The Heart as a Pump Flashcards
Pressure in the RA
0 - 8 mmHg (average 4 mmHg)
Where does blood drain into the RA from?
IVC, SVC and coronary sinus
What percentage of blood drains from ascending/descending veins?
80% IVC
20% SVC
Which valve separates the RA and RV and when is it open/closed?
Tricuspid valve
Open = diastole
Closed = ventricular systole
How much blood is pumped from the LV at rest?
75 - 80 ml
Histological appearance of cardiac myocytes?
Distinct, single nucleated cells and operate as a syncytium
What is the approximate duration of ventricular contraction in a normal heart beating at 60bpm?
300 ms
Given the heart has more than one pacemaker, why don’t different pacemakers compete to drive the heartbeat in the normal heart?
Because they fire at a slower rate
If the heart rate is 60 bpm, what is the approximate duration of diastole?
700 ms
What will happen if a valve becomes incompetent (leaks)?
There will be turbulent backflow leading to a systolic murmur
Why does the ventricle not empty completely into the arteries during systole?
Eventually the pressure gradient reverses so that arterial pressure is greater than ventricular pressure
The residual volume in the ventricles serves as a small, adjustable blood reservoir
When in the cardiac cycle would you expect to hear a murmur if a patient has aortic stenosis?
Systole
When in the cardiac cycle would you expect to hear a murmur if the mitral valve fails to open properly? (mitral stenosis)
Diastole
When in the cardiac cycle will you expect to hear a murmur if the mitral valve fails to close properly? (mitral incompetence)
Ventricular systole
What would you hear through the stethoscope in an infant with such a ‘Patent Ductus Arteriosus’?
Continuous murmur throughout systole and diastole (machinery murmur)
