Electrical Activity in the Heart

Question 1

What is the function of cardiac muscle?

Answer 1

Controls the beating of the heart

Question 2

How is heartbeat controlled?

Answer 2

1. SAN sends impulses to atrial walls, causing the atria to contract simultaneously
2. Non-conducting collagen tissue prevents impulses from SAN reaching ventricles
3. SAN conducts impulses to AVN
4. AVN conducts impulses to bundles of His
5. Bundle of His is responsible for conducting impulses to Purkyne fibres
6. Purkyne fibres carry impulses into ventricle walls, causing them to contract simultaneously

Question 3

What does an electrocardiograph do?

Answer 3

It is used to check a patient’s heart function by records the electrical activity of the heart.

Question 4

Why is there a slight delay between the SAN sending impulses to the atrial walls and the AVN sending impulses to the ventricular walls?

Answer 4

To ensure that the atria have completely emptied, which ensures that all the blood in the heart is pumped out.

Question 5

What is stroke volume?

Answer 5

The volume of blood pumped by one ventricle each time it contracts

Question 6

What is cardiac output?

Answer 6

The total volume of blood pumped by the heart in a minute

Question 7

How is cardiac output (cm3 min-1) calculated?

Answer 7

heart rate (bpm) x stroke volume (cm3)