Cardiac cycle

Question 1

when does a valve open and close

Answer 1

when the pressure is greater behind the valve

when the pressure is greater in front of valve it closes

Question 2

what is an ECG

Answer 2

a record of the overall spread of electrical activity through the heart

Question 3

describe the ECG

Answer 3

P wave - atrial depolarization

PR segment - AV nodal delay

QRS complex - ventricular depolarization (atria repolarization simultaneously)

ST segment - time during which ventricles are contracting and emptying

T wave - ventricular repolarization

TP interval - time during which ventricles are relaxing and filling

Question 4

describe what happens during mid-diastole

Answer 4

• Atrial and ventricular pressures low
• Ventricles contain ~80% of final filled volume
• Aortic and pulmonary valves closed
• Aortic pressure high

Question 5

describe what happens during late diastole

Answer 5

• P wave of ECG occurs
• Towards end of P wave atria contract - increasing
  atrial pressure - most of the blood in the atria is
  propelled into ventricles - adds ~20% to ventricular
  filling -accompanied by a small increase in
  ventricular pressure
  Volume in each ventricle at end of diastole
  is: ~130 ml - standing
  (~160 ml - lying)

Question 6

what happens during the end of diastole/early systole

Answer 6

QRS complex of ECG begins -start of ventricular
depolarization.
Ventricles contract at end of QRS complex - early
systole.
Rapid increase in ventricular pressure.
AV valves snap shut - first heart sound.
Ventricles contract but both AV and aortic valves are
shut - no blood can enter or leave.
Isovolumetric or Isometric Phase

Question 7

what happens during the ejection period

Answer 7

Ventricular pressure exceeds arterial pressure
aortic and valve pulmonary
valves open.
Blood is ejected into the
aorta and pulmonary artery.
Aortic pressure rises from diastolic minimum
of 80 mmHg to systolic peak of 120 mmHg
(Corresponding pressures in pulmonary artery
are 8 mmHg diastolic and
25 mmHg systolic)

Question 8

what happens at the end of the ventricular

Answer 8

T wave signals ventricular repolarization
Ventricles start to relax - ventricular
pressure falls below aortic pressure - aortic
valve shuts - second heart sound- and Dicrotic notch (incisura) on aortic pressure record AV valves also shut - no blood can enter or leave Isometric Ventricular Relaxation

Question 9

what happens during filling period

Answer 9

Ventricular pressure falls below atrial pressure
AV valves open
Major part of ventricular filling
Blood which entered atria during ventricular systole is released into ventricles by opening of AV
valves
Atrial and ventricular pressures
fall sharply and ventricular
volume increases rapidly

Question 10

what are the 5 major phases of the cardiac cycle

Answer 10

1. Filling period
2. Atrial contraction
3. Isovolumetric ventricular contraction
4. Ejection
5. Isovolumetric ventricular relaxation

Question 11

what generates the heart sounds and how can it be detected

Answer 11

heart action
phonocardiogram

Question 12

what are the 2 distinct heart sounds

Answer 12

1st coincides with the beginning of systole
produced by closure of the AV valves
2nd begins with the onset of diastole - closure of the aortic and pulmonary (semilunar) valves

Question 13

what are Abnormal sounds in pathological conditions known as

Answer 13

murmurs