Which of the following events takes place during atrial systole

Which of the following events takes place during atrial systole

T F

a.The ‘a’ wave in the JVP tracing
b. First heart sound
c. Opening of the aortic valve
d. Isometric phase of ventricular contraction
e.P wave in ECG

Answer
a.T
b.F
c.F
d.F
e.T

Discussion

a. The jugular venous pressure wave

Consist of three peaks

a

c

v

And two decent

x

y

a wave - During atrial systole blood regurgitate into superior vena cava and it produces a wave.
x decent - occurs when atrial contraction finish
c wave - During isovolumetric ventricular contraction , tricuspid valve bulge into the atria and increase atrial pressure . This increases pressure transmit to the great vessels and produce c wave .
v wave - due to increase atrial pressure by venous return during diastole before opening of the tricuspid valve .
y decend - The " y " descent is due to emptying of the atrium into the ventricle following the opening of the tricuspid valve.

b. Heart sound

First heart sound ( S1) –

Due to sudden closure of the AV valves at the start of ventricular systole
Duration - 0.15 s
Frequency - 25 to 45 Hz
Low pitched

Second heart sound ( S2) –

Due to closure of aortic and pulmonary valves just after the end of ventricular systole
High pitched sound
Duration -0.12 s,
Frequency - 50 Hz

Third heart sound ( S3 )

Due to rapid ventricular filling during diastole
Low – pitched sound

Fourth heart sound (S4)

Due to ventricular filling
Heard immediately before the S1

c.
Aortic valve open during ventricular contraction Read Cardiac cycle Revision note

d.
Isovolumetric ventricular contraction start just after atrial systole

e.

ECG Read ECG Revision note

P wave - atrial depolarization

QRS complex ( < 0.12 S) - ventricular depolarization and Atrial repolarization

T wave - ventricular repolarization

PR Interval (< 0.2 s ) - from onset of wave to onset of QRS complex - Due to AV nodal delay

QT Interval - beginning of QRS complex to end of T wave.
-Ventricular depolarization and repolarization

Labels: CVS, CVS MCQ, Physiology MCQ

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