The Process Of The Cardiac Cycle B2.6 Flashcards
(14 cards)
What is the cardiac cycle?
The series of muscle contractions and relaxations that pumps blood around the body
What does myogenic mean?
Eg cardiac muscle pumps in a regular pattern without nerve impulse
What are the contractions of the heart muscle initiated by?
The sinoatrial nod (SAN) on the wall of the right atrium also known as the pacemaker
What does the sinoatrial node do?
It generates electrical signals that spread out over the surface of the right and left atria, causing them to depolarise and contract. This is known as atrial systole
What does the atrioventricular node (AVN) do?
After a brief pause, the AVN generates more electrical signals that pass along to the bundle of His. The electrical activity generated passes down the muscle seperating the two ventricles and then passes up the walls of the two ventricles. As it does, it initiates the contraction of the ventricles
What is an electrocardiography?
An ECG detects the electrical activity of the heart. This works by placing electrodes on the skin to detect electrical signals and produce an eelctrocardiogram
What is the P wave caused by?
Depolarisation of the atria initiated by the electrical signals generated by the SAN
What is the QRS complex caused by?
Depolarisation of the ventricles initiated by the electrical signals generated by the AVN and transmitted along the bundle of his
What is the T wave caused by?
The Repolarisation of the ventricles
What is the path taken by the blood through the heart?
- the blood enters the right atrium from the vena cava
- it then flows via the bicuspid valve into the right ventricle
- from the right ventricle it is pumped into the pulmonary artery to the lungs
- returning from the lungs via pulmonary veins, the blood enters the left atrium
- it then flows into the left ventricle
- from the left ventricle, blood is pumped into the aorta and around the body
What happens during atrial systole?
The atrium contracts, which completes emptying the blood into the ventricle in preparation for the next stage
What does systole mean?
Contraction of either atrium or ventricle
What does diastole mean?
Relaxation of either the atrium or the ventricle
What happens in ventricular systole?
When the ventricle contracts, the pressure increases until higher than the atrium and this pushes the bscuspid valve closed and preventing back flow
