What is the Frank-Starling Mechanism?
ncreased stretch of heart -> increased force of contraction.
Increased blood volume -> stretch of myocardium
What results in increased preload?
Increased stroke volume -> increased preload (EDV) -> increased stretch -> increased force of contraction
How do you calculate mean arterial pressure (MAP)?
(SBP + 2 x DBP)/3
Where are chemoreceptors found?
Where are baroreceptors found?
2. Aorta
What is Laplace’s Law?
Wall tension = intraventricular pressure x internal radius
What happens to arterial pressure as radius increases?
As radius increases, so does tension but Pressure remains equal
What happens during cardiomyopathy?
Heart becomes significantly distended. Increased radius increases tension. Heart requires more energy to pump same amount of blood.
What happens during myocardial hypertrophy?
Thickening and stiffening of the heart muscle. Decreased elasticity, decreases compliance and contractility.
What are 4 factors affecting cardiac performance?
What 2 primary factors that effect preload?
Increased preload = increased cardiac output
What decreases preload?
Decrease in Venous return or filling
What is afterload?
Resistance to ejection during systole.
Force to eject blood from heart.
What are 2 main factors that effect afterload?
Increased afterload -> decreased cardiac output (CO)
What increases afterload?
Increased aortic pressure or increases SVR
What decreases afterload?
What 3 factors effect contractility of the heart?
What compromises intrinsic contractility of the heart?
1. Poor myocardial perfusion (Secondary to atherosclerosis) 2. Primary disease of myocardium 3. Degenerative changes with aging 4. Necrosis from MI 5. Negative ionotropic drugs
What drugs increase contractility of the heart?
Ionotropes (dobutamine, dopamine, digoxin)
What drugs decrease contractility of the heart?
What are the effects of aldosterone?
Hormone that promotes sodium retention, which can increase H2O reabsorption, increased blood volume, and increased CO (HTN)
How is blood pressure calculated?
BP = CO x SVR
How is cardiac output calculated?
CO = stroke volume x HR
What are the 2 primary causes of sustained hypertension?
2. Increased blood volume