heart valves and cardiac cycle + pace makers and action potentials Flashcards
S1 sound is closure of which valves
AV valves (Tricuspid and mitral)
S2 sound is closure of
aortic and pulmonic valves
S3 occurs when in diastole and why
early, from a sudden deceleration of blood flow into left ventricle from the left atrium
S4 late or early in diastole
late diastole,
Occurs in ventricular non-compliance
stenosis = late in diastole
regurgitation = early in diastole
both are characterized by
stenosis = narrowing/thinning of the valves
regurgitation = valve can not close properly, allowing for blood flow
stroke volume =
volume of blood pumped out of the L ventricle during systolic cardiac contraction
3 factors that affect stroke volume
contractility, afterload, and preload
increase with contractility and preload
decrease with afterload
Which ions increase contractility (SV)
o Catecholamine stimulation via B1 receptor (-> Ca2+ release)
o Intracellular [Ca2+]
o Intracellular [Na+] (due to activity of Na+/Ca2+ exchanger)
Contractility decreases with
o Extracellular [Na+] (due to activity of Na+/Ca2+ exchanger)
o B1-blockade
o HF with systolic dysfunction
o Acidosis
o Hypoxemia/hypercapnia
preload depends on which 2 factors
venous tone
circulating volume
afterload depends on which 2 things
wall tension (more wall tension = more afterload)
hypertension
myocardial oxygen demand depends on: contractility, afterload, and what else (2 more)
HR
Ventricular wall tension
cardiac output =
= SV + HR
name the phases of the cardiac cell cycle (7)
- Atrial contraction
Systole - Isovolumetric contraction
- Rapid ventricular ejection
- Reduced ventricular ejection
Diastole - Isovolumetric ventricular relaxation
- Rapid ventricular filling
- Reduced ventricular filling
atrial contraction = SA node or AV node firing
starts with SA node firing
atrial contraction = which wave on ECG
P wave
atrial contraction = contraction of both L and R atria T or F
T
Isovolumetric Contraction on the ECG
QRS complex
Isovolumetric Contraction: ventricle pressure exceed or decrease compared to atria
exceed pressure in the atria
why is blood volume constant in the ventricles during Isovolumetric Contraction
the AV valves and the semilunar valves are closed, so the blood volume within the ventricles stay the same
rapid ventricular ejection = semilunar valves open
explain why (pressure in the Ventricle, aorata, and pulmonary artery
pressure in the ventricles exceed the pressure in the aorta and pulmonary arteries, so the semilunar valves open
sudden ejection of blood from the ventricles also known as what stage of cardiac cycle
rapid ventricular ejection
Reduced ventricular ejection corresponds with what on ECG
T wave
how does reduced ventricular ejection differ from RAPID ventricular ejection
blood outflow in reduced is not due to contraction BUT inertial energy of the blood
so blood moves out at a slower rate
during ventricular diastole does aortic valve or pulmonary valve close first
aortic valve closes first
ventricular diastole = which wave on ECG
END of T wave
dicrotic notch is caused by
a fall in the aortic pressure, bc Blood starts to flow back from the aorta to the ventricles due to the fall in pressure in the ventricles
in Isovolumetric ventricular relaxation which valves are open
NONE
ISOvolumetric = valves are always shut
in Rapid ventricular filling explain pressure bw atria and ventricles
the atrial pressure exceeds the ventricular pressure
when (stage of cardiac cycle) would you likely hear S3 sounds
Rapid ventricular filling due to volume overload or ventricular dilation
explain Reduced ventricular filling
Most of the blood in the ventricles comes from passive filling (before the atria contract)
what are pacemaker cells
cardiac cells that can spontaneously create action potentials
SA node a primary or latent pacemaker cell?
primary (only primary pacemaker)
SA node rate = 60-100bpm
AV node = ?
40-60bpm
why is it important that the AV node depolarize slower than SA node
bc it allows ventricles to contract after filling with blood
location of bundle of His
through septum bw ventricles - dividing into L and R branches
do Purkinje fibers depolarize slowly or rapidly to assure that both ventricles contract at the same time
rapidly
bundle of His and Purkinje fibers bpm =
40-60bpm
Action Potential Phases in Pacemaker Cells
(three phases)
(phase 4): Slow depolarization
(phase 0) Rapid depolarization
(phase 3) Repolarization
explain Slow depolarization
- (phase 4) Slow depolarization - sodium moves into cell through channels that open in response to hyperpolarization, and slowly depolarizes cell until threshold potential is met
explain (phase 0) Rapid depolarization
strong inward calcium current, responsible for rapid depolarization
explain (phase 3) Repolarization
strong potassium current moves out of cell; responsible for repolarization
which law: the greater the diastolic filling (preload), the greater the quantity of blood pumped (stroke volume)
Frank-Starling Law
more preload= greater stroke volume
