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USMLE
CV 2
| Question | Answer |
|---|---|
| of the total body weight, what proportion is blood? | 8% the rest is body fluids and tissues |
| of the total body blood, what proportion is plasma? | 55% plasma the rest is hematocrit. |
| what is serum? | plasma without clotting factors |
| what is the makeup of plasma? | 91.5% water, 7% protein, salts, lipids, enzymes, and vitamins |
| what is the makeup of plasma proteins? | 55% albumin, 38% globulin, 7% fibrinogen |
| what are the three kinds of cells in hematocrit? | erythrocytes, leukocytes, and platelets |
| what is the typical makeup of WBCs in the blood? | 40-70% PMNS, 20-40% lymphocytes, 2-10% monocytes, 1-6% eosinophils, <1% basophils |
| what is the net filtration pressure | Pnet=[(Pc-Pi)-(πc-πi)] |
| what are 4 common causes edema? | increased capillary pressure, decreased plasma proteins, increased capillary permeability, or increased interstitial colloid pressure |
| what is a common cause of increased capillary pressure | heart failure |
| what is a common cause of decreased plasma proteins | nephrotic syndrome or liver failure |
| what may cause increased capillary permeability? | toxins, infections, burns |
| what could cause increased colloid presure? | lymphatic blockage |
| what are the three structures in the carotid sheath? | internal jugular v. (lateral), common carotid a. (medial), vagus n. (posterior) |
| in most cases, what supplies the SA and AV nodes? | RCA |
| 80% of the time, what supplies the inferior portion of the LV via the PD artery? | RCA (right dominant) |
| when do the coronary arteries fill? | during diastole |
| what supplies the anterior interventricular septum? | LAD |
| what is the most posterior part of the heart? enlargment can cause what? | left atrium; dysphagia |
| what artery gives off large obtuse marginal branches that supply the lateral and posterior walls of the LV? | circumflex |
| what supplies the anterior 2/3 of IV septum, apical portion of anterior papillary muscle, and the anterior surface of the LV? | LAD |
| where does the RCA travel? | in the right AV groove |
| what supplies the inferior and posterior wals of the ventricles and the posterior 1/3 of the IV septum? | posterior descending (typically a branch of RCA) |
| Cardiac output = ? | stroke volume x heart rate |
| what is the Fick principle? | CO = rate of O2 consumption/ (arterial O2 content - venous O2 content) |
| how do you calculate mean arterial pressure? | CO x TPR = 1/3SBP + 2/3 DBP |
| pulse pressure = ? | systolic - diastolic (approx SV) |
| stroke volume = ? | CO/HR = EDV-ESV |
| what variables affect stroke volume? | contractility, afterload, and preload - SV CAP |
| what effect does increased intracellular calcium have on contractility and SV? | increases contractility and SV |
| how does decreased extracellular sodium affect contractility and SV? | increases contractility and SV |
| 5 things that decrease contractility and SV? | B1 block, heart failure, acidosis, hypoxea/hypercapnea, Ca++ channel blockers |
| what effect does digitalis have on contractility and SV? | increases them |
| preload is equal to what volume? | end diastolic volume |
| afterload is equal to what presure? | systolic arterial pressure (proportional to peripheral resistance) |
| what effect do venous dilators (e.g. nitroglycerin) have? | decrease preload |
| what effect do vasodilators (e.g. hydralazine) have? | decrease afterload |
| this increases slightly with exercise, increased blood volume (overtransfusion), and excitement (sympathetics) | preload |
| ejection fraction = ? | SV/EDV = (EDV-ESV)/EDV = index of contractility |
| ejection fraction is normally greater than or equal to? | >55% |
| resistance is directly proportional to what? | viscosity |
| resistance is inversely proportional to what? | radius to the 4th power |
| delta P = ? | Q x R |
| resistance = ? | [delta P/Q]/[8 x viscosity x length x r to the 4th] |
| what does viscosity mostly depend on? when is it increased? | hematocrit: increased in polycythemia, hyperproteinemic states (e.g. multiple myeloma), hereditary spherocytosis |
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Asclepius
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