Cardiac Cyle Flashcards
What must happen before ventricular contraction can occur
Atrial contraction must be completed
What must happen to ensure proper pumping of the heart
Contraction of the myocardium must be coordinated
What prevents the inversion of AV valves
Cordae tendineae
What are the cordae tendineae anchored to
The papillary muscles which contract the prevent inversion
What forces the semilunar valves to shut
The increased pressure in arteries compared to ventricles
What does the ‘Lub’ sound of the heart mean
AV valves closing
What does the ‘Dub’ sound of the heart mean
semilunar valves closing
What do the intercalated discs help do
Anchor cardiac cells together
What ion starts spontaneous depolarisation in cardiac action potentials at SA node
Through Na+ channels
What ion helps reach the threshold in cardiac action potential at SA node
Ca2+ influx
During cardiac action potentials at SA node what happens when the apex is met
Ca2+ channels close and K+ open leading to repolarisation
What is the sequence of excitation in cardiac action potential
SA node generates impulse - atrial excitation begins
Impulse delayed by AV node
Impulse passes to heart apex - ventricular excitation begins
Ventricular excitation complete
How does cardiac muscle contraction occur
Action potential stimulates Ca2+ influx outside cell
Induces release of more Ca2+ from intracellular stores in the sarcoplasmic reticulum
Ca2+ binds to troponin allowing sliding of myofilaments
On an ECG what happens at P
Atrial depolarisation
On an ECG what happens at QRS
Ventricular depolarisation
