Organisms response - Heart beat

What does myogenic mean?

The heart's contraction is initiated from within the muscle itself, rather than by nerve impulses

Where does an electrical impulse originate from in the heart?

The SAN/pacemaker

Give the stages of an electrical impulse causing the heart to beat?

1. SAN produces an electrical impulse

2. Impulse travels across the atria walls

3. The atria contract

4. A layer of non-conducting collagen prevents the impulse going directly to the ventricle walls

5. Muscle tissue in the atria conducts the impulse to the AVN

6. There is a small pause to allow the atria to fully empty of blood

7. The impulse passes from the AVN down the bundle of His

8. Purkyne fibres carry the impulse from the apex of the heart to the ventricle walls

9. Heart contracts from the bottom upwards

Why do we need the non-conducting collagen to prevent the impulse going directly to the ventricle walls?

Because otherwise the atria would not be finished contracting before the ventricles contracted. This would mean the atria were not fully empty and the ventricles were not full so no blood would actually be pumped out of the heart

What is the bundle of His?

It is the atrioventricular bundle of nerves which connects the AVN to the apex of the heart

What are purkyne fibres?

Large specialised muscle fibres that conduct impulses rapidly to the apex of the ventricles from the AVN

Diagram to show the movement of an electrical impulse to create a heartbeat.

What is the functional difference between the bundle of His and the purkyne fibres?

Bundle of His carries the impulse from the atria to the apex, purkyne fibres carry the impulse from the apex to the ventricles

Where is the SAN located?

Top of right atrium wall

What is the function of the coronary artery?

To provide oxygenated blood to the heart muscle for muscle contraction

Why is it important that there is a high rate of conduction of the impulse in the purkyne fibres?

So the ventricles contract together

How would cutting nerve connections with the brain to the SAN affect the beating of the heart and why?

The heart would keep beating because it creates its own impulses. It doesn't need to be instructed by the brain

What is the role of the AVN?

Transmission of electrical signals from the atria to the ventricles and ensures a delay between atrial and ventricular contraction, allowing the atria to empty prior to ventricle contraction