Control of Heart Rate

Question 1

What are the stages of control of heart rate?

Answer 1

1) SAN initiates the heart beat - sends an electrical impulse across the atria and the atria contracts
2) non conducting tissue prevents the electrical impulse relaxing the ventricles
3) AVN delays electrical impulse - this allows atria to contact and empty before ventricles contract
4) AVN sends the electrical impulse down the bundle of his and along the purkyne fibres
5) ventricles contract from the base upwards

Question 2

Why is the left ventricle important for control of heart rate?

Answer 2

highest blood pressure
most cardiac muscle - contracts with greatest force
pumps blood to whole body

Question 3

How do you calculate the heart rate?

Answer 3

time / heart beat and then 60 seconds / your anser = …. bpm

Question 4

What are the 3 phases of the cardiac cycle?

Answer 4

atrial systole
ventricular systole
diastole

Question 5

What happens during atrial systole?

Answer 5

atria = contracted ( high blood pressure)
ventricles = relaxed (low pressure)
atrioventricular valves = open ( so blood can pass through to ventricles)
semilunar valves = closed

Question 6

What happens during the ventricular systole?

Answer 6

atria = relaxed (low)
ventricles = contracted (high)
atrioventricular valves = closed (to prevent blood being forced back into atria)
semilunar valves = open

Question 7

What happens during diastole?

Answer 7

atria = relaxed (filling but low)
ventricles = relaxed (low)
atrioventricular valves = open (so ventricles can start to fill up)
semilunar valves = closed