Cardio

Question 0

QRS complex on an ECG

Answer 0

Depolarisation of the ventricles

Question 1

P-wave on an ECG

Answer 1

Depolarisation of the atria

Question 2

T-wave on an ECG

Answer 2

Repolarisation of ventricles

Question 3

ATRIAL CONTRACTION

Answer 3

Step 1

• Initiated by P wave of ECG
• Valves between atria and ventricles open
• Semilunar valves closed

Question 4

ISOVOLUMETRIC CONTRACTION

Answer 4

Step 2

• Begins with appearance of QRS complex in ECG
• All valves closed
• First heart sound (S1)
• Ventricular pressure rises rapidly without volume change

Question 5

RAPID EJECTION

Answer 5

Step 3

• Blood flows rapidly from ventricles into arteries
• AV valves closed
• Semilunar valves open

Question 6

REDUCED EJECTION

Answer 6

Step 4

• Starts about 200 msec after QRS complex
• Ventricle repolarises
• Tension on ventricle reduces, therefore rate of ejection falls
• Blood flow results mainly from kinetic energy of blood

Question 7

ISOVOLUMETRIC RELAXATION

Answer 7

Step 5

• All valves closed
• Ventricular pressure decreases; rate determined by rate of muscle fiber relaxation
• End-systolic volume ~50ml in left ventricle
• Stroke volume was ~70ml

Question 8

RAPID FILLING

Answer 8

Step 6

• AV valves open
• Semilunar valves closed
• Caused by ventricle relaxation

Question 9

REDUCED FILLING

Answer 9

Step 7

• AV valves open
• Semilunar valves closed
• Ventricles are already considerably relaxed
• At the end of this phase, ventricle is ~90% filled

Question 10

What happens to R-R Interval and HR after excise?

Answer 10

During exercise…

Increase in heart rate corresponds to shortening of the cardiac cycle (R-R Interval decreased)