Coordination of the Cardiac Cycle

Question 1

What is bradycardia?

Answer 1

A slow heart rhythm

Question 2

What is an ectopic heart beat?

Answer 2

An extra beat or an early beat of the ventricles

Question 3

What is an electrocardiogram?

Answer 3

A trace that records the electrical activity of the heart.

Question 4

What is fibrillation?

Answer 4

Uncoordinated contraction of the atria and ventricles

Question 5

What is myogenic muscle?

Answer 5

Muscle that can initiate its own contraction.

Question 6

What is purkyne tissue?

Answer 6

Consists of specially adapted muscle fibres that conduct the wave of excitation from the AVN down the septum to the ventricles.

Question 7

What is the sino-atrial node?

Answer 7

The heart’s pacemaker. It is a small patch of tissue that sends out waves of electrical excitation at regular intervals in order to initiate contractions.

Question 8

What is tachycardia?

Answer 8

A rapid heart rhythm

Question 9

Describe the contraction of the atria. (3 steps)

Answer 9

1. The wave of excitation quickly spreads over the walls of both atria.
2. It travels along the membranes of the muscle tissue.
3. As the wave of excitation passes, it causes the cardiac muscle to contract.
   Atrial systole occurs

Question 10

Describe the contraction of the ventricles. (5 steps)

Answer 10

1. After a short delay the wave of excitation is carried along from the AVN and down the Purkyne Tissue.
2. This runs down the interventricular septum.
3. At the base of the septum, the wave of excitation spreads out over the walls of the ventricles.
4. As the excitation spreads upwards from the apex (base) of the ventricles, it causes the muscles to contract.
5. This pushes the blood up towards the major arteries at the top of the heart.