ECG Flashcards
(20 cards)
Which ions have higher concentrations outside the cell?
Sodium and calcium🦴🧂
Which ions are higher in concentration inside the cell?
Potassium 🍌
What is the charge at baseline?
Resting potential, inside the cell is negative and outside is positive, call this polarised 🧲
How do ions move rapidly across the cell membrane?
When ion channels are open
Describe action potential?
Movement of ions across the cell membrane, 3 events.. sodium entry causes decolonisation. Calcium entry causes a plateau and potassium egress (exit) causes repolarisation.
Depolarisation is
Cell more positive on inside and more negative on outside
What does the p wave show?
Depolarisation of the atria
What does the QRS complex show?
Depolarisation of ventricles
What are the two things that entry of calcium does?
Maintains depolarisation and triggers mechanical contraction
What does the t wave show?
Repolarisation of the ventricles
Why can’t you see atrial repolarisation?
Happens at the same time as ventricular depolarisation, hidden by the large and dominant QRS complex
What stimulates contractile cells to start depolarising/contracting?
Pacemaker cells
What is the role of cardiac pacemaker cells?
Create and conduct action potentials but they do not contract, so no plateau phase, can spontaneously depolarise.
Cardiac pacemaker cells have instability at baseline, why?
Slow leakage of sodium into the cells continuously, gradually the voltage rises, cases calcium channels to open. Funny current is the gradual leakage which raises voltage.
What is the order of the cardiac conduction system?
Sinoatrial node, atrioventricular node, bundle of his, left and right bundle branches, purkinje fibres
What is the primary pacemaker?
SA node
What is the T wave showing?
Repolarisation of the ventricles
P wave?
QRS?
Twave
P wave-atrial depolarisation
QRS-ventricular depolarisation
T wave-ventricular repolarisation
