pathophysio Flashcards
Muscle fibers surrounding the heart are oriented ____ which allows ____.
- circular, longitudinal, oblique
- blood to be squeezed from apex to base
cardiac output =
HR x SV
volume per min
flow
Q =∆P/R
mean arterial pressure
DP + [(SP-DP)/3]
myocardial cell types
- pacemaker: automatically depolarize
- non-pacemaker (majority): depolarize when stimulated
pacemaker cell potentials consist of:
- phase 4 depolarization: slow rise to threshold
- action potential
- repolarization
phase 4 depolarization involves:
- decreased outward flow of K
- **funny current influx of Na
- gradual influx of Ca as threshold approached
myocyte depolarization involves:
- vg Ca channel opening and influx of Ca
myocyte repolarization involves:
- Ca channels close
- K channels open
PNS ____ HR by ____.
- slows
- slowing hyperpolarization and slowing phase 4 (decreased If ICa)
SNS ____ HR by ____.
- increases (also force)
- increases phase 4 rate (increased If and ICa) and decreasing threshold
+ ionotropic effect
- increase HR and force of contraction due to increased intracellular Ca
non-pacemaker cell action potential
- phase 0: rapid influx of Na
- phase 1: inactivation of Na channel and open K channel
- phase 2: plateau (Ca K balanced); Ca influx, slow K out
- phase 3: Ca close, K predominates
- phase 4: resting phase
the slowest conduction velocity
travels through the AV node
P wave
- atrial depolarization following SA node firing
QRS complex
- ventricular depolarization
- atrial repolarization
T wave
- ventricular repolarization
PR segment
- time to pass through AV node
QT interval
- duration of ventricular AP
normal axis:
left axis deviation:
right axis deviation:
-30 to +90
< -30
> +90
pulmonary wedge pressure estimates
- left atrial pressure
ventricular systole begins with ____ and ends with ____.
- mitral valve closure
- aortic valve closure
atrial pressure waves
- a: atrial systole
- c: mitral valve closure
- v: atrial filling and emptying
stroke volume =
EDV-ESV
end diastolic volume
- volume in ventricle just before contraction
end systolic volume
- volume in ventricle right after contraction
S1
- closure of mitral and tricuspid valves
- c wave
S2
- closure of aortic and pulmonic valves
S3
- diastolic; kentucky
- during rapid filling, v wave
S3
- diastolic; tennessee
- vibration of ventricular walls in atrial contraction, a wave
systolic murmurs
- aortic/pulmonary stenosis, mitral/tricuspid regurgitation, VSD
diastolic murmurs
- aortic/pulmonary regurgitation, mitral/tricuspid stenosis
continuous murmurs
- patent ductus arteriosis
L heart pressures are ____ than R heart pressures.
greater
pressure volume loop: axes
- x: left ventricular volume
- y: left ventricular pressure
pressure volume loops: phases
- moves counter clockwise
- a: ventricular filling (mitral valve open/close)
- b: isovolumetric contraction
- c: ejection of sv (aortic valve open/close)
- d: isovolumetric relaxation
pressure volume loop: width and area
- width = SV = EDV-ESV
- area = stroke work = SV * MAP
ejection fraction
SV/EDV
SV is affected by
- preload (increases EDV and Sv)
- afterload (increase ESV, decreases SV)
- contractility (inotropy) (decreases ESV, increases SV)
preload
- stretch of cardiac myocyte prior to contraction
- maximized at EDV
heterometric regulation
- regulation of cardiac function via changing sarcomere length (i.e. preload)
afterload
- load against which heart muscle contracts to eject blood (aortic or pulmonary pressure and ventricular wall stress)
homeometric regulation
- regulation of cardiac function independent of sarcomere length (i.e. afterload)
positive inotropic effects result from:
- increased rate of delivery of Ca to myofibrils
- increased binding of Ca to troponin c
- increased rate of cross-bridge cycling
- increased HR (increased Ca)
loss of arterial compliance means that systolic pressure ____ and capillary flow ____.
- rises
- becomes pulsatile
largest pressure drop is associated with ____. 3 functions are:
- arterioles
- reduce blood pressure at capillary entrance
- distribution of blood flow between/within tissues
- dampens pressure pulses
autoregulation allows:
- local/regional control of blood flow without ANS involvement
- so tissue blood flow remains constant in spite of arterial pressure changes
distribution of blood flow between tissues is aided by:
- muscular walls of arterioles
- metarterioles
- precapillary sphincters (direct blood flow)
causes of edema
- increased venous pressure (hydrostatic)
- decreased blood osmotic pressure
- increased interstitial osmotic pressure
factors that increase O2 demand of heart
- increased afterload
- increased SV
- increased HR
How is O2 delivery to heart increased?
- increasing coronary circulation
- autoregulation with adenosine
coronary blood flow in left ventricle occurs primarily during ____.
- diastole
velocity varies ___ with total cross sectional area. slowest velocity is in ____.
- inversely
- capillaries
ERP
- plateau phase
- limits frequency of AP and avoids tetany
- allows for ventricular filling
Frank-Starling curve
- x-axis: preload, EDV, EDP, sarcomere length, venous return
- y-axis: contractile force, SV
baroreceptor signaling functions between MAP of:
- 75-150 mmHg
response to increased O2 demand
- increased afterload
- increased SV
- increased hr
