Cardiac Control, Coordination + ECGs

Question 1

Control of the Heart

Answer 1

• Constant beating unlike skeletal muscle
• Co-ordinated contraction: artial systole => ventricle systole => diastole => atrial…
• Doesn’t need external input - myogenic

Question 2

1 in Electrical Coordination - (Atrial systole)

Answer 2

Siro-Atrial Node (SAN) pacemaker starts a wave of excitation (electrical signal that makes muscle contract)

Question 3

2 in Electrical Coordination

Answer 3

Atrial-ventricular node (AVN) delays the wave of excitation allows ventricles to fill up

Then passes down the septum through the bundle of His to the apex

Question 4

3 in Electrical Coordination - (Ventricular Systole)

Answer 4

Signal reaches the apex and wave spreads through ventricular walls - contraction from the bottom up

Question 5

What are Electrocardiograms? (ECG)

Answer 5

• The electrical activity of the heart can be monitored by ECGs
• Several electrodes placed on skin and record the flow of ions throughout

Question 6

Bradycardia

Answer 6

Slow heart rate

Question 7

Tachycardia

Answer 7

Fast heart rate

Question 8

Artial fibilation

Answer 8

Artia beating more frequently than ventricles - no clear P waves seen

Question 9

1st in ECGs - P wave (little bump)

Answer 9

Wave of excitation spreads over SAN across atria causing artial systole

Question 10

2nd in ECGs - PR interval (little flat line)

Answer 10

Time taken for wave of excitation to delay + passed the septum to bundle of His

Question 11

3rd in ECGs - QRS complex (Big sharp peak is R)

Answer 11

Shows spread of excitation across ventricle causing huge contraction (ventricular systole)

Question 12

4th in ECGs - ST segment

Answer 12

The flat line between big peak and bigger bump

Question 13

5th in ECGs - T wave (bigger bump)

Answer 13

Resting/resetting

Depolarisation of ventricles during diastole