Electrical Activity of the Heart Flashcards
What does cardiac muscle form?
A functional syncytium
How is the functional syncytium connected?
Electrically by gap junctions and physically by desmosomes
Why can’t cardiac muscle exhibit tetanic contraction?
It has a long action potential and long refractory period
What can calcium regulation be used to vary?
Strength of contraction
What are pacemakers?
Cells with resting membrane potentials
What is initial depolarisation in a non-pacemaker cell due to?
Sudden increase in permeability to sodium
What is the plateau in a non-pacemaker cell due to?
Increased permeability to calcium (L-Type) and decreased permeability to potassium
What is repolarisation in a non-pacemaker cell due to?
Decrease in permeability to calcium and increase in permeability to potassium
What is different in pacemaker cells?
The sodium channels are opened by the depolarisation of the previous AP and the calcium channels are (T-Type)
What does the sinoatrial node contain?
Fastest pacemaker cells
What is the annulus fibrous?
Non-conducting
What is the atrioventricular node?
Delay box
What are the Purkinje fibres?
Rapid conduction system
In an ECG, what does the P wave correspond to?
Atrial depolarisation
What does the QRS wave correspond to?
Ventricular depolarisation
