4. Control of cardiac output Flashcards
What are the intrinsic mechanisms of the heart used to control stoke volume?
- Self regulation
- Frank-Starling Mechanism
- Increased EDV = Increased force of contraction
What is preload?
Venous pressure and venous volume return the the heart (EDP/EDV)
What is afterload?
Aortic/Pulmonary Artery pressure; what pressure the ventricle has to over come to push blood forward
What extrinsic mechanisms control Stroke Volume?
Sympathetic nerves
What is the differnce between sympathetic innervation and the Frank Starling Mechanism (FSM) on Stroke Volume?
FSM has a higher EDV where as sympathetic innervation increases the amount of blood being pumped out of the heart from the same volume
What is the Frank-Starling Mechansim?
Allows for automatic adjustment for small imbalances between L and R ventricle. Automatic balancing between CO from LHS to volume returning to RHS
What type of stimulation does FSM cause?
Inotropic Stimulation
What causes increase to actin-myosin overlap in cardiac muscle
- Increased veolume of blood in ventricle
- Increased EDV and Increased stretch results in an increased CO and force of contraction
Why does oscillating flow decrease as blood moves through the body?
Due to branching of the cardiac tree
- Increased CSA and diameter
- This is due to the increasing number of vessels
What dictates how fast blood can escape?
Systemic vascular resistance –> Arterial system has limited capacity
Non-complaint =
Rigid structure - resist expansion when internal pressure rises
- capillaries and arterioles
- Big pressure changes for small volume changes
Compliant =
Elastic structure - walls swell when internal pressure rises
- Veins and ventricles
- small changes in pressure for large changes in volume
Mean Arterial Blood Pressure =
diastolic pressure + 1/3pulse pressure
Pulse pressure =
Systolic Pressure - Diastolic pressure
What is floe directly proportional to?
- radius of vessel (biggest determinant of flow)
- pressure gradient along vessel
