41 Questions
What is the primary factor that modulates the contraction of cardiac muscles?
Ca2+ ions
What is the term for the force of contraction of cardiac muscles?
Inotropy
What is the effect of a negative inotropic effect?
The force of contraction decreases
What is the term for the property of cardiac muscle relaxation?
Lusitropy
What is the effect of a positive lusitropic effect?
The rate of myocardial relaxation increases
What is the term for the heart rate?
Chronotropy
What is the effect of a positive chronotropic effect?
The heart rate increases
What binds to Beta 1 (β1) receptors in the heart?
Norepinephrine
What happens to the left ventricular volume during the isovolumic contraction phase?
It remains the same
What is the result of the rise in pressure during the isovolumic contraction phase?
Opening of the aortic valve
What happens to the aortic flow during the rapid ejection phase?
It increases
What happens to the left ventricular volume during the rapid ejection phase?
It decreases
What is the duration of diastole compared to systole under normal conditions?
It is longer
What is the atrio-ventricular pressure difference needed to open the mitral valve?
Low
What happens to the left ventricular pressure at the beginning of the diastole?
It decreases
What happens to the left ventricular volume during the diastole?
It increases
What is the relationship between heart rate and stroke volume at a normal cardiac output?
Inverse
What is cardiac output determined by?
Heart rate and stroke volume
What happens to stroke volume when heart rate increases?
It decreases
What is the effect of high aortic valve pressure on blood ejection?
It makes blood ejection more difficult
What determines wall stress in the ventricle?
Law of Laplace
What happens to the ventricular muscle when there is an increase in arterial pressure and/or wall stress?
It must exert greater force
In what condition does wall stress have a significant effect on afterload?
All of the above
What is the formula for cardiac output?
CO = HR x SV
What is the effect of increased sympathetic activation on heart rate?
It increases
What percentage of Ca2+ is reuptaken by SERCA in sarcoplasm?
80%
What is the volume of blood in the left ventricle before systole?
EDV
What is the function of the Na-Ca exchanger in cardiac muscle cells?
Transports Ca2+ from inside to outside in exchange with Na+
What is the formula to calculate cardiac output?
HR x SV
Which event in the cardiac cycle corresponds to Phase 2?
Isovolumetric Ventricular Contraction
What is the effect of endurance training on heart rate?
It decreases
What is the percentage of blood pumped out of the left ventricle in each contraction?
67%
What is the characteristic of the PV curve during diastole?
Flat/less steep curve
What happens to the ventricles during diastole?
They become less distensible
What is the stroke volume if the EDV is 150 mL and ESV is 50 mL?
100 mL
What is the result of a large increase in volume during diastole?
Low pressure change
What is the cardiac output if the heart rate is 55 bpm and stroke volume is 100 mL?
5500 mL/min
What is the volume of blood left in the left ventricle after systole?
ESV
What is the function of Ca2+-ATPase in cardiac muscle cells?
Pumps Ca2+ out of the cell
What is the characteristic of the PV curve during systole?
Steep curve
What is the result of a small increase in volume during systole?
High pressure change
This quiz explores the physiology of cardiac muscles, including factors that modulate ECC, the role of Ca2+ ions, and the concepts of inotropy and lusitropy. Understand how these mechanisms differ from skeletal muscles.
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