MP323 - ARRHYTHMIAS Flashcards
2 main factors that determine the electrical potential across a plasma membrane
- the distribution of ions across the membrane
- the selective permeability of the cell membrane
ARP
absolute refractory period
RRP
relative refractory period
chronotropic control
- nodal tissues
- CNS, parasympathetic vs sympathetic influences
- parasympathetic predominates at rest
sympathetic fibres
- release noradrenaline
- beta-1-receptors
- increasing the permeability of the nodal cell plasma membrane to Na+ and Ca2+
parasympathetic fibres
- release acetylcholine
- M2 receptors
- increasing the permeability to K+ and decreasing the Na+ and Ca2+ permeability
parasympathetic influence on the resting membrane potential
vagal stimulation makes the resting potential more negative, and the pacemaker current slower, and raises the threshold
sympathetic influences on the resting membrane potential
catecholamines make the resting potential more excited, and speed the pacemaker current, and lower the threshold for discharge
supraventricular
- originating in the atrium or atrioventricular node
- narrow complex
ventricular
- originating in the ventricle
- broad complex
re-entry arrhythmias
- refractory period must shorten
- conduction velocity decreased due to depolarisation
- cells are within refractory period
action potential of cardiac cells - phase 0
rapid depolarisation (influx of Na+)
action potential of cardiac cells - phase 1
partial repolarisation
inward Na+ current deactivated, outflow of K+
action potential of cardiac cells - phase 2
plateau
slow inward calcium current
action potential of cardiac cells - phase 3
repolarisation
calcium current inactivates, K+ outflow
