By E. Khabir. University of Texas at Dallas.
A special division of the nervous system is the enteric nervous system discount malegra fxt 140 mg on-line impotence grounds for annulment philippines, which is responsible for controlling the digestive organs generic malegra fxt 140 mg overnight delivery erectile dysfunction doctors in ny. The enteric nervous system is exclusively found in the periphery because it is the nervous tissue in the organs of the digestive system. Signals are received at the dendrites, are passed along the cell body, and propagate along the axon towards the target, which may be another neuron, muscle tissue, or a gland. Several types of glial cells are found in the nervous system, and they can be categorized by the anatomical division in which they are found. Astrocytes are important for maintaining the chemical environment around the neuron and are crucial for regulating the blood-brain barrier. The sensory endings in the skin initiate an electrical signal that travels along the sensory axon within a nerve into the spinal cord, where it synapses with a neuron in the gray matter of the spinal cord. The temperature information represented in that electrical signal is passed to the next neuron by a chemical signal that diffuses across the small gap of the synapse and initiates a new electrical signal in the target cell. That signal travels through the sensory pathway to the brain, passing through the thalamus, where conscious perception of the water temperature is made possible by the cerebral cortex. Following integration of that information with other cognitive processes and sensory information, the brain sends a command back down to the spinal cord to initiate a motor response by controlling a skeletal muscle. The upper motor neuron has its cell body in the cerebral cortex and synapses on a cell in the gray matter of the spinal cord. The lower motor neuron is that cell in the gray matter of the spinal cord and its axon extends into the periphery where it synapses with a skeletal muscle in a neuromuscular junction. Transmembrane ion channels regulate when ions can move in or out of the cell, so that a precise signal is generated. This signal is the action potential which has a very characteristic shape based on voltage changes across the membrane in a given time period. A stimulus will start the depolarization of the membrane, and voltage-gated channels will result in further depolarization followed by repolarization of the membrane. Once that channel has returned to its resting state, a new action potential + is possible, but it must be started by a relatively stronger stimulus to overcome the K leaving the cell. The action potential travels down the axon as voltage-gated ion channels are opened by the spreading depolarization. In unmyelinated axons, this happens in a continuous fashion because there are voltage-gated channels throughout the membrane. In myelinated axons, propagation is described as saltatory because voltage-gated channels are only found at the nodes of Ranvier and the electrical events seem to “jump” from one node to the next. Saltatory conduction is faster than continuous conduction, meaning that myelinated axons propagate their signals faster. The diameter of the axon also makes a difference as ions diffusing within the cell have less resistance in a wider space. For a neuron to generate an action potential, it needs to receive input from another source, either another neuron or a sensory stimulus. That input will result in opening ion channels in the neuron, resulting in a graded potential based on the strength of the stimulus. Graded potentials can be depolarizing or hyperpolarizing and can summate to affect the probability of the neuron reaching threshold. If the sensory stimulus is received by the dendrites of a unipolar sensory neuron, such as the sensory neuron ending in the skin, the graded potential is called a generator potential because it can directly generate the action potential in the initial segment of the axon. If the sensory stimulus is received by a specialized sensory receptor cell, the graded potential is called a receptor potential. At a chemical synapse, neurotransmitter is released from the presynaptic element and diffuses across the synaptic cleft. The neurotransmitter must be inactivated or removed from the synaptic cleft so that the stimulus is limited in time. The particular characteristics of a synapse vary based on the neurotransmitter system produced by that neuron. The cholinergic system is found at the neuromuscular junction and in certain places within the nervous system. Other neurotransmitters are the result of amino acids being enzymatically changed, as in the biogenic amines, or being covalently bonded together, as in the neuropeptides.
Studies indicate that the incidence of (38) recurrent renal colic decreases with administration of diclofenac sodium order 140mg malegra fxt fast delivery erectile dysfunction doctors in massachusetts. When the pain is unremitting the treating urologist should think of alternative measures such as drainage by stenting or percutaneous nephrostomy or even removal of the stone buy discount malegra fxt 140mg varicocele causes erectile dysfunction. The prerequisite for this approach is that the patient should be comfortable this approach. Studies indicate that alpha blockers facilitate ureteral passage ,while nifedipine provides marginal benefit. Patients who opt for Medical expulsion therapy should have well controlled pain, no evidence of sepsis, and adequate functional reserve, such patients should be periodically observed for stone position and assessment of hydronephrosis. Anomalous kidneys These group of patients include those patients with stones in ectopic, horseshoe or kidneys with fusion anomalies. The factors to be taken into consideration are the stone bulk, the location of the stone, the vascular and the anatomy of the pelvicalyceal system. Ultrasound helps in gaining access in ectopic kidney apart from being a diagnostic tool. Flexible ureteroscopy will be useful tool in stones small burden stones in size with the availability of smaller flexible ureteroscopes, and access sheaths. However the surgeon should consider complete “on table” clearance in these patients as the drainage is likely to be impaired. Who does what/ and timeline Doctor 32 The treating doctor ideally should be an Urologist or a surgeon trained in Urology. He is responsible for the initial workup of the patient and subsequent management of the patient. He is responsible for counseling the patient regarding the success rates, complications and possible outcome of any given procedure. All possible treatment options in a given clinical situation should be discussed with the patient. The patient on discharge should be given instructions for follow up and measures (dietary and pharmacologic) to prevent stone recurrence. Nursing and technical staff:-The nursing staff should be trained in the aspect of maintenance and use of endourologic equipment, considering the fragility and cost of these equipments. The technical/nursing staff prepares the trolley and assists the surgeon during the procedure. Referral criteria:- The criterion for referral remains, lack of appropriate infrastructure and expertise at primary level. The indications for referral to tertiary care centre in managing stones disease are:-! The treatment of small non obstructing calyceal calculi in patients with symptoms. The role of ureteral stent placement in the Prevention of steinstrasse J Endourol 1999;13(3):151-5. A prospective multivariate analysis of factors predicting stone disintegration by extracorporeal shock wave lithotripsy: The value of high resolution non contrast computed tomography Eur Urol 2007; 51(6):1688-93. Air pockets trapped during routine coupling in dry head lithotripsy can significantly decrease the delivery of shock wave energy. Lower pole I A prospective randomized trial of extracorporeal shock wave lithotripsy and percutaneous nephrolithotomy for lower pole nephrolithiassis-initial results J Urol 2001;166(6):2072-80. Perioperative antibiotic prophylaxis in ureteroscopic stone removal Eur Urol 2003; 44(1):115-8. Flexible ureterorenoscopy for the treatment of lower pole calyx stones; influence of different lithotripsy probes and stone extraction tools on scope deflection 37 and irrigation flow. Ureteroscopic management Of ureteral calculi:Electrohydraulic versus holmium Yag lithotripsy J Urol 1997;158(4):1357-61. A systematic review of the best available evidence and the strength of that evidence.
The minor routes of excretion are saliva malegra fxt 140mg generic erectile dysfunction red 7, sweat buy 140 mg malegra fxt impotence exercises for men, tears, breast milk, vaginal fluid, nails and hair. The drug that is excreted slowly, the concentration of drug in the body is maintained and the effects of the drug will continue for longer period. Different routes of drug excretion a) Renal excretion: A major part of excretion of chemicals is metabolically unchanged or changed. The function of glomerular filtration and active tubular secretion is to remove drug out of the body, while tubular reabsorption tends to retain the drug. Only the drug which is not bound with the plasma proteins can pass through glomerulus. When the urine is acidic, the degree of ionization of basic drug increase and their reabsorption decreases. Conversely, when the urine is more alkaline, the degree of ionization of acidic drug increases and the reabsorption decreases. Excretion of drugs through bile provides a back up pathway when renal function is impaired. After excretion of drug through bile into intestine, certain amount of drug is reabsorbed into portal vein leading to an enterohepatic cycling which can prolong the action of drug e. Tetracylines which are excreted by biliary tract can be used for treatment of biliary tract infection. The drugs which do not undergo enterohepatic cycle after excretion into the bile are subsequently passed with stool e. The rate of drug excretion through lung depends on the volume of air exchange, depth of respiration, rate of pulmonary blood flow and the drug concentration gradient. Therefore lactating mothers should be cautious about the intake of these drugs because they may enter into baby through breast milk and produce harmful effects in the baby e. Clearance of a drug: It is the volume of plasma cleared of the drug by metabolism (hepatic) and excretion (renal) and other organs. Theoretical Pharmacokinetics Information about the time course of drug absorption, distribution and elimination (pharmacokinetics) can be expressed in mathematical terms and has contributed to our understanding and planning of drug regimens. Pharmacokinetic principles aid in the selection and adjustment of drug-dose schedules. Half life: Half life (t1/2) of a drug is the time taken for the concentration of drug in the blood or plasma to decline to half of original value or the amount of drug in the body to be reduced by 50%. A half-life value can be readily determined for most drugs by administering a dose of the drug to a subject, taking blood samples at various time intervals and then assaying the samples. In most of the cases the rate of disappearance of a drug from the body is reflected in the rate of lowering of its plasma concentration following a single intravenous dose, the plasma concentration of the drug is focused to fall exponentially. With drugs whose elimination is exponential, the biological half – life is independent of the dose, the route of administration and the plasma concentration. Order of kinetics Drugs are used for the treatment of diseases but the modes of administration of drugs are different. For example atenolol is administered once daily where as paracetamol needs 3-4 times administration daily. Morphine is more effective in intramuscular route, and insulin is in subcutaneous route. Drugs usually follow two processes for their phamacokinetic behaviour in the body. The rate at which absorption, distribution, metabolism and excretion occur are proportional to the concentration of drugs i. Zero order kinetic: It is independent of the amount of drug present at the particular sites of drug absorption or elimination. On repeated administration of drug after certain stage it goes on accumulating in the body and leads to toxic reactions. Steady state plasma concentration: When a drug dose is given repeatedly over a given period, a steady state is eventually reached, at which point the amount of drug absorbed is in equilibrium with that eliminated from the body. For example a drug with half life of 6 hours will be expected to be at steady state after more than 24 hours of administration. The pattern of drug accumulation during repeated administration of drug at intervals equal to its elimination half-life. For some drugs, the effects are difficult to measure, toxicity and lack of efficacy are both potential dangers, and/or the therapeutic window is narrow. In these circumstances doses must be adjusted carefully to a desired steady- state concentration by giving loading and maintenance doses.
10 of 10 - Review by E. Khabir
Votes: 155 votes
Total customer reviews: 155