scilearner

Thanks a lot for your help John It did clear somethings up. I think the water reaction is what confused me. Since water reaction is H20 <---> H+ + OH- Since this reaction has equal concentration of hydrogen ions and hydroxide ions and it is neutral, I thought if a solution has an equal concentration of acid and base it is neutral. Using the same logic I thought since this reaction H2CO3 <-----> H+ +HCO3- has equal concentration of acid (hydrogen ions) and base (bicarbonate) it would be neutral. But after reading your answer I think even though the concentrations are same bicarbonate is a weak base so it only produces little hydroxide ions so there is more acid (H+) in solution, so the solution is acidic. Hence sulfuric acid is a strong acid. So is this concept right 1. If there are equal concentration of acid and base in a solution, it is not neutral but if there are equal concentrations of hydrogen ions and hydroxide ions it is neutral. 2. How is this formula pH + pOH = 14, derived? 3. What property of bicarbonate makes it a weak base. Is there any way I can work it out, or do I simply have to memorise the weak acids and bases. Simply I'm asking is there a way to work out weak acids and bases, or do I have to memorise them. I think the strong acid and strong bases have H+ and OH- in their name, eg HCL, NaOH. Weak acid and bases, seem to need to react with some other molecule such as water to produce bases and acids. Thanks a lot

Hello everyone, I'm really confused. Here is a equation CO2 + H20 <----> H2CO3 <-----> H+ +HCO3- * Now if I increase carbon dioxide I know both both Hydrogen and bicarbonate acid increases 1. Why does this make it more acidic. The thing is what I'm thinking is if a solution has an equal concentration of an acid and base it must be neutral. In this case both hydrogen and bicarbonate have increased in same amounts, shouldn't it be neutral 2. Why is it that in formula, PH is only determined by H+ concentration, Can't we find PH using OH- concentration. 3. The definition of base says it must produce OH ions in solution, bicarbonate is not producing OH ions in solution why is it considered a base? Is carbon dioxide a base or acid? 4. I really don't get what is a weak acid, weak base etc. What is the difference between a weak acid and a base. Isn't a weak acid a base. Thanks

Thanks a lot for the response Clarissa That did clear up most of my questions. Hope you are around the forum, if I have more anaesthesia questionsv I have more questions 3) Since in epidural anesthesia, you only go to epidural space and there is less chance of damaging spinal cord, can't you give it above L1 (Not too high to block resp centre) to achieve anaesthesia in a greater region of the body. Why isn't this done regularly? 4)Is epidural also given at spinal level (meaning below L1) in normal setup? If so what is the basic difference in action between them. I understand the difference in procedure (spinal is just one shot, epidural you can continuosuly administer drugs via catheter), what I'm asking is differenc e in action? 5) If mothers in labour are given epidural, wouldn't the epidural catheter get dislodged when they are moving in pain? Sort of stupid question but just asking.

Hello everyone Here are some questions I have about spinal anaesthesia 1. I know it is usually done below L3 because that is where spinal cord ends and not done above that because spinal cord can get damaged. But can't a really skilled person give it above L3, because subarachnoid space ends before spinal cord? So if he stops at the right time wouldn't it work giving anaesthesia from a higher level. 2. Why does the spinal anaesthetic agent only act below the point it was administered. Can't it diffuse up and affect the whole spinal cord? 3. Why can you achieve higher level anaestheisa (Meaning from chest to toe) from epidural anaesthesia? 4. What is the difference between paraesthesia and numbness. Don't they both mean lack of senastion? Thanks

@Studiot: Thanks for taking your time for that lengthy response. I appreciate it Yes this is also how I understand osmotic pressure, but my question is in addition is there a chemical bonding occuring here. @Enthalpy: Thanks for the response I think you understood my question. So there are no interactions eg polar bonds between colloid and water molecules, which make it harder for water molecules to pass through membrane, because their structure is changed now because they are bound to colloids. So their is no chemistry involved here just physics @Swansont: Thanks for the response But I don't understand your technical terms. The way I understand is when ever one side is more concentrated than the other, concentrated side would naturally seek empty space and even everything out.

Hello everyone, If there is a semi permeable membrane that allows only water to pass through. Also this membrane separates the sides into A and B. There are big molecules like colloids in side A along with water. Side B has only water . What mechanism causes side A to have more osmotic pressure, and thus allow water to flow from side B to A. 1) Is it because the particles are so big , that they physically reduce the interactions of water molecules in side A with the semi permeable membrane. 2) Is it because the colloid create a chemical interaction with water molecules and prevent them from moving away. I just want to know if this osmotic pressure created by a pure physical block (like big guy covering small guy) or an actual chemical interaction (Eg big guy holding the small guy) 3) Is osmotic and oncotic pressure mean same thing. Thanks a lot

Hello everyone, 1) Now in this catheter, how does passing saline through the ballon port inflate the ballon. Are there pores at the end of the tube, which allows fluid to go into the balloon and inflate it. 1) What is the purpose of a 3 way catheter. If you want to clear out an infection I can understand you can send saline through one of the ports, but can't we do the same thing with a 2 way catheter. If we send saline through the ballon port in a 2 way catheter, wouldn't it fill the bladder after inflating the ballon and clear it. 2) Why does a 3 way catheter have 2 ballons as shown in pic. Thanks

Hello everyone, Lets say there is a membrane, which has a channel for the solute(eg sodium) and another channel for water Now if I have a hypertonic (more sodium) solution in side A, and hypotonic (less sodium) solution in side B. Which way would water go? * I'm very confused here diffusion and osmosis both occuring. Does water follow sodium or sodium follows water? Thanks

Hello everyone I still don't understand crystalloids 1) Lets say someone lost 100 ml of blood due to accident. If you are giving crystalloid therapy, why do you have to infuse 3 times the amount. What I think is when you give crystalloids IV, they go into extravascular and intravascular compartments also, not just stay in plasma . But my question is let's say I give 100 ml of crystalloid to this person, then wouldn't the patients body try to retain this 100 ml in plasma because now the hydrostatic pressures have changed due to the blood loss, shouldn't the body compensate and try to keep this in plasma. In that case why should you infuse 3 times the amount. In normal circumstances I can understand this fluid getting distributed in all the compartments. 2) Why exactly do crytalloid not stay in plasma when you infuse them. *Do they move out due to normal hydrostatic presurre *Or do they move out due to tonicity. More salt so water is sucked out from intracellular into plasma. Shouldn't this expand plasma volume. * When they move out do they distribute in ICF and ECF like in normal water composition in the body, meaning 2/3 ICF and 1/3 ECF. Thanks a lot

Hello everyone, Why do you need to create an arterio venous fistula for haemodialysis? I don't understand how it makes a good access site for dialysis. Also when not performing dialysis, wouldn't this AV fistula be bad for the body. The deoxygenated and venous blood with all its wastes mixing with arterial blood due to fistula (I'm assuming due to higher pressure in arteries, arterial blood flows to veins not vise versa but still isn't it bad for arterial blood to get mixed with venous). Also in dialysis why should the blood be pumped back into the person, isn't their a way to filter it right at the start, pumping blood back would make the person more prone to infection. Thanks :smile:

As John Cuthber has mentioned I was asking about the physics aspect of this question. I understand it somewhat after reading the articles you guys mentioned. This is how I understood it, I have highlighted the questions I have 1. Ok if a person just has a pneumothorax, you can use the water seal chamber only. If you use a drain with no water, air will go back into pleural place in inspiration . Water acts as a valve. Water can go back into pleural cavity in inspiration, but that would not happen it to gravity and long length of tube. So it would only rise a bit. My question here is if you just use a water seal chamber should it be opened to the atmosphere to prevent air pressure increasing in seal. 2. If a person has a haemothorax also, you can't use this method because, blood and water would collect in chamber and fluid level will rise altering pressure differences I think. I'm not exactly clear about the reason here can anyone explain it. 3. So you use 3 way chamber. This is how I think it works * During expiration air and fluid(eg blood) drain into tube. * Fluid collects in collection tube, air goes to water seal * Suction tube enhances the capacity to suck air. Can this system work without suction? 4. My question is what happens if you have a chamber with collection and water seal, but no suction. Then should the water seal tube be opened to the atomsphere, if not wouldn't the pressure increase causing fluid to flow back. Thanks again

Hello guys, Ok lets say there is a man with fluid in his lungs. You put a chest drain (intercostal tube). How does it drain? 1. Since the container is below the chest, when the guy expirates due to high pressure does fluid just flow to container? Can there be any retrograde flow (since container is below on the floor does gravity prevent this) 2. The article I read says with intercostal tubes, look at the water level of the container. In inspiration it must rise, and it must fall in expiration. If this doesn't happen tube is not working. What water are they talking about and also why does this phenomenon happen. Thanks :smile:

Hello, Here is single edged knife. Consider spine= blunt end blade belly = sharp cutting edge Here is the wound Now the really pointed end at the left side of the wound, is it created by blade tip or the blade belly (sharp cutting edge). This might be obvious but I'm bit confused at how this wound is created, when I look at double edged wounds. Thanks Double edged left, single edged right.

Hi everyone, I know it sounds obvious. But in cerbral oedema lets say due to vasgenic cause,the problem is cerebral vessels becoming more permeable and leaking out blood to extravascular compartment. Now how does the brain get bigger due to this. I mean for brain to get bigger, the intracellular fluid volume of brain cells must increase. So when these capillaries leak blood out, do near by brain cells absorb these water, increasing their intracellular volume and as a result we get enlarged brain? or does this leaked out fluid get stuck in brain interstitium making it bigger. I hope u understand my confusion, because leaking out fluid must make brain smaller otherwise. Thanks

Hello everyone, You usually get pulmonary oedema in conditions such as Left heart failure, where there is increased back pressure in pulmonary vasculature, which in turn increase hydrostatic pressure and then fluid in alveoli giving rise to the condition. Now my question is this fluid in alveoli is a transduate it does not contain blood, however the classic symptom of this condition is pink frothy sputum which indicates blood. Why is this the case. Thanks

Ok in metabolic acidosis, renal compensation is increase in aldosterone, which cause hydrogen and potassium excretion leading to hypokalemia. But in metabolic acidosis transcellular movement occurs and there is hyperkalemia. What is the final result for potassium level. Hyper or hypo?

Hi guys, I know this is a simple question. But when an artery is blocked it is easier to understand because, less oxygen goes to tissue so, necrosis of tissue. But when a vein is blocked, only the draining is affected, the arteries are still able to supply oxygen, but why does necrosis still occur. I'm assuming it is because when a vein is blocked, it leads to congestion, increased back pressure, which makes it difficult for arterial blood to come and perfuse tissue. Just asked to clarify (I know this is probably a pretty obvious stupid question, but I like to get it clarified). Thanks While we are at it, if u know something about this, please tell me Does the pathogenesis of cerebral venous infarction differ considerably from the pathogenesis of cerebral arterial ischemic infarction. Why does a haemorrhagic infarct occur in cerbral venous infarction.

Hi Gees, Welcome to the forum . Why is your question not on philosophy forum, that way you would get more responses http://www.scienceforums.net/forum/102-general-philosophy/ Unfortunately I fall into your e- category so I can not help. I liked ur categories though I don't know how the mind is formed, but if u want to know how it works, buddhism has some really nice ideas (u probably have already researched the area, it may or not interest you ). Anyhow that is all I have to add to this

Hi, Generally if u see a post mortem skull after a rifle shot injury, exit wound is bigger than entry wound. Shouldn't the bullet lose lots of its energy when coming out, hence smaller wound. Maybe it is spinning or something, but I want to get others views. Thanks

Hello, I'm simply confused how effective is giving aspirin in various cardiac disorder? Ok someone develops severe chest pain, presents to hospital within 3 hours due to MI?Is there any use in giving aspirin. I know aspirin disaggregates platelets, and this is primary haemostasis. Now within 3 hours I believe primary haemostasis is already done, so is their any point in giving aspirin. What I'm basically asking is how long does primary and secondary haemostasis take and also lets say a full thrombus was formed then is the only choice available is to lyse it with streptokinase, or does aspirin have an effect even after a full thrombus is formed. Then having said all that and if they are only true only use I can see of aspirin is prophylaxis in cardiac disorders or very early MI. Thanks

Thanks CharonY again I think I got it this time, tell me if I misunderstood again. 1) Ok so I give iodine, T4 production increases' 2) I give lots of iodine, lots of T4 produced. 3) This increase in T4, leads to feedback control and low level of TSH 4) Now less TSH mean less proliferation and less vascularity--- purpose served 5) Mean time high iodinee also inhibits organification of idoine, which is not related to the feedback system, but another protective measure I know it is not clear cut like this, but for basic understanding is this right My question then is if iodine is given before surgery to decrease vascularity and the way iodine does that is by increasing production of thyroxine, isn't that bad for patient who has hyperthyroidism wouldn't it exacerbate the symptoms. If u have hypothyroidism this seems like a good methods. But as CharonY mentioned it makes me think since so many thyroid disorders mess up the feedback system, why is iodine given at all before surgery to reduce vascularity, it might have no effect at all. Also how long does it take for iodine to produce high levels of thyroxine to decrease TSH?

Thanks for the reply CharonY, but I still don't understand where I went wrong. I understand the feedback system 1) I know iodine is needed for thyroxine production, but according to "wolf-chaikoff" effect, iodine in high doses actually deplete the production of thyroxine 2) This means we give high doses of iodine, free T4 would decrease, this mean due to feedback TSH would increase. 3) Now high TSH increases the vascularity of the gland. But high iodine concentration is given before thyroid surgery to decrease vascularity of the gland. Now how can high iodine do that in presence of high TSH? I get the feeling you know all this, and I may have misunderstood what you are saying. So please explain again where I went wrong. Thanks

Hi, If you give high doses of iodine thyroid hormone synthesis decreases. This means TSH level must increase. TSH function is to cause hyperplasia of the gland and increase vascularity of the gland. So how can iodine decrease vasculariy, when TSH is there to counter it. Thanks

Hi, Is it because around central vein, there is only deoxygenated blood from the vein where as in the periphery there is hepatic artery. Also why does eclampsia cause zone 1 necrosis. Thanks

Ok I see, it is just the appearance they are talking about. Thanks