CH12 heart rhythm Flashcards
1
Q
Why is heart muscle called myogenic
A
- has its own intrinsic rhythm
2
Q
Order of rhythm
A
- wave of electrical excitation occurs in pacemaker area called sino-atrial node causing atria to contract
- electrical activity from SAN is picked up by atrio-ventricular node which imposes slight delay and then stimulates bundle of His
- bundle of His splits into two branches and conducts wave of excitation to apex
- at apex fibres spread out through walls on both sides which triggers contraction of ventricles starting at apex
3
Q
What is bundle of His made of
A
Purkyne fibres
4
Q
Why does contraction of ventricles start at apex
A
- allows more efficient emptying of ventricles
5
Q
What prevents first excitation passing directly to ventricles
A
- a layer of non-conducting tissue
