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The electromotility of hair cell is due to the presence of a contractile protein menopause the musical indianapolis fosamax 35mg on line, prestin (named after a musical notation presto) womens health worcester ma buy fosamax 70mg without prescription. Role of Efferent Nerve Fibers of Hair Cells Efferent nerve fibers (Chapter 173) of hair cells also play important role during sound transduction by releasing acetylcholine womens health quote order 35 mg fosamax. Efferent nerve fiber to inner hair cell terminates on the auditory (afferent) nerve fiber where it leaves the inner hair cell pregnancy exercise classes quality 70mg fosamax. It controls the generation of action potential in auditory nerve fiber by inhibiting the release of glutamate from inner hair cells. Endolymph Scala media is filled with endolymph, which contains high concentration of potassium and low concentration of sodium. It is due to continuous secretion of potassium ions by stria vascularis into scala media. Electrical Potential Difference in potassium concentration is responsible for the development of an electrical potential difference between endolymph and perilymph. Significance of Endocochlear Potential Lower portion of the hair cells is bathed by perilymph. Head portion of hair cells penetrates the lamina reticularis and it is bathed by endolymph. High potential difference sensitizes the hair cells so that, the excitability of hair cells increases. Action potential to a click sound with moderate intensity level consists of three successive spike potentials called N1 N2 N3 representing synchronous repetitive firing in many fibers. At high frequency, the synchronization of action potential disappears and single spike occurs. There the receiver instrument converts the electrical impulses back into sound waves. Similarly, cochlea just converts the sound waves into electrical impulses of same frequency. Impulses are transmitted by auditory nerve fibers to cerebral cortex, where perception and analysis of sound occur. It is believed that, the nerve fibers can transmit maximum of 1,000 impulses per second. Thus, the telephone theory fails to explain the transmission of sound waves with frequency above 1,000 cycles per second. According to this theory, the impulses of sound waves with frequency above 1,000 cycles per second are transmitted by different groups of nerve fibers. Resonance Theory of Helmholtz Resonance theory was the first theory of hearing to emerge in 1863. Helmholtz named these basilar fibers resonators and compared them with the resonators of piano. Similarly, when the sound with a particular frequency is applied, the basilar fibers in a particular portion of basilar membrane are stimulated. Resonance theory was not accepted because the individual resonators could not be identified in cochlea. Gradually, this theory was modified into another theory called the place theory, which is more widely accepted. Place Theory According to this theory, nerve fibers from different portions (places) of organ of Corti on basilar membrane give response to sounds of different frequency. Accordingly, corresponding nerve fiber from organ of Corti gives information to the brain regarding the portion of organ of Corti that is stimulated. Frequency of sound audible to human ear lies between 20 and 20,000 Hz or cycles/second. The range of greatest sensitivity lies between 2,000 and 3,000 Hz (cycles/second). According to the first group, the analysis of sound frequency is the function of cerebral cortex and the cochlea merely transmits the sound. According to the second group of theories, the frequency analysis is done by cochlea, which later sends the information to cerebral cortex. Telephone Theory of Rutherford Telephone theory was postulated by Rutherford in 1880.
Neurogenic Shock Neurogenic shock is the type of shock characterized by sudden depression of nervous system due to extensive vasodilatation caused by loss of vasomotor tone women's health magazine boot camp generic 35 mg fosamax with visa. Ischemia of brain: Severe ischemia in medulla depresses the activity of vasomotor center ii womens health 3 day cleanse order fosamax 35mg line. Emotional conditions: Extreme emotions cause sudden and exaggerated activity of autonomic nervous system women's health lose 10 pounds discount fosamax 70mg amex, the subject faints because of neurogenic shock menstrual cramps 8 days before period cheap 70mg fosamax fast delivery. Syncope (Fainting) Syncope or fainting is the sudden and transient (shorttime) loss of consciousness and postural tone with spontaneous recovery. Vasovagal syncope or emotional fainting: Fainting is caused by sudden stimulation of vagus nerve. It is due to extreme activation of parasympathetic division of autonomic nervous system. There is sudden decrease in heart rate (bradycardia) because of inhibition of myocardium by vagus. At the same time, the blood pressure also decreases (hypotension) due to severe vasodilatation by the parasympathetic nerve fibers. Simultaneously, sympathetic tone is decreased and it also causes vasodilatation leading to hypotension. Vasovagal syncope is common in conditions like severe emotional distress and exertion. It is due to pooling of blood in lower limbs during prolonged standing resulting in decreased blood supply to the brain. Fall in blood pressure while standing is called orthostatic hypotension (Chapter 103). It is due to the failure of the heart to increase the cardiac output, when the tissues need more blood flow. Sometimes, severe cough increases intrathoracic pressure, which reduces the venous return and cardiac output leading to fainting. Chapter 116 t Circulatory Shock and Heart Failure 661 Conditions when septic shock occurs. Infection of the uterus and fallopian tube, commonly occurring in abortion by instrumentation ii. Spreading of skin infection due to bacteria like streptococci or staphylococci iv. Septic shock develops due to the depression of myocardium, dilatation of blood vessels and increased permeability of capillary membrane. Endotoxin shock Endotoxin shock is the shock developed by a bacterial toxin called endotoxin. Endotoxin shock is very common during the infection of alimentary tract by gram-negative bacteria like colon bacilli. Anaphylactic Shock Anaphylaxis means exaggerated allergic reaction to a foreign protein or antigen or any other substance to which the person has been previously sensitized (Chapter 17). It is caused by the chemical mediators such as histamine that are secreted during anaphylactic reaction. Septic Shock Sepsis is the pathological condition characterized by the presence of pathogenic organisms or their toxins in blood or tissues. Plasma expanders (solutions of sugar with high molecular weight such as dextran); such substances do not escape through capillary membrane ii. Hypertonic solutions, which cause drawing of fluid into blood from interstitial space. However, the sympathomimetic drugs should not be used for longer period since, these drugs induce severe myocardial activity. Glucocorticoids increase the glucose metabolism in damaged tissues, prevent further damage of tissues and increase the myocardial activity. The head down position (by raising the bed at the foot end) increases venous return, cardiac output and cerebral blood flow. However, this should not be used for longer periods because prolonged head down position might affect the ventilation. It is because of effect of the increased pressure exerted by abdominal viscera on diaphragm. Acute Heart Failure Acute heart failure refers to sudden and rapid onset of signs and symptoms of abnormal heart functions.
These alternate segments of contraction and relaxation give appearance of rings menstruation every 2 weeks fosamax 35 mg free shipping, resembling the chain of sausages women's health center vcu generic fosamax 70mg. After sometime women's health clinic rock springs wy cheap 70mg fosamax mastercard, the contracted segments are relaxed and the relaxed segments are contracted menopause jealousy fosamax 70mg without prescription. Peristaltic contractions start at any part of the intestine and travel towards anal end, at a velocity of 1 to 2 cm/sec. The contractions are always weak and usually disappear after traveling for few centimeter. Because of this, the average movement of chyme through small intestine is very slow and the average velocity of movement of the chyme is less than 1 cm/ sec. So, the chyme requires several hours to travel from duodenum to the end of small intestine. Peristaltic waves in small intestine increase to a great extent immediately after a meal. This is because of gastroenteric reflex, which is initiated by the distention of stomach. Impulses for this reflex are transmitted from stomach along the wall of the intestine via myenteric plexus. Peristaltic Rush Sometimes, the small intestine shows a powerful peristaltic contraction. It is caused by excessive irritation of intestinal mucosa or extreme distention of the intestine. This type of powerful contraction begins in duodenum and passes through entire length of small intestine and reaches the ileocecal valve within few minutes. Thus, it relieves the small intestine off either irritants or excessive distention. It is different from the regular peristalsis because, a large portion of stomach or intestine is involved in the contraction. It starts as a moderately active peristalsis in the body of stomach and runs through the entire length of small intestine. Thus, it takes about 10 minutes to reach the colon after taking origin from the stomach. Significance of Peristalsis in Fasting Migrating motor complex sweeps the excess digestive secretions into the colon and prevents the accumulation of the secretions in stomach and intestine. It is because of the extension of smooth muscle fibers of the intestinal wall into the villi. Movements of villi are shortening and elongation, which occur alternatively and help in emptying lymph from the central lacteal into the lymphatic system. Movements of villi are caused by local nervous reflexes, which are initiated by the presence of chyme in small intestine. Hormone secreted from the small intestinal mucosa called villikinin is also believed to play an important role in increasing the movements of villi. Still, these movements are important for mixing, propulsive and absorptive functions. Types of Movements of Large Intestine Movements of large intestine are of two types: 1. Duration of mass movement is about 10 minutes in the morning before or after breakfast. This is because of the neurogenic factors like gastrocolic reflex (see below) and parasympathetic stimulation. By the influence of an appropriate stimulus, it is expelled out Chapter 43 t Movements of Gastrointestinal Tract 279 through the anus. This is prevented by tonic constriction of anal sphincters, in the absence of the stimulus. The desire for defecation occurs when some feces enters rectum due to the mass movement. Usually, the desire for defecation is elicited by an increase in the intrarectal pressure to about 20 to 25 cm H2O.
Systemic toxic effects include leukopenia menstrual seizures 70mg fosamax free shipping, thrombocytopenia menstruation kolik buy generic fosamax 35 mg on line, mucositis menstruation for a month fosamax 70mg visa, hepatic dysfunction breast cancer prognosis generic fosamax 70 mg fast delivery, and seizures. The drug may cause severe neutropenia when used with zidovudine or other myelosuppressive agents. Fomiversin causes iritis, vitreitis, increased intraocular pressure and changes in vision. Didanosine (ddI)-Oral bioavailability of ddI is reduced by food and by chelating agents. The drug is eliminated by the kidney, and the dose must be reduced in patients with renal dysfunction. Pancreatitis is dose-limiting and occurs more frequently in alcoholic patients and those with hypertriglyceridemia. Emtricitabine-Good oral bioavailability and renal elimination with long half-life permits once-daily dosing of emtricitabine. Because of the propylene glycol in the oral solution, the drug is contraindicated in pregnancy and young children and in patients with hepatic or renal dysfunction. Peripheral neuropathy is dose-limiting and increased with coadministration of didanosine or zalcitabine. Dosage adjustment is needed in patients with renal insufficiency and nephrotoxic drugs (eg, amphotericin B, aminoglycosides) increase toxic potential. Elimination of the drug involves both hepatic metabolism to glucuronides and renal excretion. The primary toxicity of zidovudine is bone marrow suppression (additive with other immunosuppressive drugs) leading to anemia and neutropenia, which may require transfusions. Drugs that may increase plasma levels of zidovudine include azole antifungals and protease inhibitors. Nonnucleoside drugs do not require phosphorylation to be active and do not compete with nucleoside triphosphates. Resistance from mutations in the pol gene occurs very rapidly if these agents are used as monotherapy. Its blood levels are decreased by antacids, ddI, phenytoin, rifampin, and nelfinavir. Conversely, the blood levels of delavirdine are increased by azole antifungals and macrolide antibiotics. Delaviridine increases plasma levels of several benzodiazepines, nifedipine, protease inhibitors, quinidine, and warfarin. Delavirdine causes skin rash in up to 20% of patients, and the drug should be avoided in pregnancy because it is teratogenic in animals. Efavirenz is metabolized by hepatic cytochromes P450 and is frequently involved in drug interactions. The drug should be avoided in pregnancy, particularly in the first trimester because fetal abnormalities have been reported in animals at doses similar to those used in humans. Elevations in serum cholesterol, triglycerides, and transaminase levels may occur. Stevens-Johnson syndrome and a life-threatening toxic epidermal necrolysis have also been reported. Nevirapine blood levels are increased by cimetidine and macrolide antibiotics and decreased by enzyme inducers such as rifampin. This viral enzyme cleaves precursor polyproteins to form the final structural proteins of the mature virion core. Resistance is mediated via multiple point mutations in the pol gene; the extent of cross-resistance is variable depending on the specific protease inhibitor. Oral absorption of atazanavir requires an acidic environment-antacid ingestion should be separated by 12. The drug penetrates cerebrospinal and seminal fluids and undergoes biliary elimination. Darunavir contains a sulfonamide moiety and should be used with caution in sulfonamide allergy.
Renal Blood Flow It is the most important factor that is necessary for glomerular filtration breast cancer kd shoes cheap 35 mg fosamax amex. Macula densa of juxtaglomerular apparatus in the terminal portion of thick ascending limb is sensitive to the sodium chloride in the tubular fluid pregnancy first trimester symptoms purchase fosamax 70mg. When the glomerular filtrate passes through the terminal portion of thick ascending segment womens health program buy fosamax 35 mg on line, macula densa acts like a sensor menstruation vs pregnancy symptoms generic fosamax 70mg without prescription. When the concentration of sodium chloride increases in the filtrate essential filtration pressure. Glomerular Capillary Pressure Glomerular filtration rate is directly proportional to glomerular capillary pressure. Capillary pressure, in turn depends upon the renal blood flow and arterial blood pressure. Colloidal Osmotic Pressure Glomerular filtration rate is inversely proportional to colloidal osmotic pressure, which is exerted by plasma proteins in the glomerular capillary blood. Hydrostatic pressure in Bowman capsule increases in conditions like obstruction of urethra and edema of kidney beneath renal capsule. Later when all the substances are filtered from this blood, further filtration does not occur. It is because, the efferent arteriolar constriction prevents outflow of blood from glomerulus and no fresh blood enters the glomerulus for filtration. There are several other factors, which increase or decrease the sensitivity of tubuloglomerular feedback. The Chapter 52 t Urine Formation 319 accordingly, because the autoregulatory mechanism fails beyond this range. Sympathetic Stimulation Afferent and efferent arterioles are supplied by sympathetic nerves. Strong sympathetic stimulation causes severe constriction of the blood vessels by releasing the neurotransmitter substance, noradrenaline. The effect is more severe on the efferent arterioles than on the afferent arterioles. If the glomerular capillary membrane is affected as in the cases of some renal diseases, the surface area for filtration decreases. In many abnormal conditions like hypoxia, lack of blood supply, presence of toxic agents, etc. Contraction of Glomerular Mesangial Cells Glomerular mesangial cells are situated in between the glomerular capillaries. When the glomerular filtrate flows through the tubular portion of nephron, both quantitative and qualitative changes occur. Large quantity of water (more than 99%), electrolytes and other substances are reabsorbed by the tubular epithelial cells. Since the substances are taken back into the blood from the glomerular filtrate, the entire process is called tubular reabsorption. Micropuncture Technique A micropipette is inserted into the Bowman capsule and different parts of tubular portion in the nephrons of experimental animals, to collect the fluid. The fluid samples are analyzed and compared with each other to assess the changes in different parts of nephron. Stop-flow Method Ureter is obstructed so that the back pressure rises and stops the glomerular filtration. It causes some changes in the fluid present in different parts of the tubular portion. Successive samples contain the fluid from distal convoluted tubule, loops of Henle and proximal convoluted tubule respectively. Essential substances such as glucose, amino acids and vitamins are completely reabsorbed from renal tubule. Whereas the unwanted substances like metabolic waste products are not reabsorbed and excreted through urine.
