The Heart As A Pump Flashcards
What are the 4 heart valves from the right hand side to the left hand side?
Tricuspid valve (atrioventricular valve)
Pulmonic valve (semilunar valve)
Mitral valve (atrioventricular valve)
Aortic valve (semilunar valve)
What are the 4 chambers of the heart?
Right atrium
Right ventricle
Left atrium
Left ventricle
How is the heart a pump?
It is made up of 2 pumps acting in series
What pressure is pulmonary circulation?
Low pressure
What pressure is systemic circulation?
High pressure
What is Systole?
Contraction and ejection of blood from the ventricles
What is Diastole?
Relaxation and filling of the ventricles
How many leaflets does the tricuspid valve, pulmonic valve and the aortic valve have?
3 leaflets
How many leaflets does the mitral valve have?
2
Also called the Bicuspid valve
How does the thickness of the left ventricle compare to the right ventricle and why?
Left is much thicker
Systemic circulation is at a much higher pressure since it needs to pump blood around the body
What is stroke volume?
The volume of blood ejected from each ventricles per heart beat
What is the volume of blood in the average 70kg male?
5L
What is the stroke volume for the average 70kg man at rest?
70ml per beat
How are cardiac myocytes interconnected electrically?
Via intercalated discs (contain gap junctions)
What are the visible features of cardiac muscle?
Striated
Intercalated discs
Branched
Single central nuclei
What causes the opening and closing of the heart valves?
Changes in pressure between the chambers of the heart
What is the function of the chordae tendineae?
Prevents the valves from inverting leading to blood leaking back into chambers in the heart
When the aortic valve is open, is the mitral valve open or closed and why?
Mitral/Bicuspid valve closed
If aortic valve is open it means ventricular systole is occurring, mitral is closed to prevent blood flowing back into the left atria
What region of the heart are the pacemaker cells found?
Sinoatrial node
What is the role of the specialised cardiomyocytes in the sinoatrial node?
Initiate and spread action potentials
What is meant by the cells in the Sinoatrial node have autorhythmisicty?
The auto rhythmic cells of the SAN initiate their own action potential and the rest of the auto rhythmic cells of the heart conduct the action potential throughout the heart
Once the action potential has been generated at the SAN what happens next?
Action potential/wave of depolarisation spreads through the atria to the Atrioventricular node (AVN)
What is the function of the Atrioventricular Node (AVN)?
Initiates a time delay before the action potential is conducted to the ventricles
Why is the time delay initiated by the AVN important?
Gives time for the atria to finish contraction before the ventricles contract
Following the AVN, how is the action potential conducted?
Down the Bundle of His, then to the bundle branches (left and right) which run down the septum to the apex of the heart where Purkinje fibres conduct the depolarisation to the ventricles
How do the ventricles contract?
From the apex upwards
What are the 7 phases of the Cardiac cycle?
Atrial Contraction
Isovolumetric Contraction (ventricles)
Rapid Ejection (ventricles)
Reduced Ejection (ventricles)
Isovolumetric Relaxation (ventricles)
Rapid Filling (ventricles)
Reduced Filling (ventricles)
In terms of Diastole and systole, how are they affected when heart rate needs to increase?
SYSTOLE = ALWAYS SAME
DIASTOLE = SHORTER
What is a Wiggers diagram?
Diagram that illustrates changes in blood pressure and volume in the left side of the heart for each cardiac cycle
How many heart beats are there per cardiac cycle?
1 heart beat
How would a Wiggers diagram from the right hand side of the heart compare to the left hand side of the heart?
Lower pressures for the RHS
In an electrocardiogram, what does the P wave represent?
Contraction of the Atria/atrial depolarisation
In an electrocardiogram, what does the QRS complex represent?
Contraction of the ventricles/ventricular depolarisation
In an electrocardiogram, what does the T wave represent?
Ventricular repolarisation
What is End Diastolic Volume (EDV)?
The volume of blood each ventricle contains before ejection/systole
What happens during Phase 1: Atrial Contraction of the cardiac cycle?
(In terms of pressures, volumes and valves)
Atria contract
Atrial pressure increases
Left ventricular volume also increases
The mitral and tricuspid valve are open
Aortic and pulmonic valve closed
How do the ventricles fill?
Mainly during diastole when the are relaxed and recoiling
Some Atrial kick (atria contract filling final 10% of ventricles)
Why can patients survive atrial fibrillation?
The amount of blood that the contraction of the atria are responsible for filling the ventricles is not that much
At the end of Phase 1: Atrial Contraction, what is the Normal End-Diastolic volume?
About 120ml
What happens during Phase 2: Isovolumetric Contraction of the cardiac cycle?
(In terms of pressures, volumes and valves)
Ventricles contract causing rapid rise in ventricular pressure (QRS complex)
Mitral/Tricuspid valves closes (Ventricular pressure > atrial pressure)
Aortic/pulmonic valves still closed
ISOVOLUMETRIC SINCE NO CHANGE IN BLOOD VOLUME IN VENTRICLES AS VALVES ARE CLOSED
What sound is made during Phase 2: Isovolumetric Contraction and why?
S1 = Lub Noise
Lub noise made by sound of mitral and tricuspid valve closing
What happens during Phase 3: Rapid Ejection of the cardiac cycle?
(In terms of pressures, volumes and valves)
Aortic valve and pulmonic valve open when Intra ventricular pressure exceeds aortic/pulmonic pressure
Mitral/tricuspid valve still closed
RAPID DECLINE in ventricular volume as blood ejected into aorta
Atrial X descent
Then pressure in atria starts to slowly increase as they fill with blood
What happens during Phase 4: Reduced Ejection of the cardiac cycle?
(In terms of pressures, volumes and valves)
Ventricles begin to repolarise causing ventricular pressure to begin to decrease
T Wave
Aortic/pulmonary valve still open
Atrial pressure still slowly increasing
What happens during Phase 5: Isovolumetric Relaxation of the cardiac cycle?
(In terms of pressures, volumes and valves)
Intra ventricular pressure continues to fall, once its lower than aortic pressure the AORTIC VALVE CLOSES
Volume of ventricles remains the same despite the rapid decrease in pressure (valves closed)
Dicrotic notch
What is the Dicrotic notch?
Slight increase in aortic pressure caused by the closure of the aortic valve
What is Atrial X descent?
The initial decrease in atrial pressure as the atrial base is pulled down as the ventricles contract
What is the sound that is made in Phase 5: Isovolumetric Relaxation and why?
S2 = Dub
Dub noise made by aortic and pulmonary valve closing
What is End Systolic Volume (ESV)?
The volume of blood left in the ventricles after systole/ejection
How can you work at Stroke volume?
End diastolic volume - End Systolic volume
EDV - ESV
What happens during Phase 6: Rapid Filling of the cardiac cycle?
(In terms of pressures, volumes and valves)
Mitral valve and tricuspid valve open as atrial pressure exceeds intraventricular pressure
Atrial pressure then decreases as mitral valve opens = Y-descent
RAPID VENTRICULAR FILLING once mitral valve has opened
Volume of ventricles begins to increase
Phase 6: Rapid filling can produce a 3rd sound (S3), when is the normal and abnormal?
Normal in children
In adults can indicate pathology
Filing of ventricles normally silent
What happens during Phase 7: Reduced filling of the cardiac cycle?
(In terms of pressures, volumes and valves)
Rate of ventricular filling slows
Ventricles full to about 90%
Next cardiac cycle, atrial kick will fill final 10%
What is Stenosis?
When a valve doesn’t open enough obstructing blood flow
What is regurgitation/incompetence of the valve?
Valve doesn’t close all the way allowing back flow of blood
Which side of the heart is more prone to abnormal valve function and why?
LHS since it is under a higher pressure
What can cause Aortic valve stenosis?
Degeneration (senile calcification/fibrosis)
Congenital (can be bicuspid instead of 3 leaflets)
Chronic rheumatic fever
What is Chronic rheumatic fever caused by?
Streptococcal infection
Causes autoimmune response targeting heart
What blood condition can Aortic valve stenosis cause?
Microangiopathic haemolytic anaemia
What is Microangiopathic haemolytic anaemia?
When shear stress likely from a stenosed valve damages RBCs leading to them being broken down causing anemia
What are the affects of Aortic valve stenosis?
Less blood can travel through valve causing:
Increased LV pressure
Left sided heart failure
What is the effect of the increased LV pressure due to a stenosed aortic valve?
LV hypertrophy since ventricles need to work harder to force blood through valve
What does left sided heart failure cause?
Angina
Syncope
What is angina?
When the heart doesn’t receive enough oxygenated blood from he coronary arteries causing heart pain
What is syncope?
Fainting
What causes Aortic valve regurgitation?
Aortic root dilation (LEAFLETS PULLED APART)
Valve damage
What are the effects of aortic valves regurgitation?
Blood flows back into LV during diastole when it shouldn’t
Increases stroke vol
Systolic pressure inc
Diastolic pressure inc
BOUNDING PULSE
LV hypertrophy
What indicates a bounding pulse?
Head bobbing
Quinke’s sign
What is Quinke’s sign?
Nails flush red and white with every systole and diastole
Seen in aortic valve regurgitation
What is Myxomatous degeneration?
Changes in collagen structure weaken valve structure
What can cause Mitral valve regurgitation?
Myxomatous degeneration
Damaged papillary muscles (heart attack)
Rheumatic fever (leaflet fibrosis)
Left sided heart failure leading to LV dilation stretching valve
What is the main cause of Mitral valve stenosis?
Rheumatic fever (Commissural fusion of valve leaflets)
How does Mitral valve stenosis affect pressure of the left atrium?
Increased LA pressure to force blood through
What is the effect of increased LA pressure?
LA dilation/hypertrophy
Right ventricle hypertrophy since RHS must work harder to pump more blood from the pulmonary artery (sine both sides of the heart need to pump same volumes)
Pulmonary oedema
Dyspnea
Pulmonary hypertension
What are the affects of Left Atrial hypertrophy?
Atrial fibrillation (thrombus formation as blood pools in atria)
Oesophagus compression causing Dysphagia
What is Dysphagia?
Swallowing difficulties
How do the volumes of blood pumped by both sides of the heart compare?
Pump the same volumes
How long is the typical cardiac cycle?
0.9s
Approximately how long does diastole last?
0.55s
Approximately how long does systole last?
0.35s
What type of sound would be heard for a mitral valve stenosis?
Mid diastolic murmur
What sound can be heard in an aortic stenosis?
Crescendo decrescendo
