Cardiac cycle Flashcards
What is convection?
It is the mass movement of fluid caused by pressure difference
What is a sinoatrial node?
It is a group of cells located in the wall of the right atrium
What does the SA produce?
The SA spontaneously produces action potentials that travel through the heart via electrical conduction system
What is the SA also known as?
Also known as the hearts natural pacemaker
What is the heart rate influenced by?
Heart rate influenced by nerves that supply the SA node
What does the AVN coordinate?
Coordinates top of the heart
What does the AVN connect and do?
Eletrically connects the right atrium and right ventricle, delaying impulses so that the atria have time to eject blood into ventricles before ventricular contraction
What is If?
It is hyperpolarisation activated Na+ channels causing Na+ influx
Phase 0(Rapid depolarisation) in atrioventricular action potentials?
Voltage gated Na+ channels open, Na+ influx
Voltage gated Ca2+ channels open slowly
Phase 1 in atrioventricular action potentials?
Na+ channels close
Phase 2 in atrioventricular action potentials?
VGCC’s fully open-Ca2+ influx(CICR)
K+ channels open slowly
Phase 3(Rapid repolarisation) in atrioventricular action potentials?
VGCC’s close
K+ channels fully open
Phase 4(Resting phase) in atrioventricular action potentials?
Na+/K+ pump(3 Na+ out, 2K+ in)
Electrical conduction through the heart
- Electrical activity generated in SA node and spreads out via gap junctions into atria
- At AVN, conduction delayed to allow correct filling ventricles
- Conduction occurs rapidly through bundle of His into ventricles
- Conduction through purkinje fibres spreads quickly throughout the ventricles
- Ventricular contraction begins from apex
What is the P wave in an ECG?
Atrial depolarisation
What is the QRS complex in an ECG?
Ventricular depolarisation
What is the PR segment in an ECG?
AVN delay
What is the ST segment in an ECG?
Time during which ventricles are contracting and emptying
What is the T wave in an ECG?
Ventricular repolarisation
What is the TP interval in an ECG?
Time during which ventricles are relaxing filling
Cardiac cycle outline
Diastole:
Ventricular filling
Atrial contraction
Systole:
Ventricular contraction
Atrial relaxation
Cardiac diastole
Both atria and ventricles relaxedChamber and volume change in (ventricular filling/aorta contraction)
Pressure in atria>ventricles
Mitral/tricuspid valve open aided by atria contraction
Chamber and volume change in (Isovolumetric contraction)
Pressure in ventricles>atria
Mitral/tricuspid valve close
Pressure rises
Chamber and volume change (Ejection)
Pressure in ventricles>Aorta/Pulmonary artery
Valves open, ejection of blood
Atria start to refill
Chamber and volume change in (Isovolumetric relaxation)
Pressure in aorta/pulmonary artery>Ventricles
Aortic/pulmonary valves close
Equation for stroke volume
EDV-ESV=stroke volume
Ventricular pressure-volume loop
Work=change in ventricles x change in volume
Stroke work done= Area inside loop
Heart sound (S1)
Lub
Close of tricuspid/mitral valves at beginning
Heart sound (S2)
Dub
Closure of aortic/pulmonary valves at the end of ventricular systole
Heart sound (S3)
Occasional
Turbulent flow into ventricles, detected end of 1/3 diastole
Heart sound (S4)
Forceful atrial contraction against a stiff ventricle
Less in young people
