Pressure changes during the cardiac cycle.

https://www.youtube.com/watch?v=l8LHCQZCuLM

How do we analyse the electrical activity of the heart. / ECG

By attaching electrodes to the surface of the skin. The resulting trace is called an electrocardiogram or ECG.

What do the 3 sections of an ECG trace tell us

The P wave shows contraction of the atria (atrial systole.)

The QRS wave shows contraction of the ventricles (ventricular systole)

The T wave shows relaxation of the ventricles (ventricular diastole)

How do we calculate heart rate

Measure time taken for one heart beat. To do this, measure time between start of P wave, and start of the next P wave.

One heart beat takes 0.9s

Then divide 60 by the time for one heart beat, 60/0.9 = 67 beats per minute.

What happens when people have a slow heart rate and drops between 60 Bpm

This is called bradycardia. Can happen due to athletic training which increases the stroke volume of the heart.

Because heart pumps greater volume of blood per minute, the number of beats per min decreases.

What happens if a person has a heartbeat greater than 100bpm

They have tachycardia.

It can be caused by short term effects such as fear, panic or exercise.

Whats an ectopic heartbeat

Is an extra heartbeat that is not part of the heart’s usual rhythm.

In this case, the heart contracts again before first contraction has finished, followed by a short pause before normal rhythm continues.

What happens during atrial fibrillation

Irregular waves of electrical excitation pass over the atria, causing atria to contract randomly and rapidly, up to several hundred times a minute.

As normal heart rhythm is disrupted, it is a type of arrhythmia.