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    Doctor Ali is offline Senior Member 696 points
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    I'm opening this thread in terms for educational purposes; particular for USMLE Step 1. Everyone is welcome to write, share, comment, and/or give a thought in terms of Medical Education. Again this thread is meant for MEDICAL EDUCATION - NOT meant for thrashing or bashing each. This is for Medical Education Thread and I'm asking to keep it as clean as it suppose to be. When someone wants to start a new topic, it would be a good idea to start with "Did you know?" and from there, start discussing. This is meant to HELP people around for Step 1. All the best!!!!!!
    Last edited by Doctor Ali; 05-05-2012 at 12:09 PM.
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    Doctor Ali is offline Senior Member 696 points
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    Vibrio cholerae (cholera toxin) causes diarrhea by stimulating Cl- ions secretion. Cholera toxin catalyzes adenosine diphosphate (ADP) ribosylation of alpha - s subunit of the Gs protein coupled to adenylyl cyclase, permanently activating it. Intracellualar cAMP increases; as a result, Cl- channels in the luminal member open. Na+ and water follow Cl- into the lumen and lead to secretory diarrhea. Some strains of Escherichia coli cause diarrhea by a similar mechanism.
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    Doctor Ali is offline Senior Member 696 points
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    Cystic fibrosis is a disorder of pancreatic secretion, in lungs, and in liver. Results from a defect in Cl- channels that is caused by a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene on chromosome 7, deletion of Phe 508. Is associated with a deficiency of pancreatic enzymes resulting in malabsorption and steatorrhea. Increase [Cl-] in sweat test is diagnostic.


    An interesting article I found earlier this morning, was this teenage student from Toronto has conducted the research on findings of possible treatment of Cystic fibrosis. Here a link, Teen Discovers Promising Cystic Fibrosis Treatment Enjoy!!!!!
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    Doctor Ali is offline Senior Member 696 points
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    Myasthenia gravis and Graves' disease are sometimes easy to get confuse by students because they each have common phrase ".... the presence of antibodies to.....". So! Let's clarify them so that we would not confuse ourselves in the future.



    Myasthenia gravis
    Is caused by the presence of antibodies to the ACh receptor.
    Is characterized by skeletal muscle weakness and fatigability resulting from a reduced number of ACh receptors on the muscle end plate.
    The size of End Plate Potential (EPP) is reduced; therefore, it is more difficult to depolarize the muscle membrane to threshold and to
    produce action potentials.




    Graves' disease or more proper way of describing is Thyroid - Stimulating immunoglobulins

    Are components of the immunoglobulin G (IgG) fraction of plasma proteins and are antibodies to TSH receptors on the thyroid gland.
    Bind to TSH receptors and, like TSH, stimulate the thyroid gland to secrete T3 and T4.
    Circulate in concentrations in patients with Graves' disease, which is characterized by high circulating levels of thyroid hormones, and, accordingly,low concentrations of TSH (caused by feedback inhibition of thyroid hormones on the anterior pituitary).

    In normal process, Hypothalamus releases TRH. TRH binds on the TRH receptors at Anterior pituitary. Anterior pituitary releases TSH. TSH binds on TSH receptors on the thyroid gland. Thyroid gland then secretes thyroid hormone, T3 and T4, by the follicular cells via an adenylate cyclase - cAMP mechanism. More T4 is synthesized than T3. However, T3 is more biological active. In peripheral tissues, T4 is converted to T3 and rT3 by 5' - iodinase. rT3 is inactive. Because T3 is biological active, T3 down - regulates TRH receptors in the Anterior pituitary and thereby inhibits TSH secretion.
    Last edited by Doctor Ali; 06-27-2011 at 05:26 PM.
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    Doctor Ali is offline Senior Member 696 points
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    Sometimes it’s necessary to inhibit Na+/K+ ATPase (Sodium pump). Why? To increase Cardiac Out!! How? By giving Cardiac glycosides such as Oua**** and digitalis. Mechanism?

    Normal - Sodium pump - Primary Active Transport

    Na+/K+ ATPase (Na+/K+ pump) or (Sodium pump) in cell membranes transports Na+ from intracellular to extracellular fluid and K+ from extracellular to intracellular fluid. It maintains low intracellular [Na+] and high intracellular [K+]. Remember: 3 Na+ goes out and in return 2K+ comes in.



    Normal - Na+ - Ca2+ - Exchanger - Secondary Active Transport

    Many cell membranes contain Na+ - Ca2+ Exchanger that transports Ca2+ "uphill" from low intracellular[Ca2+] to high extracellular [Ca2+]. Ca2+ and Na+ move in opposite directions across the cell membrane. The energy is derived from "downhill" movement of Na+. As with cotransport, the inwardly directed Na+ gradient is maintained by the Na+/K+ pump (Primary Active Transport).


    Cardiac glycosides inhibit the Na+/K+ ATPase (Sodium pump) in the myocardium. The intracellular [Na+] increases, diminishing the Na+ gradient across the cell membrane. Na+ - Ca2+ exchanger depends on the size of the Na+ gradient and thus is diminished, producing an increase in intracellular [Ca2+]. This then increases the contraction of atrial and ventricular myocardium and increases cardiac output.

    Note: Inhibiting or poisoning Na+/K+ pump inhibits entire Secondary Active Transport. Because one of the characteristic of Secondary Active Transport is metabolic energy used indirectly from the Na+ gradient that is maintained across cell membranes. Primary Active Transport won’t affected because there are Ca2+ pump and H+/K+ pump involved too.





    Examples of Primary Active Transport
    1. Na+/K+ pump
    2. Ca2+ ATPase pump
    3. H+/K+ pump






    Examples of Secondary Active Transport
    1. Na+ - Glucose
    2. Na+/K+/2Cl-
    3. Na+ - H+ Exchanger
    4. Na+ - Ca2+ Exchanger
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    McNasty is offline Senior Member 676 points
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    standing and valsalva decrease all murmurs except mitral valve prolapse(MVP) and hypertrophic obstructive cardiomyopathy(HOCP) murmurs

    squatting increases all murmurs except MVP and HOCP

    handgriping increases MVP murmur and decreases HOCP murmur
    4th Year

  7. #7
    pbnj is offline Junior Member 517 points
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    FA 2011- Squatting increases MVP murmur.

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    McNasty's Avatar
    McNasty is offline Senior Member 676 points
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    Quote Originally Posted by pbnj View Post
    FA 2011- Squatting increases MVP murmur.
    it's a typo in FA, download the FA errata from their site and make the necessary corrections Errata | firstaidteam.com

    more clarification, 4th sentence of second paragraph The Auscultation Assistant - Mitral Valve Prolapse
    4th Year

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    pbnj is offline Junior Member 517 points
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    ok great thank you

  10. #10
    Doctor Ali is offline Senior Member 696 points
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    I had opened a Thread titled "First aid 2011 corrections" at USMLE Step 1 FORUM. For those who are using First Aid 2011, there are the corrections that you can fix them in your notes. A most recent updated will be in bottom page 1 and page 2 of the thread.
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