Cardiac cycle Flashcards
What is convection? [1 mark]
Mass movement of fluid caused by pressure distance
What is the SA node? [1 mark]
A group of cells located in the wall of the right atrium
What can the SA node do? [2 marks]
- Spontaneously produce action potential
- Acts as a pacemaker
What influences the rate of action potential production of the SA node? [1 mark]
Nerves that supply it
Where does the SA node sends its signals? [2 marks]
- Through the right atrium
- Through fibres to the AV node
What does the AV node do? [2 marks]
- Connects the right atrium and right ventricle
- Delays impulses so that atria have time to eject their blood into ventricles
What is the If (funny current) threshold? [1 mark]
-40 mV
What are the phases of an action potential in the SA node? [3 marks]
- Slow influx of Na+
- Rapid influx of Ca2+ and depolarisation
- Outflux of K+ and repolarisation
What are the phases of an action potential in the SA node? [5 marks]
- Rapid depolarisation (from Na+)
- Early repolarisation (Na+ channels close)
- Plateau phase (CICR)
- Rapid depolarisation (K+ outflux)
- Resting phase
Where does ventricular contraction occur? [1 mark]
At the apex
What does the P wave of an ECG show? [1 mark]
Atrial depolarisation and contract
What does the T wave of an ECG show? [1 mark]
Ventricular repolarisation
What does the PR segment of an ECG show? [1 mark]
Av nodal delay
What does the ST segment of an ECG show? [1 mark]
Ventricles contracting and emptying
What does the QRS complex show? [2 marks]
- Ventricular depolarisation
- Atria repolarising simultaneously
What does the TP interval show? [1 mark]
Ventricles repolarising and filling
Overview of blood flow in the heart [7 marks]
- Vena cava to right atrium
- Tricuspid valve → right ventricle
- Pulmonary valve → pulmonary arteries
- Pulmonary veins → left atrium
- Biscuspid valve → left ventricle
- Aortic valve → aorta
Overview of chamber & volume changes in the heart [4 marks]
- Ventricular filling and atrial concentration
- Isovolumetric contraction
- Ejection
- Isovolumetric relaxation
Left ventricular pressure changes [3 marks]
- Ventricular pressure slightly increases
- Pressure increases more
- Ventricular pressure decreases
Left ventricular volume change [4 marks]
- Filling ventricle contraction of atria
- No volume change (isovolumetric contraction)
- Blood ejected
- No volume change (isovolumetric relaxation)
Formula for work done [3 marks]
Work = changes in ventricle pressure × changes in volume
Right atrial cycle and jugular venous pressure changes [4 marks]
- Atrium contracting (increase in pressure)
- Atrium relaxing (pressure decrease)
- Atrium refills (increase in pressure)
- Atrium empties (decrease in pressure)
What happens to the pressure of the heart in congestive heart disease and to the jugular vein? [2 marks]
- Pressure on the right side of the heart is too large
- Jugular vein bulges out
What is the S1 (lub) sound? [2 marks]
- Closure of tricuspid/mitral values at beginning of ventricular systole.
- Can be felt when taking a pulse at the same time as hearing the heart.
What is the S2 (dub) sound? [1 mark]
Closure of aortic/pulmonary valves (semilunar valves) at end of ventricular systole.
What is the S3 (swoosh) sound [3 marks]
- Occasional
- Turbulent blood flow into ventricles, detected near end of first 1/3 diastole
- Especially in older people
What is the S4 sound? [2 marks]
- Extra sound before lub dub
- Forceful atrial contraction against a stiff ventricle
