Cardiac Output Flashcards
What is the basal cardiac output for a 70kg male?
5600 ml/min
What is the litre capability of a sedentary 70kg male?
20L / min
What is the definition of cardiac output ?
The volume of blood pumped by the left ventricle in one minute.
How do you calculate cardiac output?
Heart rate x stroke volume
How is the ejection fraction calculated ?
Stroke volume / end diastolic volume
What does the ejection fraction tell us?
How hard the heart is working
Do athletes have an increased heart rate or stroke volume?
Stroke volume
Why does the EDV in a patient with heart failure increase?
The heart is dilated
How does the sympathetic NS effect HR?
It speeds up the heart (+ve chronotropic effect)
How does the sympathetic NS speed up the heart?
It activated B1 sympathetic receptors which open up calcium channels which allows more calcium into the cells during phase 4.. Ut also speeds up AV conduction.
How does the parasympathetic nervous system effect hr?
It slows down the heart (-ve chronotropic effect)
How does the parasympathetic NS slow down the heart?
Activation of M2 receptors opens K+channels which slows the opening of Ca++ channels. Slows AV conduction.
What is heterometric regulation?
Changes in cardiac output dependent on initial length of cardiac muscle fibre
What is homeometric regulation ?
Changes in cardiac output independent on initial length of cardiac muscle fibre
What does the Frank-Starking relationship tell us?
Stroke volume and cardiac output is dependent on the degree of stretch on ventricular walls. The more blood put into the heart, the more the heart will stretch, the higher the stroke volume.
More in = more out
What are other terms given to preload and afterload?
Preload - end diastolic volume
Afterload - systemic arterial pressure against which the heart is pumping
When does decomposition occur?
This occurs when the heart is stretched too much and therefore decreases stroke volume
Will will catecholamines (noradrenaline and adrenaline) do to sympathetic NS effects?
They will amplify the effects
What type of regulation is the Frank-Stirling law?
Heterometric
Define cardiac failure.
Insufficient peripheral perfusion despite normal blood volume, a sufficient filling pressure and intact intrinsic and extrinsic compensatory mechanisms
What is the most common cause of cardiac failure?
Coronary artery disease
What is an oedema ?
Build up of fluid in a tissue
