Cardiovascular physiology IX

1. Apart from Calcium ion influx what is the other cause of a plateau in a pardiac action potential?

Decreased efflux of Potassium ions

2. What is the velocity of conduction of action potential in atrial ad ventricular muscle fibre?

0.2-0.3 s

3. What is the duration of refractory period of the ventricle?

250 – 300 milliseconds (0.25-0.30 s)

4. What is the duration of refractory period in the atria?

150 ms (0.15 s)

5. What is the difference in dimension between the cardiac muscle T-tubule from that of  skeletal muscle?

Cardiac muscle T-tubule is 5 times greater in diameter

6. What is the component that is electronegative and helps to store a greater amount of Calcium ion in the T-tubules of cardiac muscle?

Mucopolysaccharide

7. What is the recording of heart sounds called?

Phonocardiogram

8. What is the normal duration of time lag for the onset of QRS wave after P wave of an ECG?

0.16 s

9. At the period of ejection, the left ventricular pressure increases slightly above 80 mm Hg. What is the pressure increment in the right ventricle?

8-10 mm Hg

10. What connects the papillary muscles to the A-V valves?

Chordae tendineae

(Physiology; UMS 2008)