Control of cardiac output Flashcards
What is the Frank-Starling mechanism?
The greater the EDV the greater the contractile strength of the ventricles this results in an increased stroke volume. The myocardium will be more stretched due to a greater volume, therefore their increased lenght leads to an increased sensitivity to Ca2+ and therefore a much stronger contraction.
What is preload?
The end diastolic volume that stretches the right or left ventricle of the heart to its greatest dimensions.
What is afterload?
The pressure against which the heart must work to eject blood during systole
What is vascular compliance?
The ability of a blood vessel wall to expand and contract passively with changes in pressure
What are types of noncompliant blood vessels?
Capillaries and arterioles
What are types of compliant blood vessles?
Arteries and veins
How is cardiac output calculated?
Stroke volume x Heart rate
What causes vasoconstriction neuronally?
Sympathetic nerves
What causes vasodilation neuronally?
NO-releasing nerves
What causes vasoconstriction hormonally?
- Adrenaline
- Angiotensin II
- Vasopressin
What causes vasoconstriction localy?
- Myogenic response
- Endothelin-1
What causes vasodilation hormonally?
- Adrenaline
- Atrial-natriuretic peptide
What causes vasodilation localy?
- Decresed oxygen
- K+, CO2, H+
- Adenosine
- NO
- Bradykinin
What percentage of blood in the body is roughly in capilaries at rest?
~5%
Explain the NO vasodilation pathway
Blood flow against recpector on endothelial cells activated
eNOS activated
- Conversion of O2 + L-Arginine to NO + L-Citrulline
- NO diffuses into smooth muscle cells
- NO activates Guanylate cyclase (GC)
- GC coverts GTP to cGMP
- Incresed conc. of cGMP causes relaxation
