Term
| what is the cardiac output during maximum VO2? |
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Definition
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Term
| contrast the differences between vagal stimulation and sympathetic stimulation on heart rate. |
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Definition
vagal stimulation results in a very rapid decrease in HR and very rapid return to normal HR upon removal of stimulation
sympathetic stimulation results in a gradual increase in HR and a slow return to normal upon removal of stimulation |
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Term
| compare the effects of sympathetic and parasympathetic blockers on HR. |
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Definition
atropine a chronotropic drug increases HR ramatically by blocking parasympathetic outflow to the heart, and propanolol decreases HR slightly by blocking sympathetic outflow to the heart
adm. of atropine elevates HR dramatically
adm. of propranolol decreases HR slightly
when given after each other they have similar effects |
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Term
| during a resting/stressed state which division of the autonomic nervous system is more active? |
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Definition
parasympathetic is active at rest
sympathetic is active during stressed state |
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Term
| what affect does arterial pressure have on HR? |
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Definition
as arterial pressure increases HR decreases
and as arterial pressure decreases HR increases
the changes are more dramatic near normal BP |
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Term
| where are the baroreceptors located and what do they do? |
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Definition
in the carotid and aortic sinuses, and have low pressure receptors in the RA
they detect changes in BP and send signals to the ANS to alter outflow |
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Term
what happens to HR upon IV infusion and why?
what happens to HR in hypovolemic pt that is given IV fluids and why? |
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Definition
the HR increases initially due to more venous return
pressure change is sensed by RA baroreceptors
hypovolemic pt's HR would decrease, because it was elevated from low blood volume |
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Term
| where are the chemoreceptors located and what do they do? |
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Definition
next to the baroreceptors in the carotid and aortic sinuses
they detect changes in blood CO2, O2, and pH
if O2 and pH go down (CO2 up) they tell the body to breathe, and can also slow HR and cause vasoconstriction to preserve blood to vital organs |
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Term
| define a sinus arrhythmia and the role of the bainbridge reflex. |
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Definition
increase in HR due to inspiration and decrease in HR upon exhalation
inhalation causes an increase in venous return due to vacuum effect, this increases HR, and exhalation would decrease venous return therefore lowering HR |
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Term
| what are the most important controllers of HR on a moment to moment basis? |
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Definition
| baroreceptors and autonomics |
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Term
| what affects do temperature have on HR? |
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Definition
| increased temp causes higher HR |
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Term
| what affect does HR have on cardiac output? |
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Definition
| higher HR increases CO output to a point, but when the HR becomes too rapid the ventricles cannot fill efficiently and CO is reduced |
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Term
| define chronotropism/inotropism. |
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Definition
something that interferes with HR.
something that affects contractility of the heart. |
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Term
| define preload/afterload. |
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Definition
the degree of stretch of heart before contraction (EDV)
the force which the heart contracts against (arterial pressure) |
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Term
| what is the frank-starling mechanism? |
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Definition
| shows that SV increases as the preload on the heart increases, this is caused by an increase in the initial stretching of the heart |
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Term
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Definition
| the muscles ability to generate force, it is independent of preload |
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Term
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Definition
| it is the gradual increase in cardiac muscle contractility upon repeated stimulation due to buildup of intracellular calcium |
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Term
| how do inotropic drugs and heart failure affect stroke volume? |
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Definition
| inotropic drugs increase stroke volume due to increased contractility, and heart failure decreases stroke volume due to a reduced contractility |
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Term
| why does the parasympathetic nervous system have little affect on contractility of the heart? |
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Definition
| because its fibers do not extend to the ventricles, they stop at the SA node |
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Term
| true or false, the slope of the cardiac function curve is a measure of the inotropic state of the heart? |
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Definition
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Term
| what affect does an increased afterload have on contraction velocity? what affect does it have on max velocity? |
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Definition
an increase in afterload decreases contraction velocity, and a decrease in afterload increases velocity without changing V max
increasing contractility increases velocity and V max |
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Term
| what is peak isometric tension? |
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Definition
| the point of maximum afterload in which the muscle is unable to contract and no shortening occurs |
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Term
| what affect does an increased preload have on contraction velocity? what affect does it have on max velocity? |
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Definition
| an increased preload increases velocity without changing V max |
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Term
| describe the pressure volume loop and what affects change the loop? |
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Definition
it compares ventricular pressure and ventricular volume
an increase in preload increases EDV as well as SV
an increase in afterload reduces SV and beginning DV
an increase in SV reduces beginning DV |
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Term
| what does dP/dT max measure? |
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Definition
| it measures the initial slope of ventricular pressure during systole |
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Term
| describe the effect of gravity on venous pressure. |
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Definition
| blood tends to pool in the veins below the sternal angle and drain from the veins above it, this causes higher pressures in the lower veins and lower pressures in the upper veins |
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Term
| true or false, it takes less blood to increase venous pressure than to increase arterial pressure? |
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Definition
| false, it takes more to increase venous pressure |
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Term
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Definition
| those outside the central venous system |
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Term
| what is used to indirectly measure venous pressure and why? |
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Definition
the jugular venous pulse
because there is no valve between atria and veins, therefore the atria and JVP have the same pressure curves |
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Term
| about what pressure will exist in the circulatory system if the heart stopped working and why? what is the cardiac output? |
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Definition
about 7mmHg
because the arterial side is high pressure but low volume, and the venous side is low pressure but high volume
the cardiac output is zero |
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Term
what happens to CVP as cardiac output increases and why?
what happens to cardiac output as CVP increases and why? |
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Definition
it decreases, because there is less venous return
it increases, because there is more preload |
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