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.
Explain the sequence of events that causes the contraction and coordination of the ventricles contracting (ventricular diastole).
After the delay, the AVN carried the wave of excitation to the Purkyne tissue and it runs down the septum, until it reaches the septum’s base where the WoE spreads out over the ventricle walls. The WoE spreads upwards from the base of the ventricles, causing no the muscles to contract from the base upwards.
From where does the ventricles contract?
From the base upwards.
Explain why it is important that the ventricles contract from the base (apex) upwards.
As it will she’s the blood to be pushed upwards as the major arteries that take blood away from the heart are at the top of the heart.
What are the series of waves of a healthy person’s Electrodiagram trace labeled?
P, Q, R, S, T
What does wave P on the Electrodiagram trace show?
The excitation of the atria.
What does the QRS complex on an Electrodiagram trace show?
The excitation of the ventricles.
What does the ‘T’ section on an Electrodiagram of a healthy person show?
Diastole.
List four abnormal heartbeats that can be identified by comparing an Electrodiagram of this person with the ECG of a normal heartbeat.
Bradycardia
Tachycardia
Atrial fibrillation
Ectopic heartbeat
What is bradycardia?
A slow heart rhythm.
