3.1.2 Animal transport – Control of the Cardiac Cycle Flashcards
(13 cards)
Why is the cardiac muscle of the heart known as myogenic?
The contraction of the heart is initiated by the heart muscle itself rather than being under nervous control.
What is the pacemaker of the heart known as and where is it located?
The sino-atrial node (SAN) and it is located in the wall of the right atrium.
Where does the wave of depolarisation travel to from the SAN to enable atrial systole to occur?
It travels through the walls of the atria, leading to atrial systole until it gets to the layer of non-conductive tissue.
Why is the layer of non-conductive tissue between the atria and ventricles important?
It prevents the immediate contraction of the ventricles.
Following atrial systole, where does the wave of depolarisation travel, in order to lead onto ventricular systole?
The wave of depolarisation travels:
atrio-ventricular node (AVN) down the septum of the heart through the Bundle of His apex of heart up the wall of each ventricle in the purkyne fibres .
Why is it important that the atrio-ventricular node causes a time delay between atrial systole and ventricular systole?
So the atria can empty completely and the ventricles can be filled completely before the ventricles force the blood out of the heart.
Why is it important that the ventricles contract from the base/apex upwards?
So the blood is pushed out of the heart through the aorta and pulmonary artery (rather than being pushed down into the ventricles).
What does an electrocardiogram measure?
The electrical activity of the heart.
What are the 3 main parts to an ECG trace and what do they represent?
P wave – the electrical activity of the atria leading onto atrial systole.
QRS complex – the electrical activity of the ventricles leading onto ventricular systole.
T wave – the repolarisation of the ventricles during diastole.
What is tachycardia and how would it show on an ECG trace?
- A faster heart rate than average.
- There would be a shorter time delay between cardiac cycles.
What is fibrillation and how would it show on an ECG trace?
- When the heart beats with a rapid and erratic way.
- Disorganised peaks and troughs with no obvious cardiac cycle.
What is bradycardia and how would it show on an ECG trace?
- A slower heart rate than average.
- There would be a longer time delay between cardiac cycles.
What is an ectopic heartbeat and how would it show on an ECG trace?
- Where there is one extra beat during a normal trace.
- An extra cardiac cycle would be included in the ECG trace, this is out of the regular rhythm of the trace.
