The Heart contraction

Question 1

how is the heart beat initiated?

Answer 1

SAN sends an electrical impulse over the atrial walls
Causes atria to contract
Conducted to AVN, where the electrical wave of excitation is conducted down the Purkinje fibres
Causes the ventricles to contract
Layer of insulation exists between the atria and ventricles to prevent the first wave of impulse from the SAN from travelling all the way down
This layer causes a pause at the AVN

Question 2

what does a chemo-receptor do?

Answer 2

located in the aorta and the carotid artery, monitor the CO2 levels, O2 levels and pH levels in the blood

Question 3

what happens when there are low levels of O2 and pH with high levels of CO2?

Answer 3

Chemoreceptors will send an impulse through the sensory neurone
to the medulla and through the sympathetic neurone
releasing noradrenalin from the sinoatrial node
which makes the heart rate faster

Question 4

what happens when there are high levels of O2 and pH with low levels of CO2?

Answer 4

Chemoreceptors will send an impulse through the sensory neurone
to the medulla and through the parasympathetic neurone
releasing acetylcholine from the sinoatrial node which makes the heart rate slower.

Question 5

What is a baroreceptor?

Answer 5

located in the carotid artery and aorta only, detect changes in the pressure in the blood

Question 6

What happens when you have high blood pressure?

Answer 6

the parasympathetic neurone releases acetylcholine from the sinoatrial node slowing the heart rate down to lower the blood pressure.

Question 7

What happens when you have low pressure?

Answer 7

the sympathetic neurone releases noradrenalin from the sinoatrial node making the heart rate faster to raise the blood pressure.