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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
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