1.5 Control and regulation of the cardiac cycle Flashcards
How is the heart myogenic?
It generates its own electrical impulses from within the heart so it does not need external stimulation.
What is the sinoatrial (SA) node and where is it located?
Mass of specialsied cells in the upper wall of the right atrium near the opening of the vena cava.
When the SA node generates an electrical impulse, what does it cause?
It causes the muscle of the heart to contract.
What is the SA node also known as?
The Pacemaker.
What does the SA node ensure?
That the heart beats at a regular rhythm.
Where can the Atrioventricular (AV) node be found?
At the top of the wall of muscle that separates the two ventricles.
What does the AV node act like?
A turnstile.
What does the AV node briefly delay?
The electrical current coming from the AV node.
Why does it delay the electrical current?
So that the atria has time to empty and the ventricles have time to fill up with more blood.
Where does the impulse from the SA node pass through?
The AV node.
Once it is passed through the AV node, where does it go?
It then goes across the walls of the ventricles via the Purkinje fibres.
What do the Purkinje fibres carry?
The current down to the base of the heart, causing it to contract from the bottom up.
Once the heart has contracted, where is the blood pushes through?
Up and out of the ventricles.
What happens at the P wave?
Where the SA node is triggered. Electrical depolarisation of the atria occurs meaning the atrial contraction and emptying of blood into ventricles.
What happens at the PR interval?
AV node delays the signal to allow ventricles filling.
