Coronary circulation II + Venous return Flashcards
Small cardiac veins return blood FROM
Right ventricular muscle
Thebesian veins EMPTY in
All chambers
Venous return =
(Venous P - Right Atrium P) / Venous Resistance
Increased vasoconstriction will lead to (Higher or lower VR)
Lower venous return due to a higher resistance
If there is constriction due to SYMPATHETIC ACTIVATION (ex. sports) there will be an increase or decrease of VR
Increased venous return from Increased RESISTANCE –> Increased V PRESSURE pressure –> Increased venous RETURN
Blood flows from high to low pressure?
Yes
When do valves open
When pressure in 1st chamber > pressure in 2nd
Contraction causes increased pressure within a chamber?
Yes
PHASE 1 CC corresponds to
Atrial depolarization
PHASE 1, systole or diastole
Diastole, muscle relaxation
PHASE 1 (CC): Why does ventricular volume slightly increase if we are in diastole
Because there is passive flow from atria to ventricle before contraction
Increase in Atrial Pressure causes
Atrial contraction
Pa > Pv causes in valves
To open (both tricuspid and mitral)
Pa < Pv causes in valves
To close (both tricuspid and mitral)
1ST SOUND WHEN
Atrioventricular valves CLOSE (tricuspid + mitral)
When does systole begin
At the end of the 1ST sound, when the tricuspid and mitral valve close
PHASE 2 CC corresponds to
Isovolumetric contraction (systole)
What causes the beginning of ventricular contraction
Increase of ventricular pressure
Why do semilunar valves not open in PHASE 2
Because aortic and pulmonary artery P > Ventricular P
Why is Phase 2 called an ISOVOLUMETRIC CONTRACTION
Because ventricle begins to contract in a closed space since semilunar valves are not yet opened
When will ventricular ejection occur
When P ventricle > P aorta + P pulmonary artery
Valves OPEN when
P in 1st chamber > P 2nd chamber
Valves CLOSE when
P in 1st chamber < P 2nd chamber
PHASE 3 CC corresponds to
Rapid ejection (systole, muscle contraction)
Aortic and pulmonary valves open because
P ventricle»_space; P aorta + P pulmonary artery
Peak P of aorta occurs at
PHASE 3: Rapid ejection
In which phase is the max. blood ejection
At rapid ejection (systole)
PHASE 4 CC corresponds to
Reduced ejection
T wave corresponds to
Ventricular repolarization
T wave of EKG is in which phase of CC
Reduced ejection
Why is force ejection reduced at this phase?
Because ventricular pressure decreases as ventricular volume decreases
Why do semilunar valves close at PHASE 4 of reduced ejection
Because P aorta + P pulmonary artery > P ventricles
Where is the end of SYSTOLE and beginning of 2nd diastole
When semilunar valves close, end of ventricular ejection
2ND SOUND WHEN
Semilunar valves close
PHASE 5 corresponds to
Isovolumetric relaxation (diastole)
Why do ventricles relax in isovolumetric relaxation
Because P ventricular decreases and valves are closed
Why is it called isovolumetric relaxation
Because volume remains unchanged
Why is P atrial slowly increasing during isovolumetric relaxation
Because atria are being filled with blood
PHASE 6 corresponds to
Ventricular filling
When does ventricular filling start
When P atria > P ventricle so atrioventricular valves open
Why is there ventricular filling before atrial contraction during Ventricular filling phase
Because there is passive flow of blood to ventricle before the atria contracts. –> Phase 1
Which is the longest phase of the cycle
Slow ventricular filling
Difference between phase 6 and 7 in CC
Phase 6 is fast ventricular filling bc atrioventricular valves are opened
Phase 7 is slow ventricular filling bc pressure in ventricle increases, therefore the pressure gradient across AV is decreased… This causes a decreased ventricular filing
