CVS Flashcards
What is the trajectory of AP in the heart?
Normally it starts in the SA node, then it is transmitted to the AV node where there is a delay(so ventricle can be filled) and then it spreads in the ventricles via purkinje fibers
What is phase 0 of the AP?
When fast Na channels open and there is depolarization
What is phase 1 of the AP?
When there is a brief repolarization due to efflux of K
What is phase 2 of the AP?
The plateau due to Ca influx and K outflux
What is phase 3 of the AP?
When there is repolarization due to closing of the Ca channels and K efflux
What is phase 4 of the AP?
The membrane resting potential, there is some K leakage
How does the sympathetic NS affect the heart?
It secretes norepinephrine that has positive ionotropic effect, it causes phosphorylation of Ca channels in the sarcolemma (increasing the Ca in IC, increasing force) and phospholamban (stimulates SERCA, causing quicker relaxation, increasing rate). also glycosides inhibit Na-K pump, increasing IC Ca
How does the parasympathetic NS affect the heart?
It releases acetylcholine that binds to muscarinic receptors and decreasing the influx of Ca and Na and increases K channels, decreasing rate and force
_____ Side of the heart is thinner
right
Frank starling law refers to:
the increased pressure in the heart causes higher output, and increase pressure depends on the venous return
What is preload and after load?
preload refers to the amount of blood in left ventricle in the end of diastole, and afterload is the amount of pressure that the heart needs to exert to eject the blood during ventricular contraction.
What is the first sound Lub ?
closing of the mitral valve in the left during ventricular systole (while the aortic valve is open)
What is the second sound dub?
The closing of the aortic valve during diastole of the ventricle (while the mitral valve opens to fill the left ventricle)
Why is the SA node the normal pacemaker?
because its resting membrane potential is unstable due to leaking of Na, causing spontaneous depolarization
Where does the plateau last longest?
in the ventricle
What are 4 unique characteristics of the SA node AP?
unstable resting membrane potential due to Na leakage, AP (phase 0) is caused by Ca influx, the AP has the shortest duration, there is no plateau or brief repolarization (phases 1 and 2)
What are the latent pacemakers?
AV node, AV bundle and purkinje fibers
What are the waves in an ECG?
P is the depolarization of the atria, then there is depolarization of the ventricles (QRS) (while atria repolarization is not shown) then there is repolarization of the ventricles (T)