Cardiac Cycle Flashcards
(30 cards)
What is meant by end-diastolic volume?
Maximum volume of blood in the heart just before ventricles contract and at this point are relaxed?
What is meant by End-systolic volume?
The residual volume left in the heart following contraction
Give a definition of stroke volume and ow is it calculated.
Volume of blood expelled by the heart in any one cardiac cycle
End Diastolic volume-end systolic volume
How is ejection fraction calculated?
Stroke volume/End Diastolic volume x 100
What is the normal range for ejection fraction?
52-72%
What would happen to the ejection fraction with a patient with heart failure?
30-35%
What happens during Atrial Systole?
Atria contract to top up the volume of blood in the ventricles?
What wave on the ECG shows the start of atrial systole?
P wave
Which Heart sound is abnormal but heard during atrial systole and why?
S4- occurs with congestive heart failure, pulmonary embolism or tricuspid incompetence
Due to the forceful contraction of the atria in order to overcome hypertrophic ventricle
describe how ventricular depolarisation leads to contraction of ventricular muscle and how it is shown on the QRS
AP reaches ventricular myocyte.
Opens L type Ca 2+ channels; allows influx of Ca 2+
Opens Ryanodine receptor channels which allow Ca 2+ to move from sarcoplasmic reticulum to myofibrils
Ca 2+ allow actin-myosin cross bridges to form- causing sarcomere to shorten
Shown by QRS complex on the ECG
Which valves are open or closed during isovolumetric contraction?
AV valves are closed
SL valves are closed
What is Isovolumetric contraction
Contraction of the ventricles without a change in volume of the ventricles
What type of contraction is isovolumetric contraction?
isometric contraction- no shortening of muscle fibres
Changes in pressure and volume during isovolumetric contraction
Rapid increase in ventricular pressure
NO CHANGE in volume
What is rapid ejection?
When ventricular pressure>aortic pressure the semilunar valves open, leading to ejection of blood from ventricles
What type of contraction is rapid ejection?
concentric contraction- shortening of muscle fibres
Changes in pressure and volume during rapid ejection
decrease in ventricular pressure
rapid decrease in ventricular volume
increase in aortic pressure
What is reduced ejection
Remaining blood is ejected from the ventricles at a slowed rate
Ventricular pressure begins to fall however it is still greater than aortic pressure so semilunar valves remain open
Changes in pressure and volume during reduced ejection phase
decrease in ventricular pressure
slow decrease in ventricular volume
slow decrease in aortic pressure
How is Reduced ejection shown on ECG
T wave
What is isovolumetric relaxation?
Relaxation of the ventricle without change in ventricular volume
occurs when ventricular pressure<aortic pressure - forces semilunar valves to close
What sound is heard during isovolumetric relaxation phase.
S2- dub noise
Sound is made by the closure of the semilunar valves
Changes in volume and pressure during isovolumetric relaxation
Rapid decrease in ventricular volume
NO CHANGE in ventricular volume
What is the dichrotic notch and why does it occur
small increase in aortic pressure during isovolumetric relaxation
-walls of aorta are distended due to blood moving through it
-when aortic valve closes, walls rebound inwards and increase the pressure of the aorta
