L5 The Cardiac Cycle Flashcards
What is the sequence of electrical events that occur during the cardiac cycle?
The sequence includes depolarization and repolarization of the atria and ventricles.
How can electrical events in the heart be recorded?
They can be recorded on the body surface in the form of an ECG.
What does the P wave in an ECG represent?
Atrial depolarization.
What does the Q wave in an ECG signify?
Depolarization of the septum (towards the atria).
What does the R wave in an ECG indicate?
Depolarization of the ventricles (towards apex).
What does the S wave in an ECG represent?
Depolarization of the ventricles (towards atria).
What does the T wave in an ECG indicate?
Repolarization of the ventricles (towards endocardium).
What is the function of the sino-atrial (SA) node?
It acts as the primary pacemaker of the heart.
What is the role of the atrio-ventricular (AV) node?
It conducts impulses from the atria to the ventricles and slows down the conduction (AV pause).
What is the purpose of the AV pause?
It allows ventricular filling to occur before the electrical impulse is passed to the ventricle.
What is the conduction system of the heart comprised of?
- Sino-atrial (SA) node
- Atrio-ventricular (AV) node
- Bundle of His
- Right and left bundle branches
- Purkinje fibres
What is the significance of the P-Q interval in an ECG?
It reflects atrial conduction and A-V nodal delay.
What does the S-T segment in an ECG represent?
It indicates that all of the ventricle has depolarized.
What does QRS duration indicate?
Ventricular conduction velocity.
What does the Q-T interval in an ECG reflect?
Ventricular action potential duration.
What is the definition of stroke volume?
Stroke Volume = EDV - ESV (ml).
What is isovolumic contraction?
A phase where the ventricles contract without a change in volume.
What occurs during the period of ventricular ejection?
Blood is expelled from the ventricles into the aorta and pulmonary artery.
What is the definition of end-diastolic volume (EDV)?
The volume of blood in the ventricles at the end of diastole.
What is end-systolic volume (ESV)?
The volume of blood remaining in the ventricles after systole.
True or False: The left atrial pressure is higher than the left ventricular pressure when the mitral valve opens.
True.
What are the phases of the cardiac cycle?
- Diastole
- Systole
- Isovolumic contraction
- Isovolumic relaxation
What does the cardiac pacemaker hierarchy include?
- Sino-atrial (SA) node
- Atrio-ventricular (AV) node
- Bundle of His
- Purkinje fibres
Fill in the blank: The __________ allows the apex to contract before the base.
ventricular conduction system
