Q3. Electrical activity in cardiomyocytes [16 marks] For each action potential below: Identify the heart region (i.e. sino-atrial node, atrium or ventricle) in which you would expect cardiomyocytes to show

this type of electrical activity. Identify the ion(s) responsible for each of the numbered phases and the direction of movement across the cell membrane (e.g. sodium influx).