6 - Control Of The CVS Flashcards
What is the effect of increasing cardiac output?
Increased arterial pressure
Decreased venous pressure
What is the effect of increasing TPR?
Decreased arterial pressure
Increased venous pressure
TPR is inversely proportional to the body’s need for blood. What effect does this have during metabolism?
Increased metabolism = decreased TPR = decreased venous pressure and increased arterial pressure = increased cardiac output
Increased demand is met so system is stable
Cardiac Output = …
… Stroke Volume x Heart Rate
How does venous pressure affect how much ventricles fill during diastole?
Ventricles continue filling until the intra-ventricular pressure equals the venous pressure so a higher venous pressure means the ventricles will fill more
Define pre-load
End diastolic stretch of myocardium
Define after load
The force necessary to expel blood into the arteries
Explain Staling’s Law of the Heart
Greater filling of ventricles = more stretching of walls = harder contraction = more blood ejected
Describe the Staling Curve
- as venous pressure increase stroke volume increase
- up until a point when the heart is overfilled and the myocardium is stretched so stroke volume reduces
Define Contractility
The extent to which an increase in venous pressure increases stroke volume
What are the Baroreceptors?
Found in the carotid sinus
Detect changes in arterial pressure and send signals to the medulla
What factors affect end systolic volume?
- strength of contraction
- how easy it is to eject blood
What is the ‘Bainbridge Reflex’?
Volume sensors in the venous circulation
What happens when you eat a meal?
Increased metabolism = release of metabolites = vasodilation = decreased TPR = decreased venous pressure and increased arterial pressure = increased cardiac output
Increased demand met = SYSTEM STABLE
Does an increase in heart rate cause an increase in cardiac output?
Initially yes but the increased cardiac output=decreased venous pressure=decreased stroke volume = decreased cardiac output
