Conduction System Of The Heart Flashcards
(5 cards)
What is the description and function of the Sino-Atrial Node (SA Node)?
• It’s found at the top of the right atrium.
• It’s known as the heart’s natural pacemaker.
• It spontaneously generates an electrical signal to the muscles of the atria to cause the atria to contract. This contraction forces the blood from the atria down into the ventricles.
• This is atria systole (pressure in the atria increases as the atria are contracting).
• This signal impulse flows down from the SA Node to the AV Node.
What is the description and function of the Atrioventricular Node (AV Node)?
• It’s at the top of the septum.
• It causes the electrical impulse that is running through the heart to temporarily pause (only by around 0.1second).
• This is because it needs to allow the atria to stop contracting. It doesn’t want the ventricles to contract immediately because the valves between the atria are still open.
• There needs to be a moment of time for the contraction of the atria to be complete.
• After the pause, it passes the impulse to the Bundle of His.
What is the description and function of the Bundle of His?
• Located in the septum.
• It conducts the electrical impulse down from the central part of the heart, down to the base of the ventricles and into the purkinje fibres.
• The impulse has now travelled down the septum to the base of the ventricles at the bottom of the heart.
What is the description and function of the Purkinje Fibres?
• Located throughout the muscular walls of the ventricles.
• The impulse continues its flow from the Bundle of His back up towards the top of the heart via the ventricle walls.
• As the impulse travels up the ventricle walls, the muscle contracts from bottom to top, forcing the blood out of the ventricles and through the aorta or pulmonary artery at the top of the heart.
• As this contraction finishes, the heart relaxes for a short time (known as diastole) and blood starts to fill into the atria again.
• This whole process, i.e one heartbeat, takes between 0.7-1 second each time (based on an average HR of 60-100 beats per minute).
What is the order of the conduction system of the heart?
• First, the SA Node has sent an impulse to the atria and that impulse has flowed to the AV Node.
• The AV Node pauses the impulse for around a 10th of a second before passing it on to the Bundle of His.
• The impulse has now travelled down the septum to the base of the ventricles and into the Purkinje Fibres.
• As the impulse travels up the ventricle walls, the muscle contracts from bottom to top, forcing the blood out of the ventricles and through the aorta or pulmonary artery at the top of the heart.
