Cardiovascular - Electrical and Mechanical events Flashcards
What is the intrinsic conduction system?
How the heart makes itself beat (via pacemaker cells)
How does extrinsic innervation affect the intrinsic conduction system?
It either increases or decreases the conduction system
Why can the heart beat independent of the brain?
Due to the electrical impulses (action potential) generated by the SA nodes
Where are the SA nodes located?
Right atrium
Where is the AV (atrioventricular) node located?
Right Atrium
What is the patway of the impulses generated by the SA node?
- Travels to left atrium
- Travels down to AV node, where it pauses
- Then travels to the Bundle of his
- The bundle branches then conduct the impulse through the interventricular septum
- Impulse then travels up the Purkinje fibres (subendocardial conducting network) which depolarises the contractile cells of both ventricles
How do sympathetic nervous impulses affect heart rate?
Increases heart rate
How do parasympathetic nervous impulses affect heart rate?
Decrease heart rate
What other factors affect heart rate?
- Age
- Wellbeing/Health/Fitness
- Stress
- Temperature
- Gender
What is ECG?
- Electrocardiogram
- Composite of all action potentials generated by nodal and contractile cells at any given time
Essentially a graphical representation of the the cardiac conduction system
What is the ECG process?
- P Wave - Atrial depolarisation
- Q R S complex - Ventricular depolarisation
- T Wave - Ventricular repolarisation
What process is not seen on an ECG tracing?
Atrial repolarisation (it does occur but is masked by the QRS Complex)
What are the mechanical events of the heart?
- Cardiac cycle
- Diastole
- Systole
- Heart sounds
- Cardiac output
What does Systole refer to?
Contraction
What does Diastole refer to?
Relaxation