Week 16: (A) The origin of cardiac electrical activity Flashcards
What is autorhythmicity?
The heart contracting rhythmically as a result if its own AP
What are the 2 specialised types of cardiac cell?
1) contractile cells (99%)
2) auto-rhythmic cells
What type of specialised cardiac cell do not contract but do initiate or conduct APs?
auto-rhythmic cells
Do autorhythmic cells display pacemaker activity?
YES
What is pacemaker potential?
-Cell membrane’s slow drift to threshold slow, –Positive increase in voltage across the cell’s membrane
Do auto-rhythmic cells initiate APs without any nervous stimulation?
YES no nervous stimulation
Where are the 4 locations of the non-contractile cells that demonstrate auto-rhythmically?
1) The sinoatrial node (SA node)
2) The atrioventricular node (AV node)
3) The bundle of His (atrioventricular bundle)
4) Purkinje fibres
What is the normal pacemaker of the heart?
sino atrial node
How are the cells of the heart linked?
electrically
What cell generates the fastest AP in the heart?
SA node (pacemaker) 70-80 AP/min
What cell generates the 2nd fastest AP in the heart?
AV node (40-60 AP/min)
What cell generates the slowest rate of AP in the heart?
bundle of His and purkinje fibres (20-40 AP/min)
What would take over. if the SA node became inactive?
AV node
What is the rate of AP discharge in the atrial and ventricular myocardium?
0 APs per min normally
What can alter SA node discharge frequency?
para and sympathetic stimulation
