Cardiac conduction system Flashcards
What is the period through which the heart is contracting and forcing blood out called?
Systole
What is the period through which the heart is relaxing
and expanding to allow blood to enter named?
Diastole
What is the first stage of the heart contracting?
SA node initiates heart beat by generating the impulse for contraction. This is the pace maker and this is intrinsic /myogenic as it comes from within the heart
What is the second stage of the heart contracting?
Impulse initiated from SA node spreads across the atria causing it to contract and force blood into the ventricle
What is the third stage of the heart contracting?
The nerve impulse that has spread across the atria cannot spread down into the ventricles because the valves act as non-conducting material
What is the fourth stage of the heart contracting?
The blood reaches the AV node.
This conducts the impulse from the atria to the ventricles
There is a 0.1s delay as the impulse passes through AV node to give the atria time to fully contract, therefore fully filling the ventricles.
What is the fifth (final) stage of the heart contracting?
The impulse passes down the septum in a bundle of his
When it reaches the tip of the ventricle at the very bottom, they branch out into the walls of the ventricle through purkinje fibres that allow the ventricle to contract
What are the two branches and which is slow/to relax and which is fast/to contract?
Parasympathetic - Slow/relaxes
Sympathetic - Fast/contracts
What happens when there is an increase in C02/blood acidity to regulate heart rate? (Same principles for opposite but other way round.
Detected by chemoreceptors
Impulse to medulla
Releases adrenaline and sends a nerve impulse along the sympathetic pathway to the SA node
Increases stimulation of SA node and also increase strength of contraction.
