CV3 Cardiac conduction system Flashcards
(28 cards)
what is the cardiac conduction system
network of nodes, cells and signals
controls heartbeat
inherent & rhythmical electrical activity (heart creates its impulses)
makes the heart an effective pump
what are autorhythmic cells
network of specialised cardiac muscle fibres
generate spontaneous action potentials
nerve impulses from ANS and endocrine hormones modify the heartbeat
does not establish the fundamental rhythm
what’s involved in specialised cardiac muscle fibres
in SA node, AV node & Purkinjean fibres
self-excitable
pacemaker activity
can a heart still beat with the nerves cut?
a living heart removed from the body will continue to beat despite cutting nerves
from top to bottom which order do the nerve fibres go
Purkinje fibres
Atrioventricular (AV) bundle (bundle of his)
Atrioventricular (AV) node
Sinoatrial (SA) node
Right and left bundle branches
- sinoatrial (SA) node
- atrioventricular (AV) node
- atrioventricular (AV) bundle (bundle of his)
- right and left bundle branches
- Purkinje fibres
what are the three steps in ventricular action potential
- Rapid Depolarisation
- Plateau
- Repolarisation
what happens during Rapid Depolarisation
as Na+ enters
what happens during Plateau
maintained depolarisation; some K+ leaves
slows Ca2+ enters
binds to troponin
actin + myosin slide
what happens during Repolarisation
as K+ exits, & Ca2+ leaves
what is a electrocardiogram (ECG)
recording of electrical changes that accompany AP propagation that can be detected at the surface of the body
where would you place the ECG
place electrodes on 4 limbs & 6 positions on the chest
what are the 3 recognisable waves accompany each heartbeat
P wave
QRS complex
T wave
what is the P wave
atrial depolarisation
(contraction)
what is the QRS complex
onset of ventricular depolarisation
(contraction)
what is the T wave
ventricular repolarisation
(just before ventricles start to relax)
if P wave is the larger wave?
enlarged atrium
in QRS if Q is enlarged
MI
in QRS if R is enlarged
enlarged ventricles
if T is flatter
insufficient O2
coronary artery disease
if there’s a interval between P-Q
scar tissue
coronary artery disease
rheumatic fever
if the S-T segment is elevated
acute MI
depressed- insufficient O2
if the Q-T interval lengthens
myocardial damage or coronary ischaemia
conduction abnormalities
what is the healthy adult pulse at rest
average 75bpm
(60-100)
what is the healthy adult pulse at sleep
40 bpm
