2-The Heart As A Pump Flashcards
Define afterload
The load the heart must eject against
Define preload
Amount the ventricles are stretched during diastole
Define Total Peripheral Resistance (TPR)
The resistance to blood flow offered by all the systemic vasculature
Define systole
Phase of ventricular contraction
Define diastole
Phase of ventricular relaxation and filling
What is End Diastolic Volume (EDV) and when does it occur in the cardiac cycle?
EDV is the maximum ventricular volume and it occurs after atrial contraction
What is End Systolic Volume (ESV) and when in the cardiac cycle does it occur?
ESV is the volume of blood left in the ventricles after systole and occurs during isovolumetric relaxation
Define contractility
Contractility is the force of contraction for a given fibre length
What is aortic pressure equivalent to?
Afterload
What is central venous pressure equivalent to?
Preload
What is stroke volume determined by?
The degree of contraction during systole
What is EDV determined by?
The filling of the heart in diastole
Explanation: As ventricles fill, pressure increases as ventricle wall stretches. When ventricular pressure equals venous pressure no more filling occurs. Therefore increased venous pressure = increased ventricular filling in diastole
Why is internal jugular vein pressure measured?
As nothing impedes the flow of blood from right atrium to internal jugular vein therefore it represents right atrial pressure and right heart function.
What is the cardiac cycle?
The sequence of pressure changes and valve operations that occur with each heart beat
Describe the pressure changes in the internal jugular vein
1st- a wave caused by transient venous distension due to back pressure from right atrial contraction
2nd- v increase due to passive filling of right atrium from systemic veins during systole when tricuspid valve is closed
3rd - y decreases causes by a fall in right atrial pressure due to tricuspid valve opening in early diastole allowing rapid ejection from the right atria to right ventricle
What causes the 1st heart sound?
‘Lub’ is caused by the mitral valve closing as systolic contraction causes left ventricular pressure to exceed left atrial pressure
What causes the 2nd heart sound?
‘Dub’ is caused by atrial valve closing as the left ventricular pressure decreases below aortic pressure as it relaxes
Roughly how long does systole and diastole last?
Systole - 0.35 s
Diastole - 0.55 s
Name the stages of the cardiac cycle
- Atrial contraction
- Isovolumetric contraction
- Rapid ejection
- Reduced ejection
- Isovolumetric relaxation
- Rapid filling
- Reduced filling
What prevents atrioventricular valves from prolapsing during systole?
Attachments to chordae tendinae which are attached to papillary muscles that contract in systole
What is a valve stenosis?
Where the valve doesn’t open enough, so there is an obstruction when valve is normally open
What is a valve regurgitation?
Where the valve doesn’t close fully, so there is back leakage when the valve should be closed.
Where are the areas of auscultation?
Aortic valve - 2nd right intercostal space, sternal border
Pulmonary valve - 2nd left intercostal space, sternal border
Tricuspid valve - 4th left intercostal space, sternal border
Mitral valve - 5th left intercostal space, mid clavicular line
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What are the causes of atrial valve stenosis?
- Chronic rheumatic fever (inflammation leading to commissural fusion of leaflets)
- Degenerative (senile calcification/fibrosis)
- Congenital (born with bicuspid form of tricuspid valve)
