Heart Beat Flashcards
What structures are involved in the heart beating?
-SA Node
-AV Node
-Non Conducting Collagen Tissue
-Bundle of His
-Tendon
-Purkinje Fibres
What variation of tissue is Cardiac Tissue?
Myogenic-it contracts and relaxes without receiving impulses from neurons.
What would happen if cardiac tissue was left alone?
Heartbeat would be sporadic
What is heartbeat coordinated by?
SA Node located in the wall of the right atrium
What does the SA Node act as?
As a pacemaker by sending regular waves of excitation.
How many stages do the waves pass through?
4 stages
What happens in stage 1?
Waves pass through the walls of atria simultaneously, causing them to contract at the same time
What prevents the waves passing directly to ventricles?
A band of non-conducting collagen tissue
What happens in stage 2?
Waves are transferred to AV Node.
Why is there a delay before AV Node reacts?
So ventricles have time to fill with blood before they contract.
What happens in stage 3?
AV Node passes the waves to the bundle of His which passes the waves to Purkinje fibres
What is the Bundle of His?
A group of Muscle Fibres
What happens in Stage 4?
Purkinje Fibres carries waves into muscular walls of left and right ventricle causing them to contract simultaneously (bottom to top)
Mitochondria take up what percentage of each cardiac cycle?
25 to 35% producing lots of energy
How long does it take for the wave of electrical activity to travel from the SA Node to last of the ventricular cells?
220 milliseconds / 0.2 seconds
