Control of heart rate

Question 1

Explain the process of the conduction systems

Answer 1

1. The process starts in the sinoatrial node
2. The SAN sets the rhythm of the heartbeat by sending out regular waves of electrical activity to atrial walls
3. This causes the right and left atria to contract at the same time
4. A band of non-conducting collagen tissue prevents the waves of electrical activity from being passes directly from the atria to the ventricles
5. These waves of electrical activity are transferred from the SAN to the atrioventricular node
6. The AVN passes waves of electrical activity onto the Bundle of His. There is a slight delay before the AVN reacts to make sure the atria has fully emptied
7. The Bundle of His is a group of muscle fibres responsible the electrical waves from ventricles to apex of the heart. The bundle splits into Purkyne tissue
8. The Purkyne tissue carries waves of electrical activity into the muscular walls of the right and left ventricles causing them to contract simultaneously

Question 2

What does the SAN do?

Answer 2

Generates electrical impulses that causes the cardiac muscles to contract

Question 3

What does the medulla oblongata do?

Answer 3

Processes the information sent from receptors and send impulses to the SAN along sympathetic or parasympathetic

Question 4

What are baroreceptors?

Answer 4

Pressure receptors that detect high and low blood pressure

Question 5

What are chemoreceptors?

Answer 5

Chemical receptors that monitor oxygen, pH and carbon dioxide levels

Question 6

What happens when baroreceptors detect high blood pressure?

Answer 6

Impulses are sent to the medulla which sends impulses along parasympathetic neurones. They secrete acetylcholine which binds to the receptors on to the SAN. The heart rate is slowed down to reduce blood pressure.

Question 7

What happens when baroreceptors detect low blood pressure?

Answer 7

Impulses are sent to the medulla which sends impulses along sympathetic neurones. They secrete noradrenaline which binds to receptors on to the SAN. The heart rate is speed up to increase blood pressure.

Question 8

What happens when chemoreceptors detect high blood pressure?

Answer 8

Impulses are sent to the medulla which sends impulses along the parasympathetic neurone. They secrete acetylcholine whihc binds to receptors on to the SAN. Heart rate decreases to return oxygen, pH and carbon dioxide back to normal.

Question 9

What happens when chemoreceptors detect low blood pressure?

Answer 9

Impulses are sent to the medulla oblongata, which sends impulses along sympathetic neurones. They secrete noradrenaline which binds to receptors on to the SAN. Heart rate increases to return oxygen, pH and carbon dioxide back to normal.