Lecture - CVS (Bevin Cardiac Cycle) Flashcards
Briefly describe the flow of blood in the heart
So blood enters from the superior and inferior vena cava (and coronary sinus) and flows to the right atrium through the tricuspid valve into the right ventricle and then through the pulmonary trunk (after passing the pulmonary SL valve) and to the left and right pulmonary arteries (deoxygenated blood to the lungs).
The oxygenated blood returns back from the lungs through the left and right pulmonary veins and into the left atrium. Then through the bicuspid valve to the left ventricle. The left ventricle then pumps the blood through the aortic SL valves out through the aorta and into the arteries of systemic ciruclation
Which side of the heart has low vs high pressure - does this mean the blood flow output of the heart is different in the left vs right side?
High pressure in left and low in right
Nope, both have 5L/min
- What’s another name for the right AV valve and what’s another 2 names for the left AV valve?
- What does the contraction of the pap muscle help to do?
- What is the opening and closing of the AV valves dependent on? Is it passive or active process?
RIght AV = tricuspid
Left AV = bicuspid, mitral
- Passive process dependent on the pressure difference across the valve
Semilunar valves:
- What do they allow and prevent?
- How many cusps?
- Opening and close passively or actively?
- Allow flow during systole and prevent back flow during diastole
- 3 each
- Passivelllllly
- What comprises the cardiac cycle? LIke how many systoles and diastoles?
- Is it a mechanical or electrical event? Or is it vulvular?
- There are 2 phases of the cardiac cycle - what are they?
- 1 sys and 1 dia
- Eelectrical, mechanical (volume and pressure changes) annnd vulvular (open and close= sounds) so all three
- Vent dia (vent relax) and vent sys (vent contract)
Hi, describe the cardiac cycle’s mechanical, electrical and vulvular events plz
SO we have 2 phases - diastole and systole (ventricular).
Diastole:
- Ventricular isovolumetric relaxation (just after ejection)
- Ventricular filling - blood flows from atria to the ventricles
Systole:
- Ventricular isovolumetric contraction (just before ejection)
- Ventricular ejection
So cycle: ejection - iso relaxation - filling - iso contraction - ejection - iso relaxation etc
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*****I am talking about the left side of the heart here but sorta generalise it to right sometimes*****
DIastole #1: Isovolumetric ventricular relaxation
- all valves are shut so the ventricles are relaxation after their ejection without any change in volume (atria might be changing volume, not the ventricles)
- since all valves closed, there is no blood flow
- here is when you’re at your lowest volume (ESV) of the ventricles
- the ventricular pressure is falling but is still higher than the atrial pressure. Atria are filling with blood and as soon as atria’s increasing pressure gets higher than ventricle’s falling pressure - the AV valves open and blood goes from high to low pressure.
Diastole #2: Ventricular filling
- 80% of the filling is passive (gradient) because flowing from high pressure (atria) to low pressure (ventricles)
- in the last part of diastole, you have the P wave on ECG and that’s when atrial depolarisation occurs. So SA node fires, depolarises the atria and atria then contract and squeeze the remaining 20% of the blood into the ventricles. Called the atrial/ventricular top-up
- volume highest at the end (end-diastolic volume)
Systole #1: Isovolumetric ventricular contraction
- in this stage, the ventricles will first depolarise by the QRS complex and they will then develop tension and elevating the left ventricular pressure so AV valves close (mitral) here because the ventricular pressure gets higher than the atrial pressure (blood flows from high to low pressure but you have valves here to stop that happening!) So this is the first LUB sound (S1) you here - the pressure lines cross here on the graph (ventricular > atrial)
- so all valves are now closed therefore there is no change in volume
- this starts the isovolumetric contraction and the pressure generated by the ventricles overcomes the aortic pressure (AP)
- so as soon as the LVP > AP, the SL valves open and the opening of these = systole #2 (ejection)
Systole #2 - Ventricular ejection
- blood ejected through the open SL aortic valve so you increase arterial blood volume and pressure
- LVP and AP rise in parallel, reaching a maximum at mid-systole
- there is rapid ejection (2/3) and reduced ejection (late systole) where both LVP and AP begin to fall
- T wave = ventricles repolarise here
Back to Diastole #1: Isovolumatric ventricular relaxation
- LVP < AP so SL aortic (and pulmonary) valve closes aka second sound (S2) DUB
- S2 = both aortic and pulmonary SL valves (S1 both AV valves, too I’m sure)
- closure of SL = end of systole (open of SL = start of vent ejection)
- volume of blood at minimum (ESV), no blood flow……etc
Ventricular pressure:
- It’s at a minimum during what part of the cardiac cycle?
- Rises a little during when and afer what?
- When does it rise dramatially?
- It continues to rise to a max during when?
- When does it start to fall?
- Falls dramatically when?
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Arterial pressure:
- When is it at a minimum?
- Rises to a maximum when?
- When does the aortic valve close? (incisura/d____ notch)
- Continues to fall when?
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How is this figure different for the right side of the heart?
RIght side of heart is the same but low pressure system - same volume etc
So the differences:
- Pulmonary resistance is lower than totoal peripheral resistance (systemic circulation)
- Right ventricular and pulmonary artery pressures are lower than LVP and AP
How do the left and right side of the heart pressures vary?
What is stroke volume?
Left vent: 0 to 120…….Right vent: 0 to 25
Aortic: 80 to 120…….Pul art: 8 to 25 (bc less resistance)
Why can you see the three waves - a, c and v from the atria in the jugular vein?
What are the a, c and v waves?
Because there is back transmission, I think? Like a wave see in juglar bc as you push blood into ventricles, you’re also sorta pushing it to the veins and the jugular vein is the thing just before the atria so see it there
- the c wave is when the ventricles are contracting and they push the tricuspid and mitral valve back so that sorta compresses the atria and sends some back transmission too
- v wave is during ventricular ejection aka the atria are filling up so some back transmission then too, I guess?
So like, these three waves are when the atria pressures rise: a = atria contraction, c = ventricles contract and valves compress atria, annnnnnd v = atria are filling up
- So what’s roughly the duration of diatole and systole in the cardiac cycle?
- During higher heart rates, do you decrease the diastole or systole time?
- Both but diastole decreases more bc squirty bit is more important
On the ECG, what does the P, QRS and T wave represent? WHy can’t you see atrial repolarisation?
What are the 4 heart sounds?
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Normal blood flow is laminar so it’s silent
So what murmurs?
What 2 things are murmurs an important sign of?
So when will you hear the murmurs of: aortic stenosis, mitral incompetence, aortic incompetence?
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