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Cardiovascular physiology
misha.pangasa

Front Back

ACE inhibitors and angiotensin II antagonists reduce hypertension by what mechanism?


reduce angiotensin II, aldosterone, decrease blood volume


Acetylcholine activates which channels while simultaneously affecting cAMP?


inward rectifier K channels


Acetylcholine binding to muscarinic cholinergic receptors antagonizes the effects of ____________ and decreases generation of __________.


norepinephrine, cAMP


Afferent signals elicted by increased arterial pressure are sent to the cardiovascular centers via the ______________ and _______________.


carotid sinus, vagus nerves


ANF is secreted by the atria of the heart in response to what?


high blood volume/high arterial pressure


Angiotensin II is a vasodilator or vasoconstrictor?


vasoconstrictor


Aside from the force-length diagram, what other phenomenon explains the fact that pre-load affects contractility?


fibers which are stretched more have a higher affinity for Ca (different isoform of troponin than skeletal muscle)


At ~21 days, blood is flowing in a _________ to _______ direction


caudal to cranial


At ~21 days, the sinus venosus is receiving blood from which three venous locations?


vitelline, umbilical, and cardinal


At what day does vasculogenesis begin?


18


Atropine has what effect on the heart?


it antagonizes acetylcholine, and therefore increases heart rate


b-adrenergic blockers (propranolol) reduce hypertension by what mechanism?


reduce cardiac contractility


Baroreceptor sensing of high arterial pressure will have what effect on heart rate?


decrease


Based on the vascular function curve, arterial constriction will have what effect on cardiac output?


decrease


By what mechanism does angiotensin II work?


increasing concentration of Ca in cytoplasm


By what molecular mechanism does ANF work?


increasing levels of cGMP


Ca channel blockers, a-adrenergic antagonists (phentolamine), and K channel openers act to reduce hypertension by what mechanism?


relaxing smooth muscle


CO2 acts directly and locally on blood vessels as a ______________, but in response to cerebral ischemia, it acts as a ______________.


vasodilator, vasoconstrictor


Concentric hypertrophy would follow from which pathological conditions?


hypertension, strength training


Correlate the outflow track, inflow track, and ventricular cells with their corresponding progenitor regions in the primitive streak.


outflow track - cranial, inflow track - caudal, ventricular cells - midstreak


Definition of stroke volume?


volume of blood ejected from the ventricle with each beat


Differentiate between the mechanisms of Ca+ release from the SR in skeletal versus cardiac muscle


skeletal - dihydropyridine receptors are mechanically linked to an SR gate, cardiac - influxed Ca opens the SR gate


diurectics (furosemide, thiazides) reduce hypertension by what mechanism?


increase urine output, decrease blood volume


During isovolumetric ventricular relaxation and contraction, all valves are _______.


closed


During large losses of blood volume (hemorrhage), large amounts of ___________ are secreted, causing peripheral vasoconstriction.


vasopressin (antidiuretic hormone)


Eccentric hypertrophy would follow from which pathological condition?


aortic insufficiency


Even though the forces generated in the R ventricle are smaller than the L, stroke volume is approximately the same because ________________


pulmonary resistance is low


Formula for stroke volume


end diastolic volume - end systolic volume


From wher edoes the vasomotor center receive signals?


higher center (emotions) and baroreceptors in the aorta and carotid arteries


fusion of the ____________results in the pericardial cavity


2 coelomic cavities


Fusion of the endocardial tubes forms the __________


primitive heart tube


How do you calculate mean arterial pressure?


1/3 systolic + 2/3 diastolic OR diastolic + 1/3 pulse pressure


How do you calculate total peripheral resistance?


[arterial pressure - venous pressure]/cardiac output


How will a blood transfusion effect the vascular function curve?


Shift up


How will a change in blood volume and a change in arterial resistance change the vascular function curve?


shift the curve, change the slope


How will arterial dilation effect the vascular function curve?


Decrease slope


If both the SA and AV nodes fail, the _________ can act as emergency pacemakers because they have a slow but present _______________.


Purkinje fibers, diastolic phase 4 depolarization


If the SA node was damaged due to ischemia, the AV node could take over, but the AV node beats at approximately _______ beats/min as opposed to _______ beats/min from the SA node


44-50, 70


In cardiac muscle, the resting tension is much _______ at normal fiber lengths than in skeletal muscle.


higher


In pressure overlaod hypertrophy, there is predominantly an increase in ______________ which is called ________________.


wall thickness, concentric hypertrophy


In response to decreases in blood pressure, the kidneys will secrete what?


renin


In volume overload hypertrophy there is a predominant increase in ______________, which is called________________.


radius, eccentric hypertrophy


In what layer does vasculogenesis begin?


splanchnic layer of extraembryonic mesoderm


Increased cardiac output will have what effect on venous pressure?


Decrease


Increasing total peripheral resistance will have what effect on cardiac and vascular function curves?


reduce the slope of both


Is ANF a vasodilator or vasoconstrictor?


vasodilator


K channel blocking drugs mimic the effects of what cardiac syndrome?


Long QT syndrome (mutations of select K channels(


Mural stress of the ventricular wall is directly proportional to the _______ of the ventricular chamber and inversely proportional to the __________.


radius, thickness Normal Aortal pressure


Normal blood pressure in R Ventricle


15-25/2-5


Normal L Ventricular pressure


100-130/5-10


Normal mean L atrial pressure


5 - 10


Normal mean pressure in Right Atrium


2-5


Normal mean pulmonary wedge pressure


5 - 10


Normal pressure in pulmonary artery


15-25/7-12


Pacemaker channels are directly activated by which molecule?


cAMP


Parasympathetic action on the heart is mediated by what neurotransmitter?


acetylcholine


Propanolol has what effect on the heart?


it antagonizes the effects of norepinephrine, and therefore decreases the heart rate


Regarding the action potentila of ventricular myocytes, inward rectifier K channels are _________ at rest, causing the cell to ___________.


open, remain at rest


Sympathetic stimulation has what effect on arterioles?


constriction due to b-adrenergic stimulation of smooth muscle cells


The _____________ serves as a shunt enabling oxygenated blood to pass from right to left atria


foramen primum


The beginnings of the muscular ridge for the IVS form from the ________ wall of the endocardium and myocardium.


inferior


The Ca channels are structurally similar to _________ channels.


Na


The counteractive force on the depolarization by voltage gated Ca channel opening is ____________ via _______ channels


K+ efflux via voltage gated K channels


The incomplete partition between atria formed by the overlap of the upper and lower limbs of the septum secundum is known as the __________________.


foramen ovale


The initial repolarization of the ventricular myocyte is aided by the inactivation of _______ channels.


Na


The initial repolarization of the ventricular myocyte is initiated by opening of the _________ channels


voltage activated K


The initial repolarization of the ventricular myocyte is slowed into a plateau due to the opening of ____________ channels.


voltage gated Ca


The main function of the baroreceptor system is ____________


To keep arterial pressure constant and maintain cardiac output in the short term


The major effect of norepinephrine on the heart is to increase the rate of ____________


diastolic depolarization


The neurotransmitter involved in sympathetically increasing the heart rate is


norepinephrine


The phase 3 repolarization in the AP at the SA node is due to what 3 factors?


voltage gated K channels opening, Ca channels inactivating, and Ca channels deactivating bc of hyperpolarization


The precardiac mesoderm becomes the ________ during cranial-caudal-lateral-folding


tubular heart


The propagation through the atria and ventricles requires time because of the ________________, whereas the time taken to traverse the SA and AV nodes are long because of the ____________.


large distance, low velocity


The rate of beating of the Purkinje fibers is _____beats/min.


20


The SA and AV nodes have _____ maximal rates of depolarization (______), whereas the Purkinje fibers depolarize at __________.


low,


The septum primum grows _________ from the ________wall of the atrium toward toward the _________ to divide the primitive atria.


downward, dorsal, fusing AV cushions


The sinus venosus is the primitive ________ tract


inflow


The spread of the action potential over the entire heart requires about _____ milliseconds.


240


The strength of ventricular contraction dependce on the volume at what time?


The end of diastole


The upstroke of the action potential in the SA node is initiated by ________ channels because there are no _________ channels.


Ca, voltage gated Na


The vasomotor center in the medulla of the brain is responsible for what aspect of blood pressure control?


autonomic control of arterial pressure


The ventricular myocyte AP begins when _____ channels open, allowing ___ to rush in.


Na


There are fewer inward rectifier K channels in the ___________


SA node


Two parallel endocardial tubes form by _______ in the rostral splanchnic mesoderm


vasculogenesis


Upstroke velocity is dependent on ___________


types and number of voltage gated ion channels


Usually, positive inotropic effects are accounted for by what?


Inreased availability of Ca for the contractile machinery


What are the 2 effects of acetylcholine on the AP of the SA node?


1) reduce the rate of diastolic depolarization, 2) make the maximal diastolic potential more negative


What are the 3 main effects of angiotensin II?


increasing peripheral resistance by vasoconstriction, promoting synthesis of aldosterone, increasing salt and fluid reabsorption in the proximal nephron


What are the 3 major differences between SA node action potentials and ventricular myocyte Aps?


1) SA node has slower upstroke, 2) plateau phase is less distinct if even existent, 3) no steady resting potential


What are the 3 mechanisms for returning cytoplasmic Ca to low levels during repolarization?


Na-Ca exchanger in plasma membrane, ATP driven Ca effluxer in plasma membrane, ATP driven Ca effluxer in SR


What are the axes of the vascular function curve, and what does the slope correspond to?


x axis - cardiac output, y axis - venous pressure, slope - peripheral resistance


What are the non-Ca mediated mechanisms of norepinephrine''s positive inotropic effect?


phosphorylation of myosin binding protein C, PKA stimulation


What are two ways to increase stroke volume and stroke work?


Increase contractility, increase filling pressure/filling time


What effect does aldosterone have on the kidney?


reabsorption of salt and fluid in the distal nephron


What happens to the Starling curve upon addition of sympathetic stimulation?


shifts up


What hormone acts in opposition to angiotensin II?


ANF


What is a positive inotropic effect on the heart?


Anything that increases the contractility


What is afterload?


Wall stress required for ejection, estimated as systolic aortic pressure


What is cardiac output?


stroke volume x heart rate


What is Laplace''s Law?


total force that tends to stretch the ventricle is equal to the ventricular wall forces that oppose the stretch


What is normal approximate mean arterial pressure?


100


What is preload?


wall stress that balances ventricular pressure just before contraction begins - estimated as ventricular end diastolic pressure


What is pressure diuresis?


When arterial pressure increases, the kidneys increase the amount of fluid excreted as urine


What is pulse pressure?


systolic pressure - diastolic pressure


What is the Bainbridge reflex?


Baroreceptors in the atrium sense atrial stretch and increase venous return, thus eliciting a signal from the ANS to increase HR


What is the definition/formula of ejection fraction?


stroke volume/end-diastolic volume


What is the equation for mural stress?


mural stress = Pr/2d


What is the location of the cellular precursors for the coronary arteries?


proepicardium


What is the location of the cellular precursors for the epithelium and connective tissue of the pericardium, the epicardium, and the intersititial connective tissue of the myocardium?


proepicardium


What is the mechanism of caffeine-mediated positive inotropic effects?


causes release of Ca from the SR through a direct effect on Ca release channels


What is the mechanism of digitalis''s positive inotropic effect on the heart?


inhibition of Na/K pump increases cellular Na, decreases activity of the Na/Ca exchanger, increasing cellular Ca (both cytoplasmic and SR)


What is the molecular mechanism by which norepinephrine increases contractility?


(via cAMP -> PKA) activates plasma membrane Ca channels, Ca release channels in SR, and Ca pump in SR


What is the normal resting value of cardiac output?


5L/min


What is the normal resting value of stroke volume?


~70ml


What is the normal resting value of the ejection fraction?


.5 - .7


What is the order of locations for intraembryonic hematopoeisis?


1st - paraortic clusters in splanchnic mesoderm of AGM region, then liver, then bone marrow


What is the staircase effect?


Increasing the rate of contraction increases the force of contractility


What is the velocity of AP conduction through the SA node, atria, AV node, His/Purkinje fibers, and ventricles?


SA - .05, atria - 1, AV - .03, His/Purkinje - 3.5, ventricles - .4


What kinds of cells form blood islands?


angioblasts (differentiated from mesenchymal cells)


What molecule is primarily responsible for regulation of the SR Ca pump?


phospholamban (PL)


What phenomenon ensures that fibers always operate in the region where tension increases with length?


resting tension increases sharply as the fiber approaches optimal length for contraction


What ratio do Na-Ca exchangers exhibit?


3 Na to 1 Ca


When Na rushes into the cell during the upstroke, ____________ channels close.


inward rectifier K channels


When voltage gated Ca channels open, Ca rushes in or out?


in


When voltage gated K channels close at the SA node, what happens and why?


phase 4 depolarization because of a lack of inward rectifier K channels and presence of pacemaker channels


Where is the mesoderm that surrounds epithelial cells of the yolk sac derived from?


EMT from the yolk sac epithelium


Which cells are the first to produce erythrocytes?


yolk sac cells


Which measurement/parameter is useful in determining ventricular fiber length?


Central Venous Pressure


Which vessels have the highest aggregate resistance?


arterioles


Why does increasing peripheral resistance help during cerebral ischemia?


vessels supplying blood to the brain do not respond strongly to autonomic signals


Why does the cardiac curve have a reduced slope when peripheral resistance increases?


Greater force is required to maintain the same cardiac output


Why does the vascular function curve have a reduced slope when peripheral resistance increases?


Greater arterial-venous pressure differences are required to maintain the same cardiac output


Why is the myocyte in an absolute refractory phase during most of the ventricular AP?


Na channels are inactivated at membrane potentials near zero