3.2.6- Coordination Of The Cardiac Cycle Flashcards
Explain what an ectopic heartbeat is.
An extra beat or an early best of the ventricles.
What is an electro diagram (ECG)?
A trace that records the hearts electrical activity using sensors on the skin that pick up the electrical excitation created by the heart and converting this into a trace.
Define what ‘filtration’ is.
Uncoordinated contraction of the atria and ventricles in the heart.
What is ‘myogenic muscle’?
A type of muscle found in the heart that can initiate its own contraction.
Explain what Purkyne tissue is.
Consists of specially adapted muscle fibres that conduct the wave of excitation from the AVN down the septum, to the ventricles.
Explain what the sino- atrial node (SAN) is.
Described as the hearts ‘pacemaker’. A small patch of tissue that sends out waves of electrical excitation at regular intervals in order to initiate contractions. Found at the point where the vena cava empties blood into the right atrium.
What’s tachycardia?
A rapid heart rhythm.
The atria muscle tends to contract at a _______ ________ than ventricular muscle.
Higher frequency.
Explain why the cardiac cycle needs to be coordinated.
Because the myogenic nature of the tissue will cause inefficient pumping if the contractions of the chambers are not synchronised- a condition called fibrillation. Coordination prevents fibrillation.
Where is the SAN node found?
At the top of the right atrium, where the vena cava empties blood into the right atrium.
Explain how the atria are contracted and how this is coordinated.
Atrial systole- the SAN initiates a wave of excitation that quickly spreads over the walls of both atria, it travels along the membranes of the muscle tissue and as the wave of excitation passes, it caused the cardiac muscle cells to contract in atrial systole.
Where is the Atrio- ventricular node (AVN) found?
At the top of the inter ventricular septum.
Why can the wave of excitation from
The SAN not travel straight down to the ventricles from the atria?
Because there is a band of non conducting collagen tissue at the base of the atria that prevents the Wave of excitation being passed to the ventricles.
Explain what the AVN does.
It is the only route that can conduct the wave of excitation through to the ventricles. The AVN also delays the wave of excitation for a short time.
Why is it important that the AVN delays the wave of excitation energy for a short while before it’s passed to the ventricles?
It allows time for the atria to finish contracting and for the blood to flow down Into the ventricles before they begin to contract.
