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In addition to its anatomical divergence of postganglionic neurons breast cancer 7000 scratch off buy generic capecitabine 500 mg on line, sympathetic system activates hormonal mechanism to achieve its widespread responses womens health 7 flat belly 500 mg capecitabine visa. The adrenal medulla is a neuroendocrine gland breast cancer 914 3682554 discount capecitabine 500mg with amex, which is basically a modified sympathetic ganglion. The chromaffin cells of the adrenal medulla secrete both epinephrine and norepinephrine in a ratio of about 8:1 and store them in their secretory vesicles. They release hormone directly into the bloodstream in response to activation by sympathetic preganglionic fibers. Catecholamines released from adrenal medulla by sympathetic stimulation modulate many organ functions and therefore, further promote sympathetic effects. Thus, adrenomedullary secretion by sympathetic activation forms the physiological basis of divergence for widespread sympathetic responses. Basal Sympathetic Activity the sympathetic fibers impart a basal influence on many organs they innervate. Usually, functions of many viscera can be altered by changing the basal level of sympathetic discharge to the organs. For example, change in heart rate and blood pressure in response to change in posture. But, if situations warrant for greater changes, basal firing rate in sympathetic nerves can be increased Chapter 31: Sympathetic System 299 1. From adrenal medulla, epinephrine secretion is considerably more than norepinephrine. Norepinephrine secretion is limited only to the axon terminals of sympathetic fibers, and therefore its effects are restricted only to the postsynaptic receptors in the target tissues, whereas circulating epinephrine reaches almost all tissues of the body. Epinephrine potentiates sympathetic effects with greater efficacy than norepinephrine as it is more effective in stimulating both and -adrenergic receptors (though in general, epinephrine is a better receptor agonist and norepinephrine is a better receptor agonist). Effects are mediated by release of noradrenaline from sympathetic nerve endings and adrenaline from adrenal medulla. Effects via Adrenergic Receptors Catecholamines elicit their effects by acting on adrenergic receptors. The receptor has two subtypes: 1 and 2; and receptor has three subtypes: 1, 2, and 3. Stimulation of these receptors causes contraction or constriction of the structures in which they are present. Stimulation of these receptors often causes relaxation or inhibition of the structure. Effects of 2 Stimulation: 2 receptors are present in blood vessels of skeletal muscles, bronchial smooth muscles 300 Section 4: Autonomic Nervous System Contd. FightorFlight Response the fight-or-flight response is a typical widespread response of sympathetic activation. This occurs in critical situations of life when one has to either fight the situation or flee from the situation. Though many components of response are due to direct effects of sympathetic stimulation, secretion of catecholamine from adrenal medulla contributes considerably. Also, redistribution of the blood flow occurs to skeletal muscles and heart from splanchnic and cutaneous territories so that performance enhances. In lungs, increased exchange of blood gases occurs due to stimulation of the respiratory rate and dilation of bronchiolar tree.

Effects on Respiratory System Thyroid hormones increase oxygen utilization of tissues women's health clinic joondalup buy capecitabine 500mg with mastercard. Thyroxine meets this demand by stimulating the rate of respiration pregnancy verification form cheap capecitabine 500mg without a prescription, minute ventilation women's health magazine past issues capecitabine 500mg with mastercard, and ventilatory responses to hypercapnia and hypoxia. Thyroid hormones stimulate erythropoiesis by increasing the synthesis of erythropoietin. Thus, thyroxine increases release of free fatty acids and glycerol from adipose tissues. Thyroid hormones also increase turnover of lipids, by facilitating their oxidation. They stimulate synthesis of cholesterol and simulta neously promote its oxidation and biliary excretion. Therefore, the net effect is significant decrease in plasma cholesterol and total lipid. There fore, hyperdefecation is a feature of hyperthyroidism and constipation is a feature of hypothyroidism. However, mus cle weakness also occurs in hyperthyroidism, which may partly be due to increased protein catabolism in the mus cle. Thyroid abnormalities in woman result in irregularities in menstrual cycle, such as menorrhagia (increased menstrual loss) in hypothyroidism and oli gomenorrhea (decreased menstrual loss) in hyperthy roidism. Tubular reabsorption of electrolytes, glucose and water is also increased by thyroid hormones. In summary, thyroid hormones have widespread effects on metabolism, growth and development and con trol of many systemic functions (Table 57. Primary Hyperthyroidism When hyperthyroidism occurs due to pathology of the thy roid gland, the condition is called primary hyperthyroid ism. Iodine excess (Jod-Basedow phenomenon) Signs Sinus tachycardia, atrial fibrillation, systolic hypertension and increased pulse pressure, fine tremor, thyroid swell ing (goiter), increased body temperature (warm and moist skin), muscle weakness (proximal myopathy), protrusion of eyeball with retracted lid (exophthalmos). Secondary Hyperthyroidism When hyperthyroidism occurs due to the pathology out side thyroid gland, the condition is called secondary Chapter 57: Thyroid Gland 493 Anions these are chlorate, perchlorate, pertechnetate, periodate, biiodate, etc. How ever, in very high dose it prevents organic binding by itself, and therefore, prevents thyroid hormone synthesis. By preventing the action of catecholamines on b receptors, propranolol ameliorates many of the hyperthyroid features. Radioiodine It causes progressive destruction of thyroid cells and achieves euthyroid state. The dose should be appropri ately adjusted to prevent development of hypothyroidism. However, from the abovelisted drugs, most com monly used drugs are propylthiouracil, methimazole and perchlorate. Physiological Basis of Treatment Administration of antithyroid drugs is the mainstay of treatment of hyperthyroidism. They usually inhibit iodide trapping mechanism or binding of iodide with the tyrosine molecule. Antithyroid drugs are thionamides, anions, high dose of iodides, nonspecific betablockers and radioiodines. Special States of Hyperthyroidism Thyrotoxicosis Thyrotoxicosis is not synonymous with hyperthyroidism. This can also occur without hyperthyroidism as seen in thyroiditis or due to excess administration of thyroid hormones (thyrotoxicosis factitia). The commonly used thionamides are propyl thiouracil, carbimazole and methimazole (active metabo lite of carbimazole).

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Therefore pregnancy 4th week discount 500mg capecitabine overnight delivery, there is a concentration gradient for Na+ from outside to inside breast cancer yoga purchase 500mg capecitabine fast delivery, for which Na+ diffuses into the cell pregnancy implantation symptoms cheap capecitabine on line. It serves to pump back the Na+ that diffuses into the cell and K+ that diffuses out of the cell. Recording of Membrane Potential the membrane potential is recorded like recoding of activity of any excitable tissue. This is the recording of membrane potential and indicates the resting state of the neuron. Permeability of the membrane to K+: At rest, permeability of the membrane to K+ is higher than any other ion. Therefore, K+ easily diffuses out of the cell, though this is opposed by the electrical gradient. Thus, less cations are taken inside, which in other words, a relatively negativity is created inside. Name different body fluid compartments, total fluid present in the compartment and composition of ions in each compartment. Give the characteristics of an ideal indicator used for measuring body fluid volumes. Name the units of measurement, name the indicator used, give the basic principle and method of measurement of body fluid volume of different compartments. Unicellular organisms float in water or air and exchange their nutrients, waste products and gasses through their body surface, i. However, multicellular organisms, especially organisms with complex body systems have no direct access to their immediate environment, and therefore, they contact outer environment through interstitial fluid and transport systems of their body. Therefore, body fluid is compartmentalized into intracellular and extracellular fluids in complex organisms. The body compositions and distribution of fluid in different compartment are as follows: 1. The body composition of a normal adult male on average consists of 15% fat, 18% proteins, 7% minerals and 60% water. Of total body water, about two-third is present in intracellular compartment and one-third in extracellular compartment (Table 8. However, it is also calculated by injecting red cells tagged with radioactive isotopes such as 51Cr, 59Fe or 32P. It is in constant motion throughout the body and is exchanged rapidly with the circulating blood. It can not be measured directly as substances used for it rapidly equilibrate with plasma. Should remain unchanged by the body during the mixing period or the amount changed must be known. Principle of Measurement Size of fluid compartment is measured by injecting a substance and then calculating the volume of fluid in which the test substance is distributed. This is called the volume distribution of the injected substance, which is equal to the amount injected divided by concentration of the substance in the sample. If indicator leaves the compartment by excretion or metabolism during the time allowed for mixing, then calculation is done as follows: Transcellular Fluid Transcellular fluid represents fluid in the lumen of structures lined by epithelium. Measurement of Interstitial Fluid Volume Interstitial fluid volume cannot be measured directly as it is difficult to sample and no substance penetrates exclusively in this compartment. Radioactive inulin is prepared by substituting 14C for one of the carbon atoms of the molecule.

However womens health weight loss pills buy discount capecitabine on-line, few fibers of sympathetic ganglion chain extend above and below the spinal level breast cancer icd 9 discount capecitabine 500mg mastercard. The chain of sympathetic ganglia extends above and below the thoracolumbar spinal levels women's health big book of exercises uk 500mg capecitabine otc, in which branches of preganglionic fibers ascend to the cervical levels or descend to the sacral level. Thus, preganglionic axons may synapse with postganglionic neurons in the paravertebral ganglion at the same level, or ascend up or descend down to the several spinal segments and then synapse with the postganglionic neuron. Preganglionic fibers synapse with postganglionic neurons in these sympathetic ganglia that are present beyond the thoracolumbar segments of spinal cord. Cervical Ganglia There are three cervical ganglia: superior, middle, and inferior. The superior cervical ganglion provides sympathetic fibers that innervate the structures in the head. The middle and inferior cervical ganglia innervate structures in the chest, including the trachea, esophagus, heart and lungs. Often, inferior cervical ganglion and first cervical ganglion fuse to form stellate ganglion. Preganglionic fibers from T1 and T2 supply structures in head and neck, from T3 and T4 supply thoracic viscera, from T5 to T9 supply structures in upper limb, and from T6 to T12 supply upper abdominal viscera (Table 31. Lumbar and Sacral Ganglia There are three lumbar ganglia for three lumbar segments. However, there are two additional lumbar and at Chapter 31: Sympathetic System 297. Bladder, uterus, fallopian tube, testes, vas deferens, seminal vesicle, and prostate. They are so named as they overlie the celiac, superior mesenteric and inferior mesenteric arteries at their origin from the aorta respectively. Celiac ganglion: the preganglionic axons for celiac ganglion originate in the T5 to T12 spinal levels and provide innervation to the stomach, small intestine, liver, pancreas, gallbladder, spleen and kidneys. Superior mesenteric ganglion: the preganglionic fibers for superior mesenteric ganglion originate primarily in T10 to T12 and innervate the small and large intestines. Inferior mesenteric ganglion: the preganglionic fibers for inferior mesenteric ganglion originate from L1 to L3 and innervate the lower part of colon, rectum, urinary bladder, and reproductive organs. Preganglionic fibers from T10 to L2 supply structures in lower limbs, and from L1 and L2 supply lower abdominal viscera (Table 31. Prevertebral Ganglia Postsynaptic neurons for the abdominal and pelvic visceral organs arise from the prevertebral ganglia. There are three major prevertebral ganglia: celiac, superior mesenteric, and inferior Adrenal Medulla Adrenal medulla is a neuroendocrine structure. Cells of the adrenal medulla are innervated by preganglionic sympathetic fibers originating in the lower thoracic spinal segments that travel in lesser splanchnic 298 Section 4: Autonomic Nervous System nerve. Therefore, adrenal medulla is considered as a modified sympathetic ganglion that contains postganglionic cells. Preganglionic fibers terminate on the chromaffin cells that represent modified ganglion cells. However, unlike neurons, these cells have no axons though they function as neuroendocrine cells and release hormone in response to preganglionic neuron activation. For example, to achieve a target increase in cardiac output during exercise, sympathetic stimulation considerably increases heart rate and myocardial contractility. Widespread Sympathetic Response Another characteristic of sympathetic stimulation is that it produces widespread organ responses. The widespread response to sympathetic activation is due to two fundamental properties: divergence of sympathetic outflow and activation of adrenal medulla. Other Terminal Ganglia Some of the cells in heart, pancreas and urinary bladder are modified postganglionic cells.

Parasympathetic innervation (vagal fibers) stimulates whereas sympathetic innervation (fibers originate from celiac plexus) inhibits gastric motility and secretion breast cancer youth football socks purchase capecitabine online now. Axons arising from intramural plexuses innervate smooth muscles and secretory cells women's health center westwood purchase 500mg capecitabine otc. Some of the sensory fibers act as afferent link between the sensory receptors of the gastric mucosa and the intramural plexuses pregnancy 4 weeks 2 days cheap capecitabine 500mg. Few of these afferent fibers provide information about an intragastric pressure, gastric distention, chemical composition and pH of gastric content, and pain sensation originating in the stomach. The contractions that result from these action potentials are stronger than the contractions that occur in the absence of these action potentials. Acetylcholine and gastrin improve gastric contractility by enhancing the amplitude and duration of the plateau phase of gastric slow waves. Electrophysiology of Gastric Motility the peristaltic waves in the stomach occur usually at the frequency of gastric slow waves. These peristaltic waves are generated by a pacemaker zone located in the middle of the body of the stomach. The frequency of peristaltic wave is about 3 per minute in human being and the waves are conducted from body toward pylorus. The gastric slow wave has four phases that resem ble the action potentials of cardiac muscle. However, it does not overshoot and last for a longer period (10 times that of cardiac action potential). The smooth muscles of stomach contract when the depolarization of the slow wave exceeds the threshold for contraction. The force of contraction depends on the degree, frequency and duration of depolarization. Greater the depolarization and longer the muscle cells remain depolarized (above threshold), greater is the force of contraction. If stomach is allowed to remain empty for a longer duration, contractions become vigorous. The antral contractions are intense in such a situa tion and are associated with the relaxation of pyloric sphincter. Gastric Relaxations Receptive Relaxation this is the relaxation of the fundus and body of the stom ach in response to chewing and swallowing of food. Because of receptive relaxation, the intragastric pressure does not rise in spite of accumulation of a large volume of food. Normally, gastric motility induced by vagal stimulation is mediated by cholinergic fibers. Receptive relaxation is vagally mediated and adaptive relaxation is mainly a vagovagal reflex. Adaptive and Feedback Relaxations There are other two types of gastric relaxations: adaptive and feedback. The adaptive relaxation is the relaxation of stomach triggered by distension of stomach. Receptive relaxa tion starts even before food reaches stomach whereas adaptive relaxation occurs in response to stretching of stomach wall. The feedback relaxation of stomach is a reflexive relaxation that occurs due to presence of food in proximal segment of small intestine. Acidic chyme and fatty acid in intestine inhibit gastric motility by both hormonal and neural mechanisms that cause feed back relaxation of stomach. It helps in propelling food into the antrum and mixing of food with gastric juice. Therefore, food does not enter the duodenum, rather is recirculated in the stomach.

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