regulation of stroke volume and heart rate

Question 1

What sets the heart rate

Answer 1

The pacemaker cells of the sinoatrial node which cause the atria to contract and then the ventricles after the delay from the atrioventricular node

Question 2

Describe the sympathetic innervation of the heart

Answer 2

• Symopathetic nerves release noradrenaline
• circulating adrenaline from the adrenal medulla
• Both act on B1 receptors on the sinoatrial heart and increase the heart rate

Question 3

Describe the parasympathetic innervation of the heart

Answer 3

• Vagus nerves release acetylcholine
• Acts on muscarinic receptors of the SA node
• Hyperpolarises cell and causes decreased heart rates

Question 4

What is the stroke volume

Answer 4

Volume of blood pumped from the left ventricle per heart beat - the difference between end diastolic and systolic volume

Question 5

What is after load

Answer 5

The load against which the heart muscles try to contract against

Question 6

What is the result of the TPR - total peripheral resistance increasing

Answer 6

The aortic pressure will increase - the ventricle will have to work harder to push open the aortic valve and there will be less energy to eject the blood - the stroke volume will decrease

Question 7

What is the preload

Answer 7

How full the ventricle is before it begins to contract

Question 8

What is the cardiac output

Answer 8

Heart rate x stroke volume - stroke volume affects the cardiac output more