Physiology Flashcards
How is called absolute volume of blood ejected from LV with each contraction?
stroke volume
How to calculate SV? (since it’s volume - take in equation volume!)
LVEDV - end systolic volume
What is normal stroke volume? in ml
70ml
What is ejection fraction?
Relative volume of blood ejected from the LV with each contraction
How to calculate EF?
SV/LVEDV
Normal value of EF?
50 or more proc
what if difference between SV and CO?
SV - volume of each contraction
CO - volume per minute
How to count CO?
SV x HR
Why equation CO = SVxHR overestimates CO in mitral regurgitation?
because a portion of stroke volume flows backward into the left atrium with each contraction
How is compensated decreased CO in HF?
increased HR
CO=SVxHR.
eg if the heart cannot properly pump blood –> lower volume ejected; therefore need to increase HR
How can calculate CO in two ways?
CO=SVxHR
CO= rate of O2 consumption/arteriovenours O2 content difference
Arterial oxygen content is measured directly from ………..
arterial blood
Mixed venous oxygen content is measured from ………………….
pulmonary arterial blood
What catheter and principle can be used in CO determination?
Pulmonary artery catheter (Swan-Ganz)
Applying the Fick principle
The rate of oxygen consumption can be determined with an oxygen meter by measuring ………..
The rate of disappearance of oxygen in exhaled air.
arteriovenous difference in oxygen content can be calculated by ……….
arterial blood O2 content - venous blood O2 content
Decrease in CO and BP –> reduced stretch of the arterial wall –> reduced baroreceptor firing and ……………….. activation of ……….. nucleus
decreased activation of the solitary nucleus
Decreased activation of the solitary nucleus: sympathetic and parasympathetic outflow?
Increase in sympathetic outflow; decrease in parasympathetic
Result: vasoconstriction and incr. HR and contractility
ANP in decreased baroreceptors firing?
Reduced atrial stretch –> decreased ANP secretion
In hypervolemic states, blood pressure is increased, leading to …….. baroreceptor firing.
increased
In hypervolemia: sympathetic and parasympathetic flow?
Increased baroreceptor firing –> incr. solitary nucleus? –> dec. sympathetic and incr. parasympathetic
Result: decr. vascular tone, HR and contractility
ANP in hypervolemia?
Incr atrial wall stretching –> incr. ANP release –> vasodilation and diuresis
In which artery is carotid sinus?
internal carotic artery just above bifurcation
The carotid sinus reflex has an ………… limb that arises from the baroreceptors in the carotid sinus and travels to the …………. centers via the ……………. a branch of the …………….. nerve (CN IX).
Afferent limb;
medullary centers via the Hering nerve, a branch of the glossopharyngeal nerve (CN IX).
The ………….. limb of the carotid sinus carries parasympathetic impulses via the ………… (CN X)
Efferent limb; vagus nerve (CN X)
Carotid massage: sympathetic and parasympathetic?
Massage –> increased firing –> inhibition of sympathetic and activation of parasympathetic output
Nervus vagus is afferent in ………..
aortic arch
nervus vagus is efferent in ……..
carotid sinus
In carotid sinus hypersensitivity presyncope etc results from overly sensitive receptors that stimulate …………. response to tactile stimulation
stimulate vasovagal response
CSH is most commonly in …………….. (what population). What underlying conditions (2) are risk factors for CSH?
elderly men;
Underlying atherosclerotic disease and prior neck surgery
increased parasympathetic output leads to prolonged ……………….. (eg. ….-…. seconds)
prolonged sinus pause;
3-5 seconds
Decreased sympathetic outflow in CSH causes marked …………………..
Peripheral vasodilation
What 2 components in CSH leads to profound reduction in blood pressure?
Delay in ventricular contraction + decreased systemic vascular resistance
