CVS Session 2- The Heart As A Pump Flashcards
Where is the aortic valve located?
Between the left ventricle and the aorta
Where is the mitral valve located?
Between the left atrium and the left ventricle
Where is the tricuspid valve located?
Between the right atrium and the right ventricle
Where is the pulmonary valve located?
Between the right ventricle and the pulmonary artery
Which are the atrioventricular valves?
Mitral and tricuspid valves
Which are the outflow valves?
Aortic and pulmonary valves
Features of cardiac muscle (6)
- striated
- branching
- intercalated discs
- gap junctions
- one or two central nuclei per fibre
- unlike skeletal muscle, the T tubules are inline with the Z bands
What feature of cardiac muscle allows the flow of electrical current?
The fact that low resistance connections and gap junctions join muscle fibres.
How long does a single contraction last?
280-300ms
How many action potentials cause one heartbeat?
One
Where is the SA node found?
The right atrium
How long is the action potential delayed at the AV node once spread from the SA node over the atria?
120ms
Describe the route of excitation of the heart myocardium.
- the SA node fires an AP which spreads over the whole atria.
- this excitation spreads to the AV node, where it is delayed.
- it then spreads down the septum between the ventricles.
- then across the ventricles
- then from the endo to the epicardium of the ventricles.
Which way do ventricles contract and relax?
Contract- from the apex up
Relax- from the top to the apex
Why does the apex of the heart relax last?
To prevent back flow.
When heart rate increases, what is affected and how?
The length of diastole.
It is shortened.
What is the structure of ventricular muscle and why is this the case?
Ventricular muscle is organised into figure of eight bands. They squeeze the ventricles forcefully for the most efficient blood ejection out of the outflow valves.
Define systole.
The period when the myocardium is contracting.
Define diastole.
The period when the myocardium is relaxing, in between contractions.
What shuts the valves of the heart?
A small amount of regurgitation of blood.
What causes the first heart sound?
The closing of the atrioventricular valves.
What causes the second heart sound?
Closing of the outflow valves.
When does the first sound occur?
During atrial systole.
When does the second heart sound happen?
Ventricular systole.
What are murmurs caused by?
Turbulent blood flow, due to
- stenosis (narrowed valves)
- incompetence (valves not closing properly)
What is the equation for cardiac output?
CO= heart rate x stroke volume
What is the definition of cardiac output?
The volume of blood pumped per minute by the left heart.
What causes the closing of the atrioventricular valves?
Contraction of papillary muscles.
What causes the closing of the semi-lunar valves?
Regurgitation of a small amount of blood.
Where are the openings to the coronary arteries found?
In the aortic wall (right) above the right and left coronary cusps.
When does coronary artery filling occur?
During diastole.
