CVS Session 2 (Lecture 2.1) Flashcards
Which valve separates the RA from the RV?
Tricuspid
Which valve separates the LA from the LV?
Mitral
Which valve separates the LV from the aorta and the RV from the pulmonary artery?
Semilunar valves
How long is systole? How is it initiated?
280ms - action potential long, single contraction from an influx of Ca2+ influx.
What are the pacemakers of the heart?
1) Sino-atrial node
2) Atrio-ventricular node
What do pacemakers do?
Generates an action potential which spreads over the whole heart producing a coordinated contraction.
What is diastole?
When the heart is at rest OR interval between beats.
Where is the SAN located?
RA
What does the SAN do and what does it cause?
Generates an action potential that spreads over the atria causing atrial systole.
Where does the A.P go after atrial systole?
Reaches AVN where it is delayed for 120ms. Spreads down septum (via bundle of His) towards the apex.
Where does the A.P spread next after passing down towards the apex?
Spreads through the ventricular myocardium from inner (endocardial) to outer (epicardial) surface.
How does the heart contract in relation to apex?
Ventricle contracts from apex up, forces blood towards the outflow valves.
How long does ventricular systole last?
280ms
How long does diastole last?
700ms
When do the mitral/tricuspid valve open?
When atrial pressure > intraventricular pressure
When do the mitral/tricuspid valves close?
When atrial pressure < intraventricular pressure
What is needed to close the inflow valves?
Small amount of regurgitation to close flaps
When does the aortic valve open?
When left ventricular pressure > aortic pressure
When does the aortic valve close?
When left ventricular pressure < aortic pressure
What is the cardiac cycle?
The cardiac cycle is the sequence of pressure flow changes and valve operations that occur with each heartbeat.
Starting at the end of systole describe the 1st part of the cardiac cycle.
1) Ventricles contracted
2) Intra-ventricular pressure high
3) Outflow valves open
4) Blood flows into the arteries
* Ventricular pressure > atrial so inflow A/V valves closed.
Starting at ventricular relaxation describe the 2nd part of the cardiac cycle.
1) Ventricles begin to relax
2) IV pressure falls rapidly
3) IV < Aortic pressure
4) Brief backflow closes outflow valves
5) Isovolumetric relaxation (same volume)
Starting at isovolumetric relaxation describe the 3rd part of the cardiac cycle.
1) Blood return to atria
2) Atrial pressure high
3) IV pressure falls below atrial pressure
4) A/V valves open
Starting when A/V valves open, describe the 4th part of the cardiac cycle.
1) Rapid filling of the ventricles - rapid filling phase
2) Lasts 200-300ms
3) Majority of ventricular filling in this phase of early diastole.
Starting at early diastole describe the 5th part of the cardiac cycle.
1) Diastole continues with slower rate of ventricular filling
2) IV pressure rises as ventricular wall stretches
3) Unitl IV pressure = atrial so filling stops
4) Known as diastasis
Starting at atrial systole describe the 6th part of the cardiac cycle.
1) Atrial systole (SAN firing)
2) Forces small extra amount of blood into the ventricles
3) Heart can work without this phase
Starting at ventricular systole describe the 7th part of the cardiac cycle.
1) Ventricular systole
2) IV pressure rises rapidly
3) Exceeds atrial pressure so brief backflow closes AV valves
4) Isovolumetric contraction
Starting at isovolumetric contraction describe the 8th part of the cardiac cycle.
1) IV pressure rises rapidly until > arterial pressure
2) Arterial pressure has been falling from diastole
3) Outflow valves open
Starting at outflow valves opening describe the 9th part of the cardiac cycle.
1) Outflow valves open
2) Blood is ejected into the arteries
3) Rapid ejection phase
4) Arterial pressure rises
Starting at arterial pressure rising describe the 10th part of the cardiac cycle.
1) Rate of ejection of blood falls
2) Arterial + IV pressure peak towards end of systole
3) Outflow eventually caeses with blood still in ventricle
Starting at the end of systole describe the 11th part of the cardiac cycle.
Systole ends and cycle repeats!
What are the two main sounds of the heart and how do they arise?
1) First sound - lub - closure of a/v valves
2) Second sound - dub - closure of outflow valves
When do the sounds arise?
1) First sound - onset of ventricular systole
2) Second sound - end of ventricular systole
What is the interval between the first and second sound?
280 ms
What is the interval between the second and first sound?
700ms at rest, can shorten upon exertion
What would cause splitting of sounds?
Right and left valves not closing at the same time.
Where would a third and fourth sound be heard? Is this normal?
Yes it is normal
Third sound - early in diastole
Fourth sound - atrial systole
What generates a heart murmur? Give 2 causes.
Turbulent flow of blood generates murmurs.
1) Aortic stenosis - narrowed valve
2) Incompetance - valve not closing properly
When do murmurs occur?
When blood flow is at its highest
What is cardiac output?
The volume pumped per minute by the left heart is known as the Cardiac Output.
What determines the C.O?
Heart rate and stroke volume
What is HR and SV?
SV - volume ejected per cardiac cycle
HR - number of cycles per minute
At rest what is the normal SV, HR and CO?
SV = 80ml HR= 60 CO= 5L per min
