USMLE

Description:	CV 2
Category:	USMLE
Created by:	Asclepius on 2008-10-19

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