The Heart

Question 1

Draw a diagram showing the variation of heart potential during a heartbeat. (potential against time)

Answer 1

see diagram

Question 2

Drawn an ECG trace of a healthy person (surface potential mV against time s)

Answer 2

see diagram

Question 3

What does the wave at P represent?

Answer 3

The depolarisation and contraction of the atrial heart muscles when blood that has entered the heart is forced into the ventricles.

Question 4

What does the delay between p and q represent?

Answer 4

The impulse delay at the atrio-ventricular (AV) node to allow the ventricles to fill.

Question 5

What does QRS represent?

Answer 5

Is due to the depolarisation after Q and contraction after R of the ventricles’ heart muscles when blood is pushed out of the heart

Question 6

What does the wave at t represent?

Answer 6

The repolarisation and relaxation of the heart muscles after blood is pushed out of the heart from the ventricles

Question 7

Above what frequency must unwanted signals

due to muscle activity or from the mains supply must be filtered out from an ecg?

Answer 7

20Hz

Question 8

Properties of amplifier

Answer 8

High gain
High input impedance
Low noise