Flashcards in Control of Cardiac Output Deck (17):
What is maBP dependant upon?
Arterial pressure created by the heart is determined by the cardiac output and the total peripheral resistance.
What happens if TPR falls and cardiac output stays the same?
The arterial pressure will fall but the venous pressure will rise.
What happens if TPR rises and cardiac output stays the same?
The arterial pressure will increase and the venous pressure will fall.
What happens if cardiac output rises and TPR stays the same
The arterial pressure rises and the venous pressure falls.
What happens if cardiac output falls and TPR stays the same
The arterial pressure falls and the venous pressure rises.
How is the bodies metabolic demand and TPR related?
The total peripheral resistance is inversely proportional to the body’s need for blood. The demand of the body is expressed as changes in arterial and venous pressure the heart responds to this by pumping more or less blood.
What is stroke volume and what is it related to?
Stroke volume is the difference between the end diastolic volume and the end systolic volume. In diastole the ventricles are isolated form the arteries and filled by the veins. When the ventricular pressure reaches above that of the venous pressure the ventricles become isolated from the veins as well. Therefore, the higher the venous pressure the greater the volume of the ventricles.
What is the ventricular compliance curve?
A graph that shows how End diastolic volume changes with venous pressure.
What happens when ventricular muscles are stretched before contraction?
If ventricular muscles are stretched before contraction they contract harder.
What is Starling's law?
Starling’s law states that the higher the venous pressure the larger the stroke volume. Note on this graph you can use EDV and end diastolic pressure and venous pressure interchangeably.
Why does the curve plateua?
The curve plateaus because past a point the muscle will be stretched so far that the myosin and actin filaments become too far apart to interact and you lose contractibility.
Contractility refers to the efficiency at which the muscles work in the heart i.e. inotropy and this can change the cardiac output for a given EDV.
Define Pre-load and after load.
Pre-load is the wall stress at the end of diastole whilst after load is the wall stress during ejection of the left ventricle.
How does pre load, after load, TPR and starling's law effect end systolic pressure.
End systolic pressure relates to how hard the heart contracts, and how hard it is to eject blood. How hard it contracts is controlled by starling’s law and contractility. The ease of ejection is related to the TPR.
How does arterial pressure relate to cardiac output?
The harder it is to get blood out of the heart the higher the arterial pressure rises to. So if arterial pressure falls, end systolic volume will fall and the stroke volume will rise.
Describe how the baroreceptors work in the carotid sinus?
Baroreceptors in the carotid sinus sense the pressure of the artery. This part of the artery is slightly thinner allowing it to stretch with pressure and trigger a nerve. Brain then responds by increasing or decreasing the activity of the sympathetic and parasympathetic innervation.