Cardiac cycle Flashcards
What are the AV valves
Tricuspid and bicuspid
What are the semilunar valves
Pulmonary artery and aortic
Where is the SAN node
Right atrium
Where is the AVN node
Bundle of His
Sequence of diastole
- Relaxation
- Heart fills with blood getting ready to go into systole
Ventricles fill
AV valves open because pressure in atrium is higher than ventricles
Semi lunar valves are closed because pressure in atrium is lower than ventricles
Sequence of systole
- Contraction
- Ventricles contract
- Blood goes through P.A. artery to become oxygenated at lungs (right)
- Blood goes through aorta to supply the body (left)
- AV valves closed
- Semi lunar valves are open as pressure in ventricles is greater than atria
Function of coronary arteries
Supply the heart with oxygen. They come off the aorta
What is atherosclerosis
Arteries become blocked by fatty plaques - can lead to angina or heart attacks
What is the normal resting heart rate
60 - 100 beats per minute
Name for less than normal resting heart rate
Bradycardia
Name for higher than normal resting heart rate
Tachycardia
What causes heart sounds
Valves opening and closing
Intrinsic factors controlling the heart
- Starlings law
- Pacemaker rhythm
Extrinsic factors controlling the heart
- Sympathetic and parasympathetic control
- Endocrine factors
Formula for cardiac output
heart rate x stroke volume
What is pre load
Volume of blood in ventricles after diastole
What is after load
Pressure the ventricles need to overcome in order to contract
Where are baroreceptors found
Carotid sinus and aortic arch
What is chronotrophy (Endocrine factor)
Heart rate
What is ionotrophy (Endocrine factor)
Force of contraction
Effect of noradrenaline
Chronotroph and ionotroph and vasoconstrictor
Effect of acetylcholine
Neurotransmitter - decrease heart rate (AV node) - G1 protein coupled receptor - parasympathetic
What is starlings law
The more the heart fills, the stronger the force of contraction
Electrical conduction of the heart
Action potential at the SA node (right atrium), spreads across and down
Down to AV node where there is a delay - allows the atria to finish contracting
Travels down the bundle of his
AP travels in purkinje fibres which distributes it - contraction starts at the bottom
Pacemaker of the heart - SA node
What is depolarisation
Na+ moving into cell (more +ve inside), Ca2+ moving into cell (muscle contraction) - CONTRACT
What is depolarisation
K+ moving into cell (more +ve outside), Ca2+ moving out of cell - RELAX
What is Lub S1
Closing of AV valves - systole
What is Dub S2
Closing of Semilunar valves - diastole
What does P show on an ECG
Atrial depolarisation
What does the QRS complex show
Ventricular depolarisation (atrial repolarisation happening at same time)
What does T show
Ventricular repolarisation
What does QT interval show
Shortens with tachycardia
Lengthens with bradycardia
What does isovolumetric mean
Both sets of valves are closed
What are arrhythmias
Irregular heart rate
Why is ventricular fibrillation important
Irregular contraction of ventricles - leads to cardiac arrest
Treatment for arrhythmias
Pacemaker
Sequence of cardiac cycle
Mid to late diastole
Ventricular systole
Early diastole
