doctors in connecticut. Greater the depolarization and longer the muscle cells This is the relaxation of the fundus and body of the stom­ remain depolarized (above threshold) generic 20mg cialis soft with amex erectile dysfunction treatment in pune, greater is the ach in response to chewing and swallowing of food cheap 20 mg cialis soft visa erectile dysfunction due to drug use. Receptive relaxation is vagally mediated sure does not rise in spite of accumulation of a large and adaptive relaxation is mainly a vagovagal reflex. It starts as a ring of contraction that progress slowly stimulation is mediated by cholinergic fibers. It helps in propelling food into the antrum and mixing cholinergic fibers) at its nerve ending. During this gastric peristalsis, pylorus usually remains Adaptive and Feedback Relaxations closed. Therefore, food does not enter the duodenum, rather is recirculated in the stomach. The adaptive relaxation is the relaxation of stomach triggered by distension of stomach. Receptive relaxa­ During the interdigestive phase, antrum of the stomach tion starts even before food reaches stomach whereas remains silent for about 75–90 minutes, after which a adaptive relaxation occurs in response to stretching burst of electrical and motor activities occurs. The wave of contraction progresses from stomach relaxation that occurs due to presence of food in toward terminal ileum. Usually, it is repeated every 90 minutes during interdi­ back relaxation of stomach (Fig. Peristalsis Reverse Peristalsis After about half an hour following gastric filling, gastric Sometimes in abnormal situations, peristalsis occurs in peristalsis starts. The peristaltic movements are initiated by gastric slow body and proceeds toward esophagus. The pacemaker for gastric peristalsis is located in that gastric content is forced out of esophagus and the middle of the stomach close toward greater cur­ oral cavity. Note, pyloric sphincter is closed in step A, B, and C during which thorough mixing and grinding of food occurs and the food material is converted into chyme. In stage D, sphincter is partially opened that causes slow emptying of gastric content into duodenum. Usually, it occurs at a slow but toward the proximal part of the antrum and body of the controlled rate so that duodenum and jejunum comfortably stomach (Fig. This movement is called retropul- accommodate and process the chyme at a desired rate. Retropulsion is very effective in mixing and grinding Mechanism of Gastric Emptying the larger food particles into smaller ones. Then, pyloric sphincter partially opens and gastric receptive and adaptive relaxations. Gastric empty­ Physiological Significance ing occurs by three mechanisms: peristaltic contraction, antral contraction, and retropulsion (Figs. As the muscle layers in the fundus and body are thin, contractions in these parts of the stomach are weak. Peristaltic Contractions Therefore, gastric content in body of stomach settles into different layers based on their density. Fat content of the food forms an oily layer on the top the stomach and proceeds in a ring like fashion toward of the other gastric contents. These contractions mainly push food slower than the carbohydrate and protein (Applica­ into the antral part of the stomach. Liquid portion of the food flow around the mass and as the contractile waves approach pylorus. As contractions are weak in the fundus and body of Therefore, liquid is emptied faster than the solid. Major amount of mixing takes place in the antrum, as Fat ensures slow gastric emptying and slow absorption of alcohol from antrum contracts vigorously. Antral Contractions Regulation of Gastric Emptying Antral contractions help thorough mixing of food with the gastric juice. But, as the pyloric sphinc­ num and jejunum) contains receptors that detect change ter remains closed, peristaltic wave fails to push food in pH, osmotic pressure, and products of fat and protein into the duodenum, rather food returns back into the digestion. Therefore, stomach empties in small squirts with each the duodenal content the rate of gastric emptying peristaltic wave. Products of fat digestion: Products of fat digestion like as occurs in diabetes mellitus. Paralysis of propulsive movements occurs following nal content inhibit gastric emptying. Osmolality of duodenal content: the chyme entering Rapid Gastric Emptying into duodenum has higher osmolality. Therefore, states of increased vagal activity increase that detect change in osmolality of the duodenal con­ emptying. Conversely, sympathetic stimulation inhibits empty- hormones that inhibit the rate of gastric emptying. Products of protein digestion: Presence of peptides stress, a state of sympathetic overactivity. Hormones like thyroxine stimulate gastric emptying from the G cells located in the duodenum. Hence, increased appetite and − Gastrin increases antral contraction but at the hyperdefecation are features of hyperthyroidism. Stretching of duodenum: Entry of chyme into the duo­ Vomiting is usually preceded by the feeling of nausea, denum stretches the wall of duodenum. This initiates tachycardia, sweating, pallor, dizziness, and dilatation of enterogastric reflex that inhibits gastric emptying. It is associated with retching that forces contents ogastric reflex is also activated by acid in the duodenum. Con­ Vomiting is a reflex phenomenon, the center for which is sequently, whenever vagotomy is performed for the located in the medulla (Fig. The receptors present in many parts of the body pro­ dure like pyloroplasty or gastrojejunostomy is also vide inputs to the vomiting center, in the brainstem. Area postrema mediate vomiting activated by drugs gastric motility and produces gastric stasis, whenever vagotomy is (opiates, chemotherapeutic agents, etc. Vomiting activated by emotion influenced by limbic passage of food from the stomach into the duodenum. Conditions associated with dizziness and nausea increases, which forces the gastric contents to enter the esophagus. Relaxation of the lower esophageal sphincter allows Emetics and Antiemetics gastric content to enter the esophagus. Normally, the upper esophageal sphincter remains Drugs that induce vomiting are called emetics. The com­ closed and prevents regurgitation of food into the mon emetics are apomorphine, ipecac, etc. Chlorpromazine, a D2 receptor antagonist and halo- hours after meal in persons who have undergone gastrec­ peridol are also effective antiemetics. Corticosteroids, cannabinoids, and benzodiazepines are This occurs due to two causes: useful antiemetics for chemotherapy­induced vomiting. Hypoglycemia: Rapid entry of food into intestine causes quick absorption of glucose from intestine and pro­ Mechanism of Vomiting duces prompt hyperglycemia, which in turn increases insulin secretion. Insulin produces hypoglycemia that Vomiting reflex is executed in a sequence of events. Genesis of reverse peristalsis that starts from the mid­ from esophagus directly into intestine produces high dle of the jejunum. This sweeps the content of intes­ osmotic load on intestine that transfers water from tine and duodenum into the stomach. Relaxation of the pyloric sphincter that allows the dration and hypotension that lead to weakness, dizzi­ intestinal content to enter the stomach. The proximal stomach is mainly for receiving and storing food, and the distal stomach is meant for mixing and emptying food. Antral contractions help in proper mixing and grinding food that finally becomes chyme. Vomiting is mainly a central phenomenon initiated by stimulation of vomiting center in medulla, though local factors contribute to it. In examinations, “Mechanism and factors affecting gastric emptying” may come as a Long Question. Gastric relaxations, Reverse peristalsis of stomach, Electrophysiology of gastric smooth muscles, Gastric emptying, Vomiting, may come as Short Questions. In Viva, examiner may ask… What are the parts of the stomach and what are their functions, Who is the Father of Gastric Physiology, What are the special electrophysiological properties of gastric smooth muscles, Types of gastric relaxations, What is the importance of receptive and adaptive relaxation, What is the mechanism of gastric emptying, What are the factor affecting gastric emptying, What is Retropulsion, What is the specialty of gastric peristalsis, Who is the pacemaker of gastric contractions, What is hunger contraction, What are the causes of rapid and delayed gastric emptying, Reverse peristalsis of stomach, Mechanism of vomiting, What is dumping syndrome and how is it treated. The main objective of the motility of the small intestine is to thoroughly mix the chyme with the pancreatic, bile and intestinal juices so that proper digestion and absorption of the essential nutrients can take place. Jejunum constitutes 40% and ileum constitutes more than 55% of the small intestine. However, the muscularis externa consisting of outer longitudinal and inner circular muscles is well developed in small intestine (Fig. Note, muscle layer they are more in number in ileum, and they extend consisting of outer longitudinal and inner circular muscles is well into the submucosa (Fig. Note, in segmental contractions, food is grinded and thoroughly mixed between two propulsive segments. Electrophysiology of Intestinal Smooth Muscles migrating myoelectric complex, contraction of the muscu- laris mucosa, villus contractions, and movements due to the frequency of slow wave is maximum in small intestine intestinal reflexes.