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39 Cards in this Set
- Front
- Back
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2 components of cardiac output (CO) |
heart rate x stroke volume |
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normal CO |
4-7 L/min |
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variables with cardiac output |
size of person activity, age, HR, health |
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stroke volume |
the amt of blood ejected with each beat (mL per beat) |
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stroke vol is determined by |
afterload, preload, contractility, ejection fraction |
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ejection fraction |
% of bld in ventricle pumped out every beat (measurement of stroke vol in %) |
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normal ejection fraction |
60-70% |
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goal for heart rate in cardiac patients |
slow the HR for more efficiency & less demand |
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beta 1 receptors |
located in heart stimulated cause increased HR, contractility, excitability
meds- beta blockers, to lower those ^ |
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beta 2 receptors |
located in periph vascular, bronchial, smooth muscle stimulated cause vasodilation & bronchodilation
careful with lung conditions |
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alpha receptors |
located in periph vascular smooth muscle stimulated cause vasocontriction |
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cardio selective meds |
ONLY affects the beta 1 metoprolol atenolol |
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stretch receptors |
in the vena cava and RA sensitive to stretch or pressure chgs- hypovolemia, decreased pressure, increased HR |
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in regards to stretch....decreased volume does what |
increased HR the stretch receptors are not stimulated |
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peripheral chemorecptors |
in aortic arch & carotid arteries
chgs in O2 are a stimulus for increase or decrease in HR |
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decreased O2 level equals....(regarding HR) |
increased HR |
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central chemoreceptors |
respiratory center sensitive to CO2 chgs -hypercapnia (increased CO2) increases HR |
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other controls of HR |
activity emotion- especially greif body temp
all affect metabolic demand |
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preload |
volume in ventricles prior to contraction
aka- end diastolic volume |
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factors that affect preload |
bld volume- < volume= < preload vascular resistance- vasodilation = < preload, vasoconstriction = > preload pt position-gravity decreases preload atrial contraction- loss of atrial kick decreases preload only by a sm amt |
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overall increase in volume equals.... |
increased stretch increased pressure
decrease in volume does opposite |
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IV fluid bolus or blood will do what to preload |
(increase the circulating vol) increase preload |
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starling law of the heart |
the greater the stretch the greater the contraction = greater stroke volume = greater cardiac output (to a certain physiologic point) |
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afterload |
amt of resistance the heart must work (pump) against |
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what does plaque and stenosis do to afterload |
increases afterload lots of O2 being used |
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factors affecting afterload |
diastolic pressure valve function vascular resistance |
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diastolic pressure and afterload |
higher the pressure, higher the afterload = more work for the heart |
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valve function and afterload |
malfunctioning valves increase the work, increases the afterload |
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vascular resistance and afterload |
greater constriction of arteries = higher the afterload |
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overall resistance in the arterial system equals... |
how much afterload |
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what is isovolumetric contraction |
90% of O2 consumed by heart occurs during exertion it takes to overcome afterload |
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what can we look at that reflects the afterload |
diastolic blood pressure |
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contractility |
ability of muscle fibers in myocardium to stretch |
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contractility depends on |
volume, loss of muscle (MI), electrolytes (Ca+), drugs (stimulate/inhibit), hypoxia (depresses contractility) |
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volume and contractility |
*sterlings law* increase in volume, increase in stretch, increase force of contraction |
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increase in HR does what to SV |
decreases SV also decreases preload & CO
less filling time, not enough bld filling ventricle |
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aging and cardiovascular system elasticity |
increases afterload decreased elasticity in walls of bld vessels |
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aging and cardiovascular system calcification/stiffening of valves |
increases afterload |
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#1 reason for hospitalization over the age of 65 |
heart failure |
