The Cardiac Cycle Flashcards
What generates the electrical impulses that cause the heart to ‘pump’?
the sinoatrial (SA) node
What is the name given to the contraction phase of the cardiac cycle?
Systole
What is the name given to the relaxation phase of the cardiac cycle?
Diastole
What are pressure changes responsible for in the heart?
Blood movement and valve control (open/close)
What causes the pulse?
The rhythmic expansion of arteries as blood spurts from the left ventricle.
What is stage 1 of the cardiac cycle?
Stage 1: Atrial contraction and ventricular filling
Ventricles relax and blood flows into them from the atria.
- ventricles relaxed // atria contract -
Do the atria contract for the whole of the ventricular filling process?
No, 70% of blood from the atria flows passively into the ventricles. It is only for the last third of ventricular filling that the atria contract.
What is stage 2 of the cardiac cycle?
Stage 2: Ventricular contraction
The blood is pumped from the ventricles into the aorta or pulmonary artery.
- atria relaxed \ ventricles contract -
What is stage 3 of the cardiac cycle?
Stage 3: Complete cardiac diastole
There is a short period of atrial and ventricular relaxation. Semilunar valves (SLV) close to prevent backflow.
The cycle begins again.
What moment in the cardiac cycle coincides with the first heart sound?
The start of ventricular contraction.
The heartbeat occurs in response to _______ ______ generated spontaneously by the _____ ______ itself.
The heartbeat occurs in response to ELECTRICAL IMPULSES generated spontaneously by the HEART MUSCLE itself.
What does ECG stand for?
Electrocardiogram
What does the ECG pattern depict?
Impulses produced at each phase of the cycle.
What is the international letter code for the excitation of the ventricles and ventricular systole?
QRS complex
What phase of an ECG is identified by the letter T?
The T wave: recovery of the electrical activity of the ventricles, which are relaxed (ventricular diastole).
What phase of an ECG is identified by the letter P?
The P wave: excitation of the atria and atrial systole.
What is the physiological importance of the T phase?
The electrical recovery phase forces the heart to rest, preventing fatigue and lactic acid accumulation.
What is the SA node’s full name?
Sinoatrial node
Where is the SA node located?
the upper part of the wall of the RIGHT ATRIUM
What is the structure by which electrical impulses travel from the SA node to the AV node?
Internodal pathways
What happens to the cardiac muscle when it says ‘depolarisation’?
Contraction
Depolarisation = contraction
What happened to the cardiac muscle at ‘repolarisation’?
Repolarisation = rest/relax
