Conducting System of Heart

Question 1

Importance of Myocardium

Answer 1

contractile myocardium
specialised myocardium
made of nodal tissue/ conducting fibres
responsible for coordinated contractions of cardiac cycle

Question 2

components of conducting system

Answer 2

Sinoatrial node
atrioventricular node
bundle of his (L/R branches)
purkinje fibres

Question 3

Sinoatrial node

Answer 3

at cross of superior vena cava and right atrium
10x6 mm
generates electrical impulse and spreads through atrial muscles
‘pacemaker’ of heart
~60-100 bpm (every 0.8s)
bradycardia ↓, trachycardia↑
blood supply from right conorary artery
poorly striated cells scattered in fibrous connective tissue
autonomic intervention
para(sympathetic)

Question 4

internodal tract in Right atrium(RA)

Answer 4

anterior, middle and posterior
Bachmann’s bundle connects LA and RA

Question 5

atrioventricular (AV) node

Answer 5

wave of depolarisation travels through atrium wall to AV node
located in bottom of RA near opening of tricuspid valve
supplied by right conorary artery
distributes signal to ventricles via AV bundle
delays pulse 0.09 s
sympathetic speed up conduction
parasympathetic slows down

Question 6

AV bundle of his

Answer 6

AV bundle carries impulse across fibrous skeleton and membrane of interventricular septum
splits into left and right bundles to continue down septum at junction of membrane and muscular part
supplied by anterior interventricular (left anterior descending) artery

Question 7

trifascicular system

Answer 7

R/L bundle branches
only left splits into anterior and posterior fascicles
therefore 3(tri) fascicular system

Question 8

purkinje fibres

Answer 8

right side stimulates muscles of interventricular spetum and wall of right ventricle including anterior papillary muscles
lest side stimulates interventricular septum and wall of left ventricle including papillary muscles

Question 9

arrhythmias

Answer 9

problems with rate and rhythm
irregular rhythm
fast rate
chaotic waves
no P-R interval
QRS skewed

Question 10

atrificial cardiac pacemakers

Answer 10

if patient has problem with SA nodethen artificial pacemkers is implemented which uses computer to send out and time electrical impulses
placed in pectoral region
leads inserted to heart chambers and attached to endocardium via puncturing subclavian vein