Block 46 Flashcards
Coronary steal phenomenon
When myyocardial ischemia is present, drugs like adenosine and dipyridamole which are selective vasodilators for the coronary vessels, causes a redistribution of blood flow through the collateral microvessels and coronary arterioles that can reduce collateral blood flow.
- arterioles within ischemic areas are already maximally dilated prior to drug administration. However use of these agents causes vasodilation of coronary arteries in nonischemic regions. This leads to decreased perfusion pressure within the collateral microvessels supplying the ischemic myocardium diverting blood flow from ischemic areas to nonischemic areas. This phenomenon is called coronary steal and may lead to hypoperfusion and potential worsening of existing ischemia.
- adenosine and dipyridamole are often used in myocardial perfusion imaging studies to simulate the generalized coronary vasodilation caused by exercise. The coronary steal phenomenon induce ischemia in areas of the myocardium perfused by occluded vessels allowing detection of ischemic areas that would otherwise not be seen in resting heart.
Extrinsic allergic asthma
Paroxysmal breathlessness and wheezing in young patients unrelated to aspirin ingestion, inhaled irritants or stress should raise the suspicion for extrinsic allergic asthma.
- sputum microscopy will often show granule containing cell and crystaloid masses which are most likely to be eosinophils and crystalloid bodies are most likely charcot leyden crystals.
- chronic eosinophilic bonhcitis in asthmatics involves bronchial wall infiltration by numerous activated eosinophils, largely in response to IL-5 released by allergen activated Th2 cells.
Alkaptonuria - which conversion pathway is most likely to be deficient
Its an AR disorder of tyrosine metabolism. Deficiency in homogentisic acid dioxygenase block hemogenestic acid metabolism, preventing the conversion of tyrosine to fumarate.
Malignant thyroid nodules papillary
Approx 5-10% of thyroid nodules are cancerous. Malignant causes of thyroid nodules are paipillary (70%) , follicular medullary and anaplastic carcinoma respectively.
-papillary carcinoma cells are charactrized by large with overlapping nuclei containing finely dispersed chromatin , giving them a ground glass appearacne (orpha annie eye). Numerous intranuclear inclusion and grooves can be seen due to invagination of the nuclear membranes.
Psamomma bodies can be seen.
X-linked agammaglobulinemia - histology in lymph nodes
Germinal centers and primary lymphoid follicles dont form due to an absence of B cells.
ANP and BNP action
Its activates guanylate cyclase, which increases intracellular cyclic GMP and leads to downstream phtsiologic effects in various tissues. In the kidney, naturetic peptides promotes afferent glomelular arteriolar vasodilation and efferent arteriolar constrictuon, causing increased GFR, this leads to increased naturesis and diuresis.
-natriuetic peptides also directly inhibit proximal tubular sodium reabsorption and renin secretion. Decreased renin secretion results in reduced angiotensis II and aldosterone levels , further promoting naturiuresis and diuresis.
SA node ions circulation
Automaticity is made possible by slow inward sodium current that occurs during phase 4 of the action potential. Referred to as funny current. This current gradually brings the membrane potential closer to threshold at which point phase 0 depolarization occurs due to a large increase in Ca+ influx. Then phase 3 starts which represent repolarization which is caused by outward potassium current.
Benign lung tumor
The most common benign lung tumor is hamartoma (also called pulmonary chondroma). Its usually found as incidental finding on chest x-ray with the appearance of a well defined coin lesion with popcorn calcifications.
-a hamartoma is an excessive growth of a tissue type native to the organ of involvement. The lung is the most common location. Lung hamartomas often contain islands of mature hyaline cartilage, fat, smooth, muscle and clefts lined by respiratory epithelium.
In case of AV block what is responsible for automaticity in the myocardium
The AV node
Lumbosacral radiculopathy
L2- upper anteriomedial thigh -(weakness) hip flexion (iliopsaos)
L3- lower anterimedial thigh -> hip flexion, hip adduction, knee extension (quadriceps)
L4- lower anterolateral thigh, knee, medial calf & foot -> hip adduction, knee extension (quadriceps) , patellar reflex.
L5- buttocks, posterolateral thigh, anterolateral leg, dorsal foot —> foot dorsoflexion & inversion (tibialis anterior) , foot eversion (peroneus), toe extension (extensor hallucis & digitorum)
S1- buttocks, posterior thigh & calf, lateral foot —> hip extension (gluteus maximus), knee flexion (hamstrings) , foot plantarflexion (gastacnemius) , achilles reflex.
Dihydroergotamine side effects
Is an ergot alkaloid commonly used to treat acute migraine headache. This drug may induce vasospastic angina as it constricts vascular serotonergic receptors. Other possible triggers include cigarette smoking, cocaine/amphetamines and triptans.
Variant angina is caused by transient sudden and significant reduction in the luminal diameter of an epicardial coronary artery due to spasm, leading to brief myocardial ischemia.
Listeria monocytogenes
Facultative intracellular, gram positive rod with distinctive flagellar based tumbling motility typically seen at room temperature but not human body temperatures.
Listeria can multiply in cold temperatures a unique feature that allow it to grow well in refrigerated foods.
-listeriosis most often occurs in immunocompromised adults. The bacteria can access the blood stream following ingestion of contaminated food.
-ampicillin is the treatment.
Repaglinide, nateglinide
Short acting glucose lowering medications. They are functionally similar to sulfonylureas and act by binding to and closing the ATP dependent K+ channel in the pancreatic beta cell membrane, inducing depolarization and L- type calcium channel opening. The increased Ca+ influx stimulates beta cell insulin release.
-their short half life requires frequent dosing, typically with each meal, but may reduce the risk of hypoglycemia. Weight gain is common side effects.
Subclavian steal syndrome
Typically occurs due to hemodynamically significant stenosis of the subclavian artery proximal to the origin of the vertebral artery. Subclavian stenosis is typically caused by ATH, although less common etiology includes takayasu areteritis and complication from heart surgery.
The lowered distal subclavian arterial pressure leads to reversal in blood flow “steal” from contralteral vertebral artery away from brainstem.
Most patients are asymptomatic but when symptoms occur , they are typically related to arm ischemia in the affected extremity or vertebrobasilar insufficiency. Physical examination can show significant difference in brachial SBP between the affected arm and normal arm.
Infusion of ACTH fails to elevate cortisol levels suggests
-primary adrenal insufficiency , low cortisol and aldosterone, the low aldosterone leads to hyponatremia, hyperkalemia, hyperchloremia and non-anion gap metabolic acidosis
Psammoma bodies forming tumors
- Papillary thyroid carcinoma
- Meningioma,
- Mesothelioma
- Papillary serous carcinoma of ovary and endometrium.
Ribavirin mechanism of action
Its an anti viral drug active against number of DNA and RNA viruses. Its currently indicated fr HCV and RSV treatment.
- its a nucleoside antimetabolite drug that interferes with duplication of viral genetic material.
- Ribavirin is phosphorylated ntracellulary by adenosine kinase to ribavirin mono-di- and triphosphate metabolites. When it incorporated into RNA it can pair equally well with either uracil or cytosine.this causes hypermutation during RNA dependent RNA replication which is lethal to RNA viruses.
- direct inhibition of HCV RNA polymerase by rivabirin triphosphate.
Glycolysis with no net ATP , which cell
Erythrocytes can bypass the part in glycolysis that yields ATP (1,3 bisphosphate —> 3-phosphoglycerate) , ratherer, 1,3-bis —> 2,3 BPG —> 3-phosphoglycerate —> no ATP resulted.
Fat embolism
Stain called osmium tetroxide, which imparts a black color to fat is usually used to diagnose it.
- pts may develop respiratory distress, non-focal neurologic disturbance and chest lesions consistent with thrombocytopenia after suffering multiple bone fractures, all features of the fat embolism syndrome.
- fat globules discharged from bone marrow enter the marrow vascular sinusoids and then occlude pulmonary microvessels, impairing gas exchange. Microvascular occlusion in the cerebral white matter, brain stem and spinal cord causes the neurologic manifestation.
- thrombocytopenia is believed to result from platelet adherence to fat.
- systemic activation of LPL and intravascular release of toxic levels of oleic acid.
Uncal herniation
Uncal herniation initially disrupts the ipsilateral oculomotor nerve leading to a fixed dilated pupil with “down and out” eye deviation, however as the herniation progresses, injury to midbrain and upper pons resultss in mid-poisitioned and fixed pupils bilaterally with loss of vestibulocular reflexes.
-Damage to the brainstem at or below the level of the red nucleus usually causes decerebrate(extensor) posturing due to loss of descending excitation to the upper limb flexors and extensor predominance.
