Cardiology Flashcards
Where does excitation of the heart occur?
In the SA(sinoatrial node pacemaker cells)
What initiates the heartbeat?
The cluster of the specialised pacemaker cells in the SA node
Where is the SA node located?
In the upper right atrium, close to where the superior Vena Cava enters the right atrium
What drives or sets the pace for the entire heart?
The Sinoatrial node. This is said to be also in control of the Sinus rhythm.
What is meant by stable resting potential?
the cells in the SA node have no stable resting membrane potential
Where are the cells located that generate a spontaneous pacemaker potential?
In the SA node.
What happens when a threshold is reached ?
An action potential is generated.
Where are action potentials generated?
In the SA nodal cells.
Why does the slow depolarisation to a threshold happen?
It is mainly due to the funny current.
What is a funny current ?
It is a depolarising cation current that is slow due to the Na(sodium) influx through HCN channels(hyper polarisation-activated cyclic nucleotide-gated)
What happens at the end of the hyperpolarisation period?
Decrease in K efflux and Ca influx.
